US2447943A - Pulpstone - Google Patents

Description

Aug. 24, 1948. 2,447,943

G. N. JEPPSON PULPSTONE 2 Sheets-Sheet 1 Filed Oct. 50, 1945 Aug. 24, 1948.

G. N. JEPPSON PULPSTONE 2 Sheets-Sheet 2 Filed 001:. 30, 1945 GEORGE N. IJEPF'SUN I3 20 IO I5 26 repaired.

Patented Aug. 24, 1948 UNITED v, 1 STATES PATENT 2,447,943 runrs'ronn Geor e N. Jeppson, Worcester, Mass; assignor to Norton Company, Worcester, Mas's., a corporation of Massachusetts J i 1 KppIicationOctobei-SO,1945, Serial I 7 Claims. 01.51 296) a a l t The invention relates to pulpstones;

One object of the invention is to provide a strong pulpstone. Another object of the invention is to provide a pulpstonejwhichcan be easily Another object a the invention isto provide such a construction in which the portions of the block which are held by the bolts are under com pression. Another object of the invention is to provide a'sizeable surface of the block engaged by ail-clamping bolt or a washer thereon.

"Another object of the invention is: to provide a; construction having one or more of the characteris'tics indicated with clear-ance for relative moyem'entbetween the blocks and the bolts in acircumferentialdirection of the stone. Other objects will be in part obvious or in part pointed out hereinafter. i w 'The invention accordingly consists inthe features of construction, combinations of elements, arrangements of parts, and in the severalsteps and relation and order 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 'In the accompanying drawings in which is shown one of many possible embodiments of the mechanical features of this invention.

Figure 1 is a sectional view in aplane perpendice ular'tothe axis of a pulpstone constructed in accordance with theinvention;

Figure 2 is a. perspective view of an abrasive insert which is used when a broken block is replaced with a new block;

"Figure 3 is a viewer a single pulpstone block from the inner side thereof; Figure 4 is a view of'a fragment of the stone inthe same section as'sho'wn in Figure 1 but on an enlarged scale; I i k fFigure 5 is asectional'viewin anaxial plane taken along'the line 5-5 of Figure 4;

--Figure 6' is a fragmentary sectional-view, on a further enlarged scale taken along the line 5-6 of Figure 4. u I f Referring first to Figure 1 the pulps-tone comprises a plurality of bonded abrasive blocks l0 and a, central concrete core ll.

body of abrasive blocks with an outer surf-ace of revolution; While in most cases this outer surface of revolution will be a cylinder it is contemplated that other surfaces may Deformed, such as cones, ellipsoids and paraboloids. While the invention'principally relates to' pulpstbnes,

The blocks III" are arranged in circular rows to forma hollow it inay be embodied in stories for pulpirefining en E- gines or for any other purpose,

The blocks!!! may be made'of ny suitable abrasiveYsuch as silicon. carbide o r-"aluminum" oxide, bonded by any suitable, bond, vitrified bond being preferred. Other bonds' such'fas p asma; formaldehyde resin,'rubbr; shellac, ma nesium; city-chloride or metal; bond mayfb es dwrm manufacture :of the bonded abrasive is 'l t novvin and hence need not furtherlbe described3 herein. v I

- Between blocks .IU of the pulpstone is incorpo rated filler. material It "preferablyat all facesi ofithe blocks which would otherwisebeinjon -j tact witha face or faces of another block. Since; sujch filler material I 2 mlay have nofabrasivei properties, it is 'desirabletois "arrange' the blocks that therewill beno truecircleont'he surface? of the'stone entirely along the fillermaterial' 'IZ.

Thisma'y be ,done in: several different ways, such? as, by shaping the st or es tomake'j zigzag joints such as shown'in'patent to Lai $$Q i NOJ 1 4551 The filler material l2 may be ofany desired type" but preferably is a material whichadl' eres to the faces'gf the blocks l 0 and has some strength "but which will deiorm in response to excessive Qcir cumferential and axial forces, such as, caused by overheating of the, stone Iprefer'the iillerj material such as described in patent to 'Lars'sorr N6. 2,054371 and I have found that the use of syntheticru'bb'er actually improves the'quality; o'ffthisniateriall As described inv the Larsson' patent the filler material is: rubber containing enoughsulphur ,to vulcanize to a hard rubb' together with granules offcork interspersed the in to form collapsible pockets. u

' "Referring now to Figure 3 in connection with Figure}, each block it! may-have'an outerjsu'rface i3 in theshap'e of a segment ofa cylinder or cone etc; an inner surface 14 which "is flat except for a'plurality of grooves I5; apair of side surfaces;

small dihedral angles'with radial planes ofjthe stoneperpendicular to the'a xisl' shownin Figures 4, 5 and grooves 21- 2! extending from the face 14 to; pock'ets'ill. The bottoms of the pockets-20 forrrij 6,eac h stone I'D has washers"2 5in the pockets Zllseated on thseatsj nuts 30 are tightened to put a pre-tension on 910 the bolts 26 sufficient to hold the blocks l [I to the .core ll against all forces tending to remove -tii blocks I9 from the center It. E'noughpre-ten even when subjected to destructive forces will not move from the support H until the abrasive it- I self gives away.

After the required number of blocks [B have thus been provided with-bars 23, bolts 26, washers 25, washers 29 and nuts 30, they are built up intov an annulus with sheets of material l2. between them; {Iheannulus isthen securely clamped together :by circumferential clamps and the entire structure is then placed in an oven and heated to around '1'6. 0l centigr ade, for a periodof about 24 hours to vulcaniz'e thematerial T2. plurality of concentr'ic steel cagesconiprising steel hoops ifispacedapart by steel or iron spacing members, not are-'thenpl'acedinside the annulus of ,blocksin thefposition indic'ated inthe drawings. As illustrated in Figureb the hoops 35 of thetwo outer cages. canbeplaced between bolts 23. Thisentire assembly is mounted upon the bottomplate of a mold and a pair-6f iron or steel moldfs-leeves are then placed in the center thereofl, The molding equipment is not shown as it isgnow well known in; the art and 'forms no part o'f the final article.- Concrete consisting of Portland-c'eriient with sand and a Sui-table; amount of trap-rock is then poured into .place'between the mold sleeves and the annulus of the'blocks 1 0 and allowedto set I l he pulpstone c'onstr'uctet i as above described is wellable -to res'ist. mechanical stress'sand heat shock. Each block lfl'iissecurely clamped toa pair o'fluba'rs:23 whichfare preferably made of steel. I arge .pertions,of each block l0 (under the shoulders?!) are -under compression. iYet no tightenthe of anythingv isnecessary after the annulus i s' -bui ltup. The blooks l'D are'keyed to the concrete center It because concretev flows into, the grooves 15 and for-mskeys. Thesekeys drive the blocks; incases of circumferential expansion of the blocks, the deformable material "l2 provides the-saietyvalve, and this-same ma'terial serves to prevent the breakdown of therear (in relation warrants ofirot'atibn'). edges ofI the block-s.

It is almost certain that the bolts 26" willpractically'never come out of the concrete center ll. 'I h'e blocirs l-fl cannot come out unless large por-. tions of them break -ofi. This will rarely happen, but if and when it 'do es the broken block or blocks can be readily replaced. As shown in Figure '1', I may provide blocks lli'a. with portions cut out which are of theshapeofabrasive plugs [41! one of; which isshownin perspective in Figure 2. The boltheads 21 have screw driver, slots-and the bolts.

ZGTcan -be screwed outnfthe nuts\3"0. After the boltsrzfi. which held the broken block have been thus'removedthe washers 25 are inserted in the ppcltetszll: of a block 'IUa, {the bolts -26 are passed" therethrouglh, the-block 'l 011- is placed inposition sea th boners tightened] "Iihenfour pin-gs to areceniented in place and the .pulpstone is .repaired.

From an examination of Figure 4, it will be noted that the bolts 26 can be flexed a few thousandths of an inch before contacting the sleeves 28. This clearance prevents fracture of the bolts or of the blocks due to expansion of the blocks or differential expansion between the blocks and the stone. I I I .3 I

Tlie bonsai-may be made of {any suitable steel which is capable of being put under tension Without permanently deforming. It is desirable that thebolts 26 as well as the washers 25 be plated ""or i'iiade of stainless steel in order that pulp water, which does-sometimes.penetrate the porous abrasive qnatriaLof t the blocks ll], shall not cause 'theipulpstone to deteriorate by rusting of the bolts or wash ers. It is also desirable that the seats ruetruedremakes smooth surface for engagementby the washers 25 or that washers of copper or other soft metal be provided between the washers and the seats 22. Alternatively, the washers 25 can be made of steel which is'soft enough to ecnrcrm to thejir'iegularitis of the seats 22.

Another preferred feature of the pulpstone is that the bases of the blocks m are preferably.

stronger than the grindingportions of the block's lB-.- B'y base? I mean that area 'of'a'blo'ck which isinc'luded between the face l4 and the level "of the seats 22. The bases of the blocks do not at any time grind pulp and accordingly no considw erauon need b given to the a rasive properties of the bases. Iii-fact, the portions of the blocks which as tne'grinamg constitute "the 'vdmme which is radiauy outward of the was or the bolt heads 2'1. Th' e volur'ne of the blocks n the same: between the top of the bolt heads '21 and the S'e at QZZ constitutes a sort of intermediatezone which might be the same as "the outer abrasive portion-of the block or the same composition as b e I l M It is known iii the art how to make the bases of the block's strongerthan the outer or abrasive portions of theblocks. There are several different ways to do this but one means which is satisfa'J( :tor$ .co'ns ists in loading the lciwer' portion ofth mold which forms the block with abrasive of smaller grit size and possibly also providing a greater volume percentagev of abrasive. Itis' the lower part of th'e rnolcl which forms the base. I I Alternatively' 'the outer or, abrasive portions-of the blocks "I0", that is'to say,,btween the-surfaces ple, if fused alumina abrasive of I24 grit size is mixed with clays, selecting quantities to provide 4e volume per cent of abrasive and about 14.3

volume per cent of bond-,and to this is added enough coke in granule form to make 15 volume per centin the pressed article, the coke being of grit size 12-14, there results a -suitable mixture for the abrasive portionof the block which will have large pores, namely, from'grit size 12 to grit size 14. If asecond mixture is made of the same abrasive of thesa-me gri-t-size-and'the same bond, I but calculated to give volume per cent of-abra siveand 15x5 volume per cent of bond, we have a suitable mixture for the base of the block which will resulting base-much stronger than the abrasive portion of the block. These, two mixtures can 'be-simultaneously pressed to forman integralblock. Instead of using cok e -to for-m the largepores, any other material which will be eliminated during the burning of the-block may be used. An-

other example is naphthalene. I .Iihae s wnd a s ,;-.c@ i types t-p grinding, a porous abrasive containing large pores, generally referred to as induced pores gives better performance. It isdesirable .in this and other cases to form a.-.ba.se ppr-tion: of; thegblock fihich is stronger than theouter orabrasiv 13017;

Itwill be seen fromthe drawings that the seats 22 have a relatively wide area which is contacted by the washers 25." Thus a'large portion of a blockmustbreakbefore itcan come out of the pulpstone. Nor can the "blocks become loose due to contraction of the pulpstone because they are held to the concrete center under tension and the forced s-exerted between,,the seats 22 andthe washers 29 ,via nuts 30. Yet despite this f the only tightening operation'is d'one befor blocksare set in position to formv the fstonT v }jI prefer to use washers 25 to fit'the seats 2.2,"but alternativel large bolt heads might directly contact the-seats. Also While rprefer to place .the bolt heads 21 in the pocketsl ll and the;,nuts an in the concrete, this arrangement might be re versed or two nuts might be used.

A special problem was involved in the formation of the pockets 20 and the grooves 2|. Abrasive mixes in a mold behave somewhat as does a fluid but they do not fully follow Pascal's laws. Such material under pressure will form a reentrant angle in the piece if the mold is so shaped, but there are limits to the amount of material which may be pressed around corners without forming cracks in the fired article. I have found that accurate pockets 20 and grooves 2| with good seats 22 can be formed by proceeding as follows:

Provide a pair of knurled spindles of a diameter barely less than the width of the groove 2| and on the ends thereof afllx abrasive wheels or line toothed milling cutters. Space these apart the distance between pockets, etc., on parallel axes. Mount a green (before firing) block H! on a slide and move it slowly against the wheels or cutters and spindles. The wheels or cutters form the pockets 2|! while the spindles form the grooves 2|. Uniform fiat seats 22 are formed in this way.

Although the drawings show but one ring of blocks it is intended that several rings be superimposed upon each other to form a pulpstone which has a plurality of blocks across its face i. e. in an axial direction. The marginal blocks preferably have one side which is straight, that is in a true radial plane. No illustration of these features was made because per se they are old in the art.

It will thus be seen that there has been provided by this invention an article in which the various objects hereinabove set. forth together with many thoroughly practical advantages are successfully achieved. As various possible em-- bodiments might be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A pulpstone or the like comprising a concrete center of annular shape, a plurality of blocks of bonded abrasive material on the outside of said center to form an abrasive annulus, each block having an outer abrading surface, an inner surface adjacent the center, and a plurality of faces between said surfaces, each block having a pocket in each of two faces forming a seat at the bottom thereof, there being a groove in the block extending from each pocket to-the inner surface of the ,block a, bar-across, the inner.-sur-. face of the blockextending between said grooves, a sleeve against each end of thebarsand extend ing into the "concrete center, bolts inthe sleeves and extending beyond the sleeves and intoithe pockets,,and-means on eachendof the bolts both in: the pockets, and embedded in the concrete,said meansholding the belts in tension and the sleeves under-compression, and .tlratportion of the .blocks radially inward of -the seats being und er compreS; sion derived from the ,bolts and exertedagainst the seats. 2'. Apulpstone orthe like as claimed in claim 1 wherein the outer portions of the blocks, radially ou war r l v f t e wa of ..m kei s of desired abrasive characteristics, and manne portion of. the blocks. radially inward from. (the seats,- is oflstronger composition regardlesso its abrasive characteristics 1 yet vthe blocks: are inf tegral pieces.

3. A pulpstone or the like as claimed in claim 1 in which at least some of the blocks are keyed to the concrete including a projection in one part fitting a recess in the other part.

4. A pulpstone or the like comprising a concrete center of annular shape, a plurality of blocks of bonded abrasive material on the outside of said center to form an abrasive annulus, bolts in the blocks and in the center holding the blocks to the said center, some of the blocks having portions cut out radially outward from the bolts whereby said bolts have been inserted through said out out portions to secure said blocks to said center, and abrasive plugs inserted in said out out portions.

5. A pulpstone or the like comprising a concrete center of annular shape, a plurality of blocks of bonded abrasive material on the outside of said center to form an abrasive annulus, each block having an outer abrading surface, an inner surface adjacent the center, and a plurality of faces between said surfaces, each block having pockets in each of two faces forming a seat at the bottom thereof, there being a groove in the block extending from each pocket to the inner surface of the block, bars across the inner surface of the block extending between said grooves, a sleeve against each end of the bars and extending into the concrete center, bolts in the sleeves and extending beyond the sleeves and into the pockets, and means on each end of the bolts both in the pockets and embedded in the concrete, said means holding the bolts in tension and the sleeves under compression, and that portion of the blocks radially inward of the seats being under compression derived from the bolts and exerted against the seats.

6. A pulpstone or the like comprising a concrete center of annular shape, a plurality of blocks of bonded abrasive material on the outside of said center to form an abrasive annulus, each block having an outer abrading surface, an inner surface adjacent the center, and a plurality of faces between said surfaces, each block having pockets in one face and opposing pockets in an opposite face forming seats at the bottoms thereof, there being a groove in the block extending from each pocket to the inner surface of the block, bars across the inner surface of the block extending between the grooves of said opposing pockets, a sleeve against each end of the bars and extending into the concrete center, bolts in the sleeves and extending beyond the sleeves and into the pockets, and means on each end of the bolts both on

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