Abstract:
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 adjacent 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; 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.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to produce handling and sorting equipment and in particular fruit handling equipment. 
       BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    It is these issues that have brought about the present invention. 
       SUMMARY OF THE INVENTION 
       [0007]    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. 
         [0008]    Preferably the carriers are axially rotatable rollers. 
         [0009]    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. 
         [0010]    In a preferred embodiment, the exit conveyor extends at right angles to the conveyor. 
         [0011]    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. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]    An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 
           [0013]      FIG. 1  is a perspective view of produce handling equipment in accordance with one embodiment of the invention; 
           [0014]      FIG. 2  is a side elevational view of an ejection station that forms part of the handling equipment; 
           [0015]      FIG. 3  is an end elevational view of the ejection station; 
           [0016]      FIG. 4  is a plan view of rollers at the ejection station; and 
           [0017]      FIGS. 5   a, b, c, d,  and e shows an air ejection sprocket in five positions as it rotates through 30°. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    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. 
         [0019]    As shown in  FIG. 1 , the fruit handling equipment  10  or grader comprises an endless chain driven conveyor  11  that is supported between spaced drive sprockets  12 ,  13  mounted on a frame  15 . The conveyor  11  comprises a plurality of plastics rollers  20  coaxially mounted on shafts  21  that extend in a parallel spaced array across the conveyor  11 . The shafts  21  and rollers  20  are driven in a continuous loop to define the conveying surface. 
         [0020]    In the embodiment shown in  FIG. 1 , sixteen rollers  20  are positioned on each shaft  21  thereby defining sixteen lanes of fruit. 
         [0021]    As shown in  FIG. 4 , each roller  20  is defined by the outer cylindrical surface of the shaft  21  and six spaced annular ribs  22 - 27 . The outer ribs  22 ,  27  are slightly larger in diameter than the ribs  23 ,  26  whilst the centre ribs  24 ,  25  are the smallest in diameter. In use, The fruit (F) settles in the rib structure across adjacent rollers as shown in  FIG. 3  and the ribs define grooves  75  therebetween. 
         [0022]    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. 
         [0023]    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 . 
         [0024]    As shown in  FIGS. 2 and 3  the collector  40  comprises a substantially rectangular enclosure  41  having a base  42  that supports the exit conveyor  50 . A padded rear wall  43  extends vertically upwardly to join a roof  44  that has a downwardly inclined hood  45 . The front of the enclosure defines an elongate opening  46  between the underside of the hood and an elongate lip  47  on one side of the exit conveyor  50 . The lip  47  extends parallel to the exit conveyor  50  and transverse to the main conveyor  11 . Also shown in  FIG. 2 , the hood  45  acts to deflect the parabolic path of the rejected fruit down onto the exit conveyor  50 . In this way the hood  45  in combination with the lip  47  ensures that all rejected fruit lands on the exit conveyor  50  for removal. 
         [0025]    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. 
         [0026]    The mechanism for ejection of reject fruit is illustrated with particular reference to  FIGS. 2 to 5 . As shown in  FIG. 2  there is a space  29  between adjacent rollers and the fruit sit across the space resting on the frusto conical ends  22 ,  23  of the rollers  20 . The fruit are ejected by subjecting the fruit to a blast of pressurised air from the underside that has the effect of propelling the fruit upwardly. The forward motion of the conveyor  11  causes the fruit to be propelled upwardly and forwardly in a parabolic arc as shown in  FIG. 2  to land in or engage the collector  40  for deflection onto the exit conveyor  50 . 
         [0027]    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  FIG. 2 . The recesses  61  separate the arms  62  that are inclined to each other through an angle of 30°. 
         [0028]    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. 
         [0029]    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. 
         [0030]    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. 
         [0031]    This timing feature is illustrated with reference to  FIGS. 5   a - e  in which in  FIG. 5   a  the air passage is just opening at 15° before vertical as previous air passage has just closed. In  FIG. 5   b  the air passage is fully open at 7.5° before vertical. In  FIG. 5   c  the air passage is fully open and vertical. In  FIG. 5   d  the air passage is still fully open at 7.5° after vertical. Further rotation will cause air passage to start to close. In  FIG. 5   e  the air passage is closed at 15° past vertical and next air passage starts to open and the sprocket  60  has rotated through 30°. 
         [0032]    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. 
         [0033]    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. 
         [0034]    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. 
         [0035]    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. 
         [0036]    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. 
         [0037]    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. 
         [0038]    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.