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Patents Form No 5 Our Ref AS801098
NEW ZEALAND PATENTS ACT 1953
Complete After Provisional No 299454 Filed 26 September 1996
COMPLETE SPECIFICATION
LOW VOLUME AIRBORNE DISTRIBUTION DEVICE
We, LANDCARE RESEARCH NEW ZEALAND LIMITED, a New Zealand company of Canterbury Agriculture & Science Cntr, Gerald Street, Lincoln, Canterbury, New Zealand hereby declare the invention, for which We pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement
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PT0576521 Gi4129?0940TEMP ?
LOW VOLUME AIRBORNE DISTRIBUTIOM DEVICE
Field of the Invention
The present invention relates to devices for use in spreading agricultural chemicals, pellet baits and similar substances More particularly, although not exclusively, the present invention relates to a device for spreading pellet baits in low, accurately metered quantities
The device of the present invention is primarily directed towards spreading pellet baits or the like. However, it might find application in spreading other substances such as those carried in a suitable media, granular baits and substances, fertilisers, agrichemicals, tract elements and the like However the following discussion will refer primarily to pellet baits intended for possums or similar target animals
Background to the Invention
Aerial distribution of baits is a well know technique and, in New Zealand, has been used to reduce and/or control possum populations Conventionally, such baits may be spread by top dressing from aircraft hoppers or from gravity fed buckets slung underneath helicopters The following discussion will concentrate primarily on helicopter distribution techniques as this is the most appropriate (however not the only) application in which the present invention
may be used The device of the present invention may also be used as an attachment to a fixed wing aircraft
Conventional bucket spreading systems use a bucket or hopper carried beneath a helicopter where the bait material is released through an aperture in the bottom of the hopper The hopper incorporates a truncated inverted conical chute with an aperture at its apex The aperture may be opened and closed by a shutter or similar device In some constructions, the bait is directed onto a spreader disc The spreader disc is formed from a flat disc having upright plates located radially thereupon
A number of difficulties have been encountered in the use of such distribution devices when attempting to reduce delivery volumes or application rates It is often difficult to control the application rates of baits distributed in such a manner as jamming and blocking can occur in the lower part of the hopper, particularly the outlet aperture/closing device This can lead to non-uniform distribution of the baits in the target area This effect is particularly common where the baits correspond to large pellets or vegetable baits such as carrots The dimensions of commonly used compressed pellet baits are 2 - 3cm in length and 1 5 - 2cm in diameter
Motivated by constraints imposed by effectiveness, efficiency and environmental safety, the drive has recently been towards lower application rates and more accurate spreading Improvements in spreading efficiency have been assisted by the introduction of navigational guidance equipment such as GPS systems (Morgan, 1994)
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Trials in the mid 1980's indicated that bait application rates of up to 20kg/ha for pellet bait and 35kg/ha for carrot bait were unnecessary, wasteful and environmentally unsound By the late 1980s such constraints brought about the adoption of standard application rates of 5kg/ha for pellet baits and 10kg/ ha for carrots Reduction in application rates resulted in savings in terms of the cost of the pellet bait material itself Together with associated bait handling, transport and application costs, these reductions have saved around $9 million in possum control costs each year Further reductions in application rate are being recommended that potentially could save over NZD$2,000,000 more per year (Morgan et al 1997)
Bait distribution equipment used in possum control operations has been generally designed for fertiliser application rates of 50kg/ha or more and, as noted above, was less suited to or incapable of sowing baits uniformly at rates less than 5kg/ha
A further difficulty in achieving low application rates is that in conventional crop dusting or bait spreading operations, the exhaustion of the bait material in a hopper is indicated to the pilot either visually by means of the pilot checking for a bait or fertiliser plume behind the aircraft by looking at the bucket level via a mirror Both of these techniques require continuous checking At low application rates, this plume is difficult to detect and thus the time when the bucket is empty may be uncertain For this reason, it would be advantageous to couple a low distribution rate mechanism with an accurate bait level indicator
For further discussion, see
MORGAN, D R 1 994. Improving aerial control of possums by precision bait delivery Proceedings of the 1 6th Vertebrate Pest Conference University of California, Davis Pp 287-291
MORGAN, D R , THOMAS, M D , MEERKEN, D, , NELSON, P C 1997 Less 1080 bait usage in aerial operations to control possums Proceedings of the 50th NZ Plant Protection Conference 391-396
Accordingly, it is an object of the present invention to provide a controllable low delivery rate bait spreading device which overcomes or at least mitigates some of the abovementioned problems or at least provides the public with a useful choice
Disclosure of the Invention
The present invention provides for a metering device suitable for use with an airborne bait delivery bucket, the metering device including a metering distribution wheel mounted inside a casing wherein the distribution wheel comprises a plurality of separators wherein the space defined by adjacent separators and an inside surface of the casing constitutes a delivery volume,
an inlet aperture to the casing adapted to communicate with a material hopper,
a removable end plate to the casing which allows access to the delivery volumes and allows the metering wheel to be removed and replaced with one forming different delivery volumes,
an outlet aperture located so that upon rotation of the distribution
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Preferably the metering wheel comprises a hub having a plurality of separators , protruding therefrom in a paddle or plate type configuration
Preferably the separators are in two parts, a primary and secondary separator wherein the secondary separator is made from a plastics material
Preferably the casing is cylindrical and adapted so that the metering wheel fits closely therein
Preferably the outlet aperture further incorporates a delivery manifold located and oriented so as to deliver the material at a point on a spinner disc such that the material is spread in a predetermined direction
Preferably the predetermined direction corresponds to an arc of approximately 180° in which material is distributed in similar quantities either side of the bucket during aerial operations
In an alternative embodiment, the outlet aperture may incorporate a shut-off valve (preferably pneumatically operated) adapted to close off the outlet aperture
Preferably the hopper incorporates a "material" out sensor
Preferably one or more sensors are located to proximate the outlet aperture, said sensors adapted to detect the presence/absence of material passing through the outlet aperture
Preferably the casing incorporates a removable end plate which to allows access to the delivery volumes and allows the metering wheel to be removed and replaced with one forming different delivery volumes
In a further aspect the present invention provides for a delivery bucket incorporating a metering device as described above
The present invention also provides a method of distributing material in measured quantities and at a controlled rate including allowing material to be fed from a hopper to a distribution means under the force of gravity,
intercepting discrete volumes of material using a distribution wheel having a plurality of delivery volumes,
rotating said delivery wheel in such a manner as to transport the discrete volumes to a outlet aperture,
wherein the rotation rate can be varied to regulate the rate of distribution of the material
Preferably the method further includes allowing the material exiting the outlet aperture to impinge asymmetrically onto a rotating spreader disc so as to spread the material in a predetermined range of directions
Brief Description of the Drawings
The present invention will now be described by way of example only and with reference to the attached figures in which
Figure 1 illustrates a side view of a low volume delivery bucket,
Figure 2 illustrates a side view of a detail of a metering device for the delivery bucket shown in figure 1,
Figure 3 illustrates a perspective view of a metering device associated with the spreading bucket, and
Figure 4 illustrates, schematically, a top view of a spreading bucket
Figure 1 illustrates the general layout of an example of the bait distribution bucket according to the present invention The bucket broadly comprises a hopper 11 which incorporates a lower truncated cone or chute which terminates in an aperture at its apex, support legs 25a, 25b and 25c (not shown in figure 1) and aerodynamic stabilisers 12a and 1 2b (not shown in figure 1)
The bucket also includes an attachment device (not shown) located at the top of the hopper which may be integrated with the superstructure of the bucket or bucket superstructure to allow its attachment in an underslung position to a helicopter which carries it
The flight direction is indicated by the arrow A in figures 1,2 and 4
The bucket incorporates a distribution means or wheel located below the output aperture 34 of the hopper and comprises an outer casing 1 5 and
metering wheel The metering wheel consists of a central spindle 28, a hub 29, primary separators 27 and secondary separators 26
The metering wheel is driven by a drive means 14 by means of a geared drive 24 as shown in figure 1 The drive means 14 is, in the present example, electrically powered
In use, the metering wheel rotates within the casing 15 Baits are fed under gravity from the hopper 11 through the aperture 34 into the casing 1 5 The space or cavity 32 formed by the separators 26/27 and adjacent inner surface of the casing 15 It has been found that the cavity 32 is efficiently and reproducibly filled by even quite large baits 31 as shown in figure 2
The secondary separators 26 are made from a plastics material or the like This is so that the pellets or baits, adjacent an inner surface of the casing 15, are "brushed" around the inside of the casing 15 and are not crushed between the secondary separator and the side of the aperture 34 The secondary separator 26 may also need to be replaced periodically due to wear and the two piece construction of the separators 26 and 27 is particularly useful in this regard
The metering wheel is rotated in the direction indicated by the arrow B in figure 2 whereupon the bait filled cavity is rotated adjacent to the outlet aperture 23 The embodiment illustrated in figures 1 and 2 drops the bait on the centre of the spreader disc 21 It has been found that by allowing the baits to be self-fed through a reasonably large aperture 34 into the delivery cavities 32, the baits do not bind or clump which may lead to a variable and
unpredictable delivery rate. Further, highly accurate delivery rates can be achieved by driving the metering wheel at a fixed number of revolutions per minute Advantageously, the delivery rate can be varied in flight Such an adjustment maybe made in response to a tachometer relaying the rate of rotation of the delivery wheel couple with a automated or manually operation RPM's of the delivery wheel
Referung to figure 3, the hub 29 and separators 26/27 can be removed and replaced with a hub having a larger diameter This has the effect of reducing the cavity delivery volume 32 and provides another variable which can be altered so as to change the delivery rate Such an adjustment may also be useful depending on the size of the bait which is to be distributed A nylon washer may be fitted to prevent binding between the hub and casing
Further, the throat 34 may have dimensions so that the maximum volume of bait is delivered to the metering wheel Such size variations contemplate changing the shape and dimensions of the throat to allow entry into the casing 15
As the bait 31 is rotated inside the casing 15 it passes over the output aperture 23 It has been found that each metering cavity 32 empties itself virtually completely via the outlet 23 Again, this results in a predictable, accurate and controllable distribution rate even a low delivery volumes
In a preferred embodiment, the outlet aperture 23 may incorporate a manifold 16 which is constructed so as to deposit the baits onto a spreader disc 21 in a particular way Figures 1 and 2 illustrate a manifold adapted to drop the
baits symmetrically onto the centre of the disc 21 The spreader disc includes upright blades 22. The disc is rotated at a high speed which ensures that baits 31 are flung off radially outward In cases it may be desirable that the baits be spread over a swath oriented preferably approximately 180° behind the direction of flight This is illustrated in figure 4 whereby the direction of movement of the hopper A is shown along with a dotted line indicating the spread pattern (about 150°) from the rotating spreader disc The orientation and shape of the manifold in this embodiment of the invention is particularly adapted to drop the baits at a point on the spreader disc to achieve this effect
In a preferred embodiment however, the baits are dropped symmetrically over the centre of the spinner This produces a uniform dispersion pattern An alternative construction is shown in figures 3 and 4 which drops the baits asymmetrically onto the spreader disc 21
An embodiment of the present invention may incorporate a material out sensors 1 3 (not shown) As noted above, for low distribution rates the pilot is unable to, or is hampered in his ability to gauge when the hopper is empty by looking for the presence of the visible plume emitted from behind the helicopter or looking into the hopper using a mirror At the required low rates of delivery presently envisaged, it would be difficult to tell when the material is depleted
In one embodiment a sensors 13 may be used to indicate when a predetermined level has been reached The material out sensors may trigger a GPS unit which can be used to direct the pilot back to the point where the
bait ran out so that upon refilling the bucket the pilot can relocate the aircraft at that point and continue application of the material The sensor may be electrical, optical, mechanical or similar type It is considered that the construction of such a sensor is within the purview of one skilled in the art In the present preferred embodiment, there are optical sensors 13 located at the junction of the casing and manifold entrance These can be used to provide a positive indication as to the absence/presence of baits leaving the aperture 23
The metering wheel controller may include circuitry adapted to momentarily reverse the direction of the wheel when the sow control off signal is actuated This reduces the tendency for baits trapped in the metering wheel exit port to work loose and be deposited in an uncontrolled manner
Referring to the metering wheel, it is considered that the location of the metering wheel in the material stream is critical An external metering wheel will not crush or otherwise damage the pellet baits as prior art "paddle wheel" type devices operating within the hopper volume sometimes do These latter mixing devices appear to be intended to aid in the settling and subsequent flow-through of the material in the hopper and are not constrained within a shroud or casing In contrast, the present invention provides for a metering wheel which allows for highly accurate and controlled rates of delivery The modifications including the material out sensor and exit manifold further enhance the efficacy of the present distribution system and further allow for the efficient and controlled metering of a large variety of bait sizes and types The metering wheel may be relatively easily changed to provide delivery
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cavities of different sizes Also, as the delivery wheel rotation rate is electronically controlled the delivery rate can be adjusted as required, possibly in flight as a function of the ground speed of the aircraft The precise rate is determined by an appropriately calibrated tachometer in the aircraft cockpit. It is envisaged that the present system is capable of being integrated with an aircraft borne GPS system Use of such an integrated system allows for the highly accurate spreading of baits over terrain with the start and stop positions accurately recorded so as to reduce overlap and repeat spreading
A number of constructional variations are contemplated within the scope of the present invention and they include variations in the number and dimensions of the separators within the distribution wheel, the size of the metering device (including the casing 15) and the shape and orientation of the manifold which delivers the bait from the exit aperture of the metering device to the spinner disc for subsequent horizontal scattering The rotation rate of the spinner disc can also be varied depending on the spread required, the type and size of the bait material and other factors
It has been found that the present constructions does not exhibit significant binding, clumping or blockage of the baits as they flow out of the hopper 11 with generally the entire hopper contents being distributed in a highly controlled manner by the metering device
The interior of the metering device is accessible by removing a cover plate (not shown) The cover plate is secured to an open end of the metering device and secured at a number of places on its perimeter by latches 30a,b,c
and d The removal of this cover plate in its entirety allows the easy servicing and replacement of the separators 26/27
In a preferred embodiment, a pneumatically operated shut-off valve (not shown) may be fitted to the outlet aperture 23 This eliminates the possibility of baits remaining in the exit port being dropped from the bucket after the sow control is turned off
Thus by the present invention there is provided a metering device suitable for use with helicopter borne bait distribution buckets or, with appropriate constructional adaptation, fixed wing aircrafts Other applications are envisaged such as distributing fertiliser and other pellet based substances The advantages provided by the present invention in terms of the highly controllable load distribution rates may find applicability in other agricultural situations and the present novel metering device is not intended to be restricted solely to bait distribution
Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth
Although the invention has been described by way of example and with reference to particular embodiments, it is to be understood that modifications and/or improvements may be made without departing from the scope of the appended claims