GB2098517A - Centrifuge with abrasion- resistant conveyor - Google Patents

Abstract

A conveyor centrifuge is provided with an improved arrangement for mounting abrasion-resistant edge members on the distal edge of the conveyor flight. The abrasion-resistant edge members 28F are preassembled on backing tiles 26F and secured thereto by means of a mechanical connection 25A/29 e.g. by deformable lugs on the backing tile engaging in a passageway in the edge member, or vice versa, or by means of a rivet or similar mechanical device, the preassembled backing tile and edge member then being secured to the conveyor flight (22) by welds (30). <IMAGE>

Description

SPECIFICATION Centrifuge with abrasion-resistant conveyor This invention relates to centrifuges for separating solids-liquid mixtures which include a rotatable bowl and an abrasion resistant conveyor within the bowl, rotatable on a common axis therewith.

Abrasion-resistant conveyors are desirable in centrifuges to prolong centrifuge life by retarding conveyor wear. In the absence of an abrasionresistant conveyor, centrifuge life may be unacceptably short due to presence of abrasive materials in the input solids-liquid mixture or due to careless input of 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 abrasionresistant centrifuge conveyor involved melting and fusing a more abrasion-resistant material, 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 abrasion-resistant material 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 for 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 brittle character of the preformed pieces of abrasion-resistant material resulted in the pieces cracking and subsequently failing. (Most known abrasion-resistant materials are quite brittle.

Indeed, as a general rule, the more abrasionresistant is a material, the more brittle is the material). The preformed pieces of abrasionresistant material were unable to withstand stresses created when extraneous solids in the input solids-liquid mixture 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 abrasionresistant material were bonded directly to the conveyor helical flight with adhesives. In such applications, it proved impossible to achieve adequate bonding of the abrasion-resistant material pieces of the conveyor due to the difficulty in properly preparing the conveyor helical flight surface to receive the adhesive.

These adhesive-secured abrasion-resistant material pieces failed too, by loosening from the conveyor flight, due to stress created in the adhesive joints when extraneous solids in the solids-liquid mixture impacted the preformed pieces 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 input over a wide area of the conveyor sometimes caused serious warping of the conveyor whereupon it became impossible to insure good brazing adhesion of the preformed 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 damage to surrounding parts. Furthermore, conveyors having preformed pieces of abrasion-resistant material brazed directly thereto were difficult to repair by brazing replacement pieces of abrasion-resistant material in place, because such brazing again required application of heat to a broad area of the conveyor.This adversely affected the braze bonds between the conveyor and the pieces of abrasion resistant material proximate the replacement piece.

Later, abrasion-resistant materials were bonded (by brazing or with adhesives) to intermediate backing tiles formed of metals weldable to the conveyor to form assemblies which were subsequently welded to the conveyor, as disclosed in U.S. Patent 3,764,062. The approach disclosed in the '062 patent has been quite successful.

Other approaches to providing an abrasion resitant conveyor 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 contacting the conveyor and held in interlocking engagement with the lugs by shims interposed between the pieces of abrasionresistant material and the conveyor or between the pieces of abrasion-resistant material and the lugs. The shims wedge the pieces of abrasionresistant material against the lugs, preventing the pieces of abrasion-resistant material from 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 to weld a number of machined lugs to the conveyor surface so that the lugs' sloped lateral surfaces, together with the radially extending surface of the conveyor, provides a series of dovetail grooves. Pieces of abrasion-resistant material having tapered lower portions fit in the dovetail grooves and form the abrasion-resistant surface of the conveyor.

Adjacent pieces of abrasion-resistant material alternately have rectangularly and trapezoidally configured upper portions. When inserted in the grooves these alternating rectangularly and trapezoidally configured pieces wedge against each other, thereby maintaining their positions on the conveyor outer edge.

Abrasion-resistant materials used in centrifuges include carbides, ceramics, cermets and special metal castings, are typically hard and brittle and have very little impact strength.

(Carbides are the most desirable material for obtaining the abrasion-resistant property on the conveyor because carbides are more resistant to scratching, grinding and gouging abrasion, and are tougher, than ceramics and other abrasionresistant materials). Because of such physical properties, abrasion-resistant materials generally require support where they are subject to impact loading such as routinely experienced by centrifuge conveyors. One successful approach to providing support when abrasion-resistant materials are used on centrifuge conveyors is the intermediate backing tile concept disclosed in the '062 patent. The backing tile is preferably a material more ductile, and hence more shockabsorbing and more shock-resistant, than the abrasion-resistant material.

Where abrasion-resistant materials are used in centrifuges and are supported by more ductile and therefore more shock-resistant materials, the abrasion-resistant material must be tightly secured to the support material, to assure that the support material receives the shock loads experienced by the abrasion-resistant material.

Furthermore, the abrasion-resistant 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 centrifugal, thermal, corrosive and impact load conditions within centrifuge. Moreover, when the abrasion-resistant material is secured to the shock-absorbing support material and when the shock-absorbing support material is secured to the conveyor helical flight, the means securing these members together should be chosen to avoid creation of residual stresses in the abrasion-resistant material and in the shock absorbing support material.If residual stresses, however created, are present, either in any part of the abrasionresistant material assemblies secured to the conveyor outer edge or in the means 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 preferably eliminate, physical contact between the abrasionresistant material and the conveyor, to insulate the abrasion-resistant material from the effects of dynamic stresses and strains occurring in the conveyor helical flight during centrifuge operation.

Accordingly, the present invention provides a conveyor centrifuge, the distal edge of the helical flight of the conveyor of which is provided with abrasion resistant edge members, said abrasion resistant edge members being mounted on intermediate backing tiles welded to said flight and projecting radially from the distal edge thereof towards the internal wall of the centrifuge bowl, with said edge members having a distal edge aligned with or projecting a short distance beyond the distal edge of the backing tile so that said backing tiles serve to stiffen and brace the edge members against bending, wherein said edge members and said backing tiles are secured together in face to face relation by a mechanical connection comprising a securing member integral with, or otherwise secured to, one or other of said edge member and said backing tile and having a connecting portion extending substantially perpendicularly from said one or other member or tile and engaging in a passageway formed in the other of said member or tile, thereby to hold the two together.

The invention is further described with reference to the accompanying drawings, in which Figure 1 is a broken side sectional view of a centrifuge embodying the invention.

Figure 2 is a broken sectional view taken at arrows 2-2 in Figure 1, with the centrifuge bowl shown in phantom lines.

Figures 3 to 9 are sectional views of various embodiments of abrasion-resistant conveyor surface assemblies manifesting the invention, all taken at the position denoted by arrows 3-3 in Figure 2.

Figure 10 is a broken sectional view of a portion of a backing tile into which a rivet, also shown but not in section, is swaged in place to secure the abrasion-resistant member to the backing tile in the embodiment illustrated in Figure 7.

Figure 11 is a sectional view of yet another embodiment of an abrasion-resistant conveyor assembly manifesting the invention, taken at the position denoted by arrows 3-3 in Figure 2.

Figure 12 is a broken view of a shock absorbing backing tile and an abrasion resistant member with interlocking surfaces such as may be used in accordance with this invention.

Figure 13 is a broken view of a shock absorbing tile taken on line 30-30 in Figure 12.

Figure 14 is a view of an abrasion-resistant member taken at the position denoted by arrows 31-31 in Figure 12.

A centrifuge embodying the invention is illustrated in vertical section in Figure 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 common 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 1 5 (which has been largely broken away in Figure 1), is of frusto-cylindrical configuration and includes a solids discharge port 1 7 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 is shown in Figure 2.

During operation, an input slurry is introduced to the centrifuge through a feed tube 32 and passes through inlet port 18 in hub 20 into space between bowl 12 and conveyor 14. As the bowl and conveyor rotate, centrifugal forces 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 1 7. Separated liquid moves to a liquid discharge port, not shown.

Referring to Figure 2, abrasion-resistant surface assemblies 24 are mounted at the distal outer edge of helical flight 22 of the conveyor and prolong conveyor life by retarding wear of the conveyor outer edge. A plurality of assemblies 24 are mounted, preferably in abutting relationship, to present a preferably substantially continuous helical surface at the conveyor outer edge, to convey solids towards the solids discharge port and to resist abrasive wear due to extraneous materials in the solids.Each abrasion-resistant surface assembly 24 is secured together mechanically and preferably is thereafter secured to the conveyor outer edge: mechanical fastening means minimize residual stresses in the abrasionresistant material assemblies and insulate the abrasion-resistant material in the assemblies from dynamic stresses and strains which occur in the conveyor during centrifuge operation.

Referring to Figure 3 this illustrates a first embodiment of an abrasion-resistant surface assembly designated generally 24F and incorporating a mechanical connection means for securing the shock-absorbing backing tile 26F and the abrasion-resistant member 28F together in accordance with this invention. This connection means includes protruding deformable means 25A, preferably but not necessarily formed as a portion of backing 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 abrasionresistant member 28F. Passageway 29 tapers from a small diameter at the tile-member interface to a greater diameter at the abrasion-resistant member's solids displacing surface 41.When deformable means 25A is separated and the portions thereof are urged against the walls of passageway 29, the protruding deformable means effectively resists radially outward and radially inward movement of the abrasionresistant member with respect to the tile. In this embodiment, no complementary mating surfaces (in the sense that that term is defined with respect to Figure 12) are required; deformable means 25A resident in passageway 29 of the abrasion-resistant member effectively performs the function of resisting radially outward movement of the abrasion-resistant member as the conveyor rotates. The shock-absorbing backing tile 26F is secured to the conveyor helical flight via weldments 30. As a further variation, the configuration shown in Figure 3 may be reversed.

In such case; the passageway or cavity may be provided in the shock-absorbing backing tile, with a deformable protruding portion for insertion thereinto extending from the abrasion-resistant member.

Figure 4 illustrates another embodiment of 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 rivet 150, having a deformable shaft portion 152, where the rivet head resides in a counterbore 1 54 in the abrasion-resistant member. During assembly, deformable portion 1 52 is urged against the walls of the passageway 1 56 in shock-absorbing backing tile 26V, to retain abrasion-resistant member 28V in tight contact against backing tile 26V. Passageway 1 56 preferably tapers from a lesser diameter at the tile-member of passageway 156 in shockabsorbing backing tile 26V, to retain abrasionresistant member 28V in tight contact against backing tile 26V.Passageway 1 56 preferably tapers from a lesser diameter at the tile-member interface to a greater diameter at the rear surface of the shock-absorbing backing tile, remote from the tile-member interface. Preferably two deformable rivet-counterbore-passageway combinations are used to secure the abrasionresistant member to the shock-absorbing backing tile, to prevent the abrasion-resistant member from rotating with respect to the tile. The shockabsorbing backing tile is secured to the conveyor helical flight 22 via weldments 30. Similarly to the embodiment illustrated in Figure 3, the embodiment illustrated in Figure 4 does not require complementary mating surfaces of the type described with reference to Figure 12 to prevent movement of the abrasion-resistant member radially outwardly with respect to the conveyor hub.Such movement is prevented to deformable shaft portion 1 52 residing within and contacting the walls of passageway 1 56.

Figure 11 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24G wherein the mechanical connection means for shock-absorbing backing tile 26G and abrasion-resistant member 28G includes a rivet 80 secured to abrasion-resistant member 28G, preferably by brazing with the brazing done so that the braze material is entirely between rivet 80 and abrasion-resistant member 28G so corrosive material being separated within the centrifuge cannot attack the braze material.

The rivet connects the abrasion-resistant member to the shock-absorbing backing tile by virtue of at least one rivet shaft portion 81 which resides in at least a portion of passageway 82 through backing tile 26G. The shaft portion of the rivet is deformed, as shown, or welded against the interior walls of passageway 82 during fabrication of the abrasion-resistant surface assemblies.

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 be used. Backing tile 26G is secured to conveyor flight 22 by weldments 30. Similarly to the embodiment illustrated in Figure 3, the embodiment illustrated in Figure 11 does not require complementary mating surfaces of the type described with reference to Figure 12 to prevent movement of the abrasion-resistant member radially outwardly with respect to the conveyor hub. Such movement is prevented by shaft portion 81 of rivet 80 residing within 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 entirely through shock-absorbing backing tile 26G; passageway 82 may also be configured as a cavity with a closed bottom.

Figure 5 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24H wherein the mechanical connection means for securing shock-absorbing backing tile 26H and abrasion-resistant member 28H together includes a deformable metal sleeve 84 resident in both a preferably tapered passageway 82 through backing tile 26H and a preferably tapered passageway 83 through abrasion-resistant member 28H. Production 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 juncture of the backing tile and the abrasion-resistant member, to a narrow confluence where the abrasion-resistant member and backing tile abut one another. Similarly to the embodiment illustrated in Figure 4, the embodiment illustrated in Figure 5 does not require complementary mating surfaces of the type described with reference to Figure 12 to prevent movement of the abrasion-resistant member outwardly with respect to the conveyor hub. Such movement is prevented by the presence of sleeve 84 within and contacting the walls of preferably tapered passageways 82 and 83.

Figure 6 illustrates another embodiments of an abrasion-resistant surface assembly designated generally 24J wherein the mechanical connection means for securing shock-absorbing backing tile 26J and abrasion-resistant member 28J together is provided by a hard-surfaced rivet 94, preferably with a countersunk head portion 94A resident in a countersunk passageway 1 60 through abrasionresistant member 28J and with a shaft portion 94B; resident in a passageway 1 62 through backing 26J, with rivet 94 welded to backing tile 26J. The countersunk configuration of the head of rivet 94 and the corresponding countersunk passageway 160 through abrasion-resistant member 28J serve to retain the abrasion-resistant member 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 tile is again secured to the conveyor flight 22 by weldments 30. 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 passageway 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 7 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24L wherein the mechanical connection means between shock-absorbing backing tile 26L and abrasion-resistant member 28L includes a hard-surfaced rivet 94L fitted into a counterbored passageway 1 64 in abrasion-resistant member 28L with rivet 94L passing therethrough and into a passageway 166 through shock-absorbing backing tile 26L. Rivet 94L has thereabout an annular depression 95 into which a portion of shock-absorbing backing tile 26L is swaged in order to secure together the component parts of abrasion-resistant surface assembly 24L.

Swaging, to force material of the shock-absorbing backing tile into annular ring 95, produces depression 96 in the rear surface of shockabsorbing backing tile 26L. The shock-absorbing backing tile is secured to conveyor flight 22, preferably via weldments 30. Hard-surfaced rivet 94L, at least partially resident in counterbored passageway 1 64 through abrasion-resistant member 28L and swaged into place within passageway 166 in the backing tile, provides means for effectively preventing radially outward movement of the abrasion-resistant member with respect to the conveyor hub as the conveyor rotates. The configuration of shock-absorbing backing tile 26L after the swaging operation is shown in Figure 10.

Figure 8 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24M wherein the mechanical connection means for securing shock-absorbing backing tile 26M and abrasion-resistant member 28M together includes a soft, preferably stainless steel, bar 1 96 squeezed into a dovetail-shaped cavity 140 formed in abrasion-resistant member 28M with the bar then squeezed into a passageway 142 through backing tile 26M.

Passageway 142 preferably tapers from a wider mouth, at the surface of backing tile 26M which is remote from abrasion-resistant member 28M, to a narrow mouth at the juncture of the backing tile and the abrasion-resistant member. Preferably the dovertail-shaped cavity 140 in abrasion resistant member 28M and the tapered passageway 142 in the shock-absorbing backing tile are each elongated in the transverse direction (perpendicular to the paper as viewed in Figure 8) so that the soft bar, in addition to preventing radially outward movement of the abrasionresistant member with respect to the conveyor hub when the conveyor is rotating, prevents rotation of the abrasion-resistant member (about the bar) with respect to the shock-absorbing backing tile. The shock-absorbing backing tile 26M is secured to conveyor helical flight 22 via weldments 30.

Figure 9 illustrates another embodiment of an abrasion-resistant surface assembly designated generally 24U wherein the mechanical connection means for securing shock-absorbing backing tile 26U and abrasion-resistant member 28U together includes an insert 128 which has a dovetail portion 130 slidably resident in dovetail groove 126 in abrasion-resistant member 28U and has a shaft portion 132 with a countersunk head, not numbered, residing 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 via weldments 30.

In any of the embodiments of this invention a layer of shock-absorbing grout, which acts as a cushion may be provided between the abrasionresistant member and the backing tile. The grout fills voids which exist between the mating surfaces of the abrasion resistant member and the backing tile; such voids necessarily exist since it is not within the scope of present technology to machine a perfectly flat surface. Suitable grouts include pastes, 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 embodying the invention by providing additional shock-isolation of the abrasion-resistant members from the conveyor flight.

Also in accordance with the invention, the interlocking surfaces may be provided on the abrasion-resistant member and the backing tile to prevent radially outward movement of the abrasion-resistant member with respect to the conveyor helical flight as the conveyor rotates although, as already indicated, such interlocking surfaces are not necessarily required. Suitable interlocking surfaces which may be provided are shown in Figures 12, 13 and 14.As will be seen the abrasion resistant member 28 has a distal surface 40, which is distally remote with respect to the conveyor hub and faces radially outwardly with respect thereto, a radially extending solids displacing surface 41 which 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 mating surface 29, with the juncture between surface 29 and surface 42 forming a radially outwardly facing convex (with respect to the conveyor axis of rotation) vertex 55 and with the juncture of surface 29 and surface 43 forming a radially outwardly facing convex (with respect to the conveyor axis of rotation) vertex 44.Solids displacing surface 41 may be perpendicular to the conveyor axis of rotation, as shown, or may be at an angle thereto. Shockabsorbing backing tile 26 has a distal surface 50 facing outward with respect to the conveyor axis of rotation, a first 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 juncture of surfaces 51 and 27 forms an inward facing (with respect to the conveyor axis of rotation) concave vertex 54 while the juncture of surface 27 and 52 forms an inward facing (with respect to the conveyor axis of rotation) concave vertex 53.

Vertices 44, 53, 54 and 55, formed by the juncture of two surfaces, are curved lines, as best shown in Figures 30 and 31. The vertices are denominated as their concave or convex based on the shape of the line defined by the surface junctures. The junction of surfaces 51 and 27 forms vertex 54 which, as seen in Figure 13, is an edge on backing tile 26 which is concave with respect to the axis of conveyor rotation; hence vertex 54 is denominated as "concave". Juncture of surfaces 52 and 27 forms vertex 53 which, as also seen in Figure 13, 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 of surfaces 43 and 29 forms vertex 44 while juncture of surfaces 29 and 42 forms vertex 55; these vertices both are edges on abrasion-resistant member 28 which are "convex" with respect to the conveyor axis of rotation and hence are so denominated.

As the abrasion-resistant surface assembly is assembled, with the abrasion-resistant member secured in place, complementary mating surfaces 27 and 29 come into contact, inwardly facing concave vertex 54 is received by outwardly facing convex vertex 44 and outwardly facing convex vertex 55 is received by inwardly facing concave vertex 53. The angular disposition of complementary mating surfaces 27 and 29, with mating vertices 44 and 54 positioned more radially inboard with respect to the conveyor hub than mating vertices 53 and 55, prevents radially outward movement of the abrasion-resistant member when complementary mating surfaces 27 and 29 are in tight engagement and convex vertices 44 and 55 have been received by concave 54 and 53 respectively. This configuration and variants thereof, may be used in any embodiments illustrated herein.Moreover, when the phrase "complementary mating surfaces" and variants thereof are used hereinafter, they shall be understood to denote a configuration such as illustrated in Figure 12, with equivalents to the complementary mating surfaces 27 and 29 and equivalents to the mating pairs of concave and convex vertices 54, 53 and 55, 44 oriented in a similar manner, to prevent radially outward movement of the abrasionresistant member with respect to the tile as the conveyor rotates and to concomitantly effectively fix the abrasion-resistant member in place with respect to the shock-absorbing backing tile.

Variations and combination, including reversals of parts from those shown, and other modifications fall within the scope of this invention. Particutarly, the 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 flight, with grout used therebetween as required. Furthermore, 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 members may be mounted on a single shockabsorbing backing tile, if desired. The above particular description is by way of illustration and not of limitation.

Claims (11)

Claims

1. A conveyor centrifuge, the distal edge of the helical flight of the conveyor of which is provided with abrasion-resistant edge members, said abrasion resistant edge members being mounted on intermediate backing tiles welded to said flight and projecting radially from the distal edge thereof towards the internal wall of the centrifuge bowl, with said edge members having a distal edge aligned with or projecting a short distance beyond the distal edge of the backing tile so that said backing tiles serve to stiffen and brace the edge members against bending, wherein said edge members and said backing tiles are secured together in face to face relation by a mechanical connection comprising a securing member integral with, or otherwise secured to, one or other of said edge member and said backing tile and having a connecting portion extending substantially perpendicularly from said one or other member or tile and engaging in a passageway formed in the other of said member or tile, thereby to hold the two together.

2. A centrifuge according to claim 1, wherein the securing member comprises a deformable lug or lugs integrally formed on one or other of said edge member of said backing tile, said lug or lugs engaging in a passageway formed in the other of said edge member or backing tile and deformed into engagement therewith to hold the edge member and tile together.

3. A centrifuge according to claim 1, wherein the securing member is a rivet having a head seating in a recess in one or other of said edge member or said backing tile and having a shaft extending into and secured in a passageway extending through the other of said edge member or backing tile.

4. A centrifuge according to claim 3, wherein the shaft of said rivet is secured in said passageway by welding.

5. A centrifuge according to claim 3, wherein the shaft of said rivet is secured in said passageway by deforming the nose of the shaft after insertion into said passageway so as to prevent subsequent withdrawal.

6. A centrifuge according to claim 1 , wherein both said backing tile and said edge member have passageways therethrough in alignment one with the other and the securing~member comprise an elongate member the opposite ends of which engage in and are securely retained by said aligned passageways.

7. A centrifuge according to claim 6, wherein the opposite ends of the securing member are deformed into retaining engagement with each of said aligned passageways.

8. A centrifuge according to any one of the preceding claims wherein said backing tiles and edge members further having mating abutment surfaces comprising a radially inwardly directed abutment surface on the backing tile, said abutment surface lying generally in the direction of a helix subscribed about the conveyor axis, and a corresponding radially outwardly directed arcuate abutment surface on the edge member, said mating surfaces resisting movement of the abrasion-resistant members relative to the backing tile in a direction radially outward from the conveyor axis.

9. A conveyor centrifuge according to claim 8, wherein said mating abutment surfaces on said backing tile and said edge member are correspondingly undercut surfaces.

10. A centrifuge according to any one of the preceding claims wherein a film of grout or adhesive is provided between the superposed surfaces of the abrasion resistant members and the backing tiles.

11. A conveyor centrifuge according to claim 1, substantially as hereinbefore described with reference to the accompanying drawings.