US2033263A - Abrasive article - Google Patents

Description

Match 1936- F. J. TONE 7 12,033,263

ABRASIVE ARTICLE Filed April 18, 1932 3 Sheets-Sheet l INVENTOR FRANK J. TON E ATTORNEY F. J. TONE March 10, 1936.

ABRAS IVE ARTICLE Filed April 18, 1932 3 Sheets-Sheet 2 INVENTOR FRANK J. TONE ATTORNEY March 10, 1936. F. J. TONE 2,033,263

ABRAS IVE ARTICLE Filed April 18, 1932 3 Sheets-Sheet 3 mmllmm N I F J].

2-1pm i W W ATTORNEY Patented Mar. 10, 1936 UlTED ST ABRASIVE ARTICLE Application April 18, 1932, Serial No. 606,666 In Canada December 7, 1927 1Claim.

This invention relates to new and improved abrasive articles and bearing surfaces therefor and to methods of making the same, and this application is a continuation in part of my copending application Serial No. 14,402 filed March One object of the present invention is to ob tain a rapid and reasonably accurate method of securing a predetermined relation of the bearing surfaces of an abrasive wheel to its axis of rotation. The predetermined relation desired implies that the bearing surfaces shall be true surfaces of revolution about the axis of rotation of the wheel; in other words, that the sides of the wheel be coaxial at least over the bearing area.

Another object of my invention is to provide a precision bearing surface in the arbor hole of the wheel where it constitutes a bushing and/or along the lateral face of the wheel where it constitutes a flange bearing surface.

Still another object, resulting from the foregoing, is to improve the balance of the wheel and reduce its tendency to wobble and chatter in use.

It is necessary to subject the sides of abrasive wheels to some truing process because they become warped, distorted and glazed over during the curing operation, and, since abrasive wheels are required to run smoothly and evenly in operation, they cannot be used before proper bearing surfaces are provided for the flanges.

Until the present invention was made, abrasive wheels were trued in either of the following methods or a combination thereof.

1. The abrasive wheel was placed in a holder of some kind, such as a chuck, and one face dressed with a tool. The wheel was then reversed in the holder and the other face was similarly dressed.

2. The abrasive wheel was placed in a holder and passed between revolving disks which dressed off both sides at once.

3. The abrasive wheel was lapped on a large revolving disc with abrasive grain and water, first on one side and then on the other.

4. Following the above, the arbor hole was bushed with melted lead in order to provide a snug bearing against the shaft. Even this was not entirely satisfactory as the lead was somewhat plastic and tended to distort in use to a degree objectionable in high precision work.

The above methods have been found to produce wheels in which the opposite faces are sufliciently close to parallelism in straight-sided wheels, or

suificiently coaxial in the case of bevel-sided wheels, so that they are not subjected to undue stresses when held between blotters by the mounting flanges.

These methods, however, arev costly in that the involve the expenditure of considerable time and energy. I have found that they may be dispensed with by practicing my invention, which is illustrated in the attached drawings in which:

Figure 1 shows a section through a center and axis of rotation of an abrasive wheel of the more common shape, to which flange seats have 10 been applied;

Figure 2 shows a view of a face of the wheel shown in Figure 1;

Figure 2A shows a section of a bevel-sided wheel to which flange seats have been applied;

Figure 3 shows a section, similar to Figure 1, of another wheel to which flange seats have been applied;

Figure 4 shows a section through the axis of a jig (two of which are required) by which my 20 invention can be carried out;

Figure 5 is a view of the lower side of the jig shown in Figure 4;

Figure 6 is a view similar to Figure 1 of an abrasive wheel mounted between two jigs of the 25 character shown in Figures 4 and 5 and ready to be put in a'press;

Figures 7, 8, 9, and 10 are sectional views of abrasive wheels and show in an exaggerated degree some of the more common types of distor- 30 tion found in such articles;

Figures 11 and 12 are a face view and a sectional view respectively of a. template with the aid of which my invention can be carried out;

Figure 13 shows a wheel and forming plates 35 mounted between the platens of an hydraulic press; and

Figure 14 shows a section of a modified form of apparatus adapted to form a bushing bearing aswell as a flange bearing. 40

The procedure for carrying out this invention for straight-sided wheels, or for bevel-sided. wheels if necessary, may be illustrated by referring to Figures 1, 2, 11, and 12, and is as follows:

The template 2, (Figures 11 and 12) which has 5 a perforate pattern, is placed on the face 4 or 5 (Figure 1) of the abrasive wheel 3 concentrically therewith and the abrasive surface, left uncovered by the opening of the template, is covered with yieldable material 6 (a small disk I being 50 used to cover the arbor hole temporarily). The yieldable material must be capable of flow, either in powder form or as a plastic material, to a degree permitting it to practically completely and uniformly fill in the space within the tem- 55 plate and between the abrasive surface and the steel plates described below, and must be capable of adhering tightly to the abrasive surface after a curing treatment, after which treatment it must be so rigid as to be incapable of further flow under the conditions to which it is subjected in the normal service of the abrasive. It is also desirable that the coefficient of expansion of the material be as close as possible to that of the abrasive material in order that tight adhesion between the two may exist at all times.

A synthetic resinous molding powder or unvulcanized rubber or a mixture of shellac and fine sand may be satisfactorily used as the yieldable material. This yieldable material is applied to one face 4 or 5 to a uniform thickness by filling the template and, striking off the excess powder with a straight edge. This template 2 'has an outside diameter equal to the diameter of the wheel on which it is to be used, an inside diameter equal to that of the flange bearing body or flange seat required, and a thickness equal to that .of the amount of powder needed for one flange seat. It may be made of some rigid material such as fibreboard, heavy cardboard or metal. The template 2 and small disk I are then carefully removed. A surface ground 'steel plate 8 (see Figure 13) is then placed on the powder to hold it against the face of the wheel and the wheel turned over. In a similar manner the material for the second flange seat and steel plate is applied to the second face of the wheel. These steel plates must be rigid enough to prevent warping when heat is applied. The wheel, still between the steel plates, is then placed in a precision type hydraulic press and a pressure of about 250 pounds per inch square applied to the area of the flange seat while a temperature of about 350 F. is maintained at the platens 9. A precision type hydraulic press is one whose platens remain parallel when pressure is applied to an object between them. The wheel and plates are then removed from the press and the plates removed from the wheel. The flange seats thus produced are parallel within 0.003 inch in six inches. I have found that by my method I am able not only to improve the nature of the bearing surface supporting the flanges, but am able to counteract to a material degree the tendency of wheels to be out of balance due to local variations in thickness, both factors combining to give an abrasive wheel operating with a minimum of vibration or wobble. t

Figure 13 illustrates an alternative method by which the faces of an abrasive wheel may be made parallel-within 0.001 inch or less. The process is the same as the foregoing up to and including placing the wheel 3 (Figure 13) and. plates 8-8 in the press. Accurate spacer blocks I l--l| are then placed between the platens 9-9 of the press andpressure applied. These spacer blocks ll-ll, having been finished to exactly the same height, keep the platens 9-9 of the press parallel to one another. The jig, shown in Figures 4, 5, and 6, may also be used in the process. Two of these are required. Each jig consists of an outer ring l2, an inner ring 13, and a plate Id. The outer ring l2 has an outer diameter slightly larger than the diameter of the wheel; the inside diameter is that of the flange seat required. Spaces l5 hold the amount of material required for a flange seat. The space I6, between the outer ring and the plate is such that when the jigs and wheel are ready for the press,

as in Figure 6, with spacers l1 between the rings l2 and the pressure applied, the pressure needed to compress the flange seats results.

In using these jigs, the spaces IS in the two jigs are filled with the material used for the flange seat, and after striking oi the excess material with a straight edge the wheel 3' is placed on one of the jigs and centered on the jig by the pin 2|. Both the wheel and jig are now turned and placed upon the second jig. The outer rings I2 of the two jigs are kept from putting any pressure on the wheel at surfaces l8 by the spacers IT. The two jigs and wheel are then placed in the press and pressure applied.

The wheel, being suspended in a plastic medium and subjected to pressure as in the preceding methods, will automatically align itself so that the faces of the wheel will assume an average positionas nearly parallel as possible to the surface of the press platens. This is because the forces acting against the face of the wheel are at right angles to the surface of the press platens and have no' components parallel to the press platens. The forces will have components parallel to the faces of the wheel if these faces are not parallel to the press platens. The wheel being suspended in a plastic medium is free to.

move and adjust itself so that the forces acting parallel to the faces of the wheel will be in equilibrium. This tends to minimize the forces parallel to the faces of the wheel and, since the resultant forces are substantially perpendicular to the press platens, the faces of the wheel align themselves as nearly parallel as possible to the press platens.

when mounted for operation it rotates with a minimum amount of lateral displacement.

In the case of bevel-sided wheels as shown in Figure 2A, the templates, plates and jigs are made in accordance with the desired taper, and the straight edge for striking off the excess plastic mix may be manipulated as an element of the cone to which the wheel taper conforms. The flange seats resulting from these modifications will be coaxial; that is, surfaces of revolution about the axis of rotation of the wheel.

While in the foregoing discussion the practice disclosed is to cure the yieldable material while compressed between coaxial plates, it is to be understood that it is also within the scope of my invention to form the yieldable material in the manner described and complete the cure after removal of the abrasive and facing from the forming device, this minimizing the amount of equipment tied up in the processing steps.

As previously stated, I may also form precision bushing bearings in accordance with my invention, utilizing the same materials and methods described in connection with precision flange bearings either in conjunction with flange bearings or for bushings without flange bearings. To do so, a carefully sized mandrel 23 (see Figure 14) is placed through the arbor hole 24 of the wheel 3", concentric therewith, and as closely as possible at right angles to the side of the wheel. Molding compound I5 is then placed in the arbor hole between the mandrel and the wheel (also on the wheel faces as before if desired), and pressed in place and cured. To complete such wheels, a shaft is placed in the hole formed by the mandrel and the wheel rotated thereon while the periphery of the wheel is dressed with a diamond or other suitable tool to render it truly circular and concentric and to impart to it any desired contour.

This has the effect of distribut ing the mass of the wheel in such a manner that taneously compressing said layers against the sides or the wheel to a predetermined thickness by applying pressure to them from members which are parallel to one another, meanwhile supporting said wheel solely by contact with said layers, and while said layers are thus compressed curing the material of which they are composed to permanently set them in the shape thus occupied.

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