US1826300A - Abrasive wheel - Google Patents

Description

Oct. 6, 1931.

3 Sheets-Sheet 1 R. CHAPELL ABRASIVE WHEEL Filed Aug. 10. 1929 ."HM/M WITNESS Oct. 6, 1931. R CHAPELL 1,826,300

ABRAS IVE WHEEL Filed Aug. 10. 1929 5 Sheets-Sheet 2 fizz/' 6 I WW. 7' v INVENTO Patented .Oct. 6, 19 31 UNITED STATES PATENT OFFICE REVERE CHAPELL, 0F CINCINNATI, OHIO ABRASIVE WHEEL Application filed August 10, 1929. Serial No. 384,988.

operated is very high.

Heretofore, so far as I am aware, grinding wheels have been made substantially homo-- geneous throughout. For high speed abrasive wheels suflicient binding material is uniformly incorporated throughout the mix to enable the finished wheel to withstand, when new, the centrifugal force developed therein at the maximum high speed for which the wheel is designed to be used'; and the force of the blow or impact of the particles of abrasive material against the metal being ground, and to firmly hold said particles of abrasive to the wheel during their impact against the metal being abraded.

But in the practical use of abrasive wheels, the angular speed at which the wheel is rptated is determined by the surface speed at which the wheel is designed to be run when new, and the angular speed having been thus once determined, the wheel is thereafter rotated at that fixed angular speed until it is worn out, that is to say, until the diameter has been reduced to a point where it is unsafe to use the remaining ring of abrasive material surrounding the spindle, or to a point or zone whereat the wheel no longer grindsefiiciently.

The point at which a. worn abrasive wheel 4 no longer cutswith efliciency, and consequently heats, increasing the liability of the rupture of the wheel, is that diameter where there is an excess of binding material for the surface speed at which the wheel is then being actually used. No binder commonly used is an abrasive. On the contrary, it is a friction producing material as it slides over the surface being abraded. The friction of this excessive binding material, rubbing over the metal being abraded, generates a large amount of heat which weakens the wheel and increases the liability of rupture.

It is an object of my invention to obviate the difliculties above recited, by properly progressively increasing the strength of the bond or binding material in an abrasive wheel from the axis outwardly radially so that there is always at the active surface of the wheel, irrespective of the diameter to which it may have been worn, a suflicient amount of and strength in the bonding material to make the wheel of that diameter safe to use at the angular speed at which the wheel is being driven, but in which there shall be no substantial excess of said bonding material at any diameter to which the wheel may be worn.

A further object of my invention is to provide the peripheral portion of a grinding wheel, designed to be driven at a definite high surface speed, with a suflicient quantity of binding material for a wheel of that diameter and to progressively decrease or diminish the quantity of binding material in the wheel from the periphery inwardly radially so that for a fixed angular velocity, the amount of binder will be proper for any diameter to which the wheel may be worn away and reduced. 4

A further object of my invention is to provide an abrasive-wheel, preferably the high speed type, the cuttin or abrasive properties of which are substantially constant when the wheel is rotated at a fixed angular velocity, irrespective of the diameter to which the wheel may be reduced.

A further object of my invention is to provide a high speed abrasive wheel, the heat of which will not be substantially increased as the diameter is reduced, due to the wearing away of the wheel in actual use.

A further object of my invention is to provide a vitrified high speed abrasive wheel which will be strong enough to withstand the impacts to which the particles of abrasive, at the periphery thereof, are subjected, and in which the amount of bonding material is greatest at the periphery of the nished wheel and is progressively less and less radially inwardly, but sufiicient to firmly bind the particles at the periphery of the wheel irrespective of the extent to which the diameter may have been reduced in using the wheel.

A further object of my invention is to increase the quantity of vitrifiable material in a mix for a vitrescible wheel, progressively outwardlyand substantially radially, so that the I guantity of vitrified bonding material in the nished wheel is suflicient but not substantially in excess of that required to impart the necessary strength to an abrasive wheel of whatever diameter the finished wheel may be reduced in use.

Further objects of my invention will appear in the specification and claims below.

In the drawings forming. a part of this specification and in which the same reference characters are employed throughout the various views to designate the same parts,

Figs. 1 and 2 are representations, on a greatly exaggerated scale, of a cross-section through a few contiguous pieces of abrasive material packed together as they are in an abrasive wheel and with the bonding material substantially coating the pieces and lining the interstices between adjacent pieces of abrasive. In Fig. 1 is shown such a fragment of an abrasive wheel with a relatively light coating of binding material on the particles of abrasive and in Fig. 2 are shown the same pieces provided with a thicker coating.

. These figures are to illustrate the manner in which an increased quantity of bonding material augments or increases the bond between the contiguous pieces of abrasive. These figures are for illustrative purposes only and are to a great extent diagrammatic.

Fig. 3 is a fragmentary diagrammatic view of a circular mold within which is plastic material out of which abrasive wheels may be made, the mold and plastic material being shown in section and as mounted on the upper end of a vertical shaft adapted for rotation. This illustrates one manner of making my improved abrasive wheel.

ig. 4 is a diagrammatic sectional View through a finished abrasive wheel after the plastic material has been dried in the apparatus shown in Fig. 3; has had an axial hole cut therein; and has been fired, vulcanized, pressed or otherwise made rigid.

Figs. 5 and 6 are diagrammatic sectional views showing a modified manner or method of making an abrasive wheel embodying my invention and a different mode of incorporating a progressively increasing bond from the center of the wheel outwardly to the periphery.

Figs. 7 to 11 are diagrammatic views illustrative of a further modified method of making an abrasive wheel and in which concentric annuli of plastic material for making abrasive wheels are formed, each ring containing a little stronger or firmer bond between the abrasive particles than the next adjacent ring enclosed by it whereby a progressively increasing strength of bond is secured radially outwardly from the axis of the finished wheel.

Figs. 1 and 2 represent a small section of an abrasive wheel on a greatly enlarged scale,

with a few abutting or contiguous graded pieces a of carborundum or other abrasive material, packed together as in a finished abrasive wheel.

Referring to the four pieces of abrasive a a a a each piece is provided with a coating 6 of bonding material, such as vitrified clay, fused porcelain, bakelite, waterglass, rosin, or an other suitable binder. Between a and a of Fig. 1, the length a: of the bond is clearly indicated, as is also the bonds w between the pieces a and a a and a; and between a and (L The same pieces a a a and a are shown in Fig. 2, with a thicker coating 5 and the extent of the bond is increased from as to an.

These two figures illustrate very strikingly how a slight increase in the quantity of binding material substantially increases the strength of the bond between two contiguous particles of abrasive.

Thus by making a proper and varying distribution of the bonding material throughout the extent of an abrasive wheel by increasing the amount of bonding material between contiguous pieces progressively outwardly radially from the center of the Wheel, the part1- cles of abrasive at the periphery of the abra sive wheel may be bonded together more firmly and more rigidly to withstand the strains of centrifugal force and the impact of the grains or particles of abrasive against a piece of metal when the wheel is rotated at the speed at which it is designed, and the part1- cles of abrasive between those at the periphery and the inside diameter are bound together by a bonding material, the amount and strength of which is slowly pro ressively decreased inwardly radially. Such is the abrasive wheel which constitutes my invention.

One way of forming an abrasive wheel embodying my invention is illustrated diagrammatically in Fig. 3 wherein a circular mold 1 is adapted to be firmly seated on a turntable 2 mounted on the upper end of a spindle 3 in journals or bearings 4:, 4, in a suitable standard or frame 5, a part of which only is illustrated, it being understood that the frame or standard 5 may be mounted rigidly, so that the pulley 6 on the shaft or spindle 3 may be driven from a suitable motor to efiect the rotation of the turntable 2 and mold 1 mounted thereon. The mold l is filled with a suitable plastic material C, such as carborundum, mixed with an aqueous or colloidal dispersion of clay or other suitable vitrescible material.

After the mold has been filled to a sufiicient pulverized clay in aqueous suspension or dispersion, to flow through the water in which they are suspended and through the interstices between the adjacent particles a of carborundum outwardly radlally toward the outer wall of the mold 1. The amount of clay or other powdered material which may thus be thrown outwardly through the supporting liquid toward the outer circular edge of the plastic mass will depend upon the speed and length of time that the mold is so revolved.

As a result of this treatment, the quantity of binding material, such as vitrescible clay, in suspension in the water throughout the plastic mass C, will increase gradually and progressively from the center of the mold outwardly to the periphery. Thereafter the mold 1 is removed from the turntable and is placed in a drying room where the water is evaporated therefrom, leaving a greatest amount of vitrescible material at the periphery of the dried wheel and a progressively less amount towards the center.

After it has been dried, the abrasive Wheel will be substantially a mass of abrasive, lightly bound together by said vitrescible binding material, but the wheel will be relatively soft, somewhat of the consistency of dried mud. By merely rotating it, a suitable central hole 8 may be cut therethrough. Thereafter the mud wheel so formed is placed in a suitable kiln and fired, whereupon the vitrified clay or other bonding material will constitute the bond between the adjacent pieces a of abrasive material in the finished wheel 9 and the bond between the pieces of abrasive material will be greater at the periphery of the wheel than at any other part of the wheel, and from the periphery inwardly radially, gradually decreasing. 1

In Figs. 5 and 6 is shown another method of making an abrasive wheel embodying my invention. In this case the plastic material C is placed in the circular mold 1 thicker or deeper at the periphery of the mold than at the center. Upon the invertedconical surface of the plastic mass of abrasive and binder material C are placed a circular series of boards or plates 10 each in the form of a sector of a circle of a diameter of the inside of the mold 1, the sectors, when they lie in a horizontal plane forming a disk of the size of the interior of the mold.

Substantially vertical pressure is then applied to the upper surface of the sector pieces 10 to compress more of the material into the periphery of the plastic mix C than at the center. This maybe applied by subjecting the segments over the mass C in the mold 1 to the action of a plunger 11. Thereafter the mold with the plastic mass in it is transferred to the drying chamber and the mass dried as previously described after which it may be hardened by vitrifyin the binder or otherwise solidifying it, i the binder be other than a vitres'cible binder. In this manner more bonding material is progressively incorporated into the wheel from the center outwardly radially and a wheel 9 embodying my invention may thus be formed.

In Figs. 7 to 11 is indicated, in a somewhat diagrammatic manner, a third method of makmg an abrasive wheel 9 embodying my invention, the scale being larger in Figs. 8

hereafter referred to, is preferably a little greater than the depth of the mold 1, as ind cated 1n Fig. 8. Then the space between the ring 12 and the inner wall of the mold 1 is filled with a plastic mixture C of abrasive and blnder or bond in which the proportion of binder or bond to the abrasive is what is suitable to use in a wheel of that diameter and adapted to be rotated at a predetermined glven speed. Since the proportion of the bonding material to the amount of abrasive material'will vary with almost every wheel that is made, depending upon the diameter of the wheel and the speed at which it-is to be rotated, I do notintend to limit myself to any definite proportions, because those proportions are well known to the mechanic skilled in the art of making wheels of this character. The composition of the outer ring or material will be well understood by those skilled in the art, when it is stated that the proportion of the bonding material to the abrasive is that which has been found by pract1ce necessary in the making of wheels of that diameter designed to be rotated at the given high speed of rotation.

The plastic material C having thus been placed in the outer section of the mold, a second ring 14 of smaller diameter is placed within it and gages 15 provided with two notches 15 on its under edge are placed thereon, the upper edges of the rings 12 and 14 fitting in the notches 15 respectively of the gage 15. Then within this second annular channel so formed in the mold between the ring 12 and the ring 14 is deposited a plastic mixture C containing a little less of the bonding material or a bonding material not quite so strong as that in mass 0 and this channel is thus filled with lastic material C as illustrated in Fig. 9. T en a third ring 16 still smaller in diameter is similarly placed within the mold 1 and a set of gages 15 with similar notches 15 fitted over the top edges thereof. These gage strips 15 are preferably used in sets of three for each pair of rings, spaced at 60. from each other for the pair of rings to hold the rings in a fixed concentric arrangement While the mold is being filled. Then plastic material C having a little less bonding material than the plastic material C is placed in the channel between the rings 14: and 16 until this channel is filled with this plastic material G. Then a still smaller ring 17 may be placed within the ring 16 and held in place by a set of gage strips 15, as shown in Fig. 11 and the space therebetween filled with a plastic abrasive material mix C which contains a little less of a bonding material than that at present in the mix C. When the space between the rings 16 and 17 is filled, then the gages 18 and 15 are removed and the ring 12 lifted out from between the two mixes C and C This process may be repeated with smaller and smaller rings 18 and 19 and the spacebetween each pair of adjacent rings will be filled with a material having a less amount of bonding material therein than that immediately surrounding it. In this manner an exact distribution of the bonding material or the strength of the bonding material throughout the wheel radially, stronger at the periphery and gradually less strong progressively inwardly may be attained. After the mold has thus been filled and the rings removed, it is dried in the usual manner and then fired or otherwise made into a solid form.

While an abrasive wheel embodying my invention might be made using plain cylindrical rings instead of the corrugated rings 12, 14, 17, etc., I prefer the corrugated type of ring, because when the ring is removed from between the two adjacent annuli of slightly different mixtures the projections on the surfaces of one annulus of plastic material project into corresponding recesses in the adjacent annuli of plastic material and there is a more intimate union of the two annuli due to coinmingling and flowing of the fluid content of one ring into that of the other, and so that there will be no sharp clean cylindrical line of cleavage or sudden change in material in the finished wheel and so that there will be a stronger and better bond between adjacent annular sections of the finished wheel.

While this invention is particularly applicable to the making of abrasive wheels wherein the bonding material is vitrescible, it is to be understood that the processes are applicable to the construction of wheels in which other binders are used. A bakelite binder or a rubber binder are usually colloidal in nature when mixed with the abrasive in making the mud cake or plastic mass and such binding readily lends itself to the centrifugal processdescribed in connection with Figs. 3 and 4, as well as to the process of packing more mixture into the mold and compressing it as indicated in Figs. 5 and 6.

The nature of the plastic mixture or mass employed in making abrasive wheels is such that it readily lends itself to any of the modes of procedure heretofore described. The particles of carborundum or other abrasive are hard and rough, no matter how small the particles may be and when compacted together with portions of their surfaces in engagement and with the coating or bonding material squeezed out from between them in the plastic mass in the mold, those particles do not slide over each other when the plastic wheel is sub jected to a rotary movement, but they remain immovable with small voids or unfilled spaces between non-contacting parts of adjacent particles of abrasive through which a fluid binding material, particularly when of a colloidal nature, freely flow and in which the matter suspended in the supporting liquid are readily thrown outwardly by centrifugal force, through the suspending medium and through the pores or passages between the particles of abrasive toward the outer wall 01 the mold.

A wheel having a non-fluid bonding material may also readily be made by the practice of the process illustrated in Figs, 5 and 6, for from the very nature of the mixture it is easy to provide the plastic mass in the mold with an increasing quantity of the abrasive and bonding material and to compress the mass more at the periphery than at the center and progressively less between the periphery and the center as described in connection with Figs. 5 and 6.

And various bonding materials, other than those of a vitrescible nature may be used in connection with the process illustrated in Figs. 7 to 11, for it is easy to mix a graduated series of batches of the abrasive material and binder and to fill the sections of an annular sectional mold with the different grades of the mixture.

The process above described in connection with Figs. 7 to 11 may be slightly modified by varying the quality of the bonding material as the quantity of bonding material is diminished in the successive annuli of plastic mixtures of abrasive material and bond. A stronger bonding material less in quantity may be used, so that while there may be a diminution in quantity of binding material, the strength of the lesser quantity of binding material may be made equal to substantially that of the ring next adjacent and outside of it. In other words, I do not wish to be limited to a wheel in which the bonding material is of the. same quality throughout the wheel and the-quantity of it varied, for my invention contemplates the use of progressively smaller quantities of binding material inwardly radially of the Wheel without a correspondingly diminution in the strength of the bond.

From the above it will be seen that I have provided a new and highly desirable'type of abrasive wheel which can in use he reduced or worn away to a very much smaller diameter than that of the original wheel, without impairing the abrasive properties or substantially weakening the wheel when reduced in diameter and which is not subject to the heating when worn due to an excess of bond between the abrasive particles, and I have described several methods of making such a wheel, but my invention is not to be construed as limited to any or all of the processes herein described, provided such a wheel having the physical characteristics of my wheel be made by the process described or other process which may be later devised.

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

1. A high speed abrasive wheel composed of particles of abrasive material unitarily and rigidly united together by a bonding material, the proportion of bonding material to the abrasive being progressively greater radially outwardly from the inner diameter of the wheel to the periphery thereof.-

2. A high speed abrasive wheel composed of particles of abrasive material unitarily and rigidly united together by a vitrified bonding material, the proportion of bonding material to the abrasive being progressively greater radially from the inner diameter of said wheel to the periphery thereof.

3. An abrasive wheel composed of particles of abrasive material rigidly united together by a bonding material, the proportion of bonding material to the abrasive being variable and progressively greater from the inner diameter to the outer diameter thereof, and sufiicient at the periphery to safely bind the particles for the highest. angular speed for which the wheel is designed to be rotated.

4. An abrasive wheel composed of particles of abrasive material unitarily and rigidly united together by a bonding material, the quantity of bonding material between adjacent particles of abrasive in a selected point in any diameter of the wheel being less than at any point between said selected point and the periphery of the wheel and more than at any point between said selected point, and

' the inner diameter of the wheel and sufficient to safelybind the particles together when the active surfaces of said wheel are worn down to said selected point and is rotated at the angular speed for which the original unworn wheel was designed to be rotated.

In witness whereof, I have hereunto set my hand this eighth day of August,-1929.

REVERE GHAPELL,

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