Segmental abrasive wheel
US RE22457 E
Description (OCR text may contain errors)
SEGMENTAL ABRASIVE WHEEL- Original Filed April 2 1928 I Inventors wvtne as e s i 1 6601:9621 u/epp 6 00 M 3 M Elm? arasolr 3M QQ TMQW "integral with the segments. 3
Reissue Mar. 14, 1944 UNITED STATES PATENT, OFFICE SEGMENTAL ABRASIVE WHEEL George N. Jeppson and Thure Larsson, Worcester, I
/ Mass., asslgnors to Norton Company, Worceste Mass, a corporation of Massachusetts Original No. 1,865,523, dated July 5, 1932, Serial No. 266,481, April 2, 1928. Application for reissuc December 18, 1943, Serial No. 514,871. In
Canada October 4, 1928 19 Claims.
This invention relates to grinding wheels and more particularly to a segmental grinding wheel in which the-segments of abrasive grainsbonded by verified ceramic material are mounted upon a rotary support.
It has been proposed heretofore to make a large sized grinding wheel of abrasive segments (01. si -zo'i) mounted on a metal drum for use in grinding wood pulp and the like. Such a segmental wheel is however expensive to manufacture, partly because'of the size and weight of the drum but more because of the ,difliculties involved in mounting the segments on the drum. A wheel used for grinding wood pulp is subjected to enormous forces from without, owing to the fact that the logs of wood are pressed against the wheel under hydraulic pressure, as well as large internal stresses resulting from the centrifugal force set up by rotating the wheel at high speed and because of expansion and contraction of the wheel under the changes of temperature required for grinding the pulp in the presence of' hot water.
order to mount the segments rigidly and se- It has heretofore been advisable, in
curely on the metal drum, to provide each segment with a metal shoe and to have the surface of the drum carefully ground to a'smooth and accurate shape in order that the shoes of the segment may fit correctly thereon.
The primary object of this invention is to avoid the necessity of using a massive iron drum which must be accurately finished and shaped to fit the segments and which must be sufficiently rigid and strong'to hold them under the enormous strains of the grinding operation, and particularly to provide a simple, inexpensive type of segmental grinding wheel which may be readily manu'factrred and assembled andv which will serve efllciently for grinding wood pulp as well as various other types of materiah A further object or the invention is to providea unitary type of grinding wheel made up of abrasive segments mounted rigidly in position on a central support, an'd particularly one in 'whichthe central supporting body is formed as is substantially.
a monolithic structure which To the accomplishments of these objects and such others as will'be apparent to'one skilled in the art, we propose to'utilize a concrete orother monolithic structure as thesupporting-body for plurality of abrasive segments arranged on the surface thereof, and in -order that the segments may be safely held in position under the enormous stresses of a grinding operation, we
ing blocks and the adjustable bolts embedded in the concrete and securing the segments in position;
Fig. 3 is a sectional elevation on the line 8-4, Fig. 2; v
Fig. 4 is an enlarged sectional elevation similar to Fig. 3, but taken on a difierent line on Fig. 2, showing the reinforcing members which strengthen the concrete body; and
Fig. 5 is a fragmentary detail in sectional elevation showing, enlarged, the abrasive segments in their assembled position.
The embodiment of our invention illustrated in the drawing comprises a pluralityof segments 6, composed of abrasive grains bonded by suitable material, suchas vitrified ceramic material, which are mounted with their side faces I spaced apart to form. an annular grinding body. The inner portions 8 of the segments are secured in position by means of clamping blocks 9 suitably secured to the inner concrete cylinder III. In the form illustrated, the segments are secured against lateral, circumferential motion by the ribs H .on the cylinder located between the inner ends of the'segments.
The clamping block, it, in the form illustratedcomprise wedge shaped heads formed on the outer endsof rectangular webs l3. These webs may rest .onstrips of elastic ,material i5,
such as rubber or other-resilient material,- suitably placed between the'bottoms of .the webs and the ribs 1 l'to prevent the concrete from, flowing around the webs when. the centralbody iscast,
' and yet provide-a pad of sumcient springiness to permit the tightening of the clamping blocks.
Each segment,- at the lowerportions of the reentrant shoulders I8, is providedwith an inner facing shoe I I of lead cast integrally thereon and bonded intimatelylwith theporous' surface of the segment; f 'I'hese shoes H, which extend the .jull width. of the. segments} have a fitting engagement with the lower portions" of the blocksii (Fig. 5). The interstices between the adjacent faces I of the segments are filled with a suitable cementitious filler is, such as lead. which is poured in a molten state so that the heads l2 become completely covered (Fig. 5).
Each clamping block i2 is connected to a mandrel 2| within the concrete cylinder ll by a plurality of bolts 20, which are incased in the concrete. The upper ends. of the bolts are threaded into the webs I! while the lower ends ofthe bolts pass loosely through the mandrel 2!. The bolts 20, which may be somewhat elastic under tension, have nuts 22 and. washers 23 thereon, serving to secure the bolts-to the mandrel 2i, a locking nut 24 being used to prevent the parts from becoming loosened.
The concrete cylinder I0 is preferably reinforced. To this end numerous concentric circular hoops 25 are arranged as shown in Figs. 2, 3 and 4. A plurality of cross rods 28 are connected to the peripheries of the hoops 25 by a twisted wire tie 21 which is wrapped around the hoops and rods at each point of contact. The two concentric rows of hoops are also connected bywires 28 which have their respective ends twisted about the hoops. I
.To construct the grinding wheel, the reinforcing net-work composed of the hoops 25, the rods 22 and wires 28, is formed loosely around the mandrel 2|. The clamping blocks are then threaded upon the upper ends of the bolts 20, the
lower ends of which are inserted through the holes in the mandrel and then provided with the washer 22, the nut 22 and the nut 2|. The
nuts 22 and 24 are adjusted to allow the clamping blocks to be withdrawn and positioned from the mandrel the properdistance in which they may be braced by temporary wooden braces or by sleeves of metal or other material surround ing the bolts, and which may form a permanent part of the wheel structure.
After the clamping blocks are braced outwardly from the mandrel; the wedge shaped abrasive segments are slipped sidewise between the pairs of blocks l2, and they interlock with the reentra'nt'shoulders i6 and engage the lead facin shoes I1. After the various segments have been placed in position, the crevices between the seements are then wedged to hold the grinding surfaces thereon in the proper relative relation. This may necessitate adjustment of the position the concrete. The temporary braces, if they were used, are removed and the bolts 22, between the.
" mandrel and the webs I: are provided with sleeves of heavy grease. The concrete .is now poured into the space between the mandrel and the segments. -Durlng this operation the rein forcing net-work may be held in its proper central position without diiilculty. The fluid concrete flows into engagement with the bottom faces of the nts and fills the interstices between the packings ll beneath the clamping blocks and the side faces I of the segments, thus forming the ribs ll on the concrete cylinder ll. The concrete makes an intimate bcnd with the porous surface of the segments. 1
After the concrete has set, the wires can? The nuts 22 are now suillciently tightened so-that the greased bolts 2| pull the heads l2 of the clamping blocks against the facing shoes l'|, tightly squeeze the elastic strips ll between the web bottoms and the ribs II, and draw the segments down'into firm contact with the surface of the croncrete cylinder ID. This tightening process placesthe elastic bolts under longitudinal The bolts thus permit expansion of of the'clamping blocks l2 which are covered by p the filler. The end faces of the concrete cylinder are then provided with suitable flanges whereby the grinding wheel may be supported upon a driving spindle. g
It will be apparent to those skilled in this art that changes may be made in the details of construction and in the steps of the method the described and illustrated embodiment of the invention beingintended as an example of its underlying essentials. the features whereof will be definitely stated in their true scope in the'ciaims hereto appended. It will also be understood that one may construct a wheel, by this method, which grinds on one plane end face, and that various other shapes as well as sizes of wheel may be thus made. It will also be understood that we claim as new and -desire to secure by 'Letters Patent is:
v 1. That improvement in the art of making segmental grinding wheels which consists in arranging a plurality of abrasive segments independently of their final internal support in an annulus drical grinding surface, then forming the inter- 4 nal supporting structure for all the segments in situwithin the annulus, and thereafter adjustably tension elements connected to the segments for thereby forcing the segments radially inwardly into position on said structure to hold them thereagalnst in opposition to centrifugal forces exerted during subsequent operation of the wheel;
.2. That improvement in the art of making segmental grinding wheels which consists in connecting loosely by tension elements a plurality of circumferentially arranged and spaced clamping blocks to a mandrel, arranging a plurality of abrasive segments respectively between successive blocks and in operative connection to said blocks and materially spaced'from saidmandrel and capable when arranged in an annulus to form by theirsuccession of faces a cylindrical grinding surface, adjusting the connection of the tension elements to the mandrel to achieve proper relation of said faces, filling the space between the mandrel and the internal faces of the segments with a moldable material capable of solidifying 1 I bindin Y thesegments togetherand the wedges between .and of forming when solidified a support for the segments, causing said material to harden, and
thereafter settlngzthe tension of said tension elefor adjustably drawing the clamping blocks toward the mandrel x and thereby fixing. the segments rigidly in position on the support through out dimensional changescaused'in the wheel by the adjacent faces o the segment are rem ved-=16 h s and in opposition to tentrifugal forces exerted during subsequent operation of the wheel.
' 3. That improvement in the art of making segmental grinding wheels which consists in building looseLv around an annular mandrel a reinforcing net-work that has hoop means of greater radius than the radius of said mandrel; connecting loosely to the mandrel, by radially-extending adjustable tension elements, a plurality of circumferentially arranged clamping blocks having their clamping elements ngaging the ends of a plurality of abrasive segments shaped to form when in proper end-to-end relation an annulus of greater inside radius than the radius of said hoop means to thereby form the outer boundary of an annular space radially traversed by said tension elements and having said hoop means therein: arranging said plurality of abrasive segments be- .tween said clamping blocks, by adjusting said tension elements, in respective positions spaced radially from said mandrel and spaced radially outwardly from said net-work hoop means to bring their outer abrasive surfaces in proper relative relation to form a cylindrical grinding surface; and then filling the space between the mandrel and the segments and about said net-work with a moldable material capable of solidifying and of concrete molded in position within said abrasive annulus and forming a support coacting to hold said segments against grinding reactions that tend to thrust them radially inwardly, a metal annulus encased by said body of concrete and of materially loser radius than the maximum radius of the latter and spaced inwardly from said abrasive annulus, said abrasive segments being in the final wheel structure backed up by said body of concrete and forming an external cylindrical grinding surface, clamping members engaging the segments and adjustable means associated therewith comprising adjustable tie-rods having connections with said clamping members? and said metal annulus and extending radially within the concrete of said annular body and which coact by fldlustment thereof to position the clamping members and hence the abrasive segments at the proper distance from said metal annulus for the reception in the space therebetween and about engagement with the clamping elements thereof and giving said segments respective positions, by adjustment of the bolts, to respectively space them properly from said mandrel to form by their outer faces a cylindrical grinding surface, filling the annular space between the mandrel and the inner faces of said segments with a moldable material capable of solidifying and thereby form a seat and an internal support for all of the segments capable of resisting independently of said mandrel inward radial thrusts exerted thereagainst by said segments due to ultimate grinding ing reactions, and utilizing elastic tension in said Y bolts to hold said clamping blocks in position to maintain firm engagement of the segments with said seat against the action of centrifugal force during the operation of the wheel.
6. The method of making a grinding whe comprising the steps of assembling a set of abra-- prising a plurality of abrasive segments arranged as an annulus of substantial internal radius to form a large-dlametered external cylindrical abrasive surface; a metal annular member of much smaller radius than the internal radius of said annulus; an annular rotary support of large radial dimension and made of non-metallic material molded in situ in the space between said annular member and said abrasive annulus and which contacts with and fits intimately against inwardly exposed surfaces of thesegments to form the soleseat and a massive internal backing for the segments; and radially extending tie-rods within and traversing the said molded material to connect the segments to said annular member. said tie-rods being adjustable for drawing the segments radially inwardly during assembly to position their grinding surfaces in proper relative relation to form-said annulus and thereby coact to position them to form by said inwardly exposed surfaces thereof an internal annular wall for the said tie-rods of the concrete to form and mold v radially inwardly into a rigid relationship to the p annular support therefor of substantial radius support during. contraction of the wheel upon cooling and to-hold them against separation in a radial-direction from the support by th action of centrifugal forces and during expansion of the wheel under heating.
5. That improvement in the art of making segmental grinding wheels which consists in bolting loosely to an annular mandrel a plurality of clamping blocks having clamping elements with circumferential spaces within which to accommodate abrasive segments, arranging a plurality of abrasive segments in said. circumferential spaces between the clamping blocks and in interreception and molding thereagainst of saidmaterial to form said seat, said tie-rods exerting radially inward pull upon said segments and securing said segments rigidly in operative position on said support against sald'seat in opposition to the action of centrifugal force during subsequent operation of the wheel.
8.1A grinding wheel comprising a plurality of abrasive segments arranged as an annulus of substantial internal radius to form a large-diametered external; cylindrical abrasive surface; an
which are secured to .the support, and cooperating should'ers on. the segments engaged by said clamping members, for forcing the segments radially inwardly against forces occurring during grinding and which tend to dislodge them and thereby securing them against said forces with their said inner faces held in firm contact with aid supporting seat of the support.
9. A grinding wheel comprising a plurality of abrasive segments arranged in spaced relation as an abrasive annulusof substantial internal radius to form a large-diametered external cylindrical abrasive surface; a monolithic body of cement within said annulus and forming substantially the sole support for the annulus at the inner faces of the segments thereof to give direct support against grinding reactions tending to force the Y segments'radially inwardly. the outer surface of said monolithic body being molded and fitting intimately against the irregular surface of each abrasive segment to support it against said grinding reactions; adjustable means, including clamping elements engaging the abrasive segments and tension elements. extending radially into said monolithic body, for placing said tension elements under tension to draw said clamping elements into tight engagementwith the abrasive segments for forcing the segments radially inwardly into firm contact with said body and insure firmness of contact against the action of centrifugal forces and against the action of thermal changes in the wheel; and a filler in the interstices between adjacent faces of the segments.
10. A grinding wheel comprising a plurality of abrasive segments arranged in spaced relation as an annulus of substantial internal radius to form a large-diametered external cylindrical abrasive surface; an annular supporting body of substantial radial dimension molded in position within,
said annulus against and intimately fitting the inner surfaces of said abrasive segments, said body forming substantially the sole internal support for the segments to transmit driving torque to them against grinding reactions tending to displace them in circumferential direction, said segments having clamping shoulders formed in their adjacent end faces with metallic facings on said shoulders; fillers in the interstices between adiacent end faces of the segments to prevent direct body with a radial pressure that holds them against separation from the body by centrifugal forces and. during dimensional changes accompanying thermal changes in the wheel.
11. A grinding wheel comprising a monolithic externally cylindrical body having a plurality of transverse channels formed in its outer surface and circumferentially spaced and thereby providing transverse circumferentially spaced ribs; a plurality of abrasive segments having portions respectively seated in said channels whereby said ribs hold said segments against material displacement circumferentially relative to said body; a plurality of clamping blocks, each being located between and engaging the ends of adjacent segments, said blocks and segments having cooperating interlock-ing surfaces and adjustable means for securing each block to said body.
. 12. A grinding wheel comprising a cylindrical body having a plurality of channels formed laterallv therein, a plurality of abrasive segments seated in said channels, each segment having reent'rant shoulders formed on its opposite side faces and facing sho'es thereon, clamping blocks, each engaging the shoes of a pair of adjacent segments, and a filler in the interstices between adjacent faces of the segments.
13. A grinding wheel comprising a central annular mandrel; a concrete cylinder of materially greater radius than said mandrel and encasing.
the latter and extending radially outwardly from the mandrel to form a monolithic annulus of substantial radial dimension; a plurality of abrasive segments arranged in an annulusabout said cylinder and having portions intermediate of their ends embedded in the surface of said cylinder which thereby has transverse ribs formed thereon to resist grinding reactions tending to displace the segments in circumferential direction; a plurality of clamping blocks having clamping elements between the segments, said segments having shoulders at their adjacent ends and said shoulders drel and extending radially therefrom and within I said concrete cylinder,
said monolithic annulus and through said transverse ribs for connecting said clamping blocks to said mandrel to hold said segments firmly to said monolithic annulus against the action of centrifugal forces and against the action of thermal changes within the wheel, said bolts being, by said connections and said mandrel, secured to 14. A grinding wheel comprising a central mandrel, a reinforced concrete cylinder encasing the mandrel, a plurality'of abrasive segments on the surface of, said cylinder, a plurality of clamping blocks between the segments, said blocks and segments having cooperating interlocking surfaces, bolts connecting each block with the mandrel which are arranged to move freely through the concrete, and a filler in the interstices between adjacent faces of the segments. i
15. A segmental grinding wheel assemblage comprising a hollow mandrel; a series of abrasive segments surrounding but radially spaced a substantial distance from the mandrel for forming externally a large-diametered cylindrical grinding surface and internally thereof an annular space of large radial dimension; clamping blocks having clamping elements engaging the segments and having tie-rods extending radially therefrom across said annular space and provided with con,- nections to said mandrel, whereby said tie-rods and said mandrel are adapted to react against centrifugal forces exerted upon the segments during rotation of the wheel and hold the segments against outward movement thereby; means operable during assembly for adjusting the length of said tie-rods whereby the clamping blocks are adjustably secured in relation to the mandrel to position them and to locate the segments at proper radial distances from said mandrel to form an annulus providing said cylindrical grinding surforces acting radially inwardly upon the segments and to transmit driving torque to the segments in opp sition to the reactions caused by work pressed against said cylindrical grinding surface.
16. A grinding wheel comprising a mandreha series of abrasive segments arranged around but spaced at a considerable distance from the mandrel to form a grinding surface, the segments having clamping shoulders thereon, blocks having clamping elements engaging said clamping shoulders, adjustable means for forcing the blocks inwardly toward the mandrel, a cementitious filler between the segments, and a rigid molded body between the mandrel and segments having intimate contact with the segments and serving substantially as the sole internal compression support therefor, 4
17. A grinding wheel comprising a series of abrasive. segments arranged as an annulus of substantial internal radius to'form a large-diametered external cylindrical abrasive surface, said segments being provided with clamping shoulders at their adjacent end faces; clamping blocks having clamping elements engaging said shoulders whereby each segment is engaged by a clamping monolithic body of substantial radial dimension within said abrasive annulus and contacting directly with and forming a support for the segments that is resistant to forces exerted thereagainst in a radially inward direction; and ad- 'justable means including adjustable tension.
members which are embedded and extend radially in said body and which are locked after having been adjusted to place said tension elements urn ing blocks engaging said shoulders, a molded body in the space within the annulus which makes in-.
' timate contact with the segments and forms a rigid and substantially the sole internal compression support for the same, and adjustable tension members moveable within said body and engaging the blocks, said tension members being adjustable by means associated therewith comprising threaded means for tensioning them and by their tension permitting said members to be drawn inwardly to clamp the blocks tightly against the body.
19. \A grinding wheel assemblage comprising a cylindrical body of substantial radius and made element at each end face; a molded substantially of molded concrete and having transverse ribs in its external cylindrical surface; a series of abrasive segments arranged in end-to-end relation with filler means between adjacent end faces to form an abrasive annulus extending about and mounted on said body by molding said body in situ against said segments and which coacts to support them against grinding reactions tending to thrust said segments radially inwardly, said segments having clamping-shoulders in their adjacent end faces, and having portions received between said ribs to prevent circumferential displacement by grinding reactions tending to shift the segments circumferentially whereby said body serves to transmit driving torque to said segments; clamping blocks having clamping elements engaging said shoulders whereby each segment is engaged at its two ends; an internal metal annular member encased by said concrete body; tierods connected with said blocks and extending a radially into said concrete body and having connections at their-inner ends to said metal annular member, said tie-rods having sleeve means thereabout whereby they are moveably embedded in concrete of said body; and means operated d as for adjusting 1