Patent Publication Number: US-6659287-B1

Title: Apparatus and method for grading articles

Description:
TECHNICAL FIELD 
     This invention relates to a method of and apparatus for automatically sorting articles and more particularly to a method and apparatus for automatically sorting articles such as harvested fruit and vegetable crops in accordance with their shape, size and the presence and seriousness of defects. 
     It has been conventional practice when sorting such articles to establish the grades required and the criteria for each grade in advance of the sorting operation and then for workers to manually randomly sort produce in accordance with the pre-determined grades. The disadvantage of such a system is that it is necessarily labour intensive and accordingly costly. 
     An object of the present invention is to provide improvements in relation to one or more matters discussed herein and/or generally. 
     According to the invention there is provided apparatus for grading articles such as fruit and vegetables, and a method of grading articles such as fruit and vegetables as defined in the accompanying claims. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the invention apparatus for inspecting and sorting articles such as fruit and vegetables comprises a spool or roller conveyor onto which articles are presented from a discharge chute. The discharge chute may oscillate to assist alignment and movement of the articles discharged onto the conveyor. The conveyor carries the objects under a viewing device or inspection zone at which a camera-type scanning unit is mounted overhead of the conveyor in such a way that the camera can scan the articles as they pass underneath. The roller elements of the conveyor are driven to rotate during the scanning process in order that the articles thereon also rotate to afford as full a view as possible of the articles. 
     Apparatus such as a video grabber converts the visual image data provided by the camera. This information is passed to a central processing unit which analyses and evaluates the images of the individual article created by the camera as to size (length/diameter/volume), grade (rot, cracks, damage etc) and orientation as well as position in the direction of travel and the space occupied on the conveyor as the article sits in the valleys formed between successive roller elements. Any defects present are characterised into groups in accordance with pre-determined characteristics and converted into a numerical value, such as a percentage. An operator establishes, by means of a set-up screen, the required characteristics or numerical value of the particular grade to be selected for. The operator controlled program then establishes a discharge position where selected articles will be removed from the conveyor according to the required classification, that is by size, grade or direction of orientation. The central processing unit would determine the point at which the selected article is to be removed and how many actuators to activate to cause article removal devices or flip levers located just under the full length of the product to flip the article onto the take out conveyor or flume. 
     Tracking means mazy ho provided on the conveyor so as to enable the position of each article to be followed, thus facilitating removal of the particular article from the conveyor on reaching the required discharge position. 
     Articles may be removed or ejected from the conveyor at the required position by article removal devices. A plurality of devices may be provided and mounted at intervals between the roller elements and across the width of the conveyor. The devices comprise a flip lever. 
     In another embodiment of the invention said article removal elements may be in the form of projections. Said projections may be of finger-like form. The finger-like projections may be inclined forwardly with respect to their direction of angular movement when actuated. 
     In a further embodiment of the invention the flip levers may be shaped, for example, diablo shaped, to suit the particular type of articles being graded such as citrus fruits. 
     The flip lever may be pivotally mounted beneath the conveyor. Each flip lever, when activated, moves in an upward direction and passes between two successive pairs of roller elements to contact an article lying on the conveyor. The upward momentum imparted to the article as a result of contact between the flip lever combined with the forward momentum from the roller conveyor causes the article to be carried upwardly, or “flipped” onto a discharge belt or flume while the flip lever retracts. 
     Transverse overhead take-out conveyors or water flumes are provided to collect and deliver to the side of the machine those articles which are removed from the conveyor when the required position is reached. The articles are flipped up and into the take-out conveyor or flume by the flip levers in the roller conveyor system. 
     In an embodiment two or more article removal devices such as flip levers may be provided for each article to be removed, wherein the size of the article may determine the number and/or sequence of elements which are actuated at any one time. 
     Those articles remaining on the conveyor will be discharged over the end of said conveyor. In most cases these articles will represent the prime grade required. 
     Any number of discharge belts and corresponding ejector mechanisms may be provided depending on the number of classifications required during a given. operation. 
     A typical machine will have three take-out positions with the required ejector mechanisms and discharge belts in addition to the over the end separation point making a total of four although any number of take-out points may be provided, It is envisaged that the take-out points will be of modular construction and the length of the machine may be extended by adding further such points. It is also envisaged that the apparatus herein before described will replace the conventional inspection conveyor normally positioned between the station for washing/sorting of articles and packing which is generally manned by a number of people. 
     According to the invention there is also provided a method for inspecting and sorting articles such as fruit and vegetables, said method comprising the step of locating the articles on a conveyor for example by discharging the articles from a chute onto a spool or roller conveyor. The chute may be caused to oscillate to assist alignment of the articles. The articles on the conveyor pass under a viewing device or inspection zone at which the articles are inspected and scanned as they pass. The method comprises the step of analysing an image or other data from each article by a data processing and control system, said data being processed in order to classify the articles according to shape and/or size and/or defects. The method comprises the step of causing a selection of said classified articles to be removed or ejected from the conveyor in response to said classification. During the step of removal or ejection, the article is caused to be lifted from the surface of the conveyor and moved to a discharge conveyor. 
     An advantage of the invention described herein is that it provides a faster, less labour intensive and accordingly a more economical method for sorting articles such as fruit and vegetables. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: 
     FIG. 1 shows a side elevation view of the inspecting and sorting apparatus according to the invention; 
     FIG. 2 shows a sectional view taken along the line A—A of the apparatus of FIG. 1; 
     FIG. 3 shows a side elevation view of a section of a roller assembly according to the invention; 
     FIG. 4 shows a side elevation view of a flip lever; 
     FIG. 5 shows a side elevation view of a roller element; 
     FIG. 6 shows a side elevation view of a roller element, flip lever and associated actuating means; 
     FIG. 7 shows a side elevation view of three flip levers and associated roller elements, showing the position of the flip levers in relation to one another and the movement of a flip lever; 
     FIG. 8 shows a side elevation view, schematic in character of a portion of the apparatus according to the invention showing the position of an article to be sorted in relation to the roller elements and flip levers; and 
     FIGS. 9 a - 9   d  show a side view, schematic in character of the action of an alternative flip lever. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     As shown in the drawings, apparatus for conveying and inspecting articles  10  comprises a spool or roller conveyor  12 . Said roller conveyor  12  comprises a series of roller assemblies  14 . Each roller assembly  14  is formed by mounting a plurality of roller elements on a hexagonal steel shaft  16  having bushings  18  at each end and a sprocket  20  attached near one end. The roller elements  22  comprise disc shaped rollers with a central aperture  24  which is hexagonal to enable them to be received on the shaft  16 , and a round hub portion  26  on one side. 
     The aperture  24  could be of any other suitable shape such as triangular, pentagonal, or square but in practice a roller element  22  with a hexagonal-shaped aperture mounted on a correspondingly shaped shaft provides the best drive. Also mounted on the shaft  16  and between the roller elements  20  is a flip lever  28 . Said flip lever  28  comprises a round portion  30  having an aperture  32  which is round for receiving the hub  26  of the roller element  20 , a substantially horizontally extending arm or lever portion  34  and a substantially vertically extending leg portion  36 , all of which may be moulded as a single body  38  to provide the flip lever  28  with additional strength. 
     The aperture  32  may be formed off-centre with respect to the body portion  38  of the flip lever  28 . The arm portion  34  of the flip lever  28  extends in a direction opposite to that of the flow of items on the conveyor  12  (ie upstream) and extends towards and rests in the region of the top of the pivot point of the following flip lever  28  located on the next shaft  16 . The body portion  38  is shaped in the region of contact  44  to accommodate the round portion  30  of the following flip lever  28 . The leg portion  36  extends in a downwardly direction below the conveyor  12 . 
     The flip lever  28  is constructed such that the arm portion  34  is below the upper edge of the roller elements  22 , such that the upper face of the arm portion  34  is positioned just below the articles (such as fruit/vegetables to be graded) as these lie in valleys  46  formed by and between the rollers elements  22  of successive roller assemblies  14 . Smaller size or diameter articles may lie directly on top of the upper face of the arm portion  34 . The leg portion  36  of the flip lever  28  extends in a downward direction past the bottom of the roller elements  22 . By extending downwardly below the conveyor  12 , the leg portion  36  may be actuated by suitable actuating means  48  positioned beneath the flip lever  28 . The leg portion  36  is also formed with an stop or lug portion  42 . 
     The roller assemblies  14  are attached at their end points to drive chains  50  which pass over the sprockets  20  located at the end of the conveyor  12 . An electric motor drives the sprockets  20  at the discharge end of the conveyor  12 . As the motor drives the sprockets  20 , the chains  50  on each side of the roller conveyor  12  advance, along with all of the roller assemblies  14  which are carried perpendicularly between the chains  50 . 
     By alternately installing a roller element  22  then a flip lever  28  on the shaft  16 , a flip lever/roller assembly  14  may be created of any axial length. A shaft collar will be used on each end of the shaft to hold the assembly together. The length of the hub  26  and diameter of the roller element  22  is such that the flip lever  28  is free to rotate on the hub  26 . 
     The bushings  18  at the ends of the shafts  16  are used to connect pins on standard pin chain which is used to form the conveyor  12 . In this manner, the shaft  16  assembly is free to rotate on the chain pins. The endless chains on each end of the shaft  16  are carried by a plastic chain support guide as they advance. 
     The sprockets  20  mounted on the end of each shaft  16  may be driven by a spin chain system  50   a  driven independently to the main chain  50 . The spin chain moves over a solid support guide  64  which raises the chain  50   a  to engage with the sprockets  20 . This causes rotation of the sprockets  20  and the roller elements  22  up the in-feed section and under the camera  58 , and the entire roller assembly  14  may be rotated at whatever speed is desired. The flip levers  28 , being free on the hubs  26  of the roller elements  22 , are not rotated by the drive to the shaft  16 . The roller elements  20  stop rotating after the last view when the guide  64  is lowered at position  66  to disengage the chain  50   a  before the chains run onto the sprocket  20   a.    
     Actuating means for the flip levers  28  are positioned beneath the roller conveyor  12 , transverse to the direction of flow, with one rank or array of actuators for each take-off position desired. The actuators would comprise pneumatic, solenoid or other suitable devices that move an actuating cylinder, block or ramp  52  into a position in the path of the leg portion  36  of the respective flip lever  28 . Said cylinder  52  is formed with a flange or boot portion  54 . 
     Actuation of the cylinder  52  causes it to move in an upwardly direction towards the conveyor  12 . Upward movement of the cylinder  52  results in the flange or boot portion  54  extending past the downwardly extending leg portion  34  of the flip lever  28 , such that the two come into direct contact, with the cylinder  52  and flange or boot  54  acting as a trip lever. The flange or boot  54  contacts a correspondingly shaped lip or flange  40  on the leg portion  34  of the flip lever  28 . On contact, the flip lever  28  is temporarily prevented from advancing forwardly, but the continued forward movement of the roller assembly  14  on which the flip lever is mounted, causes the flip lever  28  to turn on the hub  26  of the corresponding roller element  22 , slowly at first and then with increasing angular acceleration as the forward movement of the roller assembly  14  continues. 
     The angular movement of the flip lever  28  causes the arm portion  34  thereof to rotate forwardly and contacts an article located on the conveyor  12 . Such contact causes the article to be lifted or “flipped” away from the conveyor  12 . This lifting action, together with the forward speed of the conveyor, results in an article being lifted upwardly and forwardly from the conveyor  12  onto an appropriate cross conveyor or flume  62 . Angular movement of the flip lever  28  continues until the stop portion  42  contacts a roller element  22  located on the following roller assembly  14 . The contact between the stop means  42  and the roller element  14  halts the angular movement of the flip lever and said flip lever retracts to its non-actuated position. The body portion  38  of said flip lever  28  is shaped in the region  45  to prevent the flip lever  28  fouling the corresponding roller element when said flip lever  28  is actuated. 
     In use, the typical operation of the invention is described below. A in-feed delivery unit feeds the articles to be graded and sorted evenly across the width of the roller conveyor  12 . Such devices will deliver the articles from conveyors or elevators and cause them to be evenly spread and properly positioned for effective filling of the valleys  46  on the roller conveyor  12 . 
     The articles are delivered in a continuous flow to the delivery unit where they are positioned so that as the roller conveyor  12  advances underneath, the products can drop into the valleys  46  formed between each roller assembly and will fill the valleys  46  formed between the roller assemblies  14  across the width of the conveyor  12 . 
     Excessive volume of articles would cause “doubles” to occur so it is important the feed rate is such that excessive “doubling” (two articles in one valley  46 , or overlapping) does not occur. The roller assemblies  14  are driven by their sprockets  20  at any speed of forward or reverse rotation (with respect to the conveyor&#39;s travel direction) to assist in filling the valleys  46 , ensuring singulation and preventing doubles. 
     As the articles are delivered on to the roller conveyor  12 , the roller assemblies  14  are advancing, usually but not exclusively, up an incline sufficient to help align the products in the valleys  46  formed between the rollers. The roller assemblies  14  advance at a constant rate, being pulled by the chains on either end of the roller assemblies  14 . The roller elements  22  are rotated by the sprockets  20  at either end of the shafts  16  which are being turned by a separate moving chain system. 
     The articles on the conveyor are also being rotated by the roller elements  22  as they pass underneath the camera viewing area  56  such that the articles rotate by at least one full revolution. The cameras  58  will take one or more views of the articles in order to obtain as full a view as possible of all sides of the articles. The required take-off position is determined from the position on the conveyor occupied by article when the final view of the article was taken. Accordingly, once the conveyor  12  passes under the viewing section  56 , the roller elements  22  are no longer driven to rotate. This is because when the roller elements  22  are rotating, the articles carried thereupon drift across the valleys  46  and the relative position of the article on the conveyor  12  is not stable. As the take-off position of the article is calculated from the last view of the article taken, in order to be removed at the correct position the article must not have moved from that particular point on the conveyor  12 . Articles not ejected from the conveyor  12  are carried by the roller elements  22  through the take-off section  60 . 
     At a first take-off position, articles of a certain size, grade or orientation are flipped up and forward into a cross flow take-off conveyor or flume  62 . At a further take-off point, articles of a different size, grade or orientation are flipped up and forward into a further cross flow take-off belt or flume located at this position. Long articles such as carrots where orientation is important for subsequent processing or packing, may be selectively removed at different take off points depending on the direction the carrot is facing (orientation). When flipped up into the cross flow take-off conveyance, the carrot remains pointing the same direction as it lay in the valley  46  formed between the roller elements  22 , because a plurality of flip levers  28  are actuated at the same time across its length to propel the carrot without reorientating. 
     The combination of a simple carrier system, sophisticated camera and processing system and simple forward flip lever system for removal of the products into overhead cross conveyances results in an economic way to size, grade and orient a wide variety of fruit and vegetable commodities.