Patent Application
20090306814
This invention relates to produce handling and sorting equipment and in particular fruit handling equipment.
In conventional fruit handling equipment the fruit is transported along a conveyor and rotated past a photographic zone where the fruit is photographed and often weighed. The fruit is then ejected from the conveyor in response to signals emanating from a computer that analyses the photographic images of the fruit to determine size, colour, weight, blemish and like parameters. This equipment usually has means activated by the computer to cause fruit to be selectively ejected off the side of the conveyor for collection in appropriately positioned bins.
In some fruit handling equipment the fruit is transported in parallel rows. However the number and spacing of these rows is determined by the need to eject the fruit from the side.
With small fruit such as cherry or grape tomatoes there is a need for compact and highly efficient sorting equipment. A major problem with cherry or grape tomatoes is the occurrence of splitting. A split tomato is viewed as a reject item. The usual way of sorting cherry tomatoes is to pass the tomatoes along a long conveyor in many rows and use humans to carefully watch the tomatoes as they rotate along the conveyor and then manually remove the split product. A typical conveyor can involve the use of 20 personnel to check and remove reject product. This process is highly labour intensive and thus expensive and, over time, the efficiency of the personnel deteriorates.
Most fruit sorting equipment uses mechanical ejection means, usually electrically operated solenoids to cause a tilting action that ejects the fruit sideways off the conveyor. It has also been proposed to use carefully positioned air jets to eject small fruit, especially fruit like cherry tomatoes off the side of conveyors. The use of appropriately positioned air jets can reduce the likelihood of damage to the fruit in the ejection process.
It is these issues that have brought about the present invention.
According to one aspect of the present invention there is provided produce sorting equipment comprising a conveyor driving a plurality of carriers spaced along the conveyor to support a single produce between adjacent carriers, at least one exit conveyor positioned above the carriers, an air distribution sprocket positioned below at least two of the carriers, the sprocket being rotatable about an axis perpendicular to the conveying direction of the conveyor, the sprocket having a plurality of radial arms that terminate below the carriers, each arm including an air conduit; and means to control air flow along each air conduit, the sprocket being positioned whereby as the sprocket rotates each arm passes underneath the carriers and an air blast via the conduit propels the produce supported by adjacent carriers up and off the carriers to fall onto the exit conveyor.
Preferably the carriers are axially rotatable rollers.
The sprocket may be rotated by contact with the rollers. Preferably the underside of the carriers engage a recess between the extremity of the arms so that an arm extends into the gap defined by adjacent rollers.
In a preferred embodiment, the exit conveyor extends at right angles to the conveyor.
In accordance with another aspect of the present invention there is provided an ejection system for produce handling equipment of the kind including a conveyor comprising a plurality of spaced carriers that convey produce past a viewing station which can detect a variety of parameters of the produce, the ejection system comprising a collector positioned adjacent at least two of the carriers, a rotatable sprocket positioned underneath the at least two carriers and connected to a source of compressed air, means to control release of the compressed air, the sprocket having a plurality of radially extending arms each including an air conduit whereby as the sprocket rotates under the carriers an air blast is released from the air conduit of at least one arm adjacent the produce to displace the produce off the rollers for collection in the collector.
An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:
a, b, c, d, and e shows an air ejection sprocket in five positions as it rotates through 30°.
The produce handling equipment illustrated in the accompanying drawings is specifically designed for use with cherry or grape tomatoes. However it is understood that this invention relates to a wide range of produce that has to be graded and sorted on the understanding that an air current can be used to eject the produce from the equipment.
As shown in
In the embodiment shown in
As shown in
The in-feed end E of the conveyor is inclined upwards at an angle of 90° to assist singulation of the fruit into individual indents between rollers 20. The fruit are transported in single file lines up an inclined slope to a viewing station S in which they pass under a series of cameras C. An auxiliary conveyor D is positioned under the conveyor at the viewing station to cause and control axial rotation of the rollers as they pass through the station. A similar auxiliary conveyor E is positioned under the inclined portion of the conveyor to encourage the fruit to assume sixteen lines. The rollers cause the fruit to rotate past the cameras C so that they can record images of the fruit. This information is fed to a computer (not shown) that can assess the size, colour, dimensions, and blemishes, especially splits, in the fruit, usually grape tomatoes. In a situation where the equipment is merely discarding cherry or grape tomatoes that contain splits, the computer will at the appropriate moment send a signal to ejection means 50 that will have the effect of ejecting the split tomato from the conveyor. The remaining tomatoes are collected off the end 15 of the conveyor for packaging.
Because there are sixteen closely spaced lanes it is not possible to effect sideways ejection of reject fruit. In this embodiment a mechanism has been incorporated that allows the rejected fruit to be ejected vertically off the conveyor 11. An air current is used to cause the rejected fruit to be propelled upwardly and forwardly in a parabolic path to be collected in a collector 40 positioned above the main conveyor 11. The collector 40 supports an exit conveyor 50 that is mounted perpendicularly to the direction of the main conveyor to thus transport the rejected fruit off the sides of the conveyor 11 at a plane above the level of the conveyor 11.
As shown in
It is understood that any number of exit stations can be provided on the conveyor downstream of the viewing station S and that in consequence, the computer can selectively reject fruit on a variety of different parameters such as size, shape, weight, blemish, or colour problems.
The mechanism for ejection of reject fruit is illustrated with particular reference to
The blast of pressurised air is supplied via an air distribution sprocket 60 that has spaced semicircular recesses 61 in its outer periphery defining twelve radial arms 62 or teeth each of which has an air conduit 63 extending radially along the centre of the arm 62. The sprocket 60 is mounted on a shaft 65 below the rollers 20 at a specific position in which the undersides of two adjacent rollers sit within the semicircular recesses 61 so that the forward motion of the rollers 20 on the main conveyor 11 causes the sprocket 60 to axially rotate about the shaft 65 which has its axis perpendicular to the direction of the conveyor 11. At the position where the adjacent rollers 20 locate within adjacent recesses 61 the extremity of the radial arm 62 terminates at a position approximately half way up the roller 20. This is illustrated in
The centre of the sprocket 60 has a hollow cylindrical chamber 66 that accommodates a fixed air reservoir 67 that is coupled to a solenoid valve 68 and air supply 69 from a compressor (not shown). The fixed reservoir 67 has a single radial exit 70 that merges into an enlarged plenum chamber 71 so that as the interior surface of the sprocket 60 rotates past the end of the plenum chamber 71, the plenum chamber 71 aligns up with a conduit 63 in the arm thus allowing air to flow from the reservoir 67 up through the conduit 63 against the underside of the fruit. The solenoid valve 68 controls release of the air on instruction from the computer so that compressed air can be released at the appropriate time and duration under the fruit to ensure vertical lift and ejection.
The fact that the sprocket 60 is driven by the rollers 20 means that the air jet moves in synchronisation with the rollers 20 which allows a nearly full pitch travel time for exposure to the air blast. This arrangement also has the advantage that the air jet is closer to the underside of the fruit than would be the case if a fixed air jet was simply positioned under the space between the rollers.
As described above the port timing on the sprocket 60 allows connection of the appropriate conduit 63 to the solenoid valve 68 but has no effect on air switching which is controlled by the solenoid valve 68. With a twelve arm sprocket 30° of angular rotation is available for each arm to be connected to the supply port 65 from the solenoid valve 68. The actual porting in the air reservoir 65 and rotating sprocket allow for 5° of overlap where two ports are simultaneously connected to the supply. By careful control of the solenoid timing the overlap region can be avoided leaving about 85% of the travel time available for ejection.
This timing feature is illustrated with reference to
The unhindered terminal vertical height of ejection for varied fruit size is approximately inversely proportional to mass. Timing of the solenoid valve in accordance with a computer determined volume therefore mass given that the density of the fruit it substantially constant, can be used to control the trajectory of the fruit up to a full pitch for large fruit and proportionally shorter duration for smaller fruit.
Matching ejection trajectory for different fruit size minimises damage to the fruit by controlling impact velocities. It also ensures that the fruit are ejected in a known parabolic fashion to ensure collection by the collector for transfer to the exit conveyor.
The size of the sprocket 60 is of considerable importance. For smooth engagement with the rollers 20 of the conveyor the sprocket needs at least twelve teeth or arms 62 to meet the engineering requirements of a roller engaging the sprocket. The moving conveyor rollers drive the free wheeling sprocket and the rollers must stay meshed with the arms 62 of the sprocket 60 for successful ejection of the fruit. This feature has to be offset against the requirement to minimise the delivery port length and volume to maintain the rapid response times necessary for fruit ejection at high speed. With the chosen conveyor pitch of 31.75 mm to suit grape tomatoes the radial conduit length from hub to arm tip for a twelve arm sprocket is about 60 mm (the pitch circle diameter of the sprocket is 122 mm). Using a 2.5 mm to 3 mm conduit diameter the required flow and response time is acceptable for fruit from 1 to 30 grams with a 6 bar air pressure supply.
In research it has been discovered that placing a pressurised jet of air on the underside of fruit resting on rollers of the kind described above can, as the air rushes past the rollers and fruit, set up a venturi effect in which there is a vacuum formed on the underside of the fruit that draws the fruit against the roller instead of propelling it upwardly.
To reduce the ventui effect and thus reduce the air pressure necessary to eject the fruit the air space between the fruit and the cylindrical core of the rollers is kept as large as possible to keep the air velocity between the fruit and the rollers as low as possible.
The venturi effect is particularly critical with small fruit that sit lower in the gap between adjacent rollers. The tip of the arms 63 of the sprockets are positioned to just touch the underside of small fruit thus causing a slight wobble of the fruit causing an air gap that breaks down the venturi effect. With bigger fruit that sit higher in the gap, the grooves 75 between the ribs on the rollers 20 ensure entry of ambient air thus breaking down the vacuum.
A grader of the kind described above has the capacity for very efficiently ejecting reject fruit through use of a controlled air current and provides a totally automated system for eliminating split tomatoes without the need for human intervention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005906194 | Nov 2005 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU06/01461 | 10/5/2006 | WO | 00 | 10/10/2008 |
