US2032484A

US2032484A - Segmental grinding wheel

Info

Publication number: US2032484A
Application number: US26338A
Authority: US
Inventors: George N Jeppson
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1935-06-13
Filing date: 1935-06-13
Publication date: 1936-03-03
Anticipated expiration: 1953-03-03
Also published as: FR810831A; GB468097A; DE657756C

Description

March 3, 1936. G. N. JEPPsoN SEGMETAL GRINDING WHEEL Filed June 13, 1935 n 3 8 a m GEoRG-E NjLJEPPSoN WITNEssEs Patented Mar. 3, 1936 UNITED ASTATES PATENT OFFICE i 2,032,484 sEGMEN'rAL GmNmNG WHEEL Application June 13, 1935, Serial No. 26,338

8 Claims.

This invention relates to a grinding wheel, and more particularly to a segmental type of grinding wheel especially adapted for grinding logs into wood pulp.

In the production of wood pulp for paper manufacture, many unsuccessful attempts have been made to employ grinding wheels of the type commonly utilized in the metall industry, but

such wheels have not proved satisfactory. A grinding'wheel which is sufliciently large for efilclently grinding wood pulp presents difilcult manufacturing problems, and the firing of such a large monolithic wheel usually results in its breakage or produces an abrasive body which is improperly annealed and very susceptible to breakage during use.

It is necessary to provide a very large and unusually strong abrasive Wheel for pulp grinding since the logs which are ground to produce the wood pulp are large and heavy and the Wheel must withstand enormous grinding forces. It

is common practice to make pulpstones more I than rive feet in diameter and weighing as much as eight tons. The logs are' forced against the operative face of such a stone under extremely heavy pressure, and under normalgrinding con` ditions the pulpstone is rotated at approximately 250 revolutions per minute. In order to operate such a grinding wheel, as much as 1500 horse power is usually required.

In many wood pulp grinding operations, it is usual to maintain a. relatively small'amount of water within the grinding pit, hence the heavy friction of grinding freduently causes a rapid rise in temperature of the operative wheel face. Since many of thesewheels are employed in cold climates, this variation may be from as low as zero degrees Fahrenheit to as highas that of the temperature of boiling water. Furthermore, the water in the grinding pit occasionally gets so low that it provides insuilicient cooling for the wheel and at this time an operative wheel face has been known to rise to a temperature as high as 400 F. Itis these sudden and excessive temperature changes which cause uneven expansions Within these prior types of pulpstones and result vin frequent breakage thereof. In view of the large size of pulpstones and their rapidrotational rate. breakage thereof often results in serious damage to the mill and subjects the machine operator to much danger.

In an endeavor to overcome these diillculties inherent in prior pulpstone constructions, it has been the more recent practice to provide wedge shaped arcuate wheel segments having reentrant to a central support since they cannot jformly secured in grinding position.

As also shown in the noted patents to Larsson grinding wheel. the further objectionable feature that in the portions in their opposed radial side faces. As disclosed in the prior patents to Larsson et al.,

-No. 1,736,161 of November 19, 1929 and No.

1,815,108 of July 21, 1931,` which embody such a typical construction, a single wedge block is ar- 5 i ranged toA engage clamping faces within reentrant dovetailed portions of two adjacent segments and serves to simultaneously engage and secure both segments to a central iron drum. This method of fastening the segments to a cen- 10 tral rotatable support has not been found entirely satisfactory due to the fact that it hinders uniform lateral expansion of the individual segments when subjected to sudden rises in temperature due to the friction of grinding. This 15 impeding of uniform expansion ofthe segments may be suilicient to cause wheel breakage across the narrow throat of bonded abrasive material which extends between the reentrant dovetailed portions within the opposed faces of each seg- 20 K ment. Furthermore, in view of the inherent fragility of the vitried segments forming such a grinding wheel, many difficulties are encounteredl in this method of clamping the segments be uni- 25 et al., the segments may be secured in spaced relation on their central support to aid in compensating for lateral expansions thereof oc- 30 casioned by heat of grinding and, if desired, these spaces between the individual segments may be suitably filled with a deformable or compressible material. Grinding wheels of this gen-l eral type have not only been expensive to pro- 35 duce, but have also presented many practical problems due to the internal stresses and strains set up within the individual segments during manufacture and later during their use in the Pulpstones of this type have 40 event of breakage, the entire wheel must be removed from its mounting and returned to the manufacturer to be completely rebuilt since the' segments within the wheel are not individually 45 secured to their central hub. Unless the mill owner has gone to the heavy additional expense of providing a spare pulpstone to be used during such a contingency, breakage of a pulpstone necessitates a complete shut-down of the mill 50 until the stone has been returned to the manufacture repaired and then sent back to the mill for use.

It is, therefore, the primary object of this invention to provide a segmental type of grinding 'videasegmentaltypeofgrinding wheel wherein the maybe uniformly andindividuailysecm'edtoacentralsupportin suchamannerthattheyarefreetoindividually expand and contract under the influence of tem perature changes vand relieve internal wheel stresses dining a grinding operation. thereby and composed of a plurality of bonded abrasive ts rigidly secured to a central rotatable support independently of'each other and in 'such a manner that the segments may individually expand and relieve Ainternal wheel stresses-'during grinding. 'Ihe central rotatable support may be composed `of any suitable moldable material .which may be cast in position against the bot.-

tomsofthe'segmentstoformampportinghub therefor. To correctly position and rigidly-support the segments in propucooperative grinding relation and provide a grinding wheel having a substantially continuous cylindrical grinding surface, each segment has one ormore anchoring members such as nuts imbedded within its bese portion and adjacent to the central wheel support. These anchoring members are in such spaced relation that they may aid in uniformly securing the segments in grinding position.

In order to secure each sector in grinding position under a desired clamping pressure, each anchoring member is connected to a suitable elongated tension member, such as a clamping bolt, which is slidably mounted within but adjustably secured under a predetermined initial tension to a sleeve member imbedded within and integrally secured to the central wheel support. These anchoring bolts preferably embody elastic properties, so that they may serve to resiliently secure the segments in grinding position on their central support under an initial predetermined but elastic tension to compensate for individual expansions of each wheel segment during a grinding operation. The. segments are preferably mounted in spaced relation to each other and the crevices therebetween may be filled with various deformable or compressible materials which will adhere to the opposed faces of the adjacent segments and aid in compensating for lateral expansions of theindividual segments towards each other as caused by the heat of a grinding operation. A

The present invention is illustrated by the attached drawing wherein:

Fig. 1 is a fragmentary sectional view through a portion of my grinding wheel which illustrates my preferred type of segmental wheel construction;

Fig. 2 is a sectional viewvof a portion of my grinding wheel taken along the line 2--2 of Fig. l; and

Fig. 3 is a sectional view showing a modified type of my grinding wheel construction.

In the preferred type of my invention, asillustrated in Figs. 1 and 2, I have provided a. plurality of wheel sectors or segments I assembled as an annulus upon a central rotatable support to form an integral grinding Vbeseatedonarotatablecentral member, such as a pulpstone.ofanydesiredsiaeandhavingacylin drical grinding faceadaptedtoperforma heavy duty grinding-operatimsuch asthegrindingof logsintowoodpulp. 'Ihesesegmentsarecompoeed of abrasive grains, such as crystalline alumina,siliconcarbideorothersuitable granular abrasive material bonded together into the desired sectoror wheel segment shape by a matured bond, suchasavitriiledceramiematerial ofthe nature of porcelainoirglass.v The segments are provided with curved outer abrading faces II stantially continuous peripheral grinding wheel face i3, opposed side faces Il, end faces Il, and innersupportingfaces Il whicharearrangedto member or hub Il, and preferably a monolithic center composed of concrete or other cementitious material which may be cast in position. The

abrasive segments are made as separate articles of manufacture independent of the central sup- Y which cooperate with each other to form a subpori:iaandtheyaresoconstructedthattheyv may be individually and fawened to the central support by-sultable anchoringde- .vices without producing uneven stresses and strains within'the segments during grinding or weakening their relatively fragile stmcture.

'My preferred type of anchoringmembers, as illustrated, may comprise nuts 2i, each of which ls imbedded within a cavity 22 cast or otherwise formed below the inner supporting face il and within the bottom portionof each segment. These nuts are rigidly and permanently secured within the cavities in desired locations by Babbitt metal, Portland cement, sulphur or .other suitable materials which may be cast in position around each nut to integrally secure it tothe wheel segment. I preferably provide a suilicient number of these imbedded nuts in such spaced relation to each otherthat each segment may be uniformly mounted on the central support il in desired grinding position. Each nut may be further provided with a knurled or otherwise roughened outer face 25 and the cavities 22 may be provided with sharp reentrant portions, such as grooves 26, in the sides thereof which aid in rigidly and permanently locking the nuts vin their required imbedded positions. 'As illustrated, one or preferably several clamping members arranged in desired spaced relation may be employed to secure each segment individually to the central support i8.

Each wheel segment is supported in a predetermined location upon a mating face 2l of the monolithic central supporting member I9, and in my preferred construction these mating faces il and 2B ofthe segments and the central support are made fiat to aid in uniformly supporting and rotating the segments during the grinding operation. If desired, the bottom face i1 of each segment may be coated with a thin sheet of paper, paint or other material to prevent the cementitious or moldable material of the support I8 from adhering to the segment. In order to removably and individually secure the segments in position on the central support i9, the imbedded nuts 2| are secured under a predetermined tension to a central mandrel Il coaxial with the grinding annulus by means of bolts 32 slidably mounted within metal sleeves 3l which are imbedded within the central support i9 and extend between nuts 2i and mandrel Il. If desired, the outer faces M of the metal sleeves may be roughened to aid the material of the een.

sov

drei, as well vas relieving the central wheel sup-v port of any initial stresses v4and strains. usually caused by clamping devices. I preferably provide the bolts t! with 4certain elastic properties'which wheel, as mustraa .m rigs. i and 2, r cement a permit them to expand and contractwithln the sleeves It and thus compensate for expansions and contractions within the individual wheel segments during a grinding operation. as disclosed in the prior -patent toLarsson et al., No.'l,l3 8.l61.

l I have thus provided a construction wherein my abrasive segments'are not only removably clamped in position but also are so mounted that each or the clamping bolts may be maintained at an initial tension without exerting any clamping forces upon the central wheel support;

'I'he sleeves 33, bolts and anchoring nuts 2i are so positioned relative to each other and within the 'wheel that the abrasive segments are individually fastened to the centralsupportin a predetermined spaced relation to each other with the opposed sideand end faces of acija'cent'segments slightlyseparated from each other. The crevices thus formed between: the adjacent segments may be filled with a compressible material such, for example, as a soft Babbitt metal, lead, zinc, a mixture-of sulphur-and ground coke commonly known bythe trade name of "LavasuP, rubber or other suitable deformable materials which will aid in laterally supporting the segments and yet permit lateral expansions ofthe individual segments during grinding as caused by temperature changes within the wheel.

In assembling my preferred type of grinding sheet of paper over the supporting face Il of the segmentor otherwise suitably coat the bottom face of the segment, as by paint, to fill the surface pores thereof and prevent the material of the central wheel support Il from entering into the pore structure of the segment and from adhering thereto when' the central support is cast in position'. A clampingbolt t! is then secured within each nut 2i. thereby rigidly fastening one or more bolts to each wheel segment. A sleeve tl' is slid over-each bolt and the inner ends of the bolts protruding from said sleeves areins'erted through correspondingly-located holes Il within the central mandrel Il. A nut I. is threaded on the inner end of -each bolt and brought ,into kengagement with the mandrel, as shown, to individually and removably clamp'the segments in the v form of an annulus and in desired spaced relation to each other.v 'Ihe nuts are preferably tightened against' the mandrel sufficiently to stretch each bolt slightly but not beyond its elastic limit so that the sleeves will support the entire clamping force exerted by the bolts and the segments will be reslliently secured/in position under a predetermined tension'lin such s. manner that expansion of the wheel during grinding may be filled with a cementitious material, such asconcrete or other suitable material whichmay be cast in position to form the central wheel support It. To prevent the material il from entering within the crevices between .the segments during the molding operation thereof. the bottom portions of said crevices adjacent to surfaces I1v may be filled with a moldablematerial, such as putty, or said crevices may becovered by strips of fibrous material, such as paper or Acloth.

stretched thereacross and secured to the surfaces l i1 of adjacent segments. When the moldable material forming the central support has become set. the interstices between adjacent segmentV faces I4 and between segment faces il may be nues with a deformable material, auth as Babbitt metal, lead, Lavasul", rubber or other suitable compressible materials well known in the art.

The provision of a wheel construction of this type minimizes wheel breakage since any internal stresses within the segments will be compensated for in each segment by means of the clamping bolts 32 which are arranged to compensate for individual segment expansions. Hence, stresses 4 and strains within the wheel during grinding will not tend to accumulate throughout the entire wheel and attain magnitude sumcient to cause wheel breakage. In other words, in a construction of this type, each segment is arranged to resiliently expandand contract by itself in grinding position and in the event that wheel breakage 'should' occur due to improper wheel use, one or more segments may be individually replaced in the field without necessitating shipping of the entire grinding wheel back to the factory to be completely rebuilt, as has been necessary heretofore. In accomplishing a repair of this type, the broken segment may be removed by loosening nuts 36 securing it in position and breaking out the filling material t8 within the crevices between the segments. A new segment may then.

be inserted in the same position and secured under desired tension by means'of nuts, 36, after which the crevices between adjacent segments may be again filled with a suitable material, as heretofore described.

A modined form of my invention, as shown in Fig. '3 of the drawing, comprises a plurality of separately manufactured bonded abrasive segments B0 of the same general material, shape and size as the segments employed in my preferred type of invention. 'I'hese segments are provided with arcuate outer grinding faces 5I which cooperate with each other in the assembled wheel to form an operative peripheral wheel face 53. As in my preferred type of invention, the segments are also provided with substantially radial 65 v opposed side faces, end faces 65 and inner supporting faces 51 which are arranged to be firmly seated upon a rotatable central support or hub l! composed of a suitable cementitious material,

such as concrete or other material which may be cast or molded in position against the bottom of thev segments during wheel assembly to proy which are arranged to individually engage the central wheel support itself. As illustrated, the

lower portion of each segment is provided with one or a plurality of spaced recessed or reentrant cavities l2 within which anchoring members such as nuts 6 3 are imbedded. 'Ihese nuts are permanently and rigidly secured in position within said cavities by a cementitious material 84, such as Babbitt metal, Portland cement, sulphur or other suitable materials which may be cast in position about each nut and i111 the cavities. The nuts are preferably provided with -knurled outer faces l! and the cavities are provided with grooves orreentrant portions in their side faces to aid in securing the cement B4 and nuts 63 integrally to the segments. One or preferably a plurality of these nuts are secured within the bottom of each segment in such spaced relation that each segment may be uniformly secured in position upon the central rotatable support I9.

The segments are each secured in position with their respective inner faces l1 seated upon correspondingly shaped faces 10 of the molded central support 59, and these mating faces are preferably made flat to evenly support the segments and aid in imparting rotation thereto. As in my preferred construction, the bottom face of each segment may be. coated with a thin sheet of paper or paint to prevent the cementitious material of the central support 59 from entering the segments and adhering thereto during wheel assembly. To rigidly and permanently secure the segments in position, each imbedded nut 63 is engaged by an elongated clamping tension member, such as a bolt 14, threaded therein. A sleeve 15 is slidably mounted on each bolt and clamped in position between nut 83 and a clamping nut 11 threaded upon the inner end of each bolt. Hence, it will be appreciated that each nut 11 may be so tightened against an end of sleeve 15 that each clamping bolt may be secured toV its segment under an initial predetermined clamping pressure. As in my Preferred type of construction. these bolts 14 may be provided with certain elastic properties which compensate for wheel expansions during a grinding operation, asv described in the prior patent to Larsson et al. No. 1,736,161. A portion of each clamping.Y device including sleeves 16, nuts 11 and the protruding ends of bolts 14 are imbedded within the cementitious central support 59 which firmly adheres thereto and serves to hold the segments in position.

If desired, the outer face of sleeves 1B may be roughened or provided with knurled portions to aid the cementitious material of the central support in securing them in position as integral members therewith. Hence, any expansive forces within the grinding wheel during grinding operations, such as those normally caused by the heat of grinding, may be compensated for by the elastic properties of bolts 14 which are free to expand and contract within the sleeves 15. The sleeves are made of suitable length and the bolts may be provided with such elastic properties as are necessary to. meet the requirements of each individual wheel. In a construction of this type, each segment will be individually clamped in position under an initial -tension which may be regulated prior to wheel assembly, but this tension is resisted entirely by the sleeves 1I and is not transmitted to the central wheel support Il, as is the case in prior segmental grinding wheel constructions employing segments clamped to a central support. If desired, the lsegments may be located in spaced relation during assembly and, as in my preferred type of invention, the spaces between the adjacent segment faces may be filled with a suitable deformable material to further aid in compensating for lateral expansions of the segments.

In the manufacture of this modified type of my invention, the nuts 0I are suitably secured within the cavities l2 by means of cementitious material and bolts 14 are firmly screw threaded into the nuts. A sleeve is slid over each of the bolts 14 and a nut 11 is threaded on the protruding end of each bolt and thereafter tightened against the sleeve under a predetermined initial tension. It will thus be noted that each bolt 14 is secured under a predetermined initial tension before assembly of the grinding wheel. 'Ihe segments are then mounted by means of suitable clamps or guides in the form of an annulus and the cementitious wheel support l! is cast against the bottom faces l1 of each segment and around the sleeves 1l and nuts 11, thereby forming an' integral grindingl unit. If desired, the segments may be mounted'in spaced relation to each other and a suitable deformable material cast in the crevices therebetween, as described in my preferred type of invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: s

1. A grinding member comprising 'a bonded abrasive block, a support therefor composed of a material molded in situ, an anchoring device including an elongated elastic tension member arranged to secure the abrasive block upon the support, and means embedded within the support which maintains the tension member under an initial predetermined tension, thereby resiliently fastening the abrasive block upon its support and compensating for expansion and ccntraetion within the grinding member.

2. A grinding wheel comprising a plurality of bonded abrasive segments arranged in the form of an annulus. a rotatable central support therefor composed of ay material cast in position against the bottoms of the segments. an anchoring device securing each segment upon the support including an elongated elastic tension member, and means embedded .within the support.

which secures the tension member thereto and permits free expansive and contractive movement'thereof.

3. A grinding wheel comprising a plurality of bonded abrasive segments arranged in the form' of an annulus having a peripheral grinding face, a rotatable central support therefor composed of a material cast in .position against the abrasive annulus, anchoring devices fastening the segments upon the support, each of said devices including an elongated elastic tension member connectible with a segment. a member embedded within the support which secures the tension member in position but permits slidable movement thereof, and means engageable with the embedded member for securing the tension member under an initial tension, thereby resiliently fastening each segment in grinding position and compensating for expansions within the wheel during grinding. Y

4. A grinding wheel comprising a plurality of bonded abrasive segments, a rotatable hollow central support therefor. composed of a material molded in situ, anchoring devices securing the segments upon the support. each ci said devices including a sleeve member embedded within the support, an elastic tension member movable within each sleeve, means at one end of each tension member integrally securing it to a `segment and means at the other end of each tension member arranged td individually and removably secure the segments in positionl under a predetermined but resilient tension to compensate for wheel expansions during grinding.

5. A grinding wheel comprising a plurality of spaced bonded abrasive segments arranged in the form of an abrasive annulus having a substantially continuous grinding face, a rotatable central support therefor composed of a material molded in position against the bottom oi the segments, an anchoring device individually and resiliently fastening each segment upon the support in grinding position which includes an elon-I gated elastic tension member arranged to compensate ior expansion and contraction within the Wheel, means at one end oi said member embedded within the bottom of a segment and integrally secured thereto, and means embedded within the support and engageable with said tension member which permits free expansive and contractive movement thereof and serves to maintain said member under an initial predetermined tension so that the segments may be individually and resiliently secured in position under a predetermined tension. l

6. A grinding wheel comprising a plurality o! bonded abrasive segments arranged as an abrasive annulus, a rotatable central support therefor, anchoring devices securing the segments tc the support including elongated elastic tension members which compensate for expansions and contractions withinthe wheel during grinding and means to exert a predetermined initial tension upon each tension member without exerting any clamping force between the segments and their support.

'7. A grinding wheel comprising a plurality ot bonded abrasive segments arranged in the form of an abrasive annulus, a rotatable central support therefor composed of a cementitious material cast in position against the bottom of the segments, an anchoring device individually securing each segment to the support including an elongated elastic bolt arranged to expand and contract during grinding and compensate for expansive stresses and strains within the wheel, a sleeve member integrally secured to and embedded within the support which permits a relative slidable movement of the bolt therein, means removably engageable with one end of the bolt embedded within a segment, and means removably engageable with the other end o! said bolt and engageable with said sleeve to resiliently secure each segment in position under a predetermined tension.

8. A grinding wheel comprising a plurality of separately manufactured bonded abrasive segments assembled as an annulus having a cylindrical grinding face, a rotatable central support therefor composed of a material cast in po'sltion against the bottoms of the segments, a plurality of spaced anchoring devices arranged to individually and removably secure each segment upon its central support, each anchoring device including an elongated elastic tension bolt arranged to compensate for individual expansions oi' the segments during grinding, anchoring members embedded within the bottom portion of each segment and removably engageable with said elastic bolts, a rigid sleeve member embedded within and integral with the support. each sleeve engaging an anchoring member andpermitting slidable movement of an elastic bolt therein, and means adjustably and removably engageable with an elastic bolt and sleeve which maintains said bolt under an initial predetermined tension and resiliently but removably secures each segment in position in such a manner that it may be replaced irrespective ci other segments in the wheel.

GEORGE N. JmrjPsoN.