Note: Descriptions are shown in the official language in which they were submitted.
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~`
i~7~82'~
~- 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
, . . .
- :ç~
1~ 8~'~
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
~ .
.
1~7~8~
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
.
1~7~8?~4
B
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.
'
' '
8c
1 ~ 7~
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.
F
.
:
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
11
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.
.
., ,
.
8~4
12
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
13
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
. - .. .. ...
~ 7~8~,~
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
:.. ~ .... . ..... . .. ..
8?~,~
17
~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
.. , . _ .. ,,. .... _ ... . ............................ .... , .. .. .. , . .. ... _ .. .. ..... . .. ..... .
.. , .~
~7~8~4
18
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~ ~ .
19
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
21
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~
22
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
23
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~
26
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
27
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~
28
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~
29
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
31
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
33
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
34
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~
36
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~ ~
37
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~
38
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~.~
39
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~
- 40 -
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~
- 41 -
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~
- 42 -
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~
- 44 -
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.
