Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BA~crR~ ~ cr rHE INVENTION
The invention relates to spraying apparatus for
distributing liquid.s and relates particularly to -the low
volume distribution of chemical aids to growing crops.
.Apparatus according to the invention is also suitable for
low volume spraying of chemicals for many other.purposes,
such as for control of tsetse flies, mosquitoes, flies
and loeusts, and other forms of spraying for public
health purposes.
Our eo-pending British Patent Application No.
7929867 (Published Patent Specifieation No. 2,057,299A)
discloses spraying apparatus comprising a rotary atomiser
and an axial fan coupled to the atomiser to form a rotat-
able unit therewith, the axial fan being situated within
a cowl which is shaped aerodynamieally to control a blast
of air generated by the axial fan when the unit is
rotated, whereby, in use, the blast of air passes over
the atomiser to disperse the droplets produced thereby.
The present invention provides modifications and develop-
ments of the apparatus described and claimed in theabove-mentioned patent application, and in particular
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provides an arrangement for improving the dispersion of
droplets from -the atomiser.
SUMMARY OF THE INVENTION
.
According to the invention there is provided
spraying apparatus comprising a rotary a-tomiser and an
axial fan coupled to the atomiser to form a rotatable
Ul1it therewith, wherein the rotary a-tomiser comprises a
tubular spindle for receiving a liquid to be sprayed, a
hollow foraminous atomising cylinder rotatable around the
spindle, means being provided to permit flow of liquid
outwardly from the tubular spindle and through the
foraminous atomising cylinder, and one or more vanes
mounted within the foraminous cylinder radially outwardly
of the tubular spindle and rotatable with the cylinder so
as to intercept and ef~ect an initial breaking up of the
liquid flow as it passes outwardly from the spindle to
the foraminous cylinder.
The initial breaking up of the flow of liquid
before it reaches the inner surface of the foraminous
cylinder improves the dispersion of droplets from the
apparatus so that an extremely low volume o~ liquid may
be widely dispersed over a large area.
There may be provided a plurality of elongate
vanes spaced around the axis of rotation of the foramin-
ous cylinder and extending parallel thereto. Each saidvane may lie in a plane extending substantially radially
with respect to the foraminous cylinder. For example,
there may be provided three vanes equally spaced around
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the axis of rotation of the cylinder.
The rotary atomiser may also comprise a perfor-
ate diffuser ~ube disposed concentrically between the
tubular spindle and the foraminous cylinder. Preferably
the vanes are located adjacen-t the internal surface of
the diffuser tube.
In use, the apparatus may be mounted in a
location where the axial fan is rotated by an air blast,
and -thus rotates the atomiser, the droplets from the
atomiser being dispersed by the air blast. For example,
the apparatus may be mounted in the slipstream of a crop-
spraying aircraft. Alternatively, means may be provided
for driving the rotatable unit, in which case the axial
fan itself produces the blast of a ir for dispersing the
droplets. In this case, the axial fan may be situated
wi-thin a cowl which is shaped i~erodynamically to control
the blast of air, as described in the above-mentioned
British Patent Specification No. 2,057,299A.
BRIEF DESCRIPTION OF THE DRAWINGS
;'0 Figure 1 is an axial section through a unit
comprising a rotary atomiser and axial fan,
Figure 2 is a section through an hydraulically
driven spraying unit incorporating the atomiser of Figure
1 ,
~5 Figure 3 is a front view of the unit of Figure
2, and
Fugure 4 is a scrap section on -the line A-A of
Figure 3.
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N OF THE PREFERRrn F~nDIMLnl
Referring to Figure 1 9 the spraying apparatus
comprises a rotary atomiser 10 and an axial fan 11 coupled
together to form a single rotatable unit.
The atomiser comprises a fixed tubular spindle
12 which is supported on a mounting bar 13 and is provided
at one end with a union 14 to which is coImected a
flexible conduit ~or supplying the liquid to be sprayed
to the interior of the spindle 12. The opposite end of
the spindle 12 is closed by an end plug 15 and radial
holes 16 are formed in the walls of the spindle 12 adjacent
the end plug so that the liquid under pressure may pa~s
radially outwardly of the spindle.
The hub 17 of the axial fan 11 is rotatably
mounted on the spindle 12 by means o~ bearings 18. The
hub is formed in two parts 19 iand 20 which are held
together by screws 21. The cylindrical root ends of three
fan blades 22 are clamped in circular sockets forme~1 by
cooperating shaped parts of the hub portions 19 and 20,
the arrangement being such that the pitch angle of the
blades may be adjusted by loosening the screws 21 and
separating the hub portions 19 and 20. The blades 22 may
then be turned to adjust their pitch whereafter the screws
21 are tightened up again to clamp the blades in their
new position. The fan blades may be formed from plastics
material, such as "Delrin".
Although three fan blades are shown, any other
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suitable number of blades may be employed. ~or example,
five blades may be used.
A diffuser -tube 23 proJects from one face of the
hub por-tion 20 and encircles -the end of the tubular
5 spindle 12. The diffuser tube 23 may be formed from
stainless steel and has a perforated surface, the perfora~
tions preferably extending over 80% of the surface of the
tube, -to allow the liquid passing fro~ -the spindle 12 to
pass through the diffuser -tube. Equally spaced around the
~~. internal surface of the dif~user tube 23 are three longi~
tudinall~ extending vanes 24 each vane lying in a gener-
ally radial plane. The vanes are secured at one end to
an annular disc 2L~a which encircles the spindle 12, and
a-t the other end to a disc 2~b which is bolted to an end
cap 27. The vanes 24 serve to intercept and effect
initial breaking up of the liquLd as it passes outwardly
from the spindle 12 and before it passes through the
diffuser tube 23. Although three ~anes are shown, any
other suitable number may be used, and the vanes may also
be of other shapes. For example, the vanes may extend
spirally as they extend longitudinally of the diffuser
tube.
Encircling the diffuser tube 23 and spaced
radially outwardly therefrom is a foraminous atomising
cylinder 25, which may be formed from metal gauze. One
end of the cylinder 25 is attached to a radially project~
ing flange 26 on the hub portion 20 and -the opposite end
is secured to the aforementioned end cap 27.
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As shown in Figures 2 and 3, -the axial fan 11
rota-tes within the downstream end of a fixed cowl 28.
The ro-tary atomiser 10 projects clear of the downstream
end of the cowl 28. The cowl may be formed from metal
or plas-tics 9 such as glass fibre reinforced plastics.
In use -the unit comprising the fan 11 and
a-tomiser 10 is rotated and the liquid to be sprayed is
delivered under pressure to the interior of the spindle
12. The liquid under pressure passes radially outwardly
through the holes 16 in the spindle and is intercepted
and broken up into droplets by the vanes 24 before pass-
ing through the diffuser tube 23. The droplets continue
to move radially outwardly and pass through the gauze
atomising cylinder 25 where they are further broken up
to form extremely fine droplets. As the droplets pass
out,wardly through -the gauze cylinder 25 they become
entrained in the blast of air from the axial fan 11,
-the blast being controlled and directed by the cowl 28,
and -the droplets are dispersed as a fine spray over the
area towards which the unit is directed~ The combination
of the particular arrangement of the atomiser and ~he
controlled blast of air causes extremely small ~olu~es
of liquid to be dispersed over a very wide area bu-t in a
controlled fashion, the dispersion being controlled by the
pressure of the liquid and the pitch angle of the axial
fan 11.
As best seen in Figure 2, a pulley 42 is
coupled to the hub 17 of the axial fan and is driven
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through a drive belt 31 from a pulley 43. The pulley 43
may be driven from the output shaft of an internal
combustion engine or, as shown in Figures 2 and 3, may be
coupled to the output shaft of an hydraulic motor 44.
The hydraulic motor 44 is driven in known manner by
hydraulic fluid under pressure passing along flexible
conduits. The hydraulic fluid may be pressurised by a
portable power-driven fluid pump.
In a further alternative arrangement, not shown,
the rotary atomiser is driven by a pneumatic motor, the
motor being provided with air under pressure from any
known portable air pump.
The aforementioned mounting bar 13 supporting
the atomiser uni-t and the cowl 28 is connected to a
support by support stays 45. The ends of the bar 1~ are
connected to the support stays 45 by adjustable clamping
screws 46 so that the bar 13, and hence the cowl and
atomising uni-t~ may be tilted with respec-t to the
support stays 45 by loosening the clamping screws 46,
adjusting the position of the atomiser and cowl and then
retightening the clamping screws. This arrangement is
possible using an hydraulic or pneumatic motor since the
motor can tilt with the atomiser unit due to the flexi-
bility of the conduits supplying the hydraulic fluid
or air under pressure to the motor. This tilting arrange-
ment enables the angle of the cowl and a-tomiser unit to
be adjusted with respect to the support as required.
The atomiser unit described with relation to
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Figure 1 has many appllcations and may be used in vehicle
mounted spraying apparatus or in other large transportable
spra~ing equipment or on aircraft.
In the case where a plurality of atomisers are
mounted on a vehicle, for example on a spray bar on a
tractor, the hydraulic or pneumatic motors of the atomi-
sers are supplied with hydraulic fluid or air under
pressure from a single pump mounted on the vehicle.
The rotatable unit comprising the axial fan 11
and atomiser 10 may also be used in situations where an
air blast is separately provided~ the cowl being omitted
and the axial fan in this case merely acting as a turbine
which is acted on by the air blast to rotate the atomiser.
The provision of adjustable pi-tch blades allows them to
be adjusted -to the optimum pitch angle for such use.
For example, the ro-tatable uni-t may be moun-ted on the
conventional spray bar of a crop-spraying aircraft so
that the axial fan rotates in -the slipstream of the
aircraft, the slipstream also dispersing the spray of
droplets emitted by the rotating atomiser. ~he ro-tatable
unit may also be used to adap-t a conventional air blast
orchard sprayer to low-volume spraying by mounting the
unit in the air blast from the sprayer so that, again~
the a~ial fan acts as a turbine which rotates the
atomiser, the air blast also serving to disperse -the
droplets from the rotating atomiser.
In the above-described arrangements the
rotating dispersion element of the atomiser is in the form
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of a cylindrical wire gauze. It will be appreciated
however that other forms of rotating element may be used.
Thus the wire gauze cylinder may be replaced by any
other form of foraminous cylinder. For example, the
cylinder may be formed from foamed metal which provides
a labyrinth path for the liquid as it flows outwardly
from the central spindle under centrifugal force.
Rotary atomisers employing such a construction are
described in British Patent Specification No. 1,486,427.
1;~ Alternatively, the atomiser may comprise a plurality of
axially spaced rotating discs, the liquid flowing
outwardly over the surfaces of the discs and being
dispersed as fine droplets from -the outer peripheries
thereof.
