US2052194A - Abrasive wheel - Google Patents

Description

A. J SANDORFF ABRASIVE WHEEL Aug. 25, 1936.

Filed March 8, 1935 fil /"ad fwaifiiifiiie ATTORNEYS;

Patented Aug. 25, 1936 UNITED STATES Z,052,l9t

ABRASIVE WHEEL Alfred J. Sandorff, Niagara Falls, N. Y., assignor to General Abrasive Company, Inc., a corporation of New York Application March. 8, 1935, Serial No. 9,98?

6 Claims.

This invention relates to an abrasive wheel, more particularly of the type known as a vitrified wheel; and has for one of its objects the strengthening of the wheel so that it may be run at a greater speed than has heretofore been possible in the use of a vitrified abrasive wheel.

Another object of the invention is to increase the wear factor of the wheel.

Another object of the invention is to provide a vitrified grinding wheel which may be run at a surface speed equal to or greater than an organic bonded wheel.

Another object of the invention is the provision ofia wheel which will remove the metal faster and yet last longer than the usual vitrified wheel.

Another object of the invention is the formation of an abrasive wheel which may be used to remove metal faster and yet last as long or longer than a synthetic resin wheel.

Another object of the invention is the impregnation of the wheel with a non-flowing, cohesive substance which may be hardened to increase the strength of the wheel.

Another object of the invention is to provide a grinding wheel having the strength of an organic bonded wheel and the porous free cutting structure of a vitrified wheel.

With these and other objects in view, the invention consists of certain novel features of construction, as will be more fully described, and particularly'pointed out in the appended claims.

In the accompanying drawing:

Fig. 1 is an edge view of a grinding wheel illustrating in the solid black portions a cohesive substance as contained therein;

Fig. 2 is a sectional view illustrating somewhat diagrammatically the method of forcing the cohesive substance into the pores of the wheel;

Fig. 3 is a diagrammatic, microscopic view of the structure of the wheel prior to the insertion of the cohesive-material thereinto;

Fig. 4 is a similar view illustrating the cohesive Lmaterial as inserted into the pores of the wheel to strengthen the same.

Abrasive wheels can be generally divided into two classes, to wit: vitrified and organic. The vitrified grinding wheels are used at maximum speeds of six thousand five hundred surface feet per minute. These wheels are unsafe to operate at a greater speed, as their strength is such that at higher speeds they are liable to fly apart.

Because of the greater strength of the bonds for the organic abrasive wheels, such as synthetic resins and the like, they can be used at a speed of nine thousand flve hundred surface feet per minute; and because of this greater speed, the organic wheel can do more work in a given time than the vitrified wheel. The dense structure, however, of the organic wheel is in sharp contrast to the open porous structure of the vitrified wheel, 5 and the vitrified wheel will out much freer than the organic wheel. Further, because of the cost of raw materials, the vitrified wheel is less expensive to manufacture than the organic wheel. In order to obtain the free cutting action of the vitrified wheel and at the same time a surface speed equal to that of the organic wheel, I have strengthened the vitrified wheel by impregnating the same with a substantial amount of an organic substance such as rubber and vulcanizing the rubber so that after treatment it is fully as strong as or stronger than the organic wheel and may be run at a speed as great as or greater than that of the organic wheel; and as the pores of the-finished wheel are not completely filled, the free cutting action thereof is maintained and even with this treatment it is cheaper to manufacture than the organic wheel; and the following is a more detailed description of the present embodiment of this invention, illustrating the preferred means by which these advantageous results may be accomplished:

With reference to the drawing, I have illustrated in Figure 2 a receptacle l0 suitably supported on a base It and provided on its bottom wall with a soft rubber cushion l2 which supports a vitrified grinding wheel i3 having the usual porous structure indicated in Figure 3, comprising granules l5 which are held together by means of a vitrified bonding material i5 with pores or spaces l4 between the bond.

There is then placed in the receptacle an organic cohesive substance 24 which will not flow under ordinary normal atmospheric condition of temperature but will flow under abnormal conditions of either temperature or pressure. One illustration of this cohesive substance consists of a milled mixture of 60% rubber an 40% sulphur softened with an equal par of carbon tetrachloride or sufficient other solvent so that it will not new except under pressure. v

I then force this softened rubber sulphur mixture into the pores of the grinding wheel by means of a piston l6 having a leather washer ll on the under surface thereof which is secured in place by a stiff plate I8 and fastening screw I9 with nut 20 thereon. This piston is forced downwardly by a plunger 2| under a pressure of substantially one ton per square inch. This action causes the softened compound of rubber-sulphur and solvent to be forced into the pores oi the wheel, and in fact, completely through a wheel of usual thickness and out the opposite side. Upon the release of pressure and the removal of the wheel from the compartment, the substance 24 being sufficiently' viscous not to fiow under normal or atmospheric conditions, will remain in the wheel as there forced. It will of course be readily understood that some other abnormal atmospheric condition may be caused to exist, such for instance, as an increased temperature for the cohesive substance which will cause it to become sufiiciently fiuent to enter the pores of the wheel, and then when the wheel is restored to atmospheric conditions, the substance which has entered the pores will stay there. The

- essential characteristic is that the substance will be so constituted as to be capable of entering the pores and after it enters the pores the conditions or constituents of the substance will be so changed as to keep it there.

I then permit the solvent or carbon tetrachloride in the wheel to evaporate or drive the same ofi slowly at substantially 125,-150 F.

- and one in which the breaking strength is sufiiciently high so that it may be rotated at the increased speed necessary to cause it to cut as fast or faster than the organic bonded wheels which are more expensive.

' The proportions which I have cited above do not cause the solid portion-s to fill the pores of the final finished wheel completely and probably decrease its porosity not more than to and I have found that with as little as 7% by weight of rubber impregnation of the wheel the breaking strength is increased 100% which is suflicient for the purposes desired and still leaves the pores sufliciently open so asto permit a free cutting action thereof.

It will be further understood that when the rubber is impressed into the pores that certain air pockets may be formed in the individual pores which confine or trap the air within under pressure, and when the applied pressure is released the air in these pockets will expand, to some extent, thereby restoring to the wheel the open structure which it had before treatment,

. and which trapping of air is thus of advantage.

Further, by this method, even though the pores were completely filled during the manufacture of the wheel, upon evaporation where the solvent is in equal parts with the rubber sulphur mixture, there will be only a 50% filling of the pores because of the evaporation of this 50% of sol-' vent before vulcanization. Of course, if it is desired that a smaler amount of rubber be impregnated in the wheel, the carbon tetrachloride may be increased in proportion so as to provide a less solid filler, care being taken to prevent a condition so fluidas to run out when pressure is released. It will be readily apparent that various proportions of rubberand sulphur may be used to form the filling composition, however, I have aosaiea obtained satisfactory results with the 70% rubber and sulphur, and this range may be varied widely, if desired.

The pressure used for impregnation may be varied and the impregnation may be from one or both sides of the wheel or from the periphery, this depending to a large extent upon the coarseness of the grains of abrasive used and the method of moulding and fusing the composition.

The foregoing description is directed towards the method and construction illustrated, but I desire it to be understood that I reserve the privilege of resorting to all the equivalent changes to which the construction and method are susceptible, the invention being defined and limited only by the terms of the appended claims.

I claim:

l. The method of making a filled abrasive wheel which comprises the steps of initially forming a porous vitrified ceramic bonded abrasive wheel, providing a settable cohesive substance containing a solvent in an amount sufficient to render the mixture viscous yet be incapable of flowing under normal atmospheric conditions, said solvent further being in an amount proportioned to provide a definite percentage of open pores in the final product after removal there-.

from, impregnating the pores of the wheel by changing said conditions to cause said filling substance to be incorporated into the entire open pore structure of thewheel body and to completely' fill the same, removing from said filled- 2. The method of making a filled abrasive wheel which comprises the steps of initially forming a porous vitrified ceramic bonded abrasive wheel, impregnating the pores of the wheel by forcibly incorporating therein a vulcanizable mixture containing rubber, sulphur and a rubber solvent, said 'mixture being of a consistency which is incapable of readily flowing under normal atmospheric", conditions but becomes sufiiciently fluid under the pressure conditions during the filling operation to enter into the entire open pore structure of the body to completely fill the same, evaporating all of the solvent to deposit the rubber in. the pores and be permanently retained'therein .after vulcanization yet leave them open and of a predetermined volume percentage which is directly proportional to the quantity of said solvent used, and thereafter vulcanizing the rubber in said body.

3. The method of making a filled abrasive 4 wheel which consistsin forming a porous vitrified ceramic bonded abrasive wheel, impregnating the pores of the wheel by forcibly incorporating a vulcanizable cohesive substance comprising a mixture of rubber and sulphur and a equal quantity of carbon tetrachloride solvent into the entire open pore structure of the body under pressure, said solvent being in an amount proportioned to provide a predetermined percentage of open poresin the final product after evaporation therefrom, evaporating all of the solvent in the absorbed filling substance to leave the pores open and deposit said rubber which will be permanently retained therein after vulcanization, and thereafter vulcanizing the rubber in the wheel.

4. The method of making a filled abrasive wheel having an open pore structure of predetermined porosity in the final article comprising the steps of initially providing a pre-fabricated rigid porous abrasive wheel of abrasive grains integrally united together by a vitrified bond, pre-' paring a vulcanizable rubber bonding compositionhaving a plastic co-hesive consistency which is incapable 'of flowing at normal atmospheric conditions but which becomes fiowable upon being subjected to pressure conditions above normal, said composition being formed by mixing unvulcanized rubber and sulphur and incorporating therewith a rubber solvent agent of a vaporizable charrcter, in which total ingredients the solvent present is pre-calculated to equal in volume the .total volume percentage of open pores desired as the residual porosity in the final article, said solvent being incorporated in the rubber-sulphur mixture in an amount sufilcient to soften the mixture but notsufilcient to cause it to fiow at normal atmospheric conditions, surrounding and covering the wheel with the prepared softened rubber composition, subjecting the softened rubber bonding composition to pressure above atmospheric pressure to cause fiowing of the rubber composition and to force it into thewheel pores, while maintaining said pressure conditions until the rubber bond completely penetrates and fills the entire open pore structure of the wheel throughout its entire thickness, re-' leasing said pressure to restore the operating conditions to those of a normal atmosphere to cause the absorbed rubber bond in the filled pores to return to a viscous non-flowing condition, removing all of the solvent by evaporation from the rubber bond in the filled pores to remove it who]- ly from the absorbed rubber bonding material.

to concentrate and deposit allof the solids there'- -of in said pores, in which a partial filling of the latter is effected and a resultant pore structure is produced of predetermined volume percentage.

5. The method of making a filled abrasive wheel having an open pore structure of predetermined porosity in the final article comprising the steps .of initially providing a pre-fabricated rigid porous abrasive wheel of abrasive grains integrally united together by a vitrified bond, preticle, said solvent being incorporated in the rub-' ber-sulphur mixture in an amount sufficient to soften the mixture but not s.ifiicient to cause it to fiow at normal atmospheric conditions, surrounding and covering the wheel with the prepared softened rubber composition, subjecting the softened rubber bonding composition to pressure above atmospheric pressure to cause fiowing of the rubber composition and to force it into the wheel pores, while maintaining said pressure conditions until the rubber bond com-. 3

pletely penetrates and fills the entire open pore structure of the wheel throughout its entire thickness, releasing said pressure to restore the operating conditions to those of a normal atmosphere to cause the absorbed rubber: bond in the filled pores to return to a viscous non-fiowing condition, removing all of the solvent by evaporation from the rubber bond in the filled pores to removeit wholly from the absorbed rubber bonding material to concentrate and deposit all of the solids thereof in said pores, in which a partial filling of the latter is effected and a resultant pore structure is produced of predeter mined volume percentage, and thereafter vulcanizing the rubber bond.

6. The .method of making a filled abrasive wheel having anopen pore structure of predetermined porosity in the final article comprising the steps of initially providing a pre-fabricated rigid porous abrasive wheel of abrasive grains integrally united together by .a vitrified bond, preparing a vulcanizable rubber bonding composition having a plastic co-hesive consistency which is incapable of flowing at normal atmospheric conditions but which becomes fiowable .upon being subjected to pressure conditions above normal, said composition being formed by mixing unvulcanized rubber and sulphur and incorporating therewith a rubber solvent agent of a vaporizable character, in which total ingredients the solvent present is pre-calculated to equal in volume the total volume percentage of open pores desired as the residual porosity in the final article, said solvent being incorporated in the rubber-sulphur mixture in an amount suificient to soften the mixture but not sufilcient to cause it to flow at normal atmospheric conditions, supporting the, wheel within a receptacle upon a support therein in a fiat position upon an end face but with the other end face and the peripheral face of said wheel being out of contact with the receptacle parts, surrounding and covering the wheel thus arranged with the prepared softened rubber composition, subjecting the softened rubber bonding composition to pressure above atmospheric pressure to cause flowing of the rubber composition and to force it into the wheel pores, while maintaining said pressure conditions until the rubber bond completely penetrates and fills the entire open pore structure of the wheel throughout its entire thickness, releasing said pressure to restore the operating conditions to those of 9. normal atmosphere to .cause the absorbed rubber bond in the filled pores to. return to a viscous non-fiowingco'ndition, removing all of the solvent by evaporation from the rubber bond inthe filled pores to remove it wholly from the absorbed rubber bonding material to concentrate and deposit all of the solids thereof in said pores, in which a partial filling of the latter is eflected and a resultant pore structure isproduced of predetermined volume percentage, and thereafter vulcanizing the rubber bond.

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