Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02559626 1999-O1-27
IMPROVED CONVEYOR TUBE AND DISTRIBUTION
HEADER FOR AIR CONVEYOR
This is a divisional application of application Serial Number 2,260,439 filed
January 27, 1999.
FIELD OF THE INVENTION
This invention relates to improved apparatus for the delivery of particulate
material, which apparatus is specially adapted for use with an agricultural
pneumatic
conveyance device such as an air seeder.
BACKGROUND OF THE INVENTION
Seed and fertiliser products are distributed from a hopper or aircart to a
delivery tool via a pneumatic conveyor tube. The travel path is initially
substantially
lateral over the first part of the distance from the supply hopper to the
delivery tool.
Then, the conveyor tube is provided with a substantially vertical orientation
and its
upper end connects with a flow dividing header. The header directs the air-
entrained
product into a number of conduits connected with the ground openers and
delivery
tools. In some cases the conduits of the header communicate with secondary
headers
before distributing the product to individual delivery tools. It is important
to achieve
an even distribution of product to each conduit from the header to apply equal
amounts of product in each furrow. An uneven distribution results in
inefficient soil
and fertiliser usage, and affects the uniformity of the produce growth. A term
commonly used is the coefficient of variation (CV) which is a measure of the
uniformity of distribution across the distribution apparatus. A CV of 15% or
greater is
deemed unacceptable. A CV below 5% is considered very good.
The variation in distribution is effected by a number of factors. For
instance,
grain travelling in the conveyor tube tends to travel along the inside
surface,
particularly following any bend for redirection to vertical. The outlet of the
conveyor
tube delivers the material to a spreader in the distribution header which
separates the
material into channels arranged circumferentially about the header. Thus, if
the
product material is more heavily concentrated at
CA 02559626 1999-O1-27
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one side of the conveyor tube, distribution will not be even. To deliver the
product more evenly into the header, a number of designs have been proposed
to create turbulence in the conveyor tube forcing the product away from the
inside surface, and to centre the stream of product entering the header.
United States Patent No. 4,717,289 issued to S. Popowich in 1988
discloses a corrugated delivery tube for use with a horizontal distribution
head.
Corrugations tend to direct material from the side walls in a substantially
horizontal system with gravity also affecting the stream. In a substantially
vertical orientation, many materials may follow the corrugated surface without
experiencing enough turbulence to achieve the desired result.
A vertical header system allows a larger number of separation channels
to be arranged circumferentially, without constricting the size of the
channels
which constriction would increase the pressure requirements and potentially
cause more damage to the seed.
Canadian Application No. 2,111,611 to G. Bourgault published in June
1995 discloses the use of a central baffle to divide the material into two
streams
as it is redirected through a 90 degree bend and centering deflector rings.
This
is a relatively complicated structure to manufacture. Further, the seed and
other
material is exposed to a plurality of deflecting surfaces and since they are
travelling at high speed this increases the possibility of damaging the seed
in
particular.
The use of a dimpled distribution tube is disclosed in Canadian Patent
1,167,704 issued to D. Kelm in 1984. A regular pattern of dimples, or interior
projections, creates turbulence within the material flow. This design includes
a
number of variations in an attempt to improve the uniformity of distribution.
Both cylindrical and conical tube sections are disclosed having regularly
spaced
dimples. An alternative embodiment places a dimpled section between two 45
degree bend sections to act on the material more gradually. This design
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improves the distribution of material considerably over the previous designs.
However, the CV results of the Kelm device are somewhat inconsistent depending
on
the product used and the rate of delivery.
Various product materials, e.g. peas, wheat, canola and fertilisers exhibit
different responses to turbulent flow. The objective is to provide a uniform
stream of
material to the dividing spreader of the header. Since any number and
combination of
materials may be distributed by the same equipment, it is desirable to find an
optimised median system suitable for the full range of products to provide the
necessary versatility.
Kelm identified that changing the placement of the dimpled tube section
within the conveying system has an effect on the CV from the distribution
head.
However, it is not practical to reconfigure the conveying system for different
products
or application conditions.
The distribution head design also has a substantial effect on the CV. The
prior
art has provided a wide variety of distribution heads. Some heads promote
turbulence
in the flow while others make attempts to reduce turbulence in the head.
Reference
maybe had to Kelm CA 1,097,149; Weiste AU 437,160; EP 211,295; Wurth SU
1,496,668; Gillespie U.S. 3,189,230; Oberg et al U.S. 4,191,500; Smith et al
4,413,935; Widmer et al U.S. 4,562,968 and Memory CA 2,073,237-A among others.
Although several of these designs were partially successful it is the opinion
of those
skilled in this field that there is room for improvement insofar as effect on
CV is
concerned.
SUMMARY OF THE INVENTION
It is an objective to provide improved distribution heads specifically adapted
for use with conveyor tubes described hereafter for producing more even
product
distribution despite changing variables including product size, shape, density
and
mixture.
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A distribution head for use in a system for conveying air-entrained material
in
accordance with one aspect of the invention has a flow inlet for receiving the
air-
entrained material from a conveyor tube, a plurality of angularly spaced apart
outlet
ports and flow divider means for dividing the incoming flow into generally
equal
parts and directing the divided portions of the flow outwardly through the
respective
outlet ports. The flow divider means may include a flow divider chamber
defined
within said distribution head and a flow deflector disposed within said
chamber and
having flow confining ridges thereon separated by smoothly contoured valleys
each
associated with a respective one of said outlet ports.
The distribution head in the preferred embodiment defines a central axis with
said flow inlet being aligned with and concentric with said central axis and
said outlet
ports being in said angularly spaced apart relation and extending radially
outwardly
from said central axis, said flow deflector having a nose centred on said
central axis
and said flow confining ridges commencing downstream of said nose and curving
gradually around from combined axial and radial directions adjacent said nose
into
generally radial directions while the contoured valleys between said ridges
gradually
become deeper to ultimately merge with interior surfaces of the outlet ports.
The outlet ports preferably are of circular cross-section and are equally
angularly spaced about said central axis with said outlet ports extending
normal to
said central axis and lying in a common plane.
The distribution head advantageously may include three main sections namely,
a bottom section having said inlet therein and having first recesses defining
the
bottom halves of said ports, a top section adapted to matingly engage said
bottom
section and having second recesses complementing said first recesses to define
said
outlet ports, and an insert section defining said flow deflector adapted to
seat in said
top and bottom sections with said nose portion directed toward said flow inlet
and
axially aligned therewith.
Preferably said flow inlet tapers inwardly in the flow direction to accelerate
and centre the flow before it meets the flow deflector.
Further features of the invention will become apparent from the following
description of preferred embodiments of the invention.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevation view of the conveyor tube in accordance with a
preferred embodiment of the invention and having a distribution head, also in
accordance with a preferred embodiment of the invention, mounted at the upper
end
of the conveyor tube;
Fig. 2 is a longitudinal section of the conveyor tube and distribution head of
Fig. 1 shown in perspective;
Fig. 3 is a section view of the conveyor tube taken along line 3-3 of Fig. 1
and
illustrating the manner in which adjacent rows of projections are angularly
offset
relative to one another;
Fig. 4 is a further somewhat diagrammatic side elevation view of the conveyor
tube wherein several variables affecting the performance have been identified;
Fig. 5 is an exploded view of the distribution head showing the top lid, flow
deflector insert, and the top and bottom sections of the head;
Fig. 6 is a further exploded view of the distribution head but with the
several
components of same shown in the perspective;
Fig. 7 is a view of the distribution head and conveyor tube in section with
the
section plane extending along the axis of an opposed pair of outlet ports and
lying in
the vertical central axis of the distribution head;
Figs. 8A is a perspective view of the lower surface of the bottom section of
the
distribution head;
Fig. 8B is a bottom plan view of the top section of the distribution head;
Fig. 9 is a perspective view of the lower surfaces of the flow deflector
insert
illustrating the shape of the flow confining ridges and contoured valleys
between the
ridges;
Figs. 10, 11 and 12 are bottom plan, side elevation and top plan views
respectively of the flow deflecting insert illustrated in Fig. 9; and
Figs. 13, 14 and 15 are perspective, end elevation and side elevation views of
the nose of the flow deflector insert.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Refernng firstly to Figs. 1 and 2 there is shown an upright conveyor tube 10
having a distribution head 12 mounted to the upper end of same. As described
in the
above-noted patent to Kelm, for example, the lower or inlet end 14 of the
conveyor
tube receives air-entrained granular material such as seed and/or fertiliser
by way of a
blower and metering devices (both not shown) mounted on an air cart in a
manner
well known in the art. As this air-entrained material passes upwardly through
the
conveyor tube 10, inwardly directed and spaced apart projections 16 disposed
in the
vertical section of the conveyor tube, and which will be described in full
detail
hereinafter, serve to impart a controlled degree of turbulence in the upwardly
moving
flow, which flow then passes into the distribution head 12. The distribution
head 12 is
designed to swing the flow from the vertical direction around into horizontal
directions and to divide the flow thus received substantially equally among
the several
outlet ports 18 which extend radially outwardly from the distribution head in
equally
angularly spaced relationship to each other. These outlet ports 18 are
connected to
flexible hoses (not shown) secured to ports 18 by clamps 20, each of which
hoses
leads to a respective delivery tool. Any secondary header may be of similar
construction as distribution head 12 and may employ a conveyor tube
essentially the
same as conveyor tube 10. It is also noted that the novel head 12 and tube 10
may be
employed in the primary and/or any secondary distribution system as required
to
achieve the desired results.) As noted previously, it is of importance that
the delivery
tools across the width of the machine receive substantially equal flows of
product
material so as to achieve a coefficient of variation (CV) of substantially
less than 15%
and preferably a CV not greater than about 5%.
Distribution Head
Referring now to Figures 5-12, the multi-port distribution head is shown in
detail. The distribution header is symmetrical about its central vertical axis
designated X-X. As best seen in Figs. 5 and 6, the distribution head 12
comprises
four main parts namely, a top cover 22, a flow deflecting insert 24, a top
section 26
and a bottom section 28.
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_7_
The top and bottom sections 26, 28 as well as the flow deflector 24 are
preferably moulded from a polyurethane glass filled plastics material, which
material
resists wear due to abrasion resulting from the materials being handled and
which at
the same time provides for economy in the manufacturing processes.
The distribution head 12 is provided with a centrally located flow inlet
spigot
30 which is snugly received in the upper end of the conveyor tube 10 (Figs. 2
and 7).
Radial flange 31 fixed to the upper end of conveyor tube 10 is provided with
spaced
apertures through which fasteners 33 extend into head 12 to secure the latter
in
position on the upper end of tube 10. The inlet spigot 30 is integrally formed
with the
bottom section 28 of the head. The top and bottom sections 26, 28 of the head
together define the above-noted plurality of radially outwardly projecting
outlet ports
18 with said outlet ports extending in equally angularly spaced relationship
to each
other all around the vertical central axis of symmetry X-X of the distribution
head 12
and with the outlet end portions of said ports all lying in a common plane
normal to
said central axis X-X.
The function of the flow divider insert 24 is to divide the incoming flow
received via the flow inlet 30 into substantially equal parts while directing
the divided
portions of the flow outwardly through the respective outlet ports 18.
Accordingly, the
distribution head 12 includes a flow divider chamber 32 (Fig. 7) defined
within the
distribution head 12 with the above-noted flow deflector insert 24 being
seated within
the top section 26 of the head. The flow deflector 24 (Figs. 9-12) is provided
with a
downwardly directed nose 34 accurately centred on the vertical central axis X-
X of
the distribution head. Flow deflector 24 is also provided with a plurality of
radially
arranged flow confining ridges 36 separated by smoothly contoured valleys 38
each of
which is associated with a respective one of the outlet ports 18. In greater
detail, the
flow confining ridges 36 commence immediately downstream of the nose 34,
initially
being very shallow, with said ridges 36 thence curving gradually around from
combined radial and axial directions adjacent the nose 34 into generally
radial
directions while the contoured valleys 38 between the ridges gradually become
deeper
such that these valleys in the flow deflector insert 24 ultimately coincide or
match up
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_g_
with the interior surfaces of the outlet port portions 18' defined by the top
section 26
of the head.
The bottom section 28 of the head 12 is also provided, immediately
downstream of the flow inlet spigot 30, with a plurality of shallow concave
transition
surfaces 40 each of which leads from the inlet spigot into a respective one of
the
radially disposed outlet port portions 18' as defined in said bottom section
28.
Additionally, the interior surface 42 of the flow inlet spigot 30 gradually
tapers
inwardly in the direction of the flow to accelerate and centre the flow before
it meets
the flow deflector insert 24. All of these features serve to ensure that the
upwardly
moving flow entering via the flow inlet spigot 30 is well centred on the
central axis
which helps ensure the flow is divided into equal parts and is at the same
time
smoothly swung around from a vertical direction into substantially horizontal
directions and passed in generally equal parts with a minimum of flow
restriction
outwardly through the respective outlet ports 18.
Generally speaking air flow velocities within the conveyor tube 10 and the
distribution header 12 are conventional, i.e. within the range persons skilled
in this art
would normally use for comparable prior art equipment.
For good results it is important to ensure that the three main sections 24,
26,
28 of the distribution head 12 are accurately fitted together. With reference
to Figures
5 and 6, for example, it will be noted that the bottom section 28 is provided
with a
plurality of conical projections 44 disposed in radially spaced apart
relationship and
each adapted to enter into a correspondingly shaped recess 46 located in the
top
section 26 of the header. In addition, in order to ensure accurate positioning
of the
flow deflector insert 24, the outer perimeter of the insert is provided with
an
outwardly projecting annular ledge 48. This ledge 48 is snugly received in a
shallow
annular step-like recess 50 provided in the top section 26 of the head 12.
This ensures
that the flow deflector 24 is accurately centred within the top section 26.
Furthermore,
to ensure that the flow deflector 24 is accurately positioned angularly, the
step-like
recess 50 in the top section is provided with angularly spaced apart semi-
circular tabs
52 which co-operate with correspondingly sized semi-circular notches 54
provided in
the outwardly projecting flange 48 of the flow deflector 24. Fasteners (not
shown)
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extending through aligned apertures 51, 53 in the top and bottom sections 26,
28 serve
to secure these sections together. Flow deflector insert 24 is held in place
by the top
cover 22 which, in turn, is secured by spaced apart spring clips 55 (Figs. 2
and 7) of
suitable design.
Reference will now be had to the nose 34 of the flow deflector which was
briefly referred to above. This nose 34 is shown in detail in Figs. 13 to 15.
The nose
34 has an elongated cylindrical stem 60 which fits snugly into a central bore
62
defined in the flow divider insert. A transverse aperture 64 is provided in
the distal
end of the stem 60 to receive a pin to retain the nose in the flow deflector
24. The
nose 34 is provided with an annular shoulder 68 which abuts up against a
narrow
annular radially directed surface 70 surrounding the central bore 62 of the
flow
deflector. The nose 34 is of a generally truncated conical shape with the
extreme
proximal end ?2 of the nose being flat adjacent its central longitudinal axis
with such
flat portion thence merging with the conical wall 74 of the nose via an
arcuately
curved annular transition portion 76.
The nose 34 should be made of a relatively hard long wearing material thereby
to resist abrasion and wear created by the incoming particulate material which
of
course impinges heavily on the nose 34 during operation. It is of course
important that
the nose 34 be absolutely symmetrical all about the central axis X-X of the
distribution head 12 since any deviation from symmetry will adversely affect
the flow
division process.
While the distribution head shown in the drawings is provided with ten outlet
ports 18, it should of course be realised that the number of outlet ports 18
can be
varied depending upon the circumstances. Commonly used distribution head
embodiments employ anywhere from seven to twelve equally angularly spaced
outlet
ports which are sized to ensure that the flow velocity outwardly of each
outlet port is
sufficient as to ensure continued entrainment of the materials being conveyed
thus
assisting in avoiding clogging problems.
The following table provides some typical dimensions for the distribution
head, such dimensions being for illustrative purposes only and not for
purposes of
limitation.
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TABLE
I (see
Fig.
7)
D1 - head diameter 7.5 inches
d - radial port inner diameter 1.5 inches
D2 - flow inlet inner diameter 2.5 inches
T - flow deflector top to nose tip 1.625 inches
distance
N - number of outlet ports 7 to 14
Conveyor Tube
The upright conveyor tube 10 referred to previously in connection with Figure
1 will now be described in detail.
As noted previously, the lower or inlet end 14 of the conveyor tube receives
the air entrained granular material from the aircart and as the air entrained
material
passes upwardly through the conveyor tube 10, the multiplicity of inwardly
directed
and spaced apart projections 16 disposed in the vertical section of the
conveyor tube
impart a controlled degree of turbulence in the upwardly moving flow, which
turbulent flow then passes into the distribution head 12 which acts on the
flow in the
manner described previously.
As shown in the drawings, Figs. 1-4, the tube 10 includes a straight section
80
of uniform diameter which is vertically positioned when in use and which has a
multiplicity of inwardly directed spaced apart projections 16. These
projections 16
form a plurality of spaced annular rows 82, which rows extend around the
lengthways
central axis of the tube. The space between at least some of the annular rows
82
decreases in the direction of material travel through the tube 10, i.e. in the
direction of
flow through the tube from the inlet portion to the outlet portion thereof. As
shown in
the drawings, annular rows 82 of projections 16 which are closest to the
distribution
head 12 are more closely spaced than rows nearer to the tube inlet.
For a 2.5 inch (6.3 cms) outside diameter tube with six rows of dimples, the
spacings starting at the bottom row could be, for example, 2.25, 2, 1.5, 1.5,
1.5 inches,
(5.72, 5.08, 3.81, 3.81, 3.81 cms) i.e. the smallest spacings are near the
outlet end.
The inwardly directed projections 16 are preferably formed by way of
"dimples" which are made in the wall of the tube 10 from the exterior, with
the
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relatively thin-wall tube being deformed inwardly to form the corresponding
projections 16 . The dimples may be made with a round nose punch such that the
projections have a semi-spherical or bulbous shape.
It should also be noted that the projections 16 forming the plurality of
annular
rows 82 are arranged such that projections forming any one row are angularly
offset
by a selected angle A (Fig. 3) about the lengthways axis of the tube with
respect to the
projections 16 of an adjacent row. This ensures that all of the material being
conveyed
is subjected to a measure of turbulence, particularly material which might
otherwise
tend to travel closely along an interior surface of the tube.
It will be noted that the lower or inlet end portion 14 of the conveyor tube
10
includes a smoothly curved elbow section 84 leading into the inlet portion of
the
straight section. The curved elbow section may subtend an angle from about 70
DEG
to about 90 DEG although with an increasing angle there is a greater tendency
for the
material to move away from the centre of the tube under the influence of
centrifugal
force and to follow along the inside wall of the tube 10. Accordingly, this
angle
should be kept as small as conveniently possible and preferably not greater
than about
75°.
Another feature of the conveyor tube 10 is that the above-noted straight
section 80 has a first space 86 devoid of projections between the elbow
section and
the first row of projections at the inlet portion and a second space 88 devoid
of
projections between the last row of projections and the outlet end of the
straight
section, i.e. the end wherein the inlet spigot of the distribution header is
fitted.
A substantial number of tests have been carried out and the results of these
tests are set out in Table II which appears hereafter. Some of the variables
which are
of importance are briefly discussed below.
1. Variable Row Spacing
The varied row spacing has been discussed above. It was found that for
constant row spacing, i.e. the row spacing between any two rows being the
same, there was an optimum CV value for each product tested. However, to
ensure that the conveyor tube 10 worked acceptably well for all products the
row spacing was varied as described above and as further noted in the tables.
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By varying the row spacing an acceptable CV was provided for virtually all
products which one might desire to use.
2. Uniform Projection Depth With Projections Concentrically Positioned
Within the Tube
Experiments have revealed that the projections 16 (and the dimples which
form them) should be concentric within the tube 10. In one preferred
embodiment of the invention the inwardly directed extremities of the
projections lie in a base circle having a nominal diameter of about 2 inches
(5
cms), this base circle of course being centred with the vertical central axis
of
the straight portion 80 of the tube. This is based on a tube nominal outside
diameter of 2.5 inches (6.3 cms), the tube wall being of 16 gauge thickness
steel. Stated more accurately for this example, it is desirable that the base
circle diameter be 2.00 inches (5.08 cms) + 0, minus 0.030 inches (0.076 cms),
giving a tolerance range of 1.97 inches to 2.00 inches (5 to 5.08 cms) for
this
particular example. A range of tube diameters to cover this desired clearance
is from about 2.25 to 2.75 inches (5.71 to 6.98 cms). It does not appear that
tube diameters outside this range will be accepted by the industry.
3. The Top Space Is Also of Significance
A top space of less than 2 inches (5 cms) appears to be detrimental while 2.5
inches (6.3 cms) appears to be optimal for most products. This short length of
space free of projections appears to give the product being conveyed a short
period of time to " even out" before it encounters the distribution head 12.
The
bottom space is less important but should be less than about 2.5 inches (6.3
cms).
4. The Number Of Annular Rows Of Projections Is Also Of Some
Consequence
For a conveyor tube as described having a nominal diameter of about 2.5
inches (6.3 cms) four to eight rows of projections could be used but 6 rows of
projections are found to work best to allow an acceptable compromise in CV's
for all reasonable products.
5. The Number Of Columns Of Projections Is Also Of Some Consequence
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The columns of projections 16 extend in the lengthways directions of the tubes
and the number of columns in the 2.5 inch (6.3 cms) tube was varied between
eight and twelve. Twelve columns of projections provided the most acceptable
compromise for all products.
6. ELBOW BEND ANGLE
The elbow bend angle range has been discussed above and while it can be
varied between 70 and 90 DEG , the lower the bend angle the better, with the
most acceptable compromise in the CVs being at bend angles not greater than
about 75 DEG .
The results of extensive tests carned out on various designs of a conveyor
tube
and the effect on the CVs for various products being conveyed are set out in
Table II
in some detail. Reference may be had to Fig. 4 for an understanding of the
various
terms used. Note also the term " dimple" is used in place of the term
"projection" in
the table, it being understood that they have the same meaning. All of these
tests were
conducted utilising distribution heads conforming substantially to that
described
herein. It would be possible to use the conveyor tube with other forms of
distribution
head but CVs inferior to those shown in the tests could be expected since it
is
important that the distribution head be capable of functioning in an efficient
manner
and the distribution head described above has been designed such that it works
best
with conveyor tubes of the type described herein. In other words, while it is
believed
that both the conveyor tube as described and the distribution head as
described will
work reasonably well with other comparable equipment, it is the combination of
the
two which provides the best results.
With further reference to Table II the tests conducted on the " dimpled" tubes
10 were progressive in nature. One set of tests was used to determine the
ideal values
for a certain variable at a time. It should be noted that the data tables
presented are
only representative of the hundreds of tests conducted. It should be noted
that the
application rate (lb/acre) of the product being tested affects the CV. Only
identical
products with similar application rates can be compared with one another.
CA 02559626 1999-O1-27
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Most of the comparisons are made to analyse the effects of the variables on a
variety of products. While all products are important, it should be noted that
canola
and fertiliser represent opposite ends of the spectrum of product
characteristics.
The fixed criteria of the tube essentially were the elbow angle, offset,
dimple
tube height and diameter.
If the results from test QA are compared with those of test RA, it is seen
that
canola prefers a narrower dimple spacing while wheat prefers a wider spacing.
The
results also indicate that canola prefers a large top space and wheat prefers
a large
bottom space.
Generally, it can be said that canola and high rate fertilisers prefer an
aggressive pattern. Wheat seems to prefer a less aggressive pattern.
Therefore, it was
decided to use only 6 rows at a 3/16" dimple depth. The pattern becomes less
aggressive and allows more space to be allocated to the top and bottom spaces.
The
results of test PG confirm this.
The PG test results also reveal something further. Although the dimple pattern
is quite aggressive and has a large top space, canola CV's are still quite
high. This
shows that there is a limit to the ideal top space for canola. A top space of
smaller
than 2" or larger than 3" will produce adverse effects on canola.
Using the varying row spacing (see " Design" Tl and T6) allows for the
requirements all products tested to be met in order to produce acceptable
CV's. The
less aggressive wide spaced rows of dimples at the bottom are more suited for
wheat;
the more aggressive closer row spacing at the top is better for canola.
The ultimate goal was to find a pattern that produced acceptable CV's for all
range of products. Therefore, the final preferred design settled on (see the
test headed
" Design" ) is the best compromise between all the products.
CA 02559626 1999-O1-27
-IS-
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