CA1171824A

CA1171824A - Hard-surfacing decanter conveyors

Info

Publication number: CA1171824A
Application number: CA000327823A
Authority: CA
Inventors: Leonard Shapiro
Original assignee: Pennwalt Corp
Current assignee: Arkema Inc
Priority date: 1979-05-15
Filing date: 1979-05-17
Publication date: 1984-07-31
Also published as: SE427901B; GB2048728B; GB2048728A; SE7904275L; DE2924047A1; NL7904014A

Abstract

i ABSTRACT OF THE DISCLOSURE

A centrifuge for separating a solids-liquid mixture has a rotatable bowl, a conveyor within the bowl and rotatable on a common axis therewith and abrasion-, resistant surface assemblies secured to the conveyor at radially outboard positions.

Description

1~L7~ 4 CENTRIFUGE WITH ABRASION-RESISTANT CONVEYOR

~IR 2359) BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
Thls invention relates to centrifuges for separating solids~ uid mixtures which include a rotatable bowl and an abrasion-res1stant conveyor within the bowl, rotatable on a common axis therewith.
DESCRIPTION OF THE PRIOR ART
Abrasion-resistant conveyors are desirable in centrifuges to prolong centrifuge llfe by retarding 3~`

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~- 2 conveyor wear. In the absence of an abrasion-resistant conveyor, centrifuge life may be unacceptably short due to presence Or abrasive materi.als in the input solids-liquid mixture or ~ue to careless input o~ solids-liquid mixtures for which the centrifuge was not designed and which contain - extraneous materials (tramp metals, large stones, etc.) not anticipated by the centrifuge process engineers. Such abrasive materials cause the centrifuge conveyor to wear quickly.
Early techniques for producing an abrasion-resistant centrifuge conveyor involved melting and fusing a more abrasion-resistant rnaterial, such as a nickel or cobalt alloy, directly onto the conveyor helical flight using an oxy-acetylene gas torch, in a manner similar to welding or brazing.
Later, preformed pieces of abrasi.on-resi.stant nlaterial were mechanically secured, typically with bolts, directly to the conveyor outer edge. (As used herein, the word "mechanical," and variations thereof, when modifying an expression of means ror performing the function of structurally connecting.and fastening two members, denotes those means which function without requiring simultaneous application of heat to both of the two members for the members to be immovably secured one to another:) The britt~e character of the preforrned pieces Or abrasion-resistant material resulted in the pieces cracking and -~L~7~8~4 subsequently failing. (Most known abrasion-resistant materials are quite brittle. Indeed, as a general rule, the more abrasion-resistant is a material, the more brlttle is the material.) The preformed pieces of abrasion-resistant material were unable to withstand stressescreated when extraneous solids in the input solids-liquid mlxture impacted the preformed pieces,of abrasion-resistant material. Loosening and unscrewing of the bolts also resulted in failure of the preformed pieces.
Subsequently, preformed pieces of abrasion-resistant material were bonded directly to the conveyor hellcal flight with adhesiyes. In such applications, it proved impossible to achieve adequate bonding of the abrasion-resistant material pieces to the conveyor due to the diPficulty in properly preparing the conveyor helical fllght surface to receive the adhesive. These adhesive-secured abrasion-resistant material pleces failed too, by loosenlng Prom the conveyor flight, due to stress created , in the adhesive ~oints when extraneous solids in the solids-liquid mixture impacted the preformed pie~es of abrasion-resistant material.
When preformed Pieces of abrasion-resistant material were brazed directly to the helical flight, unsatisfactory results were again obtained--the high heat 25 input over a wide area of the conveyor sometlmes caused serious warping of the conveyor whereupon lt became l~possible to lnsure good brazing adhesion of the preformed ,, _, . . .. . ...................................... .. . . . . . . .. .. .
' , 1~7`~8~4 pieces to the conveyor. Particularly in the cases of centrifuge conveyors operated at high speeds, imperfect braze bonds between the preformed pieces and the conveyor were susceptible to breakage with consequent risk of da~age to surrounding parts. Furthermore, conveyors having preformed pieaes of abrasion-resistant material brazed directly thereto were difficult to repair by brazing réplacement pieces of abrasion-resistant material in place, because such brazing again required application of heat to 10 a broad area of the conveyor. This adversely affected the braze bonds between the conveyor and the pieces of abrasion resistant material proximabe the replacement piece.
Later, abrasion-resistant materials were bonded (by brazing or with adhesives) to intermediate backing tiles 15 formed of metals weldable to the conveyor to form assemblies which were subsequently welded to the conveyor, as disclosed . ln U S. patent 3,764,062. The approach disclosed ln the '062 patent has been quite successful.
Other approaches to providlng an abrasion-resistant 20 ¢onveyor include that of West German Offenlegungsschrift

2,450,337, which discloses lugs secured to the conveyor near the conveyor distal edge, with pieces of abrasion-resistant material contactlng the conveyor and held in interlocking engagement with the lugs by shims interposed between the 25 pieces of abrasion-resistant material and the conveyor or between the pieces of abrasion-resistant material and the lugs. The shims wedge the pieces of abrasion-resistant , . . .

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material against the lugs, preventing the pieces of abrasion-resistant material ~rom moving radially outwardly with respect to the conveyor. In the constructions disclosed in Offenlegungsschrift 2,450,337, the pieces of abrasion-resistant material abut the conveyor and hence are not stress-isolated from the conveyor.
Yet another approach is that of Bird Machine Cornpany, as disclosed in U,S. patent No. 3,977,515, issued August 31st, 1976, for llard-Surfaced 10 Screw Conveyor for Centrifuges, which is to weld a number of machined lugs to the conveyor surPace so that the lugs' sloped lateral ~urfaces, together with the radially extend-ing surface of the conveyor, provide a series of dovetail grooves. Pieces of abrasion-resistant material having 15 tapered lower portions fit in the dovetail grooves and form the abrasion-resistant surface of the conveyor. Ad~acent pieces of abraslon-resistant material alternately have rectangularly and trapezoidally configured upper portions.
When inserted in the grooves these alternating rectangularly 20 and trapezoidally conf~gured pieces wedge against each other, thereby malnta~ning their positions on the conveyor outer edge.
Abrasion-resistant materials used ~n centrifuges include carbides, ceramics, cermets and special metal 25 castlngs, are typically hard and brittle and have very llttle impact strength. (Carbides are the most desirable . material for obtaining the abrasion-resistant property on 1~7~8~4 the conveyor because carbides are more resistant to scratching, grinding and gouging abrasion, and are tougher, than ceramics and other abrasion-resistant materials).
Becau~e of such physical properties, a~rasion-resistant materials generally require support wher~ they are subject to impact loading such as routinely experienced by centrifuge conveyors. One successful approach to providing support when abr~sion-resistant materials are used on centri~uge conveyors is the intermediate backing tile 10 concept disclosed in the '062 patent. The backing tile is pre~erably a material more ductile, and hence more shock-absorbing and ~ore shock-resistant, than the abrasion-resistant material.
Where abrasion-resistant materials are used in 15 centrifuges and are supported by more ductile and therefore ~ore shock-resistant materials, the abrasion-resistant materlal must be tightly secured to the support material, to assure that the support material receives the shock loads experlenced by the abrasion-resistant material. Furthermore, 20 the abrasion-reslstant material, the shock-absorbing support material, the means securing the abrasion-resistant material to the shock-absorbing support material to the conveyor must all withstand high centri~ugal, thermal, corrosive and impact load conditions within centri~uges. ~oreover, when the 25 abrasion-resistant material is secured tothe shock-absorbing support material and when the shock-absorbing support material is secured to the conveyor helical ~light, the means securing ~ .

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these members together should be chosen to avoid creation of residual stresses in the abrasion-resistant material and in the shock absorbing support material. I~ residual stresses, however created, are present, either in any part of the abrasion-resistant material assemblies secured to the conye~or outer edge or in the ~eans used to secure the assemblies together and to the conveyor outer edge, the residual stresses necessarily increase the failure rate of the abrasion-resistant material assemblies and accordingly shorten the conveyor service life.
Also, it is desirable to minimize, and pre~erably eliminate, physical contact between the abrasion-resistant material and the conveyor, to insulate the abrasion-resistant material from the effects of dynamic stresses and strains occuring in the conveyor helical fllght during centrifuge operation.

SUMMARY OF THR INVENTION
To further increase service life of abrasion-resistant conveyors used in centrifuges by minimizing residual stresses in abrasion-resistant material assemblies secured to the conveyor outer edge and by insulating the abrasion-resistant material fr~m dynamic stresses and strains occuring in the conveyor during centrifuge operation, this invention provides centrifuge apparatus with abrasion-resistant material assemblies mounted at the conveyor outeredge ~hich use ~echanical attachments to secure an abrasion-resistant member to a shock-absorbing backing tiie. The .

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mechanical attachments may also be u~ed to secure the shock-abscrbing backing tlle to the conveyor helical rli~ht. The mechanical attachments are preferably made Or corros~on-resistant materials whlch retain their stren~th at high temperatures. Use of such mechanical attachements allows the elimination Or exposed brazed ~olnts between members within the centriruge; the braze material is preferably shielded from the mixture being separated wlthln the centri~uge. Thls is deslrable since some mlxtures ~eparated ln centrl~uges are not only hot but also chemically attack braze materlal.
Thus, in one aspect, the invention provides improved hard surfacing for a helically formed, metal screw conveyor of a centrifuge, said conveyor extending in radial direction along a line between its rotational axis and its distal surface, ~aid conveyor being rotatable transverse to said radial line about said axis, comprising:
a. a preformed backing member made of a metal whlch 1~ weldable to ~aid conveyor, b. a preformed wear-resistant member, c. mean~ securing at least one wear-resistant member to sald backing member to provide a unitary subassembly which i8 sub~equently mounted on the conveyor, w~th male and female formatlon~ on the respect~ve members interengaging At a surface between them whlch, in use, extend~ along a helical line about , ' ~ ' ' .~

7~ ~ 4 - 8a -sa~d axis generally following the dl~tal edge of ~aid conveyor, said formations holding said wear-resistant member against movement in radial direction, d. 6aid wear-resistant member having a di6tal portion extending in radial direction substantially beyond the distal surface of said conveyor, e. said backing member being welded to said conveyor, with said backin~ member extending between 6aid conveyor and said wear-resi~tant member in radial direction substantially beyond the di~tal surface of said conveyor, the distal portion of said wear-resistant member being braced by said conveyor through said backlng member against deflection in ax~al direction toward 6aid conveyor.
In ~nother aspect, the invention provides improved hard surfacing for a helically formed, metal screw conveyor of a centri$uge, said conveyor extending in outward radial dlrection along a line between its rotational axis and its distal ~urface relative to said axis, said conveyor being rotatable tran~verse to ~aid radial line about said axis, com-pri~ings crie~ of prefon~ed backin~ embe~ made of ~et-l whlch 1- weld~ble to ~id conveyor b. weld holding said backing member to said conveyor, with each backing member extendlng in radial dircction ~ub~tantially beyond the di~tal surface Oe ~aid conveyor, F

~, L8;~4 _ - 8b -c. a preformed wear-resistant member, engaging its as~ociated backing member at a contact surface between them whic~, in w e, extends along a helical line about said axis generally following the distal edge of ssid conveyor, d. ~aid wear-resistant member having a distal portion extending in radial direction substantially beyond the distal surface of ~aid conveyor, with ~aid backing member dispo~ed betwcen said conveyor and said wear-resistant member, the di~tal portion of said wear-re~istant member being braced by said conveyor through said backing member against deflection {n axial di~ection towards said conveyor, e. a passaeeway for each associsted wear-resis~ant ~ember and backing member, extending through at lea-~t one o~
~aid ~embers to said contact surface between them, f. and qecuring mean~ extending through each pa~sageway for securing each wear-resistant membe~ to its as~ociated backing member, thereby providlng a unitary assembly of said member~ and holding said wear-resistant mcmber against movement in radial direction, e~ ~aid weld being acces~ible for unitarily replacing ~aid assembly, Br1er Description Or the Drawlngs -F1gure 1 ls a broken side sectlonal v1ew Or a centr1ruge embodyine the lnvention.
~ igure 2 1s a broken sectlonal v1ew taken at arrows 2-2 ln ~lgure 1, w1th the centrlfuge bowl shown ln phantom llnes.

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Flgure 3 ls a sche~atic sectlonal vlew of a pre~erred embodiment o~ an abraslon-resistant conveyor surface assembly e~bodying the invention, taken at arrows

3-3 in Figure 2.
Figure 4 ls a sectlonal view taken at arrow 4-4 in Figure 3.
Flgures 5 and 6 are sectional views of other embodiments o~ abraslon-resistant conveyor surface assemblles ~anl~esting the lnYentlon~ both taken at the positlon denoted by arrows 3-3 in Figure 2.

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8?~4 Figure 7 is a perspective view of an urging means member portion of the abrasion-resistant conveyor surface assembly illustrated in Figure 6.
Figures 8 through 23 are sectional views of other embodiments of abrasion-resistant conveyor surface assemblies manifesting the invention, all taken at the position denoted b~J arrows 3-3 in Figure 2.
Figure 24 is a sectional view taken at arrows 24-24 in Figure 23.
Figures 25 and 26 are sectional views of other embodiments of abrasion-resistant conveyor surface assemblies manifesting the invention, both taken at ~he posltion denoted by arrows 3-3 in Figure 2.
Figure 27 is a broken view of a shock-absorbing lS backlng tile and an abrasion_res~stant member of an abrasion-resistant conveyor surface assembly embodying the invention, lllustrating tile-member interlocking.
Figure 28 ls a sectional view of yet another embodiment of an abrasion-resistant conveyor surface assembly manifesting the invention, taken at the position denoted by arrows 3-3 in Figure 2.
Figure 29 is a broken sectional view of a portion of a backing tile lnto which a rivet, also shown but not i.n section, is swaged in placed to secure the abrasion-resistant member to the backing tlle in the embodimentillustrated in Flgure 17.
Figure 30 is a broken view Or a shock-absorbing backing tile taken at the position denoted by arrows 30-30 1~7~8~4 in Figure 27.
! Figure 3I is a ~iew of an abrasion-resistant member taken at the position denoted by arrows 31-31 in Figure 27.
~igure 32 is a sectional view of yet another embodiment of an abrasion-resistant conveyor assembly manifesting the invention, taken at the posit on denoted by arrows 3-3 in Flgure 2.
Description of the Preferred Embodiments A centrifuge embodying the invention is illustrated in vertical section in ~igure 1, and is designated generally 10. The centrifuge includes a rotatable bowl 12 with a screw conveyor designated generally 14 therewithin, with the screw conveyor rotatable on a com~on axis with the bowl.
During operation the bowl and conveyor are rotated at slightly different speeds by motor and gear means, which have been substantially broken away and are denoted 13.
Bowl 12 rotates on bearings within a housing 15 (which has been largely broken away in ~igure 1), is of frusto-cylindrical configuration and includes a solids dischargeport 17 in the frustum end thereof. Conveyor 14 includes a generally central hub 20 with a helical flight 22 extending radially therefrom. Mounted at the distal edges of flight 22 are a plurality of preferably abutting, and in any case at least closely spaced, abrasion-resistant surface assemblies designated generally 24; relationship of these assemblies 24 to conveyor flight 22 ls shown in Figure 2.
During operation, an input slurry ls introduced ~7~8~4 t~ the centrifuge through ~ feed tube 32 and pass~s through inlet port 18 in hub 20 into space between bowl 12 and conveyor 14. As the bowl and conveyor rotate, centrifugal ~orces cause the heavier, more dense solids to move radially outwardly with respect to the conveyor~ to positions proximate the bowl interior surface 34. The conveyor, rotating at a slightly different speed than the bowl, moves the separated solids towards solids discharge port 17. Separated li-quid moves to a liquid discharge 10 port, not shown.
Referring to Flgure 2, abrasion-resistant surface assemblies 24 are mounted at the distal outer edge of helical flight 22 o~ the conve~or and prolong conveyor life by retarding wéar of the conveyor outer edge. A plurality 15 of assemblles 24 are mounted, preferably in abutting relationship, to present a preferably substantially continuous helical surface at the conveyor outer edge, to convey sollds towards the solids discharge port and to reslst abrasive wear due to extraneous materials in the 20 sollds. Each abrasion-resistant surface assembly 24 is secured together mechanically and preferably is thereafter secured to the conveyor outer edge: mechanical fastening ~eans mlnimize residual stresses in the abrastion-resistant 25 materlal assemblies and insulate the abrasion-resistant materlal in the assemblies from dynamlc stresses and strains which occur in the conveyor during centrifuge operation.

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8~4 Referring to Figure 3, which sets rorth the best mode presently contemplated ~or carrying out the invention, a first embodiment of an abrasion-resistant surface assembly, designated generally 24, ~s secured to a distal edge of conveyor ~light 22, pre~erably by weldments 38, and includes a shock-absorbing backlng tile 26, preferably welded to conveyor flight 22, and an abrasion-resistant member 28 mechanically secured to backing tile 26 by locking bar 36.
The abrasion-resistant me~ber is separated and therefore shock and vibration isolated from the conveyor flight by the backing tile. ~For additional shock-isolation of abrasion-resistant member 28 rrom the conveyor flight, shock-absorbing grout, which acts as a cushion, is preferably provided between the abrasion-resistant member and the backing tile~ The grout ~ills voids which exist between the mating surfaces of the abrasion-resistant member and the backlng tile; such voids necessarily exist since it is not within the scope o~ present technology to machine a perfectly rlat surface. Suitable grouts include pastes, 20 lead foils, etc. The grout is not an indispensable portion of the invention but use of grout is desirable since the grout further enhances the reliability of centrifuges embodylng the invention by providing additional shock-isolation of the abrasion-resistant members from the 25 conveyor flight. Unless otherwise stated hereinbelow, in e~ch embodiment use of grout between the abrasion-resistant member and the shock-absorbing backing tile is understood.) , ~ .

~7~L8~4 Interlocking complementary mating surfaces 27 and 29, of tile 26 and abrasion-resistant member 28 respective-ly, prevent radially outward movement of abrasion-resistant me~ber 28 with respect to conveyor flight 22 during centrifuge operation. Locking bar 36 contacts both the abrasion-resist~nt member and the backing tile at positions remote from c~mplementary mating surfaces 27 and 29 and serves as means for mechanically connecting the abrasion-resistant member to the backing tile. Locking bar 36 10 passes through at least one passageway in backing tile 26 and has a transversely extending section 36~ which abuts a canted inboard lower surface 60 of the abrasion-resistant member, so that bar 36 thereby additionally acts as means for urging the abrasion-resistant member radially outwardly 15 with respect to the conveyor hub (upwardly as viewed in Figure 3) untlI complementary mating surfaces 27 and 29 are tightly engaged. Lower surface 60 is canted towards the conveyor hub as lower surface 60 extends from solids displacing surface 41 of abrasion-resistant member 28.
The canted configuration of lower surface 60 results in the abrasion-resistant member moving radially outwardly, as the locking bar 36 is wedged into place during assembly of the abraslon-resistant surface assembly 24, to engage complementary mating surfaces 27 and 29. Such 25 canted surfaces, and var~ants thereof, are used ln many embodiments illustrated herein to affect engagement of complementary mating surfaces of the backing tiles and the 1~7~8~4 abrasion-resistant members when the abrasion-resistant sur~ace assemblies are produced. (The phrase "canted surface" and variants thereof are used to denote a confi.guration similar to that illustrated in Figure 3, i.e. a surface which slopes towards the conveyor hub as the sur~ace extends in the axial direction with respect to the conyeyor.) Bar 36 is maintained in position by a neck portion 36C, which passes through passageway 140 in backing tile 26, 10 and by a head portion 36A which is deformed against the backing tilè after bar 36 has been positioned in the backing tile passageway. This construction is best shown in Figure

4. Transverse portion 36B of locking bar 36 is preferably interference fitted between canted inboard lower surface 60 15 Of abraslon-resistant member 28 and backing tile 26.
Locking bar head 36A is a deformable material such as steel and, after the locking bar has been inserted into a passage-way through the backing tile, is deformed against backing tile 26 to retain the locking bar urging means in contact 20with the abrasion-resistant member and the backing tile.
The configuration of the abrasion-resistant member and the backing tile which provides interlocking engagement of these two members, preventing radially outward movement of the abrasion-resistant member with 25respect to the conveyor helical fllght as the conveyor rota~es, is beæt shown in Figures 27, 30 and 31. Abrasion-resistant member 28 has a distal surface 40, which is ~-~ distally re~ote with respect to the conveyor hub and faces . - .. .. ...

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radially outwardly wlth respect thereto, a radially extending solids displacing surface 41 whi.ch extends generally outwardly with respect to the conveyor axis of rotation and faces generally towards the solids discharge port, a first rear surface 42 and a second rear surface 43 connected via angularly disposed complementary ~ating surface 29, with the juncture between surface 29 and surface 42 forming a radially outwardly facing cc.nvex (with respect to the conveyor axis of rotation) vertex 55 and with the juncture of surface 29 and surface 43 fDrming a radially outwardly facing convex (with respect to the conveyor axis of rotation2 yertex 44. Solids displacin~
surface 41 may be perpendicular to the conveyor axis of rotation, as shown, or may be at an angle thereto. Shock-abæorblng backing tile 26 has a distal surface 50 facing outward wlth respect to the conveyor axis of rotation, a flrst forward surface 52 and a second forward surface 51 connected to surface 52 by angularly disposed (with respect to the conveyor axis of rotation) complementary mating surface 27. The ~uncture of surfaces 51 and 27 forms an inward facing (with respect to the conveyor axis of rotation) concave vertex 54 while the Juncture of surfaces 27 and 52 forms an inward facing (with respect to the conveyor axis of rotatlon) concave vertex 53.
. Vertices 44, 53, 54 and 55, formed by the ~uncture o~ two surfaces, are curyed llnes, as best shown in Figures 30 and 31. The vertices are denominated as elther concave or convex based on the shape of the line defined by the ~7~8~,~

surface ~unctures. The iunction of surfaces 51 and 27forms vertex 54 which, as seen in Figure 30, is an edge on .-backing tile 26 which is concave with respect to the axis of conveyor rotation; hence vertex 5ll is denominated as "concave"... Juncture o~ surfaces 52 and 27 forms vertex 53 which, as also seen in Figure 30, is an edge on backing tile 26 which is concave with respect to the axis of conveyor rotation and hence vertex 53 is also denominated as "concave". Juncture o~ surfaces 43 and 29 forms vertex 44 while juncture of surfaces 2~ and 42 forms vertex 55;
these vertices both are edges on abrasion-resistant ~e~ber 28 which are "convex" with respect to the conveyor axis of rotation and hence are so denominated.
As abrasion-resistant member 28 is forced into engagement with backing tile 26 by one of the various -mechanical securing means w~t.hin the scope of the invention, such as locking bar 36 illustrated in Figures 3 and 4, abrasion-resistant member 28 moves radially outwardly with respect to the conveyor hub, with abrasion-resistant member second rear surface 42 in sliding contact with backing tile first forward surface 52. As the abrasion-resistant surface assembly is assembled, with the abrasion-resistant member secured ln place, cornplemen.tary mati.ng surfaces 27 and 29 co~e into contact, inwardly faclng concave vertex 54 is received by outwardly facing convex vertex 44 and outwardly f~cing convex vertex 55 is received by inwardly facing concave vertex 53. The angular disposition of complementary :.. ~ .... . ..... . .. ..

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~ating surfaces 27 and 2~, with ~ting vertices 44 and 54 .
posltioned more radially inboard with respect to the conveyor hub than mating vertices 53 and 55, prevents r~d~all~ outward move~ent of the abrasion-resistant member when complementary mating surfaces 27 a~d 29 are in tight engagement and convex vertices 44 and 55 have been received by concave vertices 54 and 53 respectively. This configuration, and variants thereof, is used in many embodiments illustrated herein. Moreover, when the phrase "complementary mating surfaces" and variants thereo~ are used hereinafter, they shall be understood to denote a con~iguration such as illustrated in Figure 27, with equivalents to the complementary mating surfaces 27 and 29 and e~uivalents to the mating pairs of concave and convex vertices 54, 53 and 55, 44 oriented in a similar manner, to prevent radially outward ~ovement of the abrasion-resistant member with respect to the tile as the conveyor rotates and to concomltantly effectively fix the abrasion-resistant member in place with respect to the shock-absorbing backing tile.
Figure 5 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24A
wherein the mechanical connection means for securing shock-absorbing backing tlle 26A and abraslon-resistant member 28A to~ether lncludes a wedge plate 62 secured in place by one or ~ore screws 44 passing through passageway 150 in back~.ng tile 26A and threadably engaging corresponding tapped .. , . _ .. ,,. .... _ ... . ............................ .... , .. .. .. , . .. ... _ .. .. ..... . .. ..... .

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~7~8~4 holes in wedge plate 62. Backing tile 26A is secured to the distal edge of helical flight 22, preferably by weldments 30. Wedge plate 62 abuts canted lower surface 60 o~ abrasion-resistant member 82A. As screw 44 is tightened, it urges wed~e plate 62 to the left as ~iewed in Figure 5; due to the canting o~ surface 60 and of the unnumbered surface of the wedge plate which slidably contacts surface 60, leftward movement of wedge plate 62 urges abrasion-resistant member 28A radially outward with 10 respect to the conveyor hub (upwards as viewed in Figure 5) with complementary mating surfaces 27 and 29 thus being forced into tight engagement. Screw 44 serves as means for mechanically securing the wedge plate urging means to the shock-absorbing backing tile.
Figure 6 illustrates another embodiment of an abracion-resistant surface assembly designated generally 24B wherein the mechanical connection means for securing shock-absorbing backing tile 26B and abrasion-resistant member 28B together includes a wedge plate 62A secured in 20 place by means of two pins 63 which extend from the wedge plate through a passageway 180 in the backing tile and are welded to a rear surface of backing tile 26B. Backing tile 26B is secured to the distal edge of helical flight 22, pre~erably by weldments 30. Wedge plate 62A abuts canted 25 lower surface 60 of abrasion-resistant member 28B. When pins 63 are welded to the rear surface of backing tile 26B, a~ter wedge plate 62A has been forced, with an interference ~~ fit, into the recess formed by sur~ace 60 of the abrasion-8~ ~ .

resistant member and by a notch, unnumbered, in the backing tile, abrasion-resistant member 28B is effectively restrained against movement by wedging action of wedge plate 62A and contact of complementary mating surfaces 27 and 29. The conf-iguration of wedge plate 62A and the curved shape of pins 63, which facilitates welding of the pins to backing tile 26B, are best illustrated in Figure 7.
Figure 8 illustrates another embodiment of an abrasion-resistant surface assembly designated generaliy 24C wherein the mechanical connection means for securing shock-absorbing backing tile 26C and abrasion-resistant member 28C together includes a wedge plate 62~ secured in place by a screw 44A which is threadably engaged with a tapped hole in wedge plate 62B and which passes through both the shock-absorbin~ backing tile 26C and the conveyor helical flight 22. Shock absorbing backing tile 26C is secured to conveyor helical flight 22 by weldments 30 and by compression force exertëd thereon by wedge plate 62B as screw 44A is tightened. Complementary mating surfaces 27 and 29 are provided on abrasion-resistant member 28C and shock-absorbing backing tile 26C respectively, to prevent radially outward movement of the abrasion-resistant member with respect to the conveyor hub. Wedge pl~te 62B fits between canted lower surface 60 of abrasion-resistant member 28C and a shoulder 64 formed in the shock-absorbing backing tile. During assembly, as screw 44A ls threaded into wedge plate 62B, the canted confi~uration of surface 60, .. ~, .. , - . , . .. . . ., .. , . . . .. . .. . . . .. . .. _ . ...

, , ~7~ 8~4 where it abuts wedge plate 62B, effectively urges the complementary mating surfaces o~ the abrasion-resistant me~ber and the shock absorbent backing tile into tight engagement ~y forcing abrasion-resistant member 28C
S vertically upward as yiewed in Figure 8. Although in the embodiment illustrated in Figure 8 the shock-absorbing backing tile has been secured to the conveyor by weldménts 30, in another embodiment holes through the conveyor flight and the shock-absorbing backing tile are tapped (in addition to the hole in wedge plate 62B), so that when screw 44A is threadably engaged through conveyor flight 22~ shock-absorbing backing tile 26C and into wedge plate 6~B, the co~ponent parts of abrasion-resistant assembly 24C are secured together, without the necessity of welding the backing tile to the conveyor helical flight.
Figure 9 illustrates another embodiment of an abraslon-reslstant sur~ace assembly designated generally 24D wherein the mechanical connection for shoc~-absorblng backing tile 26D and abraslon-resistant member 28D is provided by means of dovetail groove-configured cavity cut into shock-absorbing backing tile 26D and a complementally configured dovetail portion of abrasion-resistant member 28D slidably resldent therein. Shock-ab~orbing backing tile 26D is secured to conveyor flight 22, preferably by weldmer.ts 30. The vertex forming the more radially outboard portion o~ the dovetail grooVe, denoted by clrcle A in F'igure 9, is confi~ured substantially as silown in Figure 27 and as described above with re~erence thereto. These complementary ~1.7~8~4 mating surfaces o~ the abrasion-resistant member and the shock-absorbing backing tile effectively prevent movement of the abrasion-resistant member radially outward ~ith respect to the conveyor hub. Canted lower surface 60 of abrasion-resistant ~e~ber 28D diverges from angularly disposed complementary mating surface 29 of the abrasion-resistant member, as one proceeds axially away from the solids displacing surface 41. Similar y, the lower shoulder formed in the shock-absorbing backing tile 26D, which, as viewed in Figure 9, forms the lower portion of the dovetail groove, is configured to complementally receive surface 60 when the abrasion-resistant member is slidably inserted into the shock-absorbing backing tile.
This configuration prevents the abrasion-resistant member from moving, with respect to the backing tile, radially lnwardly towards the conveyor hub. Assembly of the dovetail portion of abrasion-resistant member 28D lnto the dovetail groove portlon of shock-absorbing backlng tlle 26D 1~
preferably performed before backing t~le 26D is welded to the conveyor hellcal flight.
Figure 10 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24E wherein the mechanical connection means for securing shock-absorbing backing tlle 26E and abraslon-reslstant ~ember 28E together ls proylded by a deformable portlon 25, extendlng from shock-absorbing backing tile 26E, which portion is bent a~ainst abrasion-resistant member 28E during , ~7~.8~

assembly to urge the abrasion-resistant member radially outwardly with respect to the conveyor hub and thereby retain the complementary mating surfaces (which are not numbered in Figure 10~ of abrasion-resistant member 28E
and shock-absorbing backing tile 26E in tight contact. The backing tile is undercut~ as s-hown at 190, to make portion 25 more deformable. Shock absorbing backing tile 26E is again secured to conveyor helical flight 22, preferably by weldments 30. The abrasion-resistant surface assembly is depicted in thé assembled condition in Figure 10, with deformable portion 25 bent into place against abrasion-resist;ant member 28E. The position of deformable portion 25 before bending is shown in dotted lines.
Figure 11 illustrates another embodiment of an ab~asiOn-reslstant surface assembly designated generally 24F wherein the mechanical connection means for securing shock-absorbing backing tile 26F and abrasion-resistant ~ember 28~' together includes protruding deformable means 25A7 preferably but not necessarily formed as a portion of backin~ tile 26F. Deformable means 25A preferably extends from a central area of backing tile 26F and resides at least partially in a tapered passageway 29 through abrasion-resistant member 28F. Passageway 29 tapers from a smaller diameter at the tile-member interface to a greater diameter at the abraslon-resistant member~s solids displacing surface 41, When de~ormable means 25A is separated and the portions thereof are urged agalnst the walls of passageway 29, the ~7~ 4 protruding deformable means effectively resists radially outward and radially inward movement of the abrasion-resistant member with respect to the tile. In this embodiment, no complementary mating surfaces (~n the sense that that term is defined with respect to Figure 27) are required; deformable means 25A resident in passageway 29 of the abrasion-reslstant member effectively performs the function of resisting radially outward movement of the abrasion-resistant member as the conveyor rotates. The shock-absorbing backing tile 26~ i~ again secured to the conveyor helical flight, preferably via weldments 30. As a ~ariation, passageway 29 need not extend entirely through abrasion-resistant member 28F; passageway 29 may also be con~igured as a cavity with a closed bottom. As a further ~ariation, the configuration shown in Flgure il may be reversed. In such case, the passage~ay or cavity may be provlded ln the shock-absorbing backing tlle, with a deformable protruding portion for insertion thereinto extending from the abrasion-resistant member.
Figure 12 illustrates another embodiment o~ an abrasion-resistant surface assembly designed generally 24V
wherein the mechanical connection means for securing shock-absorbing backing tile 26V and abrasion-resistant member 28V together includes a rlvet 150, ha~ing a deformable sh~ft portion 152, where the rivet head resides in a counterbore 154 in the abrasion-resistant member. During assembl~, de~ormable portion 152 is urged again~t the walls ._, ....... . . . .. .... . .. .. ...... . . . . .

, 8~4 21~
of passagewa.y 156 in shock-absorbing backing tile 26V, to retain abrasion-resistant member 28V in tight contact against backing tile 26V. Passageway 156 preferably tapers . ~rom a lesser dia~eter at the tile-member ~nterface to a greater diameter at the rear surf~ce of'the shock-absorbing backing tile, remote from the tile-member interface.
Preferably two deformable riyet-counterbore-passageway co~binations arc used to secure the abrasion-resistant member to the shock-absorbing backing tile, to prevent the abrasion-resistant member from rotating with respect to the tile. The shock-absorbing backing tile is secured to the conyeyor helical flight 22, preferably via weldments 30.
Similarly to the embodi~ent illustrated in Figure 11, the e~bodiment lllustrated in Figure 12 does not require co~plem,entary mating surfaces of the type described with reference to Figure 27 to pre~ent movement of the abrasion-res,istant member radially outwardly with respect to the con~eyor htlb. Such ~ovement is prevented by deformable sha~t portion 152 residing within and contacting the walls of passageway 156.
Figure 32 illustrates another embodi.ment of an abraslon-resistant surface assembly designated generally 24G wherein the mechanical connectlon means for shock-absorb-lng backing tile 26G and abrasion-resistant member 28G
includes a rivet 80 secured to abrasion-resistant member 28G, preferably by brazing w,ith the brazing done so that the braze material is entirely between rivet 80 and abrasion-reslstant member 28G so corrosi~e materials being separated 7~ 24 within the centrifuge CAnnot attack the braze material.
The rivet connects the abrasion=resistant member to the shock-absorbing backing tile by yirtue of at least one rivet shaft portion 81 which resides in at least a portion of passageway 82 through backing tile 26~. The shaft portion of the rivet is de~ormed, as shown, or welded against the interior walls of passageway 82 during fabrica-tion of the abrasion-resistant surface assemblieæ.
Alternately, adhesives may be used to secure the shaft portion 81 of rivet 80 to backing tile 26G and may also be used to secure rivet 80 to abrasion-resistant member 28G;
brazing could also ~e used. Backing tile 26G is secured to conyeyor f'light 22, prePerably by weldments 30. Similarly to the embodiment illustrated in Figure 11, the embodiment lllustrated in Figure 32 does not require complementary ~ating surf'aces o~ the type described with ref'erence to F~gure 27 to prevent movement of the abrasion-resistant ~ember radially outwardly with respect to the conveyor hub.
Su¢h movement is prevented by shaf't portion 81 of rivet 80 residing withln and contacting the walls of passageway 82 and by rivet head residing in a counterbore formed in abrasion-resistant member 26G. Moreover, as a variation, passageway 82 need not extend entire]y through shock-absorbir,g backing tile 25G; passageway 82 may also be configured as a ca~ity with a closed bottom.
~ $gure 13 illustrates another embod-lment of an abrasion-resistant sur~ace as&embly designated generally 24H

., , . , " ,. ... ..... . ... . . ... . . .. .. .. . .

8~

whereln the mechanical connection means for securing shoc~-absorbing backin~ tile 26H and abrasion-resistant member 28H together includes a deformable metal sleeve 84 resldent in both a preferably tapered passageway 82 through backing tile 26H and a ~referably tapered passage-way 83 through abrasion-resistant member 28H. Produ~tion of abrasion resistant surface assembly 24H is accomplished by inserting sleeve 84 into passageways 82 and 83, after abrasion-resistant member 28H has been positioned on backing tile 26H so as to align the two passageways at the tile-member interface, whereupon sleeve 84 is expanded against the walls of passageways 82 and 83~by a suitable hand or machine tool. Passageways 82 and 83 each preferably taper from wider mouths at the surfaces of the backing tile and the abrasion-resistant member which are remote the ~uncture of the backing tile and the abrasion-resistant member, to a narrow confluence where the abrasion-resistant member and backing tlle abut one another. Similarly to the embodiment illustrated in F~gure 12, the embodiment illustrated in Flgure 13 does not require complementary mating surfaces of the type described with reference to Figure 27 to prevent movement of the abrasion-resistant member outwardly with respect to the conveyor hub. Such movement læ prevented by the presence of sleeve 84 within and contacting the walls of preferably tapered passageways 82 and 83. Moreover, as a ~ariatlon either or both of passageways 82 ard 84 may be configured as cavities .. , ... , . . . , . . . ,. .... , .. ~. ..

8~4 with closed bottoms and~ instead of sleeve 84, a solid plug, secured in the cavities by an adhesive, may be substituted.
Figure 14 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24I wherein the mechanical connection means for shock-absorbing backing tile 26I and abrasion-resistant member 28I includes a downwardly extending lip nortion 90 of backing tile 26I. The connection means also includes a deformable portion 25, extending from shock-absorbing backing tile 26I, which during assembly is bent against abraslon-resistant member 28I to urge the abrasion-resistant member radially outwardly with respect to the conveyor hub and thereby retain the abrasion-resistant member and the shock-absorbing backing tile in tight contact. Interposed between abrasion-resistant member 28I and shock-absorbing backlng tlle 2~I is a backup insert 92, preferably formed of stainless steel, which fits into vertex 44 and cushions the abrasion-resistant ~ember as it ls urged against lip 90 when tile portion 25 is deformed against canted lower surface 60 of the abrasion-resistant member. Shock-absorbing backing tile 26I is preferably formed from a continuous stainless steel extrusion which is rolled and then secured to conveyor flight 22 by weldments 30.
In the embodiment illustrated in Figure 14, when it is desired to replace a worn or cracked abrasion-resistant ~ember, the abrasion-resistant member is fractured and then ,.. . .

7~8~

removed from between lip 90 and deformable portion 25.
Deformable portion 25 is then bent open, by bending portion 25 downward~y as viewed in Figure 14, whereupon a new abrasion-resistant member is positioned, along with a new backup insert 92, until the vertex of t~e backup insert contacts lip 90, whereupon de~ormable portion 25 is bent against canted lower surfàce 60. In this embodiment, complementary ~ating surfaces of the type illustrated in Figure 27 are not provided; interference of lip 90 with the vertex of insert g2 is sufficient to prevent radially outward movement of abrasion-resistant member 28I with respect to the conveyor hub as the conveyor rotates. As a variation, if the abraslon-resistant member is formed of a sufficientlv malleable material, deformable portion 25 may be ~abricated as an extension of the abrasion-resistant' member with the dePor~a,ble ~ortion.bent against the shock-absorblng backing tlle during assembly of the tile-member combination, to secure the abrasion-reslstant member in place.
~igure 15 illustrates another embodiment of an abrasion-resistant surface assembly designated gen~rally 24J wherein the mechanical connection means for securing shock-absorbi.ng backlng tile 26J' and abrasion-resistant ~ember 28 T together is pr~vided by a hard-surfaced rivet 94, preferably with a countersunk head portion 94A resldent ~n a countersunk passageway 160 through abrasion-resistant member 28~ and wlth a shaft portlon 94B resldent ln a ~ . ~

8~

passageway 162 th~u~h b~ck~ng 26J, with rivet 94 welded to baeklng tile 26~. The countersunk configuration of the head of rivet 94 and the corresponding countersunk p~ss~geway 160 thr~ugh abrasion-resistant member 28J serve to retain the abrasion-resistant ~ember in position once the rivet is welded to the backing tile. Preferably two rivets are used, to prevent the abrasion-resistant member from rotating. The backing tlle ~s again secured to the conveyor ~light 22, preferably b~ weldments 3a. As a variation, either passageway~ 160 or passageway 162 may be configured as a cavity with a closed bottom, with the rivet 94 passing through the remaining passage~ay and into the cavity. The rivet may also be secured with adhesives, or the cavity may be tapped and a machine screw substituted for the rivet.
Figure 16 illustrates another embodiment of an abrasion-reslstant surface assembly designated generally 24K
wherein the mechanical connection means for securlng shock-~bsorbing backing tile 26K and abrasion-resistant member 28K together includes a wedge plate 62K secured in place by welding the wedge plate to ~ shoulder formed in backing tile 26K. Abrasion-resistant member 28K has a canted lower surface 60 abutted by wedge plate 62K. Once wedge plate 62K is positioned and welded in place, the complementary mating sur~aces o~ abrasion-resistant member 28K and backup tile 25 26K e~ectively prevent radially outward movement of the ab~asion-res~stant ~e~ber ~lth respect to the conveyor hub as the conve~or rotates. Shock-absorbing backing tile 26K is _ _ .......... ... . . .... ... . . .. .......... ......

73~.8~4 a~a~n secured to conveyor flight 22, preferably by weldments 30.
~ igure 17 ~llustrates another embodiment of an abrasion-resistant s~r~ace assembly designated generally 24L wherein the ~echanical connection means between shock-absorbing backing tile 26L and abrasion-resistant member 28L includes ~ hard-sur~aced rivet 94L fitted into a cou~terbored passageway 164 in abrasion-resistant member 28L with rive~c 94L pass~ng therethrough and into a passage-way 166 through shock-absorbing backing tile 26L. Rivet ~4L has thereabout an annular depression 95 into which a portion oP shock-absoPbing backing tile 2~L is swaged in order to secure together the co~pone,nt parts of abrasion-res~stant sur~ace assembl~ 24L. Swaging, to ~orce material of the shock-absorbing backing tile into annular ring 95, pr~duces depression 96 ~n the rear surface Or shock-absorbing backing tile 26L~ The shock-absorbing backing tile is secured to conveyor flight 22, preferably vla weldments 30.
Hard-surfaced rivet 94L, at least partially resident in counterbored passageway 164 through abrasion-resistant member 28L and swaged into place within passageway 166 in th,e backing tlle, provides means ~or effectively preventing radially outward movement of the abraslon-resistant member ~ith re~pect to the conveyor hub as the conveyor rotates.
The configuration of shock-absorbing backing tlle 26L after the swaging operation is shown in Figure 29, ~ ~7~8~4 Figure 18 illustrates another e~bodi~ent of an abrasion-resistant surPace asse~bly designated generally 24M wherein the mechanical connection means ~or securing shock-a~soPbing back~n~ t~le 26M and ~brasion-reslstant ~e~ber 28M together ~ncludes a soft, pre~erably stainless steel, bar 196 squeezed into a dovetail-shaped cavity 140 ~or~ed ln abrasion-res~stant ~e~ber 28M with the bar then s~ueezed into a ~assa~eway~ 142 thro~gh backing tile 26M.
~assageway 142 preferabl~ tapers ~r-am a wider mouth, at the surface of backing tlle 26~ which is remote from abrasion-resistant ~ember 28M, to a narrow mouth at the ~uncture of the backing tile and the abrasion-resistant member.
Pre~erably the do~etail-shaped cavity 140 in abrasion-resistant member 28M and the tapered PassagewaY 142 in the lS shock~absorbin~ backing tile are each elongated in the transrerse direction (perpendlcular to the paper as viewed ~n P~gure 18~ S0 that ~he so~t bar, ln addltion to preventing rad~all~Y outward move~ent of the abrasion-resi.stant member .
~th respect to the con~eyor hub when the conveyor is 20 rotating, preYents rotation of the abrasion-resistant ~e~ber ~.about the bar~ with respect to the shock-absorbing b~cking tlle. The shock-absorblng backing tile 26M is pre~erably secured to conYeyor helical ~llght 22 via weld~ent& 30.
~igure 19 illustrates another embodiment of an abrasion-reslstant sur~ace assembly desi.gnated generally 24N wherein the ~echanical c~nnection ~eans between shock-, ~ , ' , 7:~8.~4 absorbing backing tile 26~ and abrasion-resistant ~e~ber 28N ls provided by ~ so~t w~re 98 swaged into a dovetall groove 100 Pormed in the shoçk-absorbing backing tile with so~t wire 98 abutting canted lower surface 60 of abrasion-resistant member 28N. As wire 98 iS swaged into placeagainst canted lower surPace 60, abrasion-resistant member 28N is forced radially outward with respect to the conveyor hub (upward as viewed in ~igure 19~ until complementary ~ating surfaces of the abrasion-resistant member and the shQck-absorbing backing tile, which have not been numbered~
are engaged. Engagement of these surfaces prevents further radiall~ outward move~ent of the abrasion-resistant member With respect to the shock-absorbing backing tlle as the centrlfuge conveyor rotates. The shock-absorbing backing 15 tile 26N is preferably secured to conveyor helical flight 22 vla weldments 30. ln this embodiment, the soft wire has at least a portion ~hi`ch is de~ormable and bent agalnst either the tile or the abrasion-resistant member or both the tile and the abrasion-resistant member, to retain the 20 wi~e in place. The so~t wire acts as means for urging the unnumbered complementary mating surfaces into engagement and contacts both the tile and the abrasion-resistant member.
As a ~ariation, the so~t wire urging means may be mechanically secured to either the tile or the abraslon-25 resistant me~ber. One pre~erred configuration o~ wire 98be~re it is de~ormed ~s shown in dotted lines.

, . ,., .,,,, , ,,, ., ~.,,, ,., . ~ .

8~4 Figure 20 illustra.tes another embodiment of an abrasion-resistant sur~ace assembly designated generally 24P wherein the mechanlcal connection means for securing shock-absorbing backing tile 26P and abrasion-resistant member 28P together includes a clamp member 102 which abuts canted lower sur~ace 60 o~ abrasion-resistant member 28P
and extends through a passageway in shock-absorbing backing tile 26P to the rear sur~ace o~ the tile where clamp member 102 is secured to shock-absorbing backing tile 26P, preferably via weldrnents 104. Once clamp member 102 is secured in place abutting canted lower surface 60 of abrasion-resistant member 28P, the abrasion-resistant member is urged radially outwardly with respect to the conveyor hub, until complementary mating surfaces o~ the abrasion-resistant member and the shock-absorbing backing t~le engage one another. When this occurs, additional ~o~ement of the abrasion-reslstant member radially outward wlth respect to the conveyor hub ls precluded; moreover, abutment of clamp member 102 against canted lower surface 60 prevents movement of the abrasion-resistant member 28P
wlth respect to the shock-absorbing backing tile 26P. The shock-absorbing backing tile is secured to the conveyor helical fl~ght 22, preferably via weldments 30.
Fl~ure 21 illustrates another embodiment of an abrasion-resistant surPace assembly deslgnated generally 24Q wherein the mechanlcal connect~on means between shock-absorbing backing tile 2~Q and abrasion-reslstant member 8~ 4 28Q lncludes an intermediate plate member 106, preferably formed of a relatiuely soft~ shock-absorbing material, secured in place by a screw 108 threaded into plate 106 through a counterbored hole 110 in shock-absorbing backing tile 26Q. Intermediate plate me~ber 106'and abrasion-resistant member 28Q have c~mplementary mating surfaces which, when engaged, prevent radially outward movement o~
abrasion-resistant me~ber 28Q with respect to the helical conveyor hub while the conveyor is rotating. Canted lower sur~ace 60 o~ abrasion-resistant member 28Q is received by a sloped shoulder 112 formed in the shock-absorbing backing t'ile. Shoulder 112, the co~plementary mating surface portion of plate member 106 and first forward surface 52 of shock-absorbing backing tile 26~ together form a dovetail groove within which a dovetail~shaped extended portion of abrasion-res~tant member 28~ resldes. Canted lower &urface 60 and sloped shoulder 112 are complemental mating surfaces and are both disposed at an an~le so that the two sur~aces are closer to the centrifuge conveyor hub at a position more removed from the abrasion-resistant member's sollds displacing surface 41 than at the ~unction of lower surface 60 and solids displaclng surface 41. With this configuration, canted lower surface 60 and sloped shoulder 112, when engaged, effectively resist radially inward movement of the abrasion-resistant member with respect to the tile. Shock-absor'~ing backing tile 26Q is preferably secured to conveyor helical flight 22 ~ia weldments 30.

"

.

: ~ 7~2~

Figure 22 illustrates another embodiment of an abrasion-resistant surPace assembly de.signated generally 24R wherein ~echanical connection means for securing shock-absorbing back~ng tlle 26R and abrasion-resistant member 28R together is ~or~ed by a protruding dovetail portion 114R of abrasion-resistant member 28R, which extends fPom a central area of abrasion-resistant member 28R in a directi~n away ~rom radially extending solids displacing surface 41R. This dovetail-shaped extension ~its- into a dovetail groove 116 formed in shock-absorbing backing tile 26R. The shocking-absorbing backing tile 26R
l& pre~erably secured to conveyor helical flight 22 via weldments 30. When a centrifuge utllizing the embodiment of abrasion-resistant sur~ace assemblies illustrated in 15 Figure 22 i9 asse~bled, the shock-absorbing backing tiles are positioned such that doyetail grooves 116 of ad~acent shock-absorbing backing tiles are aligned. Once the shock-absorbing backlng tiles 26R are so positioned, the abrasion-reslstant members 28R are Pi.t.ted therein, by sliding a 20 P.eries of abrasion-reslstant members 28R into the helically extending dovetail-shaped groove formed by the individual dovetail-shaped grooves 116 in the individual shock-absorbing backing tileæ which have been mounted on the distal edge of the conYeyor helical Plight, The last backing tile inserted 25 into the groo~e must he retained therein by suitable means whi,ch prevents transverse movement of theabrasion-resistant ~e~ber w~th respect to the associated backing tlle. One ~ 7~.~.Z~

suitable means is ~he struG~ure disclosed ln F~gures 23 and 24 and described below, As an alternatiye mode Or assembly of the abrasion-resistant surface asse~bly illustrated in Figure 22, the individual abras~on-resistant members are first inserted into the dovetail-shaped grooves in the correspond-ing individual shock-absorbing backing tiles whereupon the individual backing tiles are welded, one or a few at a , time, to the conveyor helical ~light.
A variation o~ the embodiment illustrated in Figure 22 is provided when a do~etail groove, to directly receive the dovetail-shaped extensions 114R of abrasion resistant members 28R~ is ~ormed in the conveyor helical fllght. This eliminates the need for shock-absorbing backing tlle 26R.
~lgures 23 and 24 illustrate another embodiment of an abrasion-resistant surface assembly designated generally 24S wherein the mechanical connection means for securing s,hock-absorbing backing tile 26S and abrasion-reslstant ~e~ber 28S together is provided by a deformable staple 118 whlch preferably fits entirely around the backing tile 26S, but in any case is at least partially circum~acent to the tile, and has portlons 118S whlch are deformable against abraslon-resistant member 28S, The deformable portions 118S of staple 118 fit into a rectangular cutout 120 in abrasion-reslstant member 28S and effectively restrain the ' abrasion-resistant member against movement away from the .. ~,.. _ ., , . , .. ~ .. . . . .. .... ........ .. .

.

.

8~ ~

shock-absorbin~ backing tile. Shock-absorbing backing tile 26S is secured to the ~onyeyor helical flight, preferably Yia weldments 30. Alt~ough not illustrated, in another embodiment the position o~ staple 118 is reversed with portions 118S deformed against the shock-absorbi.ng backing tile while the main backbone portion 118' of staple 118 abuts the abrasion-resistant member, rather than the shock-absorbing backing tile as illustrated in Figures 23 and 24.
Figure 25 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24T wherein the mechanical connection means for securing shock-absorbing backing t.lle 26T and abrasion-resistant ~ember 28T together includes a double dovetail-shaped insert 122 which is slidabl~ resident ln opposed dovetail grooves 124 and 126 formed in shock-absorbing backing tile 26T and ~br~sion-resistant member 28T respecti~ely. Shock-absorbing backing tlle 26T is secured to conveyor helical flight 22, preferably ~ia weldments 30. Double dovetall--shaped insert.
122 has complementary mating surfaces conflgured for close, slidlng mating with dovetail grooves 124 and 126 to resist radially outward movement of abrasion-resistant member 28T
with respect to shock-absorbing backing tile 26T. Trans-yerse movement of abrasion-reslstant member 28T and insert 122 is prevented by ad~acent, preferably abuttlng, abrasion-resistant me~bers and ad~acent, preferably abutting, doubledoyeta~l-shaped inserts associated with a series of si~ock-absorDlng Dacking tiles secured around the radi.al . ................ . . ........ . . ........... ... . . .. . .

.8~

extremity of conveyor helical flight 22.
Figure 26 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24U wherein the mechanical connection means for securing shock-absorbing backing tile 26~ and abrasion-resistant member 28U together includes an insert 128 which has a dovetail portion 130 slidably resident in do~etail groove 126 in abrasion-resistant member 28U and has a shaft portion 132, with a countersunk head, not numbered, residing 10 in a countersunk, dovetail-shaped opening to a passageway 134 through shock-absorbing backing tile 26U. The backing tile is secured to helical flight 22, preferably via weldments 30.
Figure 28 illustrates another embodiment of an 15 abrasion-resistant surface assembly designated 24V wherein the mechanical connection means for securing shock-absorbing backing tile 26V and abrasion-resistant member 28V together is provided by adhesive disposed between at least a portion of tile 26V and a portion of abrasion-resistant member 28V.
20 The adhesive has been shown in Figure 28 as a layer l90;
when the abrasion-resistant surface assembly is fabricated, the adhesive can be dispersed in any manner and, indeed, the adhesive need not be a layer which compl~tely separatPs the back.ing tile from the abrasion-resistant member as depicted 25 in Figure 28~ The backing tile is secured to the conveyor helical flight 22, preferably via weldments 30. S~itable ~, . ,.

~7~8~.~

adhesives include those members of the epoxy family which are resistant to high temperatures and corrosive mixtures encountered within centrifuges. Of course, when an adhesive is used to bond the abrasion-resistant mem~er to the shock-absorbing backing tile, grout is not normally used betweenthe member and the tile.
Variations and combinations, including re~ersals of parts from those shown, and other modifications fall within the scope of this invention. Particularly, the lO means described herein for securing the various embodiments of the abrasion-resistant member to an associated shock-absorbing backing tile may also be used to secure the shock-absorbing backing tiles to the conveyor helical fliyht, with grout used therebetween as required. Furthermore, it is not 15 necessary that the abrasion-resistant members and the shock-absorbing backing tiles be matched on a one-to-one basis. Several abrasion-resistant members may be mounted on a single shock-absorbing backing tile, if desired. The above particular description is by way of illustration and 20 not of limitation. Changes, omissions, additions, substitu-tions, and/or modifications may be made without departing from the spirit of the invention.

~7~.8~

SUPPLEMENTARY DISCLOSURE
According to another aspect of the present invention, improved hard surfacing is provided wherein subassemblies of back-ing tiles and wear-resistant members are initially subassembled, prior to welding to the conveyor, by the interengagement or inter-locking of each wear-resistant member to its associated backing tile. The backing tile is provided with an undercut groove which receives a dovetail or other male ormation on the wear-resistant member, whereby the member is held against movement in radial direction. A suitable adhesive or grout is preferably applied to the inter-engaging parts and also between the broad, mutually facing surfaces of the backing tile and t~.e wear-resistant member, thus providing a.joint of high manufac~uring and structural quality at the point of interengagement, and also for effective transfer of pressure between the ~road surfaces of the two parts. Thus, dissimilar materials may ~e used in one subassem~led part to achieve improved strength, dura~ility and manufacturing efficiency at satisfactory cost.
In addition, by having the backing tile extend radially between the conveyor and the wear-resistant member, well beyond the distal surface of the conveyor, the distal tip portion of the wear-resistant mem~er is braced against axial deflection.
This reduces the chances that this fragile part of tungsten carbide wi'll be fractured if it strikes a large, hard object in the solids moved by the conveyor.
~,~

8.~9~

The construction of the present invention lends itself well to precision manufacture, i.e. the backing tile may be an investment casting and the wear-resistant member may be formed in a powder metal press.
Figs. 33 to 35 are views of another embo~iMent of the present invention, wherein Fig. 33 is an elevational view of a subassembly, Fig. 34 is a sectional view taken along line34-34 of Fig. 33, and Fig. 35 is an exploded prospective view of the parts in Fig. 34-As shown in Figs. 33 to 35, this preferred orm of the invention provites improved hard surfacing for the helically formed, metal screw conveyor 14 of the centrifuge 10. The asaem61ies 24X of this embodiment each include a backing member or tile 26X, which is weldable to the conveyor flights 22, ant a pair of tungsten car~ide wear-resistant members 28X Calso called abrasion-resistant members herein). The members 28X are su6assembled to their respective backing tiles 26X and bonded together with a heat reacti~e grout or adhesive 300 prior to being mounted on the conveyor, as will be explained.
Each backing tile 26X is preferably made from a high molybdenum, corrosion resistant material such as Hastelloy , a product of the 5tellite Division of Cabot Corporation. Although a backing tile 26X may be machined, it is ideally made as a precision investment casting, a process which accurately produces intricate shapes. A groove or female formation 302 formed in the axially facing surface of the tile 26X, which is undercut aiong its upper edge 304, is an example of a shape which may ~e accurately formed by investment casting.

,, .
T.M.

.

~7~

It is a feature of the present invention that the female formations 302 of the backing tile 26X interengage the male forma-tions 306 of the wear-resistant mem~er 28X along a surface 308 at the undercut edge 304 of the groove, thereby positively and securely holding the member 2~8X against radial movement. This construction also holds the mem6er 28X against tilting motion about undercut edge 304.
When assembled and in use the groove 302 extends about the rotational axis of the conveyor 14, generally following the helical form of the conveyor flights 22 on which the hard surfacing is mounted. When the hard surfacing is in place, neighboring wear resistant members 28X abut at their side edges and thus augment the adhesive 300 in keeping the members 28X assembled to the backing tiles 26X.
As best seen in Fig.34, the wear-resistant member 28X ex-tents in radial direction substantially beyond the distal edge 310 of the conveyor 14. Provision is also made to brace the cantilevered portion of this fragile member, in orter to prevent its fracture in the event of forceful contact with any large, heavy object. Such provision is effected by providing the backing tile or member 26X with a shoulder 312 and a tapered tip 314. The shoulder 312 rests on the distal edge 310 of the conveyor flight 22, thereby providing accurate location and firm support on the conveyor. The backing tile 26X extends between the conveyor flight 22 and the wear-resistant member 28X in radial direction substan-tially beyond the distal edge 310 of the conveyor and then tapers towart the tistal edge 316 of member 28X, As shown, the tistance .. . .

- ~7~8~4 - 43 _ that mem~er extends beyond the backing tile 26X is less than the thickness of the tile 26X. By this arrangement, the member 28X
is braced through the backing tile 26X by the conveyor flight 22 against axial deflection in the tirection of the conveyor flight 22.
By employing a pair or a plurality of wear-resistant members 28X in each assembly 24~, these parts are now so narrow that they are within the mold height of a powder metal compacting press. The members 28X are preferably formed from powderèd metal or ceramic, preferably sintered tungsten carbide. To do so, the beveled edge 318 of the member 28X is formed by placing the forming surfac~ therefor parallel to the direction of die travel.
The backing tiles and the wear-resistant members made as described above are dimensionally accurate and, therefore, a hard surfacing assembly of high quality is produced. When mounted on a conveyor the hard surfacing so made presents a better appearance than many previous hard surfacing techniques, and the li~elihood of flow disturbances due to surface irregularities is minimized.
The adhesive material used for producing a grouted joint 300 by filling the space between mutually facing surfaces may be ~ine mortar, cement, or ceramic material, but epoxy material is preferred, Armstrong*A-701 epoxy material, which is corrosion resistant and heat reactive at 350 to 400F, is a commercially available adhesive satisfactory for this purpose.
The means for securing a backing tile and abrasion-resis-tant member together is sometimes provided by adhesive disposed between at least a portion of tile and a portion of abrasion-resistant member. The adhesive may be shown as a layer, but the adhesive need not be a layer which completely separates the T .M.

- ~7~8~

backing tile from the abrasion-resistant member. The backing tile is secured tO the conveyor helical flight 22, preferably by welds 30. Suitable adhesives include those members of the epoxy family which are resistant to high temperatures and also to corrosive materials in feed delivered for separation to centrifuges.
Variations and combinations, including reversals of parts from those shown, and other modifications fall within the scope of this invention. Furthermore, as in the case of the above embodiment, it is not necessary that the abrasion-resistant members and the shock-absorbing backing tiles be matched on a one-to-one basis, Several abrasion-resistant ~embers may be mounted on a single shock-absorbing backing tile, if desired.
The above particular description is by way of illustration and not of limitation. Changes, omissions, additions, substitutions, and/or modifications may be made without departing from the spirit of the invention.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Improved hard surfacing for a helically formed, metal screw conveyor of a centrifuge, said conveyor extending in radial direction along a line between its rotational axis and its distal surface, said conveyor being rotatable transverse to said radial line about said axis, comprising:
a. a preformed backing member made of a metal which is weldable to said conveyor, b. a preformed wear-resistant member, c. means securing at least one wear-resistant member to said backing member to provide a unitary subassembly which is subsequently mounted on the conveyor, with male and female formations on the respective members interenqaging at a surface between them which, in use, extends along a helical line about said axis generally following the distal edge of said conveyor, said formations holding said wear-resistant member against movement in radial direction, d. said wear-resistant member having a distal portion extending in radial direction substantially beyond the distal surface of said conveyor, e. said backing member being welded to said conveyor, with said backing member extending between said conveyor and said wear-resistant member in radial direction substantially beyond the distal surface of said conveyor, the distal portion of said wear-resistant member being braced by said conveyor through said backing member against deflection in axial direction toward said conveyor.

2. Hard surfacing according to claim 1 wherein said female formations are defined by a groove formed in an axially facing surface portion of said backing member, the outer edge of said groove being undercut for receiving said male formations.

3. Hard surfacing according to claim 2 wherein said formations further include engaging surfaces on the respective members holding said wear-resistant member against tilting movement about said undercut edge.

4. Hard surfacing according to claim 1 wherein said wear-resistant members are made of sintered tungsten carbide.

5. Hard surfacing according to claim 1 wherein said conveyor and said backing tile are each made of a ductile material.

6. Hard surfacing according to claim 1 wherein said male formations are of dovetail configuration.

7. Hard surfacing according to claim 1 wherein said backing member has a shoulder resting on the distal edge of said conveyor, and wherein said backing member tapers from said shoulder to its distal edge, said wear-resistant member ex-tending outwardly beyond said backing member a distance that is less than the thickness of said backing member at its distal edge.

8. Hard surfacing according to claim 1 wherein a plurality of wear-resistant members are bonded to each backing member.

9. Hard surfacing according to claim 1 wherein said male and female formations are of dovetail configuration, said wear-resistant member having a portion thereof extending distally from said male formations.

10. Improved hard surfacing for a helically formed, metal screw conveyor of a centrifuge, said conveyor extending in outward radial direction along a line between its rotational axis and its distal surface relative to said axis, said conveyor being rotatable transverse to said radial line about said axis, comprising:
a. a series of preformed backing member made of a metal which is weldable to said conveyor b. a weld holding said backing member to said conveyor, with each backing member extending in radial direction substantially beyond the distal surface of said conveyor, c. a preformed wear-resistant member, engaging its associated backing member at a contact surface between them which, in use, extends along a helical line about said axis generally following the distal edge of said conveyor, d. said wear-resistant member having a distal portion extending in radial direction substantially beyond the distal surface of said conveyor, with said backing member disposed between said conveyor and said wear-resistant member, the distal portion of said wear-resistant member being braced by said conveyor through said backing member against deflection in axial direction towards said conveyor, e. a passageway for each associated wear-resistant member and backing member, extending through at least one of said members to said contact surface between them, f. and securing means extending through each passageway for securing each wear-resistant member to its associated backing member, thereby providing a unitary assembly of said members and holding said wear-resistant member against movement in radial direction, g. said weld being accessible for unitarily replacing said assembly.

11. Hard surfacing according to claim 10 wherein said securing means is removable, whereby a wear-resistant member optionally may be replaced without removing its associated backing member from said conveyor.

12. Hard surfacing according to claim 10 wherein said passage-way is formed in said wear-resistant member, and said contact surface is on said backing member facing said wear-resistant member, said securing means being formed on said contact surface extending through said passageway and securing the wear-resistant member to the backing member.

13. Hard surfacing according to claim 12 wherein said securing means is a deformable member which is deformable for securing said members together.

14. Hard surfacing according to claim 10 wherein said passage-way is formed in said wear-resistant member and said backing member end extends through said contact surface, said securing means extending through said passageway and securing the wear-resistant member to the backing member.

15. Hard surfacing according to claim 14 wherein said passage-way includes at least one portion which tapers toward said contact surface, and said securing means is deformable on at least one end thereof into engagement with said passageway.

16. Hard surfacing according to claim 15 wherein said securing means is a rivet.

17. Hard surfacing according to claim 10 wherein said passage-way is formed in said backing member, and said contact surface is on said wear-resistant member facing backing member, said securing means extending through said passageway and securing the wear-resistant member to the backing member.

18. Hard surfacing according to claim 17 wherein said securing means has a shank extending through said passageway and a head larger than said shank secured to said wear-resistant member.

19. Hard surfacing according to claim 18 wherein said shank is deformed to secure said wear-resistant member to said backing member.

20. Hard surfacing according to claim 19 wherein said head is metallurgically bonded to said wear-resistant member on the surface thereof facing said contact surface.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

21. Hard surfacing according to claim 1 further including grout between mutually facing, spaced surfaces of said members.

22. Hard surfacing according to claim 1 wherein the means securing the wear-resistant member to said backing member in-cludes an adhesive material.

23. Hard surfacing according to claim 22, wherein said ad-hesive material is heat reactive to form an adhesive bond between said members.

24. Hard surfacing according to claim 1 wherein said female formations are defined by a groove formed in an axially facing surface portion of said backing member, the outer edge of said groove being undercut to receive said male formations, there being a plurality of wear-resistant members sub-assembled to each backing member, said wear-resistant member being made of sintered tungsten carbide, said conveyor and said backing member being made of a ductile material, the means securing the wear-resistant members and the backing member including an adhesive epoxy material, said backing member having a shoulder portion resting on the distal edge of said conveyor.

25. Hard surface according to claim 1 wherein said backing member and said wear-resistant member having comp-lementary mating surfaces configured for resisting radially outward movement of said wear-resistant member with respect to said backing member; and further including mechanical connection means, contacting said wear-resistant member and said backing member, remote from said mating surfaces, for biasing said wear-resistant member and said backing member into engagement.

26. Hard surfacing according to claim 25 wherein said biasing means is disposed between a portion of said wear-resistant member and a portion of said backing member.

27. Hard surfacing according to claim 25 wherein said biasing means has a deformable portion, bent against said wear-resistant member, retaining said biasing means in contact with said wear-resistant member and said backing member.

28. Hard surfacing according to claim 25 further compris-ing means for mechanically securing said biasing means to said backing member.

29. Hard surfacing according to claim 1 wherein said backing member and said wear-resistant member have complementary mating surfaces configured to resist radially outward movement of said wear-resistant member with respect to said backing member and wherein said backing member includes a deformable portion, bent against said wear-resistant member, holding said complementary mating surfaces of said wear-resistant member and said backing member in engagement.