US2652321A - Grinding wheel - Google Patents

Description

E. 0. TEAGUE GRINDING WHEEL Original Filed Sept. 7, 1950 Inverofor AGLJ ERNEST DOUGLAS By 13 RNEY Patented Sept. 15, 1953 2,652,321 GRINDING WHEEL Ernest Douglas Teague, Welwyn Garden City,

England, assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Original application September 7,

1950, Serial No.

183,552, now Patent No. 2,624,660, dated January 6, 1953. Divided and this application September 2, 1952, Serial No. 307,468

4 Claims.

The invention relates to grinding Wheels particularly to that variety thereof known as cop wheels, which are used to cut stone and other hard non-metallic materials. This applicationis a division of my copending application Serial No. 183,552, filed September '7, 1950 now Patent 2,624;660.

One object of the invention is to provide a superior coping wheel. Another object of the nvention is to provide a coping wheel which can be used in dry grinding operations and which will cut at a high rate without fracturing. Another object of the invention is to provide a copin wheel which can be used under conditions which will make it very hot Without fracturing. Another opject of the invention is to provide a coping wheel which can pe used under such conditions that it becomes very hot and which nevertheless has a high rate of cut and relatively low wheel wear.

Other objects will be in part obvious or in part pointed out hereinafter.

In the accompanying drawings illustrating two of many possible embodiments of the mechanical features of this invention,

Figure l is a side elevation of a typical steel center for a coping wheel, the boundaries of the abrasive material to be molded thereon being indicated by dotted lines,

Figure 2 is a fragmentary diametral cross-sectional view on a larger scale than Figure 1 of a coping wheel constructed in accordance with th invention,

Figure 3 is a cross-sectional view similar to Figure 2 illustrating another embodiment of t invention.

For the manufacture of a coping wheel in accordance with the invention, I provide a steel center such as the steel center Hi. This steel center It as illustrated in Figure 1 is a typical shape of steel center for coping wheels, the shape in cross section of the peripheral portion being shown in Figures 2 and 3. This steel center ID has cut-outs It at the periphery thereof forming a plurality of peripheral dovetails l2. Desirably also a plurality of holes l3 are provided in the peripheral portion M in which the dovetails I2 are formed; this peripheral portion [4 is Separated from the hub portion I 5 by means of shoulders 16, one on each side of the center It. The hub portion [5 has a central hole ll so that the center Ill can be mounted upon a spindle. The sides of the hub portion l5 may be plane pa allel surfaces and the sides of the peripheral portion 14 may also be plane parallel surfaces. The

section planes of Figures 2 and 3 are not taken through the cut-outs II or holes It. The foregoing description of the steel center It is illustrative and other shapes and styles of steel centers may be used in accordance with this invention. It will be seen that the steel center It is essentially a disc modified by the features above described.

On the steel center It] is molded an annular portion 20 of abrasive and phenolic resin bond. This annular portion 20 is continuous around the entire steel center It and interlocks with the dovetails l2 and holes I 3. Between the steel center l0 and the annular portion Zil is a layer Zla of thermoplastic resin as shown in Figure 2 or a layer 2 lb of thermoplastic resin including granular, refractory or abrasive material, as shown in Figure 3.

The abrasive material in the annular portion 20 is preferably silicon carbide abrasive since this abrasive is preferred for the grinding of most stones such as granite, marble or the like, or t e grinding of other hard non-metallic materials such as porcelain, glass and concrete. However,

within the scope of the invention other abrasives may be used such as aluminum oxide abrasive including the product of the electric furnace or natural corundum or emery.

The bond in the annular portion 20 is a phenol formaldehyde resin of any desired variety. Commercial resins usually contain a minor proportion of cresol formaldehyde and such resins can be used advantageously in this invention. Furthermore I use the Word phenol in the broad sense to include phenolic bodies such as cresol and sylenol. These, as well as phenol in the stricter sense, comprise a benzene ring with an OH group thereon. In making up the mixture furfural can be used as a plasticizer in which case there Will result some furyl methylene linkages as well as methylene linkages. The uncured resin may have a substantial proportion of hexamethylenetetramine therein to speed the curing. In any case the resin bond should be cured to a thermo-irr-eversible condition. This resin bond I will term thermo-irreversible phenol-formaldehyde resin. This class of material and the manner of curin and compounding it is now well known in the abrasive art and also in other arts and therefore needs no further description. The proportions of the abrasive and of the thermo-irreversible phenolforinaldehyde resin, the grit size of the abrasive, the porosity of the annular portion 213 may all be varied within the usual limits and in accordance with the practices now Well known in the abrasive art and particularly adapted for coping wheels- These matters, therefore, need no further elucidation herein.

The layer 21a consists of and the layer Zib comprises vinyl resin.

The vinyl resins include styrene which can be termed vinyl benzene, vinyl acetate, and the methacrylate resins. Of the latter, there are many varieties including methyl methacrylate and allyl methacrylate, ethylene glycol dimethacrylate, glycerol trimethacrylate, penta glycerol trirnethacrylate, trimethylene glycol dimethacrylate. Also copolymers of any of the above Wit each other or with styrene or with acrylic acid, acrylic anhydride, methacrylic acid, and methacrylic anhydride can be used.

In order to form the annular portion 20 with the layer 2m of thermoplastic resin thereunder on the center It, the following procedure may be adopted: the steel center H is thoroughly cleaned on both sides of the peripheral portion Hi and on both. sides of the hub portion l5 near the shouders it to remove grease therefrom, and this may be done by immersing these portions in a suitable grease solvent such as gasolene. These portions are then coated with a solution of thermoplastic resin. Any suitable solvent may be used, acetone, methyl alcohol and ethyl alcohol being examples. The thermoplastic resin solution is then allowed to dry at room temperature and then another coating of the solution is applied. These steps are repeated. until a layer of thermoplastic resin of the required thickness is obtained. That is to say, the solution is brushed on, dried, more of the solution is brushed, I

dried again, still more of the solution is brushed on, dried again, and these steps are repeated over and over until the layer has been built up to the required thickness. This required thickness is not less than one thirty-second of an inch and may be varied in accordance with the grit size of the abrasive in the annular portion 20, being greater the greater the grit size. There is, however, no upper limit to the thickness of the layer Zia excepting that that part of the annular portion 26 outside of the layer 2 Ed on either side should have a thickness at least as great as that of the layer 2 la within it.

For the vinyl resins in general acetone is good; for styrene benzene (CcHe) is preferred.

In order to form the annular portion 29 a suitable mold can be used. A layer of a mixture of uncured phenol-formaldehyde resin and abrasive can be placed in the mold, then the center Ill with the layer Zia can be placed thereon, then a further layer of resin and abrasive can be added and levelled oil, the top plate of the mold can then be placed in position, the contents of the mold can then be pressed in an hydraulic press thereafter the center H! with pressed layer Etc and pressed annular portion 25 can be stripped from the mold and cured in an oven. This technique of molding, pressing and curing grinding wheels including coping wheels is now well known in the art so it need not further be d scribed herein. Also various ways of compounding a mixture of uncured resin and abrasive are well known and need not be further described. However it is pointed out that, just prior to inserting the center It with the layer 2 la into the mold, the last brushing on of the solution of thermoplastic resin should be done without any subsequent drying step as this promotes adhesion of the layer 2m to the annular portion 29. The curing in an oven should be sufficient that is to 4 a high enough temperature and for a long enough time to convert the uncured phenol-formaldehyde resin to the thermo-irreversible stage, the temperatures and times necessary to do this being also well known. During this curing the remainder of any solvent in the thermoplastic resin is driven off and the layer 2 la becomes rigid and adheres firmly to the center It! but it is still slightly plastic when heated.

For the formation of the annular portion 26 with the layer 2 lb of thermoplastic resin thereunder on the center ill I may proceed as above with the following differences: a first coating of the solution of thermoplastic resin is applied and dried at room temperature. Abrasive grain, refractory grain or other inert (at the temperatures involved) granular material is coated with the thermoplastic resin and this can be done by mixing the granular material with a solution of such resin and subsequently drying to evaporate the solvent, and these steps may be repeated several times to build up a substantial layer of the resin on each granule, three repeats of the coating process being sufficient and even one such coating being adequate in many cases. The granular material can be ordinary sand such as quartz sand, or abrasive such as aluminum oxide abrasive or silicon carbide abrasive can be used. The grit size of this granular material can be varied but ordinarily should not be greater than the grit size of the abrasive in the annular portion 20; I have had good results using granular material of 60 mesh grit size for this purpose. If the granules of the granular material stick together screening or other procedure should be employed to separate the individual granules at least for the most part. The granular, refractory or abrasive material in the layer Zlb may be properly described genericaly as inert material. It functions as an inert filler.

Now the steel center is brushed a second time with the solution of resin and while the coating thus produced is still in a tacky condition the center is rolled in the coated granular material above described. Then, if the thickness of the coating is not yet sufficient, the coating is air dried. Application of solution, rolling and air drying is then continued or repeated until the desired thickness of coating has been attained, but as in the previous case the last applied portion of the coating is not permitted to air dry but rather the molding operation previously described is undertaken while the coating which now constitutes the layer 241) is still in a tacky condition. The rest of the procedure is or may be as above described. The thickness of the layer 2lb should also be not less than one thirty-second of an inch and may be varied in accordance with the grit size of the abrasive in the annular portion 20, being greater the greater the grit size, and there is likewise no upper limit to the thickness of the layer 21b gilrcepting as stated in connection with the layer The excellence of thermo-irreversible phenolformaldehyde resin as a bond for the manufacture of coping wheels is already known. That is to say coping wheels having the abrasive portion bonded with thermo-irreversible phenolformaldehyde resin give superior results when measured by proper standards to coping wheels the abrasive portion of which is bonded with any other organic bond now known. However the abrasive portion, when bonded with thermolrreversible phenol-formaldehyde resin, has frequently fractured especially when the coping wheels have been used in dry grinding. Dry grinding operations heat the abrasive portion and in so much as the steel center may be relatively cool, being a good conductor of heat, and furthermore since the coefficient of thermal-expansion of the abrasive portion and the steel center is different, breakages have been frequent. The present invention, however, solves this difficulty in that the plasticity of the layers Ma and Zlb is such as substantially to eliminate this cause of wheel breakage. Expansion of the annular portion 20 relative to the steel center I is accommodated by the layer 2 la or the layer 2Ib which, especially when heated, will deform, stretch or bend instead of breaking. Furthermore I have found that the adhesion of the layers 2 la and 2 I b to the steel center Ill and to the portion 20 is entirely satisfactory. Thus the invention rovides a coping wheel which is highly efficient in operation, can be used in dry grinding operations, and will not readily fracture.

I have illustrated and described two practical embodiments of the invention. I now prefer the embodiment shown in Figure 3 where the layer 2111 underlies the abrasive portion 20. This is for the reason that the layer Zlb is a little stronger than the layer 2la. However for many wheels the layer 2 la is adequate and it is a little simpler to make a wheel having the layer 2la than it is to make a wheel having the layer Zlb.

It will thus be seen that there has been provided by this invention a grinding wheel particularly of that variety known as a coping wheel in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiments above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A coping wheel comprising a steel center, an annular abrasive portion of abrasive grain bonded with thermo-irreversible phenol-formaldehyde resin on the periphery of said steel center, and a layer of vinyl resin between said abrasive portion and said steel center on both sides of said steel center, said layer being at least one thirtysecond of an inch thick and said annular abrasive portion outside of the layer of vinyl resin on both sides having a thickness at least as great as that of the layer of vinyl resin within it.

2. A coping wheel as claimed in claim 1 in which the layer of vinyl resin includes particles of inert material.

3. A coping wheel comprising a steel center, an annular abrasive portion of abrasive grain bonded with thermo-irreversible phenol-formaldehyde resin at least one thirty-second of an inch thick on the periphery of said steel center, and a layer of vinyl resin between said abrasive portion and said steel center on both sides of said steel center, said layer being at least one thirty-second of an inch thick and said annular abrasive portion outside of the layer of vinyl resin on both sides having a thickness at least as great as that of the layer of vinyl resin within it.

4. A coping wheel as claimed in claim 3 in which the layer of vinyl resin includes particles of inert material.

ERNEST DOUGLAS TEAGUE.

No references cited.

Claims (1)

1. A COPING WHEEL COMPRISING A STEEL CENTER, AND ANNULAR ABRASIVE PORTION OF ABRASIVE GRAIN BONDED WITH THERMO-IRREVERSIBLE PHENOL-FORMALDEHYDE RESIN ON THE PERIPHERY OF SAID STEEL CENTER, AND A LAYER OF VINYL RESIN BETWEEN SAID ABRASIVE PORTION AND SAID STEEL CENTER ON BOTH SIDES OF SAID STEEL CENTER, SAID LAYER BEING AT LEAST ONE THIRTYSECOND OF AN INCH THICK AND SAID ANNULAR ABRASIVE PORTION OUTSIDE OF THE LAYER OF VINYL RESIN ON BOTH SIDES HAVING A THICKNESS AT LEAST AS GREAT AS THAT OF THE LAYER OF VINYL RESIN WITHIN IT.

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