U.S. patent application number 11/965146 was filed with the patent office on 2008-05-01 for elevating conveyor.
Invention is credited to Peter John Olds.
Application Number | 20080099310 11/965146 |
Document ID | / |
Family ID | 30005064 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080099310 |
Kind Code |
A1 |
Olds; Peter John |
May 1, 2008 |
ELEVATING CONVEYOR
Abstract
An elevating conveyor for flowable material comprises an inlet
(14) and an outlet (20) at opposite ends of a tubular barrel (1)
surrounding a helical elevating member (2). Elevating member (2) is
restrained against rotation about a longitudinal axis and tubular
barrel (1) is co-axially rotated about elevating member (2) by a
drive mechanism (16).
Inventors: |
Olds; Peter John;
(Maryborough, AU) |
Correspondence
Address: |
DALY, CROWLEY, MOFFORD & DURKEE, LLP
SUITE 301A
354A TURNPIKE STREET
CANTON
MA
02021-2714
US
|
Family ID: |
30005064 |
Appl. No.: |
11/965146 |
Filed: |
December 27, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10547292 |
Jul 21, 2005 |
7314131 |
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PCT/AU04/00091 |
Jan 27, 2004 |
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11965146 |
Dec 27, 2007 |
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Current U.S.
Class: |
198/671 |
Current CPC
Class: |
B65G 2201/045 20130101;
B65G 33/20 20130101; B65G 65/463 20130101 |
Class at
Publication: |
198/671 |
International
Class: |
B65G 33/20 20060101
B65G033/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2003 |
AU |
2003900362 |
Claims
1. An elongate elevating conveyor for flowable materials, said
conveyor comprising:-- an inlet and an outlet; a helical elevating
member supported, in use, with a longitudinal axis in a
substantially upright position, said elevating member being secured
at least one end to a support structure, said elevating member
being secured against rotation about said longitudinal axis; a
tubular barrel surrounding said elevating member and rotatable
coaxially therewith said tubular barrel being rotatably journalled
in bearing members spaced intermediate opposite ends of said
barrel, said bearing members being secured to said support
structure; and, a drive mechanism to rotatably drive said tubular
barrel, said conveyor characterized in that a predefined working
clearance between a cylindrical volume occupied by said helical
elevating member and an inner surface of said tubular barrel is
such that, in use, a stable layer of flowable material is formed
against said inner surface of said tubular barrel, said stable
layer urging a mass of flowable material within said barrel along
an upward helical path by frictional engagement between said stable
layer and said mass of flowable material.
Description
FIELD OF THE INVENTION
[0001] This invention is concerned with methods and apparatus for
the conveyance or elevation of flowable materials from a base
position to an elevated position.
[0002] The invention is concerned particularly although not
exclusively with upright helical conveyor mechanisms wherein a
helical elevator member functions as a stator and, a tubular
housing surrounding the helical elevator mechanism functions as a
rotor.
BACKGROUND OF THE INVENTION
[0003] There are many forms of conveyor mechanisms for transporting
materials from one position to another and the choice of conveyor
mechanism is affected by many factors including the physical nature
of material to be conveyed, the horizontal and/or vertical
distances to be traversed, capital cost, on-going maintenance costs
and the like.
[0004] While there is a wide range of conveyors available for
horizontal or slightly inclined transportation paths, there are
relatively few forms of conveyor available for elevation of
materials along an upright transportation path falling within the
range of from, say, 45.degree. to a horizontal datum to 90.degree.
or perpendicular to a horizontal datum. Even then, the suitability
of a conveyor or elevating system is often dictated by the nature
of the materials to be handled. Where floor space requirements are
not critical, tubular screw augers may be used to elevate flowable
particulate materials such as cereal grains through an angle of
from about 30 to 40 degrees and a multiplicity of screw augers
located on vertically spaced landings is required to elevate the
grain over any significant height. Where floor space is more
critical, bucket elevators are often employed. For very fine or low
mass particulate materials, pneumatic conveyors may be used to good
effect.
[0005] Several major shortcomings are apparent in conventional
materials elevators utilized in the field of foodstuffs handling.
Many foodstuffs such as potato crisps are highly fragile while
others such as soy beans, freeze dried coffee granules are easily
damaged even with the gentlest handling. Pneumatic conveying of
aggressively abrasive particulate material such as foundry sands
gives rise to very high maintenance costs due to wear, particularly
in the region of conveyor ducts, where a change of direction is
required.
[0006] Generally speaking, the difficulties encountered in the
elevation of flowable materials has led to custom designed
conveyor/elevator systems or otherwise an unsatisfactory compromise
with apparatus not particularly suited to the materials being
transported or the environment in which the elevating apparatus is
required to operate.
[0007] Conventional screw augers, even when inclined at an angle of
less than 45.degree. to a horizontal datum are known to damage many
particulate materials due to pressurization in the auger barrel
with the accumulation of finely crushed detritus making it
difficult to maintain cleanliness. Vertical or near vertical
operation of a conventional screw auger appears to be unknown
because of extreme pressure build up within the auger barrel due to
friction and this in turn leads to excessive power requirements.
Depending upon the clearance between the screw flight and the inner
wall of the auger barrel, backflow will occur with larger
clearances while crushing of the particulate material with
excessive screw and barrel wear will occur with small
clearances.
[0008] For any long screw augers, it is necessary to support the
rotatable screw with "hanger" bearings at spaced intervals within
the auger tube. A hanger bearing is located centrally of the auger
tube by radially extending brackets and the bearings each support
the auger shaft in a region of discontinuity in the auger flight
necessitating a "back pressure" to feed material across the
discontinuity gap to the next auger flight.
[0009] It is known to operate a screw auger type conveyor wherein
the barrel is rotatable, at least partially relative to the auger
screw.
[0010] U.S. Pat. No. 3,349,894 describes an inclined screw auger
elevator for frangible materials such as potato or corn chips. The
screw comprises a cupped helical flight with upturned outer edges
and the tubular conveyor barrel rotates with the screw. Very
careful attention must be paid to feed rates and screw rotational
speed to avoid crushing of the frangible particulate material in
use.
[0011] U.S. Pat. No. 3,279,592 describes a horizontal screw auger
conveyor wherein the auger screw and the tubular barrel rotate
together to avoid wear from relative rotation therebetween. A
plurality of apertures along the barrel permit distribution of the
particulate material to a multiplicity of delivery stations along
the path of the conveyor.
[0012] U.S. Pat. No. 3,031,064 describes a horizontal screw auger
conveyor having a split barrel wherein each barrel portion is
selectively rotatable coaxially with the screw auger and each
barrel is adapted to distribute particulate material at spaced
delivery stations via hinged closures manually movable between a
closed position and an open position under the influence of gravity
by rotating a respective tube portion through about
180.degree..
[0013] Australian Patent Application 24574/77 discloses a
horizontal screw auger having a helical slot formed in the tubular
barrel. The tubular barrel is able to be rotationally oscillated in
the same direction of rotation as the screw or counter thereto to
selectively deposit material in an elongate delivery station
beneath the auger barrel.
[0014] International Publication WO 95/26310 describes a feeder
tube conveyor in the form of a horizontal screw auger with a
plurality of inlet openings spaced helically about the portion of
the tubular screw barrel located within a hopper of difficult to
feed fibrous material. Associated with each inlet opening is an
activator to disturb the fibrous material in the hopper above the
screw barrel to prevent bridging of the material in the hopper. The
auger barrel is rotatable with the screw but its direction of
rotation may be reversed to clear blockages in the inlet
openings.
[0015] German Patent Application DE 3 708 208 is concerned with a
filling apparatus for thick pasty materials wherein a feed hopper
and a tubular barrel are caused to rotate independently relative to
a vertical stationary screw auger. The upper flight of the screw
auger is shaped as a sweep to urge material into the mouth of the
barrel and to flow downwardly therethrough.
[0016] U.S. Pat. No. 4,077,527 discloses an apparatus for
horizontally transporting and dispensing a very fine particulate
material wherein a conduit rotates about a stationary coil spring
located within the conduit. The spring is fastened externally of a
discharge end of the conduit and the inlet comprises a plurality of
apertures in the conduit. The inlet communicates directly with a
pressure fed hopper to receive a powdered feed of less than 50
micron particle size. The inlet end of the spring is allowed to
float to permit axial extension of the spring under load.
[0017] It is an aim of the present invention to overcome or
ameliorate at least some of the disadvantages associated with prior
art elevating conveyors for flowable materials. As used herein, the
expression "flowable materials" includes particulate materials,
slurries, viscous liquids and the like but is not limited
thereto.
SUMMARY OF THE INVENTION
[0018] Accordingly to one aspect of the invention there is provided
an elongate elevating conveyor for flowable materials, said
conveyor comprising:--
[0019] an inlet and an outlet;
[0020] a helical elevating member supported, in use, with a
longitudinal axis in a substantially upright position, said
elevating member being secured at least one end to a support
structure, said elevating member being secured against rotation
about said longitudinal axis;
[0021] a tubular barrel surrounding said elevating member and
rotatable coaxially therewith said tubular barrel being rotatably
journalled in bearing members spaced intermediate opposite ends of
said barrel, said bearing members being secured to said support
structure; and,
[0022] a drive mechanism to rotatably drive said tubular barrel,
said conveyor characterized in that a predefined working clearance
between a cylindrical volume occupied by said helical elevating
member and an inner surface of said tubular barrel is such that, in
use, a stable layer of flowable material is formed against said
inner surface of said tubular barrel, said stable layer urging a
mass of flowable material within said barrel along an upward
helical path by frictional engagement between said stable layer and
said mass of flowable material.
[0023] Suitably, the inlet may be located adjacent a lower end of
said tubular barrel.
[0024] Alternatively, the inlet may be located adjacent a top end
of a hollow tubular support shaft for said elevating member.
[0025] If required, a conveyor feed mechanism may be associated
with said inlet to feed flowable material to said elevating
conveyor at a predetermined rate.
[0026] Preferably, said conveyor feed mechanism comprises at least
one sweep member mounted on said tubular barrel for rotation
therewith, said sweep member projecting outwardly from an outer
wall surface of said tubular barrel.
[0027] If required, one or more apertures may be formed in said
tubular barrel adjacent a respective at least one sweep member.
[0028] Said at least one sweep member may be adjustable to
selectively increase or decrease a swept volume as said tubular
barrel rotates.
[0029] The sweep member may be adjustable in length.
[0030] Alternatively, the sweep member may be adjustable in
width.
[0031] Preferably, the sweep member is angularly adjustable
relative to said outer wall surface of said tubular barrel.
[0032] If required, at least portion of said sweep member may be
resiliently flexible.
[0033] Suitably, a feed hopper surrounds an inlet located adjacent
a lower end of said tubular barrel.
[0034] The tubular barrel may be rotatably journalled in spaced
bearing members secured to a support structure.
[0035] Preferably, said support structure comprises a frame.
[0036] Suitably, said elevating member is secured at opposite ends
of said frame member.
[0037] If required, said elevating member may be adjustably mounted
in same frame to permit, in use, tension to be applied to said
elevating member in the direction of the longitudinal axis of said
elevating member.
[0038] The helical elevating member may comprise a helically wound
rod-like member with a central hollow cylindrical space extending
over a longitudinal axis of said helically wound member.
[0039] Alternatively, the helical elevating member may comprise a
helically wound ribbon blade.
[0040] The helical elevating member may comprise a central
shaft.
[0041] If required, the central shaft may comprise a hollow
shaft.
[0042] Suitably, said hollow shaft is adapted, in use, to permit
circulation of a working fluid therethrough to permit said
elevating conveyor to function as a heat exchanger for fluid
materials being conveyed therein.
[0043] Preferably, a working clearance between a cylindrical volume
occupied by said helical elevating member and an inner surface of
said tubular barrel is greater than a mean particle diameter of
packable flowable particulate material.
[0044] Alternatively, a working clearance between a cylindrical
volume occupied by said helical elevating member and an inner
surface of said tubular barrel is less than a mean particle
diameter of non-packable material.
[0045] The drive mechanism may comprise a drive motor mounted on
said support structure, said drive motor being drivably engageable
with a drive transmission mechanism coupled to said tubular
barrel.
[0046] Preferably, a collector is positioned about said outlet to
collect flowable material issuing from said outlet.
[0047] According to another aspect of the invention there is
provided a method for elevation of a flowable material, said method
comprising the steps of:--
[0048] feeding a flowable material to an inlet of an elevating
conveyor comprising a stationary helical elevating member
surrounded by a rotatable tubular barrel with a predefined working
clearance between said helical elevating member and an inner
surface of said barrel; and,
[0049] rotating said barrel at a speed sufficient to urge said
flowable material towards said inner wall of said barrel to form a
stable layer of flowable material thereon, whereby a mass of
flowable material within said tubular barrel is urged upwardly
along a helical path by frictional engagement between said mass of
flowable material and said stable layer.
[0050] If required, said tubular barrel may be rotated at a speed
sufficient to form a static layer of flowable material in a
clearance space between a cylindrical volume occupied by said
helical elevating member and an inner surface of said tubular
barrel.
[0051] Preferably, fluid material is elevated in said conveyor as a
hollow cylindrical mass.
[0052] If required, flowable material is fed to said inlet at a
rate to substantially occupy a free volume within a cylindrical
volume occupied by said elevating member during rotation of said
tubular barrel.
[0053] Alternatively, flowable material is fed to said inlet at a
rate to occupy less than a free volume within a cylindrical volume
occupied by said elevating member during rotation of said tubular
member.
[0054] Suitably, a feed rate of said flowable material to said
inlet is selectively varied by changing the configuration of a
sweep member mounted on said tubular barrel.
[0055] The configuration of said sweep member may be changed by
altering the dimensions of said sweep member.
[0056] Alternatively, the configuration of said sweep member may be
changed by altering an angular disposition of said sweep member
relative to an outer surface of said tubular barrel.
[0057] If required, the feed rate of said flowable material to said
inlet is selectively variable by altering a rotational speed of
said tubular barrel.
[0058] The flowable material may be introduced into an inlet at an
upper end of a hollow central shaft of said elevating member to
flow countercurrent to a mass of flowable material being elevated
within said conveyor.
[0059] Suitably, a flowable material containing a liquid and
particulate solids mixture may be separated by subjecting the
mixture to a centripetal force as the tubular barrel rotates and
collecting liquid from a region adjacent a longitudinal axis of
said elevating member and collecting condensed solids from a region
adjacent an outer edge of the helical elevating member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] In order that the invention may be more fully understood and
put into practical effect, reference will now be made to preferred
embodiments illustrated in the accompanying drawings in
which:--
[0061] FIG. 1 shows schematically a cross-sectional side elevation
of an elevating conveyor according to the invention;
[0062] FIG. 2 shows schematically an alternative configuration of
the invention;
[0063] FIG. 3 shows yet another embodiment of the invention;
[0064] FIG. 4 shows an adaptation of one embodiment of the
invention;
[0065] FIG. 5 shows a further adaptation of an embodiment of the
invention; and
[0066] FIG. 6 shows a still further embodiment of the
invention.
[0067] For the sake of clarity, like reference numerals are
employed for like features in the drawings where appropriate.
[0068] Throughout this specification and claims which follow,
unless the context requires otherwise, the word "comprise", and
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated integer or group of integers or
steps but not the exclusion of any other integer or group of
integers.
DETAILED DESCRIPTION OF THE INVENTION
[0069] In FIG. 1, the elevating conveyor comprises a tubular barrel
1 surrounding a helical elevating member 2 comprising a central
shaft 3 with a helical ribbon blade flight 4 extending about the
circumference of shaft 3. Shaft 3 is fixedly mounted via bracket 5a
to a base 5 of a support structure in the form of a frame 6. Shaft
3 is also fixedly mounted to a head member 7 of frame 6 via a
threaded shaft 8 and is tensionable by means of threaded nut 9.
Another threaded nut 10 functions as a lock nut when the shaft 3
has been tensioned to a required value.
[0070] The base of frame 6 is located in a hopper 11 containing a
packable particulate material 12 such as sharp foundry casting
sand. A sweep member 13 projects outwardly from an outer surface of
tubular barrel 1 adjacent an opening 14 (shown in phantom) therein
and extends forwardly in a direction of rotation of barrel 1 at an
angular disposition to the outer surface of barrel 1.
[0071] Barrel 1 is rotatably journalled in bearings 15 mounted on
the support structure frame 6 and is rotatably driven by an
electric drive motor 16 coupled via a drive transmission comprising
pulleys 17,18 and drive belts 19. Suitably, drive motor 16 is also
supported by frame 6.
[0072] Located at the upper outlet end 20 of tubular barrel 1 is a
collector 21 to collect particulate material as it emerges from
outlet end 20. A chute 22 is connected to collector 21 to direct
collected material to a storage hopper or the like (not shown).
[0073] In use, with helical elevating member 2 mounted as a
stationary member with tubular barrel 1 rotating thereabout, sand
in hopper 11 is swept into the space between shaft 3 and the inner
wall 23 of tubular barrel 1 and, under the influence of centripetal
force, is urged outwardly against the inner wall of tubular barrel
1.
[0074] Initially the mass of sand resting against the inner wall 23
rotates with the rotating barrel 1 until it engages on upper
surface of an upwardly tapering helical flight 4. Continued
rotation of barrel 1 urges a mass of sand to follow an upright path
guided by flight 4 as a result of frictional engagement between the
mass of sand and a thin layer of sand urged against the inner wall
23, the thickness of the thin layer corresponding to a clearance
between the outer edge of flight 4 and inner wall 23.
[0075] At the feed end of the barrel 1, sweep 13 continues to
introduce sand into the space between shaft 3 and inner wall 23
such that sand progresses upwardly through barrel 1 until it
emerges at the outlet 20 and is thrown radially into collector 21
by flight 4 as the barrel 1 rotates.
[0076] Whilst not wishing to be bound by any particular hypothesis,
the distinction between an elevating conveyor according to the
present invention and a vertically oriented conventional screw
auger with a stationary barrel and rotating screw is considered to
arise from a substantially reduced level of friction between
relatively moving components in the present invention.
[0077] In a conventional screw auger, reliance is made upon keeping
the angle of inclination of the barrel below about 45.degree. C. to
ensure that the quantity of flowable particulate material between
successive auger flights does not fill the tube diametrically. It
is known that when a conventional screw auger is oriented
vertically particulate material tends to move as a rotating
cylinder. Where the screw clearance is smaller than the mean
particle diameter, compaction of the particulate material occurs
with a resultant increase in frictional load on the auger screw,
increased power requirement, increased wear in both the screw and
barrel and compression damage to frangible non-packing particulate
materials such as cereal grains and the like. With packing
particulate materials such as foundry sands, a vertically oriented
screw auger usually will jam. Where there is a greater screw
clearance, backflow will occur with resultant efficiency losses and
damage to frangible particulate materials.
[0078] The present invention on the other hand exhibits differing
phenomena depending mainly upon the nature of particulate materials
to be conveyed along an upright path.
[0079] With a packing particulate material such as foundry sand, it
is noted that where the flight clearance is greater than the mean
particle size, a stable layer of sand is formed against the inner
barrel wall due to centripetal force. As the barrel rotates, this
layer of sand provides a limited frictional engagement with a
cylindrical or hollow cylindrical mass of sand which readily shears
at the edge of the helical flight so that as the effective column
of sand moves upwardly in a helical path, the only compacting force
which is applied to it is the relatively small centripetal force.
Depending upon the nature of the particulate material being fed,
the feed rate of the material and the rotational rate of the
barrel, it is possible that the boundary between the layer rotating
with the barrel and the mass of material moving upwardly could be
quite sharply defined with a large difference in relative
rotational speeds or alternatively the boundary could be less well
defined with a region of material having a rotational velocity
gradient from a relatively slow radially inner region to a greater
rotational velocity in a radially outer region.
[0080] For larger packing particles having a much greater mean
diameter or for non-packing particles such as substantially
spherical objects, a flight clearance less than the mean particle
size may be preferred.
[0081] In the elevation of relatively fine particulate matter such
as foundry sand, it is noted that regardless of the speed of
rotation of the tubular barrel there is no tendency for the helical
elevator member to "whip" as does a rotating auger in a
conventional screw auger. This is considered to arise due to a
self-centreing action due to the build up of a layer of sand on the
inner wall of the tube. As a consequence, wear which might
otherwise be caused by engagement between the helical elevating
member and the rotating tube is substantially eliminated. This also
permits very tall elevating conveyors to be constructed.
[0082] FIG. 2 shows an alternative embodiment of the invention
wherein the helical elevating member comprises a helically wound
coil 30 of rectangular steel bar which may be tensioned by
screw-threaded shafts 31,32 secured in upper and lower frame mounts
33,34 respectively. For the sake of clarity the support frame
structure and barrel drive mechanisms have been omitted. It readily
will be apparent to a person skilled in the art that the frame
member 6 as shown in FIG. 1 is not essential as all of the
components of the elevating conveyors may be supported, for
example, on a structural wall or the like.
[0083] FIG. 3 shows schematically an alternative embodiment of the
invention wherein the central shaft 3 of the helical elevating
member has a hollow bore 40 extending therethrough.
[0084] In this embodiment the apparatus may be employed to form a
slurry or paste from dry particulate materials and a liquid. For
example, a dry mix of sand, cement and aggregate may be contained
in a lower feed hopper (not shown). As tubular barrel 1 rotates,
water is metered into the open mouth 42 of tubular shaft 3
whereupon it emerges in the base of the base of the hopper (not
shown) and mixes with the dry ingredients as they are conveyed
upwardly under the influence of rotating tube 1. Such an embodiment
may have application in the preparation of food products requiring
gentle mixing without compression.
[0085] FIG. 4 shows a modification to the apparatus of FIG. 3
wherein the elevator member 2 is adapted to function as a heat
exchanger.
[0086] In order to convey some viscous liquids such as molasses, it
can be advantageous to elevate the temperature of the molasses even
by 5.degree. to 10.degree. C. to reduce its viscosity. As shown, a
viscous liquid such as molasses is supplied to hopper 11 via
conduit 50 and a level 51 of liquid is maintained by any suitable
flow metering means (not shown) wherein the level 51 is maintained
above the lower end of tubular barrel 1. In the configuration
shown, a sweep is not required as in the configurations of FIGS. 1
to 3.
[0087] Molasses flows into the region between the shaft 3 and the
inner wall of barrel 1 and due to its viscosity, a frictional drag
is applied by the inner wall of barrel 1 as it rotates thereby
urging the molasses to follow a helical elevating path. To assist
in maintaining flow, the inner bore 40 of tubular shaft 3 is
coupled via conduits 52,53 to a heater or heat exchange device 54
and a circulating pump 55 to circulate a heated working fluid
through elevating member 2. As shown by arrows 56, the direction of
circulation of the working fluid is concurrent although, if
required, a countercurrent flow may readily be obtained. As the
heated working fluid circulates through elevating member 2 it
functions as a heat exchanger as the molasses or other viscous
liquid ascends the helical conveyor path to reduce the viscosity of
the liquid to a desired degree. When the reduced viscosity liquid
emerges from the top of tubular barrel 1, it is collected by
collector 21 and directed to a storage tank or the like (not shown)
by outlet chute 22.
[0088] It readily will be apparent to a person skilled in the art
that the elevator conveyor of FIG. 4 may be adapted for heat
treatment or cooking of foodstuffs whilst elevating the foodstuff
materials to a predetermined height.
[0089] FIG. 5 shows yet another adaptation of the invention for
separation of solids from liquids or for dewatering of
slurries.
[0090] In FIG. 5, a slurry is delivered to feed hopper 11 via a
conduit 50 and a separate liquid take-off conduit 60 communicates
with a hollow bore 40 of tubular shaft 3 which has a plurality of
apertures 61 in the wall thereof communicating with the hollow bore
40.
[0091] As tubular barrel 1 rotates, the slurry is swept into the
feed inlet region 14 of the elevating conveyor 2 by sweep 13 and
under the influence of centripetal force, the particulate solids
suspended in the slurry migrate outwardly towards the inner wall of
barrel 1 as the slurry is elevated about a helical pathway.
Supernatant liquid, substantially free of solids, is drawn off via
conduit 60 while the dewatered solids material is collected in
collector 21 and directed to a storage hopper or the like (not
shown).
[0092] In both of the embodiments of FIGS. 4 and 5, it will be
noted that as elevator member 2 remains stationary, rotary gland
joints are not required for fluid communication with the central
bore of shaft 3.
[0093] FIG. 6 shows yet another modification of the apparatus shown
in FIG. 1.
[0094] As shown in FIG. 6, the helical elevating member 2 having a
helical ribbon blade flight 4 terminates at its lower end at a
position just above the sweep 13 and feed inlet region 14 adjacent
thereto. A feed guide 70 in the form of a hollow frusted cone is
secured to the lower end of shaft 3 by grub screws 70a and also to
base 5 whereby, in use, larger diameter articles such as macadamia
nuts 71 are swept upwardly over the surface of feed guide 70 into
the region of the elevator flight 4 to avoid crushing of the
macadamia nuts between the sweep 13 and the flight 4 which might
otherwise occur with the configuration of FIG. 1 as the barrel 1
rotates. Sweep 13 may include a flexible rubber or polymeric tip 72
to avoid damage to the nuts in hopper 11 as barrel 1 rotates.
Alternatively, the sweep 13 may be comprised entirely of a flexible
or resiliently flexible polymeric material.
[0095] Also mounted on barrel 1 are agitator fingers 73 supported
on brackets 74. Agitator fingers 73 prevent clumping or bridging of
feed material near the feed inlet region 14.
[0096] Mounted on base 5 are spaced parallel projections 74 which
engage flats 75 secured on shaft 3 to prevent rotation of shaft 3
due to torsional forces applied thereto by flowable material while
barrel 1 rotates. A threaded nut 76 secures the lower end of shaft
3 in base 5.
[0097] The following examples illustrate the wide range of flowable
materials which may be elevated with an elevating conveyor
according to the invention.
EXAMPLE 1
[0098] In this example, an elevating conveyor having the general
configuration of that shown in FIG. 1 was employed. The barrel was
5 metres tall and comprised a 100 mm o.d. stainless steel tube with
a 1.6 mm wall thickness. The barrel was driven by a 2 kW variable
speed electric motor via a 4:1 multiple V-belt drive
transmission.
[0099] The helical elevating member comprised an 82 mm diameter
ribbon blade helix with a 70 mm pitch supported on a 22 mm centre
core.
[0100] With a feedstock of wheat and an initial barrel rotation
speed of 10 r.p.m., wheat emerged from the outlet chute after the
barrel filled. The rotational speed was increased stepwise up to a
maximum of 320 r.p.m. at which a delivery rate of slightly in
excess of 6 tonnes per hour was measured. It was noted the delivery
rate of the wheat from the slowest to fastest rotational speeds was
approximately proportional to rotational speeds.
[0101] In a second part of this test, the elevating conveyor was
inclined at 45.degree. substantially identical delivery rates were
achieved for wheat grains over the same rotational rate spectrum of
from 10 r.p.m. to 320 r.p.m.
[0102] Interestingly, without adjusting the tension in the support
core for the helical flight, it was noted that when the barrel
initially began rotation without any wheat contained therein, the
helical flight was heard to be scraping on the inside wall of the
barrel. Once the barrel began to fill with wheat, the scraping
noise rapidly diminished as the barrel filled with wheat thereby
supporting the hypothesis that under normal operating conditions,
the helical flight was subjected to a self-centreing action.
EXAMPLE 2
[0103] The elevating conveyor described in EXAMPLE 1 was then used
in a vertical orientation with dry foundry sand as a feedstock.
[0104] Once again, it was found that the delivery rate of sand
increased more or less proportionately to rotational speed from an
initial rate of 10 r.p.m. to what appeared to be an optimal speed
of 320 r.p.m. at which the delivery rate was determined to be 6
tonnes of sand per hour.
[0105] By monitoring the current load for the 2 kW drive motor
another interesting phenomenon was identified. From an initial
rotational speed of 10 r.p.m. to about 100-120 r.p.m., current load
increased approximately proportionately to rotational speed from
about 6-7 amps up to about 13 amps. As rotational speed was
increased up to about 200 r.p.m., the current load remained
substantially unchanged at about 13 amps, but as rotational speed
was increased gradually from about 200 r.p.m. to 320 r.p.m., the
current load appeared to decrease proportionately to rotational
speed increase from about 13 amps back to about 6-7 amps at 320
r.p.m.
[0106] It is believed that the phenomenon observed was due to the
fact that at slow speeds, the entire internal volume of the barrel
is filled with flowable material. As rotational speed of the barrel
is increased, it is believed that a boundary layer is formed on the
inside surface of the barrel under the influence of centripetal
force whereby there is no longer a substantial frictional force
exerted between the column of flowable material in the barrel and
the inside wall surface of the barrel. It is considered that there
exists a region between the rotating boundary layer of flowable
material and the inner "core" material where the material flows
over itself.
[0107] It is also considered that, depending upon the nature of the
flowable material, optimum delivery rates with minimized power
requirements are achieved when the flowable material does not
completely fill the interior volume of the barrel. The rate of feed
at optimised barrel rotation speeds may be adjusted by adjusting
the "bite" of the sweep members adjacent the inlet ports of the
barrel or by changing the number of sweep member/inlet port
combinations.
[0108] Utilizing a prototype elevating conveyor of the type shown
in FIG. 2 of the accompanying drawings, it was noted that at an
optimum delivery rate for wheat grains, it was possible to insert a
timber rod down the hollow central region of the helical flight
without sensing the presence of granular material. At lower
delivery rates, the presence of granular material in the hollow
central region was clearly felt.
EXAMPLE 3
[0109] The apparatus of EXAMPLE 1 was modified by replacing the 82
mm diameter by 70 mm pitch ribbon blade helical elevating member
with a 76 mm diameter by 70 mm pitch ribbon blade helical elevating
member supported on a 22 mm central core.
[0110] In this test, the feedstock was dried soybeans having an
average particle size in the range of from 6 to 8 mm. Optimum
delivery rate of 4.5 tonnes per hour was achieved at a rotational
speed of 320 r.p.m.
[0111] Even although soybeans are notoriously fragile and easily
damaged in fairly gentle conveyors such as bucket conveyors, no
damage was noted after soybeans were cycled continuously through
the elevating conveyor for over two hours.
EXAMPLE 4
[0112] The apparatus of FIG. 6 was employed to convey non-shelled
macadamia nuts, typically having a diameter in the range of from 19
mm to 29 mm.
[0113] The barrel comprised a 100 mm o.d. stainless steel tube with
a 1.6 mm wall thickness and a helical ribbon blade flight of 82 mm
in diameter with a pitch of 70 mm supported on a 22 mm central core
was located within the barrel. Unlike the apparatus shown in FIG.
1, the lower end of the helical ribbon blade flight was mounted on
the top of a frusto-conical feed guide about 75 mm in height and
having a base diameter of 100 mm. With this configuration, the
upper part of the frusto-conical feed guide is located within the
rotating barrel adjacent the inlet ports in the barrel whereby the
lower end of the helical flight is just above the inlet port and
the top of the guide. In this manner, the nuts feed upwardly into
the region of the helical flight without the risk of being crushed
by being wedged against the circumferential edge of the flight as
the sweep rotates thereabout.
[0114] Unlike finer particulate materials, no boundary layer of
nuts is formed on the inner wall of the rotating barrel, however
the delivery rate appeared to be directly proportional to the
rotational speed of the barrel. Similarly, it was noted over the
speed range employed that there was a negligible change in power
consumption suggesting that the nuts simply rolled up the helical
pathway under the influence of friction with the inner wall of the
barrel.
[0115] For shelled macadamia nuts, the smaller 76 mm diameter auger
of EXAMPLE 3 was employed and no damage to the nut kernels was
noted even after cycling the kernels through the elevating conveyor
for extended periods.
[0116] Cracked macadamia shells, which are commonly used as a
furnace fuel in a co-generation plant, also were handled with ease
notwithstanding the highly irregular shaped particles having a
particle size in the range of from about 3 mm to 10 mm. For this
test, the 76 mm diameter helical elevating member of EXAMPLE 3 was
again used, and it was noted that a boundary layer of shell
particles formed against the inner wall of the barrel as it
rotated.
[0117] The above specific examples demonstrate the versatility of
the elevating conveyor according to the invention. To date,
successful trials have been conducted on fine and coarse sand (both
wet and dry), a wide range of cereal grains, soybeans, navy beans,
steel shot (1.8 mm), flour, breadcrumbs, macadamia nuts (shelled
and unshelled as well as cracked shells), coffee beans,
freeze-dried coffee granules, molasses, ammonium nitrate prills
(3-4 mm diameter), bauxite granules (6-8 mm diameter), blanched
peanut kernels and powdered hydrated lime.
[0118] A significant advantage of the present invention is the lack
of damage shown when highly frangible particulate materials such as
freeze-dried coffee granules, soybeans and whole nut kernels are
elevated in a conveyor according to the invention. Moreover, for
very fine particulate materials such as hydrated lime, flour and
the like, the apparatus according to the invention is characterized
by an almost complete absence of airborne dust in the discharge
chute during operation.
[0119] It readily will be apparent to a person skilled in the art
that many modifications and variations may be made to the various
aspects of the invention without departing from the spirit and
scope thereof.
[0120] For example, for certain applications, depending upon the
abrasiveness of the flowable material being handled, the tubular
barrel and/or the helical elevating member may be fabricated from
plastics material, or if made from metal, these metal components
may be coated with wear resistant and/or corrosion resistant
coatings such as TEFLON (Trade Mark) or the like. Similarly, the
pitch of the helix may be variable along its length, either
increasing or decreasing from bottom to top depending upon the
nature of the material being conveyed.
* * * * *