AU612996B2 - Composite grinding wheel - Google Patents

Description

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(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: S Priority: Related Art: Name and Address of Applicant: Address for Service: Norton Company 1 New Bond Street Worcester Massachusetts 01606-2698 UNITED STATES OF AMERICA Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Hales, 2000, Australia Complete Specification for the invention entitled: Composite Grinding Wheel The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 \IV I I 1 U I -I ul r, i i-i I I OUR REF: 45158 S&F CODE: 57100 FEI E STAMP TO VALUE OF 5845/2 AfACH ED M AL O FICER. zone (12) or section made up of bonded particles of a material that is softer than the abrasive grain and therefore less abrasive. The wheel is especially suitable for being held in clamps (16) or a chuck when being used, with the clamps or ~u V

ABSTRACT

huck A two zoned grcontacting the wheel havingon the upper less a lowerasive section (14) thuso r zone composatly reduci of bonded abr on sai d clamp or chuck.pper zone (12) or section made up of bonded particles of a material that is softer than the abrasive grain and therefore less thasve The wheel is especially suitable for being held in I- clamps (16) or a chuck when being used, with the clamps or :1 ;shuck contacting the wheel on the upper less abrasive section I4 (12) thus greatly reducing wear on said clamp or chuck.

Ii U A I I I.

e in R- -s asopu 4 uI IUB15 UecJoaration was the first application made in a convention country in respect of the invention the subject of the application.

Declared at Worcester, MA

TO:

THE COMMISSIONER GF PATENTS COMMONWEALTH OF AUSTRALIA.

thi 2ndday of November 19 87 -(-Fill signate of Declarant-no initials) Frank Shihfang Chow Assistant Secretary Li_ I I I-YI I-IILY~~

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IIYIL ii ~LIIU-9- 4 1 The invention relates to composite grinding wheels and more specifically to grinding wheels which in use are held and driven by a chuck or clamping means which makes contact with the periphery of the wheel.

There is a type of grinding operation in which a side face of a grinding w'eel is applied to the work being ground rather than the peripheral face.

Such a wheel may be attached to the grinding machine in a variety of ways.

One such wheel is the so-called plate mou.ited wheel such as that described in U.S. Patent No. 2,479,078. This wheel is made up of a back plate, shown as B in the drawing, which is permanently attached to a grinding wheel A with a cement or adhesive. The wheel is attached to the shaft of a grinding machine through the hole in the back plate B by a suitable attaching means. Another wheel of this type is that taught in U.S. Patent No. 4,292,768. In this case, referring to the drawing, there is a grinding wheel which is permanently and integrally attached to a metal plate (7 and and a clamping flange (9) for clamping the plate of grinding wheel against a support flange. Upon mounting, the upper portion of the mounting plate and the clamping flange (9) are centered around a collar (12) which protrudes r A 2 from the support flange. The upper part of the mounting plate is held in position, before clamping, by engagement of edges of two radial notches (14) below the retaining studs (16) of the two spindles (15) of the support flange Two locking spindles (19) which are rigidly secured to the clamping flange angularly immobilize the assembly by engagement in two corresponding holes (17) of the support flange.

These types of wheels and their method of mounting require that the wheel include a permanently affixed mounting means i.e. the mounting plate is fabricated as part of the wheel.

A further wheel of this type, i.e. one where the grinding surface is a side face of the wheel rather than its peripheral surface, is the subject of U.S. Patent No. 639,035. The wheel, which happens to be a segmental wheel, does not include an integral ,mounting plate such as that taught by the previously mentioned patents, as a permanent part of the wheel.

S 20 Instead the wheel is held and driven by a chuck which S1 is made up of, again referring to the drawing, a circular base with a centrally located hole (2) which is the means through which the chuck is attached to the shaft of a motor. The base has an annular flange extending around its outer edge and a second flange concentric with the outer flange (3) but located within the latter thus forming a channel between them. The grinding wheel is located in the thusly formed channel Clamping plates (7) are located between the inner wall of the grinding wheel and the outer wall of the inner flange Screws pass through holes in the inner flange (4) making contact with the clamping plates forcing them against the inner surface of the wheel which causes the outer surface of the abrasive wheel to be forced against the inner surface of the outer flange Spacer blocks (10) are inserted in the annular i~ QI i -3space or channel to prevent any rearward movement by the abrasive wheel segments and to reduce the amount of wheel that would be unuseable if the entire volume of the annular channel had to be filled with grinding wheel in order to take advantage of the support provided by the bottom or back surface of the channel A second exam~ple of a chuck arrangement for Ii holding and driving a grinding wheel is that of U.S.

Patent No. 1,928,314 which is a somewhat more complex chucking arrangement than that of the past-mentioned patent. Thus chuck's relevance to the present invention resides in the fact that the chucking device causes or results in a forced contact between the abrasive wheel (again a segmental wheel), the flange (12) of the metal base plate and the wedge member U Frequent changing i.e. replacement of the wheel in such a chuck, or a chuck such as that of U.S.

639,035, will cauoe substantial wear on those surfaces of the chuck with which the abrasive wheel makes contact not to mention the not infrequent occurance where the chuck is initially not adjusted tightly enough against the wheel so that very damaging slippage between chuc-k and wheel occurs when the machine is initial~y applied to the work.

There are also grinding wheel chucks which utilize clamps which forceably grasp the outer periphery or peripheral surface of a cylinder type wheel which is solid as opposed to segmental. The present invention is concerned with the wear on chucking devices caused by both segmental and nonsegmental abrasive wheels and eliminates or greatly reduces such chuck wear.

The present invention is a composite wheel which is monolithic but made up of sections with differing compositions. Composite wheels per se generally, are not new. U.S. Patent No. 1,616,531 I -2 V_ I X. 4 -4describes a composite wheel consisting of three distinct layers or sections, a hard central abrasive section (10) sandwiched by two addition abrasive sections (11 and 12) which are softer by virtue of the fact that they are bonded with a softer, weaker bond than the bond used in the central section; this type of wheel is a cutting-off wheel and is used in such a manner that the peripheral edge makes contact with and cuts the material being processed. U.S. Patent No.

3,067,551 is another multizoned or multisectional wheel which also grinds on its peripheral face and not a side face. The purpose of this wheel is to accomplish with a single wheel, what normally takes two wheels to do i.e. remove a desired amount of metal at an economically rapid rate while imparting a high quality finish to the work piece. This objective is reached by constructing a wheel with a sandwich configuration as shown, in its simpler form, in Figure 1 of the drawing where the peripheral grinding surface S presents to the work piece, a section C containing coarse abrasive grain for rapid metal removal flanked by two sections F containing fine abrasive. Both types of sections do contain abrasive and abrasive of the same type such as silicon carbide. The wheel is used by causing it to rotate at high speed, bringing the grinding surface S into contact with the work piece at one end and causing wheel to traverse the work piece in a given direction. In the direction of travel, the work piece first is subjected to one of the fine abrasive containing sections F which results in very little metal removal. However, following that leading F section is the coarse abrasive containing C section which does remove a substantial amount of metal. Lastly, the work piece is subject to the other fine abrasive section F which then polishes or removes the rough marks left by the coarse section C. The direction of the wheel is then reversed repeating the process. This wheel does not grind on a side face and the entire thickness of the wheel contains highly abrasive particles. The invention wheel differs in that it is used on a side face and contains relatively nonabrasive material in its nongrinding portion.

Lastly, there is U.S. Patent No. 3,867,795. The wheel disclosed is used, to some degree, on a side face thereof; it 12 actually used partically on a side face and partically on the peripheral face. The wheel is also made up of two sections, a primary grinding section or layer (20) and a secondary abrading section Both sections do contact the work piece and do grind i.e. remove metal. The invention wheel by contrast, is not used in such a manner that both sections of the wheel contact the work piece and the back (less abrasive) section is 4 where the holding and driving means makes exclusive contact. The Howard patent is relevant for its teaching of layered wheel wherein the back layer may contain a less abrasive material, e.g. garnet, silica, emery, flint and quartz. These materials are useable in the wheel of the present invention.

In accordance with the present invention there is provided a grinding wheel of the cylindrical type for use with a clamping means firmly holding said grinding wheel on a section of a peripheral face, so that the clamping means and the grinding wheel may be driven, comprising a first and a second section, said second section constituting a grinding section composed of abrasive grain and a bond therefor, wherein a side face of said second section contacts a workpiece, said first section being the section of said wheel which interfaces on its peripheral face with said clamping means, the first section being composed of particles that are less abrasive than said abrasive grain for reduing wear on said clamping means, and a bond therefor, wherein the first and second sections have the following volume percent composition: abrasive or less abrasive particles 20-70% resinoid or vitreous bond 2-60%/ fine filler and/or grinding aid 0-50% porosity 0-60% said abrasive grain having an average particle size of 100 to 4000 microns and said less abrasive particles having an average particle size of 44 to 4000 microns.

rhk/0266E 4' ilc-i-i; a- -u 4 5A BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a perspective sectional view through the wheel of the present invention.

Figure 2 is a perspective view of the wheel of the present invention showing, schematically, the 4.4 '4 0 C' 0 00 4, 0 4,a

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rhk/0266E Ic A -6 clamping jaws of a chuck in contact with and holding said wheel.

The invention is an improved grinding wheel of the cylinder type, or that type of wheel that grinds on a side surface rather than on its peripheral surface, as is the case with most grinding wheels, and is held by a chuck or holding means. The wheel of the invention may be a segmental wheel such as those shown in U.S. Patent 639,035 1,928,314 in which case chucks or holding means such as those shown in those patents must be used. However, the wheel may be a unitary i.e. a one piece wheel 10 such as that shown in the drawing; in that case the chuck will have to be segmented, i.e. a moveable jaw type chuck such as that Ii 15 schematically shown in Figure 2, which grips the wheel on the peripheral face. Figure 2 shows the invention wheel 10 with sections 12 and 14, with the jaws or clamping elements 16 of the chuck interfacing with the peripheral face of the upper abrasive grain free section 12.

Frequent clamping and unclamping a wheel which contains abrasive grain throughout its thickness causes severe wear on the steel jaws 16 of the chuck.

By making the upper section of the wheel with less abrasive particles, that wear is eliminated or greatly reduced depending on the hardness of the particulate material used. The thickness of the less abrasive upper section 12 of the wheel 10 can vary but it should be at least thick enough to accomodate the entire surface of jaws 16 that will be in contact with the wheel. The wheel 10 is made up of two zones or sections as shown in Figure 1, a lower section 14 made up of abrasive grains having a Mohs hardness of at least 8 and a vitrified or organic polymer bond for the abrasive grains, and an upper section 12 in Figure 1 which is composed of particles which are substantially less abrasive than the abrasive grains 7 in the lower section 14, the less abrasive particles having a Mohn hardness of from 2 to less than 8 and being bonded with the same vitrified or organic polymer bond as are the abrasive particles in the lower section 14. The wheels are made in the conventional manner.

Any abrasive grain can be employed in the lower or grinding section so long as it has a Mohs hardness of at least 8, as pointed out above.

However, the preferred abrasive is one selected from the group consisting of silicon carbide, fused alumina, cofused alumina-zirconia, sintered alumina, cosintered alumina-zirconia, cubic boron nitride, diamond, and mixtures thereof. The abrasive grain can have a particle size of from 100 to 4000 microns. The bond for the abrasive grain may be any vitrified bond sor any organic polymer based bond such as phenolformaldehyde, polyester, epoxy, urethane, polybenzimidazole and the like. The bonds may also 20 include any of the fillers and grinding aids known in .the art that are amenable with the two types of bonds.

The upper section can be made up of any of a large number of particulate materials so long as it is less abrasive than the abrasive grain in the lower section of the grinding wheel, including glass fibers, organic fibers, crushed nut shells, hard wood chips, and mixtures of these materials where the bond therefor is an organic polymer bond. Also suitable are metal powders such as steel, iron, copper, aluminum and mixtures thereof. When the bond is of the vitrified type the preferred particulate material for the upper section is kyanite, wollastonite, mullite, garnet, quartz, fluorite, mica, nephaline syenite, barium sulfate, calcium carbonate, and of course any mixture or combination of these materials.

Obviously, these particulate materials may be utilized with organic polymer based bonds as well. The average A -8particle of this material in the upper section 1La be from 44 to 4000 microns.

Finally, the abrasive grain containing section 14 and the less abrasive particle containing section 12 va-hav- following volume percent I' composition in order to produce a grinding wheel with adequate physical strength and grinding properties: K abrasive grain or less abrasive particles 20-70% resinoid or vitreous bond 2-60% fine filler and/or grinding aid 0-50% porosity 0-60% EX A M PLE A railroad track grinding wheel, according to the invention, having an outside diameter of 25.9 J 15 cm (10.19 inches), an inside diameter of 14.9 cm (5.87 inches) and a thickness of 7.62 cm (3 inches) was made in the following manner: A 13.6 kg (30 lb) quantity of a conventional grinding wheel mix was prepared in the known manner.

The mix, on a weight percent basis, was made up of 58.6% cofused alumina-zirconia abrasive having an average grain size of 1190 microns, 18% fused aluminum oxide abrasive having an average particle size of 1190 microns, 9.7% of commercial powdered 2-stage phenolformaldehyde resin, 11.9% of barium sulfate filler vjth an average particle size of about 5 microns, and 1.8% quick lime with an average particle size of about 4 microns; the mix also contained 60 -ml of furfuraldehyde per pound of resin which was added to the abrasive grain just prior to addition of the above described bond materials i.e. resin, barium sulfate and lime which were prebatched with 131 ml of Carbosota before being added to the furfuraldehyde wetted abrasive grain. 5.98 kg (13.19 lb) of this mix was placed in a standard steel mold set-up which had an of 25.9 cm (10.19 inches) fitted with an abor with an O.D. of 14.9 cm (5.87 inches).

'1 9 9.07 kg (20 Ib) of a second mix was made in the same manner as described above except that this mix had a weight percent composition of 74.7% kyanite with an average particle size of 250 microns, 13% powdered 2-stage phenol-formaldehyde resin, 10.5% of wollastonite filler with an average particle size of 14 by 80 microns, and 1.8% quick lime; this mix also utilized furfuraldehyde in the amount of 63 cc per pound of resin which had previously been blended with 12 cc of chlorinated paraffin per pound of resin, and cc of tridecyl alcohol per pound of dry resin.

1.66 kg (3.66 lb) of this mix was placed on top of the i first mix in the mold, the top plate put in place and i the contents of the mold pressed to a thickness of l 15 7.68 cm (3.03 inches) at atmospheric temperature. The green wheel was removed from the mold and heat treated I for 20 hours with a maximum soak temperature of 185*C.

The resulting approximately 7.68 cm (3.03 inches) i thick wheel had an upper section measuring approximately 1.9 cm (0.75 inch) thick containing the less I abrasive kyanite in place of the usual highly abrasive cofused alumina-zirconia abrasive.

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Claims (8)

1. A grinding wheel of the cylindrical type for use with a clamping means firmly holding said grinding wheel on a section of a .peripheral face, so that the clamping means and the grinding wheel may be driven, comprising a first and a second section, said second section constituting a grinding section composed of abrasive grain and a bond therefor, wherein a side face of said second section contacts a workpiece, said first section being the section of said wheel which interfaces on its peripheral face with said clamping means, the first section being couiposed of particles that are less abrasive than said abrasive grain for reducing wear on said clamping means, and a bond therefor, wherein the first and second sections have the following volume percent composition: abrasive or less abrasive particles 20-70% resinoid or vitreous bond 2-60% fir- filler and/or grinding aid 0-50% porosity 0-60% said Pbrasive grain having an average particle size of 'i00 to 4000 microns and said less abrasive particles having an average particle size of 44 to 400 microns.

2. A grinding wheel according to claim 1, wherein said particles in said first section are glass fiber&, organic fibers, crushed nut shells, wood chips, or a mixture of two or more such particles.

3. A grinding wheel according to claim i, wherein said particles in said first section are of steel, iron, copper or aluminium, or there is a mixture of two or more such particles.

4. A grinding wheel according to claim 1, wherein said abrasive grain is of silicon carbide, fused alumina, co-fused alumina-zirconia, sintered alumina, consintered alumina-zirconia, cubic boron nitride or diamond, or there is a mixture of two or more such grains, and said particles in said first section are of kyanite, andalusite, wollastonite, mullite, garnet, quartz, fluorite, mica, nephaline syenite, barium sulfate, calcium carbonate or cryolite, or there is a mixture of two or more such grains.

A grinding wheel according to any one of the preceding claims, wherein the bonds for said first and second sections are organic polymer-based. 7 rh^/0266E 1 i _I~LL 11

6. A grinding wheel according to any one of claims 1-4, wherein the bonds for said first and second sections are vitreous bonds.

7. A grinding wheel according to any one of the preceding claims, wherein said abrasive grain in said first section has a Mohs hardness of at least 8 and said particles in said first section have a Mohs hardness of from 2 to less than 8.

8. A grinding wheel according to claim 1, substaiitially as hereinbefore described with reference to the Example. DATED this SECOND day of MAY 1991 o s o ri o o o 0r 0 00 oC o o oo Norton Company Patent Attorneys for the Applicant SPRUSON FERGUSON 00 d 0 o 0 000 rhk/0266E I -4 a