Suction harvester for aquatic plants and animals

A suction harvester for aquatic plants and animals comprising a variable rate centrifugal pump capable of handling solids mounted on a vessel and connected to a manoeuvrable nozzle. The operator can control the placement of the nozzle and degree of suction applied by the pump to selectively harvest weed or algal mats, etc. from the bed of the water body. A location or manoeuvring system for the vessel in shallow water is also described, comprising spiked wheels driven by independent motors on the end of adjustable arms, the spikes engaging the bed of the water body for accurate location and propulsion with minimum disturbance.

TECHNICAL FIELD 
This invention relates to a suction harvester for aquatic plants and 
animals and has been devised particularly though not solely for the 
control of nuisance aquatic plant or animal species. 
BACKGROUND ART 
In the past various types of aquatic harvesters or weed cutters have been 
provided, operating on a principle whereby aquatic plants are mechanically 
cut at the end of a moving conveyor belt which then carries the plants on 
board the harvester. Such harvesters have the disadvantage that the 
harvesting is not selective in that all material above the height of the 
cutting blades is removed. Such machinery is also of considerable weight, 
requiring a comparatively deep draught vessel in order to accommodate the 
machinery in a vessel of manoeuvrable proportions. This is a disadvantage 
with an aquatic harvester which is frequently required to operate in 
shallow water as aquatic plants are most prevelant in shallow water due to 
light penetration. 
Some known aquatic harvesters are supported by wheels or tracks which run 
on the sea bed (or lake bed, etc.) to support the harvester, rather than 
being supported by a float vessel. Such land based machinery has the 
disadvantage that it can often cause ecological damage to the sea bed due 
to the disturbance caused by the wheels or tracks. 
It is a further feature of known types of floating harvesters that they are 
normally powered by devices such as paddle wheels which are inefficient in 
their use of energy, and more importantly, provide no reference to the 
bottom of the water body. Drift due to wind and currents makes precise 
harvesting of an area difficult, if not impossible. Wheeled or tracked 
harvesting machinery provides good ground reference but causes 
considerable disturbance to the substrate and damage to the ecology of the 
aquatic environment. 
It is therefore an object of the present invention to provide a suction 
harvester for aquatic plants and harvesters which will obviate or minimise 
the foregoing disadvantages in a simple yet effective manner, or which 
will at least provide the public with a useful choice. 
DISCLOSURE OF INVENTION 
Accordingly, in one aspect the invention consists in a method of harvesting 
aquatic plants and animals comprising the steps of: 
(1) providing a vessel incorporating a manoeuvrable nozzle protruding 
therefrom connected to a pump arranged to suck water through the nozzle; 
(2) manoeuvring the vessel and/or the nozzle to locate the nozzle in a 
position adjacent aquatic plants or animals desired to be harvested; 
(3) operating the pump to suck water and entrained aquatic plants or 
animals through the nozzle; and 
(4) discharging the water and entrained aquatic plants or animals from the 
pump to a desired discharge location. 
Preferably the pump comprises a variable rate pump and the method includes 
selecting the flow rate of water through the pump to control the degree of 
suction applied to the nozzle. 
Preferably the nozzle is manoeuvred through a controlled sweep pattern 
relative to the vessel during operation of the pump. 
Preferably the vessel is manoeuvred in shallow water by controlled rotation 
of a plurality of wheels with radially extending spikes, the wheels having 
substantially horizontal axes and being mounted to the vessel such that 
the wheels may be raised or lowered to engage the ends of the lowermost 
spikes with the bed of the body of water in which the vessel is floating. 
In a further aspect the invention consists in a harvester for aquatic 
plants and animals comprising a suport vessel, a manoeuvrable nozzle 
protruding from the vessel, and a pump arranged to suck water and 
entrained aquatic plants or animals through the nozzle and discharge them 
to a desired discharge location. 
Preferably the nozzle forms the outer end of a nozzle arm extending 
radially outwardly from a substantially vertical pivot mounted on the 
vessel, and wherein actuation means are provided arranged to rotationally 
oscillate the nozzle arm about the pivot causing the nozzle to sweep back 
and forth through a predetermined arc. 
Preferably the height of the nozzle arm is adjustable relative to the 
vessel. 
Preferably the pump has a variable flow rate controlled by an operator of 
the harvester. 
Preferably the pump is provided with an auxiliary priming pump arranged to 
supply water under pressure into the suction chamber of the main pump, the 
priming pump being operable on demand by an operator to back flush the 
nozzle and clear any blockage therein. 
Preferably the vessel is provided with a plurality of wheels controllably 
rotatable by drive means about substantially horizontal axes, each wheel 
having a plurality of radially extending spikes and being mounted to the 
vessel such that the wheels may be raised or lowered to engage the ends of 
the lowermost spikes with the bed of the body of water in which the vessel 
is floating. 
Preferably each wheel is mounted on the end of an arm attached to the 
vessel by way of a substantially horizontal pivot, each wheel being able 
to be raised or lowered by pivoting the arm relative to the vessel.

MODES FOR CARRYING OUT THE INVENTION 
In the preferred form of the invention a suction harvester for aquatic 
plants and/or animals is constructed as follows. 
The harvester comprises a vessel of any convenient configuration but 
preferably in the form of a barge formed from two sealed pontoons (1) 
located either side of and secured to a central open-top barge (2) which 
is preferably of shorter length than the pontoons (1), leaving an area of 
open water between the pontoons at the front of the vessel. The central 
barge (2) is used to support and locate an engine (3) (preferably a diesel 
engine) coupled to hydraulic pumps (4) and (5). Also within the central 
barge (2) there is located a centrifugal pump (6) driven by way of a 
coupling (7) from a hydraulic motor (8) connected to and driven by the 
hydraulic pump (4) by way of hydraulic lines (9). 
The hydraulic motor (8) is preferably a variable speed hydraulic motor 
controlled by suitable hydraulic valving (not shown) under the control of 
an operator from his position in a control cabin (10). The control cabin 
is preferably located at the front end of the vessel so that the operator 
has a good view of the suction nozzle (as described below). 
The centrifugal pump (6) is preferably a high volume centrifugal pump 
capable of handling solid materials and is typically of the induced vortex 
type. When operating with certain aquatic materials it may be necessary to 
employ a mascerating impeller in the pump to cut entrained material to a 
size which will not bind the pump. 
The inlet (11) to the pump (6) is connected by way of a flexible hose (12) 
to a hollow nozzle arm (13) which terminates at its forward end in a 
nozzle (14) protruding forwardly from the vessel. The outlet (15) from the 
pump (6) is also coupled to a flexible hose (16) for discharge of material 
from the pump to a desired discharge location. 
A gland pump (17) is provided, driven by the motor (3), and arranged to 
pump water from an inlet immersed in a strainer (not shown) at the rear of 
the vessel to the bearing of the main pump (6). 
The main pump (6) is primed by an auxiliary centrifugal priming pump (18) 
driven by a hydraulic motor (19) supplied with hydraulic fluid under 
pressure from the hydraulic pump (5) which is driven by the motor (3) and 
also used to provide hydraulic fluid under pressure to various hydraulic 
rams on the harvester as will be described further below. The auxiliary 
priming pump (18) draws water from an inlet immersed beneath the vessel 
and supplies that water under pressure through a conduit (20) by way of a 
non-return valve (21) into the inlet chamber of the main pump (6). In this 
way the auxiliary priming pump may be used to fill the inlet to the main 
pump (6) with water to prime the main pump prior to operation. 
Reservoirs of hydraulic fluid and of fuel for the motor (3) may be 
conveniently located in tanks (22) and (23) located in the pontoons (1). 
The nozzle arm (13) is located and manoeuvred by an apparatus which will 
now be described with particular reference to FIGS. 4 and 5. 
The nozzle arm (13) is supported by a vertical shaft (24) which is 
typically welded to the nozzle arm at point (25). As an optional feature 
the nozzle arm which is shown horizontally mounted in the attached 
drawings, may be secured to the vertical shaft (24) by way of a horizontal 
pivot, enabling the nozzle arm to be tilted downwardly to a predetermined 
inclination. 
The vertical shaft (24) is located within a tube (25) and axially supported 
within the tube by way of a collar (26) so that the shaft protrudes from 
the top and bottom of the tube (25). The tube (25) is in turn located by a 
platform (27) and support bracing (28). 
The platform (27) is in turn located by rollers (28) engaged with vertical 
columns (29) extending upwardly from a platform (30) located on the 
pontoons (1). The height of the platform (27) may be adjusted relative to 
the support platform (30) by moving the rollers (28) up and down within 
channels in the columns (29) under the control of a double acting 
hydraulic ram (31) secured at its lower end (32) to the platform (30) and 
having its upper end (33) connected to support struts (34) which in turn 
engage with and support the platform (27) and the vertical tube (25). In 
this manner the entire platform (27), the tube (25), shaft (24) and nozzle 
arm (13) may be moved vertically by operation of the hydraulic ram (31) 
supplied with hydraulic pressure from the pump (5) controlled by a valve 
operated by an operator in the cabin (10). 
The nozzle arm (13) is caused to rotationally oscillate about the pivot 
formed by the vertical shaft (24) by way of an actuating mechanism 
comprising radial arms (35) (FIG. 5) extending outwardly from the shaft 
(24) and connected at their outer ends to yokes (36) connected in turn of 
the actuating rods (37) of hydraulic rams (38), anchored at their opposite 
ends to a support bracket (39) on the platform (27). The hydraulic rams 
(38) are operated by hydraulic fluid supplied from the pump (5) through a 
pressure operated hydraulic pilot valve, activated automatically at the 
end of each sweep of the nozzle arm (13), reversing the flow of hydraulic 
oil through the rams (38) and consequently the direction of oscillation of 
the nozzle arm (13). The sweep speed is controllable by a valve in the 
operator's cabin (10) and the length of the sweep is adjustable by 
altering the distance along the radial arms (34) and (35) at which the 
yokes (36) are located. 
In this manner the nozzle arm (13) may be caused to oscillate about the 
pivot of the shaft (24) through a predetermined arc at a speed controlled 
by the operator, while the height of the nozzle arm and hence of the 
nozzle (14) may also be controlled by the operator by way of hydraulic ram 
(31). 
The vessel may be propelled in deep water by any suitable propulsion means 
such as an outboard motor or a drive leg powered directed or indirectly by 
the motor (3), or alternatively may be towed to a desired shallow water 
location for operation. Once in the shallow water location the vessel is 
positioned and manoeuvred by way of wheels (40) having horizontal axes and 
mounted on the ends of arms (41) pivotally mounted to the sides of the 
pontoons (1) by way of horizontal pivot pins (42) and rotatable thereabout 
by hydraulic rams (43) operable between trunions (44) on the arms (41) and 
support lugs (45) attached to the pontoon. Operation of the hydraulic rams 
(43) causes the arms (41) to rotate and hence raise or lower the wheels 
(40) relative to the vessel. In the preferred form of the invention two 
such sets of wheels and arms are provided located on either side of the 
vessel and protruding forwardly therefrom as shown in FIGS. 1 and 2. 
Each wheel (40) is provided with radially extending spikes (46) which can 
engage with the sea bed (or the bed of any other water body in which the 
water is floating) upon lowering of the arm to a desired depth. Each wheel 
is provided with a hydraulic drive motor (47) able to rotate the wheel 
when powered by hydraulic fluid supplied under pressure from the pump (5) 
by way of control valves in the operator's cabin (10). By operating those 
control valves the operator can independently rotate each of the drive 
motors (47) at a desired speed and hence cause each spiked wheel to move 
forwardly or backwardly propelling or manoeuvring the vessel to a desired 
location. The two drive motors (47) may of course be operated 
independently, e.g. one forward and one in reverse, to cause the vessel to 
turn in a desired manner. 
Where required for further location of the vessel a further pair of arms 
(48) may also be provided at the rear of the vessel pivotally mounted to 
the pontoons by way of pivots (49A) controlled by hydraulic rams (50) in a 
similar manner to the arms (41), pivots (42) and hydraulic rams (43), 
respectively. The arms (48) are also provided with spiked wheels (49) 
which are free to free-wheel on the ends of the arms (48) and are not 
provided with hydraulic drive motors. 
In use the harvester is positioned in a location where it is desired to 
harvest aquatic plants or animals whereupon the vessel may be manoeuvred 
into a desired location and held in that location by engaging the spiked 
wheels (40) and (49) with the sea bed and manipulating the hydraulic 
motors (47) accordingly. The pump (6) may then be driven at a desired 
speed by the hydraulic motor (8) causing water to be sucked into the pump 
from the nozzle (14) and discharged through the outlet hose (16). The 
nozzle (14) is vertically positioned by the operator by way of the 
hydraulic ram (31) so as to locate the nozzle at the desired depth and the 
nozzle is then oscillated over a predetermined sweep path by operation of 
the hydraulic rams (38). The operator in the cabin (10) may control the 
sweep rate of the nozzle, and the degree of suction applied by the pump 
(6) so as to achieve the desired harvesting effect which may vary 
depending on the location and the plant or animal which it is desired to 
harvest. The direct suction principle allows the force applied to the 
material to be harvested to be altered by adjusting pump speed and the 
operating depth of the nozzle in the water column. In this way a range of 
harvesting functions is made possible. For example, management plans may 
require the total clearing of an area for recreational purposes, or the 
removal of floating algal mats to visually enhance an area, or the removal 
of entangled algi and dead plant material from a seagrass bed to improve 
light penetration. The ability of this harvester to remove material 
selectively has important implications, particularly in ecologically 
sensitive areas. 
Because the machinery used in the harvester according to the invention is 
comparatively light in weight, it is possible to mount the harvester in a 
shallow draught barge formed from the pontoons (1) and (2) so as to be 
operable in shallow water. As light penetration is a major factor in 
limiting the depth of water in which aquatic plants will grow, the ability 
of the harvester to operate in very shallow waters is important. With the 
bouyancy provided by the two pontoons (1) and the smaller central barge 
(2), the suction harvester of the type shown in the drawings draws 
approximately 175 mm fully laden and its moving nozzle (14) is capable of 
harvesting in less than 300 mm of water without entraining significant 
amounts of air from the surface. The operating depth could be further 
reduced by providing a sheild over the nozzle (14) to inhibit vortex 
action. The shallow draught capability of the harvester according to the 
invention significantly increases the area of a shallow water body over 
which the harvester can operate and so reduces the need for, and the 
ecological damage caused by, land based machinery used in an aquatic 
environment. 
It is a further feature of the harvester according to the invention that 
the water and aquatic material is passed through the main pump (6) and 
discharged through the flexible hose (16) which can deliver to any desired 
location. Such locations could typically be: 
(a) to a mesh separator basket situated on the harvester; 
(b) to a mesh separator basket on a transporter pontoon; 
(c) directly over the side of the vessel should disruption of algal beds be 
the prime objective; or 
(d) to a buoyed delivery hose to pump materials to the shore. 
It is a further feature of the harvester according to the invention that 
the propulsion and manoeuvring system provided by the spiked wheels (40) 
and (49) provides good ground reference and so makes accurate harvesting 
possible. Little energy is required to propel the vessel by this method 
and disturbance to the substrate and ecology is kept to a minimum. It is 
also possible to control the location of the vessel accurately against 
drift due to wind and currents. 
It is a further feature of the invention that the auxiliary priming pump 
(18) may be used during operation to clear any blockage that may occur in 
the nozzle (14). Should such a blockage occur the operator can simply stop 
the pump (6) by operating the control valve to the hydraulic motor (8), 
and then activate the priming pump (18) by way of hydraulic motor (19) 
causing excess priming water to back flow through the nozzle (14) and 
force any blockage from the nozzle end.