US 2327846 A
Description (OCR text may contain errors)
Patented Aug. 24, 1943 zone GRINDING WHEEL Samuel S. Kistler, West Boylston, Mass, assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts No Drawing. Original application August 19,
1939, Serial No. 291,008. Divided and this application January 16, 1941, Serial No. 374,706
6 Claims.- (Cl. 51-295) The invention relates to abrasive articles. This application is a division from copending application Serial No. 291,008 filed August 19, 1939, now Patent No. 2,243,049, dated May 20, 1941, which was stated to be a continuation in part of copending application Serial No. 217,020 filed July 1, 1938.
One object of theinventio'n'is to increase the cutting efiiciency of a grinding-wheel. Another object of the invention is to provide a filler in of organic bond, for example, rubber and the' a grinding wheel which has a chemical action on metal work pieces. Another object of the invention is to provide at the cutting zone in a grinding operation an acid, without covering the work piece generally with acid. Another object of the invention is to provide a wheel containing an acid filler without detrimentally afiecting the wheel. Another object of the invention is' to provide a filler which shall prevent the wheel from loading.
Another object of the invention is to set up in a grinding wheel a chemical reaction between metal chips removed from a work piece and lodged in the portion thereof which shall loosen such chips, thus eliminating loading. Another object of the invention is to provide a filler for a grinding wheel which reacts on the hot metal chips removed from a work piece in the grinding action so as to prevent such chips from sticking to the wheel, thus preventing loading in the first place. Other objects will be in part obvious or in part pointed out hereinafter.
The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts,.and in the several steps and relation andorder of each of said steps to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.
I have discovered that the efficiency and cutting ability of a grinding wheel may be materially improved by'incorporating in the wheel a finely divided, strongly acidic inorganic compound, or one which decomposes under heat toa strongly acid substance, which should be in the solid as distinguished from the liquid state. For
such strongly acidic substance I may select one or more of the group consisting of polyvinyl chloride 'and' polyvinylidene dichloride, rubber hydrochloride, and other chlorinated saturated aliphatic straight chain polymers which decompose with the liberation of hydrogen chloride.
Grinding wheels and also other abrasive bodies according to this invention may be made from the polyvinyl chloride.
- heated at-about 60 C. for two days, thus causing any of the usual abrasives, for example, silicon carbide or other hard carbides, alumina in any of its forms including electric 'iurnace fused alumina, corundum and emery, alsodiamonds, and these may-be bonded with any desired type various resins, both natural and synthetic, in-
cluding shellac and phenol formaldehyde resin; and the alkyds (polymers of polybasic acids and polyhydric alcohols), the vinyl type of resins (such as polystyrene, polyvinyl acetate and polymethyl vinyl ketone), and others such as polymethyl methacrylate and other methacrylates.
The foregoing bonds are all of them acid insoluble.
tions, but ordinarily we prefer that this fillercomprise from one to ten per cent by volume of the total wheel structure. According to the invention one may make a wheel of this composition by mixing the abrasive grains with the dry polyvinyl chloride powder and the liquid mixture'of the monomeric methyl methacrylate and methacrylic acid may be poured into a mold containing the mixture of abrasive grains and The liquid monomers may contain 0.02% of benzoyl peroxide as a catalyst. The mold containing the abrasive grains wet with the liquid monomers may then be the bonding substance to be copolymerized in the presence of the abrasive grains in intimate association with the polyvinyl. chloride. According to the invention one may proportion the materials in order to provide an abrasive volume of 43.9%, a bond volume of 46.6%, and a pore volume of 9.5%. The 46.6% of bond of the total wheel volume in this particular wheel may be made up of 43.4% of the copolymerized resin and 3.2% of polyvinyl chloride. According to the invention one may use any of the resins mentioned above with this acid substance or with the other acidic agents,
According to the invention one may also make a grinding wheel with shellac bond, but in which the shellac in its dry powdered form is intermixed with the solid acidic substance used the modifying agent. mixture with the dry abrasive grains, then place the mixture in-a mold and heat it to set the shellac and bond the grains. One may proceed similarly with the other types of resin bonds. and may incorporate the acidic substance either in the bond or intermix it with the abrasive grains as desired[ According to the invention one may substitute any of the acid substances above specified for the polyvinyl chloride in the example given, and may employ any of the com- .patible resins as bonds in intermixture with these acidic solids. One may incorporate the vinyl resins in the abrasive article by pouring the liquid monomers over the mixture of abrasive grains and dry acidic agent, as above described.
If desired, the low fusing resins may be first made as a molding powder and then intermixed in its polymerized condition with the grains and acidic substance and then the article may be pressed at a high temperature to cause plastic flow of the resin into intimate association with the solid substances. Many other types of resins may be used in carrying out the invention, such as polymerized vinyl acetate or chloride, styrene,
methacrylic acid, methyl methacrylate, or com- 3' binations of such substances. All these resins are acid insoluble substances.
Having thus given concrete embodiments of the invention, the same should not be limited by the theories which are to be given as to the :1v
reasons for improved efficiency of grinding wheels made in accordance therewith. Every grinding wheel tosome degree has a tendency to load, that is, to accumulate particles of the material which is being ground. Loading is widely variable, depending on the abrasive and the bond and the hardness of the structure of the wheel and the amount of pore space in the wheel and the grit size of the abrasive in the wheel and the material being ground and the peripheral velocity of the wheel and of the work piece and the area of contact and pressure between the wheel and work piece. All these factors are, of course, widely variable so loading may be very much more of a problem in certain instances than in others. Loading may involve an actual deposit of material from the work piece into the pores of the grinding wheel or a sticking of the mate- One may mix this bond rial of the work piece to the abrasive grains or to the bond or combinations of these. Most grinding operations involve the generation of heat at the point of contact if the grinding is being performed efiiciently. Tearing away of chips from the work piece, especially in grinding metal, creates a shower of sparks, each spark representing a red or White hot fragment of metal or other substance. These sparks are over 500 C. in temperature. It is believed that the tendency of red or white hot metal, especially in finely divided particles, to weld itself to any adjacent surfaces is a primary factor in the loading phenomena. It is believed that the presence, at the point of contact between the metal or other substance being ground and the abrasive and bond, of a strongly acidic compound inhibits to a large degree the sticking of the red or white hot particles to the substance of the grinding wheel, Probably this action occurs more strongly in the case of grinding metals than in the case of grinding other substances,
but at all events the great majority of grinding operations are performed on metal wo-k pieces.
It is believed that the reaction of the strongly acidic solid substance is far greater with respect to hot particles than with respect to cold particles. Also, the heat serves to liberate the acid HCl from' polyvinyl chloride, polyvinylidine dichloride and rubber hydrochloride. Thus the chief effect of the incorporation of a strongly acidic substance into the wheel is to prevent loading in the first place although it is believed there is some action in loosening any metal'chips which may have become lodged in the pores of the wheel.
Polyvinyl chloride, polyvinylidine dichloride and rubber hydrochloride are related compounds and upon decomposition they all liberate hydrogen chloride which is a strong acid. They can, of course, be decomposed by heating and the temperature of grinding at the grinding line is sufficient to decompose them. Polyvinyl chloride may be written thus:
II CIHCl Rubber hydrochloride It will thus be seen that there has been provided by this invention an article and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments might be made of the mechanical features of the above invention and as the art herein described might be varied '31 .various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative and not in a limiting sense.
1. As a new article of manufacture, a. grinding wheel comprising abrasive grains, acid insoluble organic bondholding the abrasive grains to gether, and a filler of polyvinyl chloride.
2. As a new article of manufacture, a grinding wheel comprising abrasive grains, acid insoluble organic bond holding the abrasive grains together, and a filler of rubber hydrochloride.
3. As a new article of manufacture, a grinding wheel comprising abrasive grains, acid insoluble organic bond holding the abrasive grains together, and a filler that is substantially nonvolatile and stable at ordinary temperatures comprising a chlorinated saturated aliphatic straight chain polymer capable of releasing hydrogen chloride under the heat effect at the grinding line.
4. As a new article of manufacture, a grinding wheel comprising abrasive grains, acid insoluble organic bond holding the abrasive grains together, and a filler of polyvinylidene dichloride.
5. As anew article of manufacture, a grinding wheel comprising abrasive grains bonded together by an acid insoluble organic bond having incorporated therein and distributed therethrough individual small entities of a chlorinated saturated aliphatic straight chain polymer, saidentities becoming exposed at the grinding linein course of abrading action of the wheel and said polymer being capable of releasing hydrogen chloride under the heat efiect produced at the grinding line.
6. As a new article of manufacture, a grindingwheel comprising an acid insoluble organic bond 2 mg action of said grinding wheel.
SAMUEL S. KISTLER.