Patent Publication Number: US-8985341-B2

Title: System and method for grading articles and selectively mixing graded articles

Description:
BACKGROUND 
     The invention relates generally to apparatus and methods for grading or sorting solid objects and more particularly to systems for mixing batches of graded objects to form selected mixtures of objects of various grades. 
     Graders are used to sort solid objects into different sizes, or grades. Solid objects that are graded include food products, such as fruits, vegetables, nuts, shellfish, portions of meat, poultry, and fish, and non-food products, such as ball bearings, castings, and aggregates. Graders are typically operated with the products in each grade permanently separated by grade for subsequent handling. In some instances, however, it is necessary to combine grades or even different products into specific mixes of products. For example, customers for chicken wings may require a mixture of 60% drummettes and 40% flats of certain grades. But forming and maintaining these specific mixtures is labor-intensive. 
     Thus, there is a need for efficiently forming specified mixtures of graded product. 
     SUMMARY 
     A method embodying features of the invention for forming mixtures of graded products comprises: (a) grading one or more products into a plurality of product grade zones; (b) accumulating predetermined quantities of graded products in each product grade zone; (c) forming individual batches of the predetermined quantities of graded products; (d) determining a destination for each of the individual batches from predetermined product mix settings; (e) conveying the individual batches to the destinations; and (f) forming mixtures of graded products by depositing the batches in destinations determined from the predetermined product mix settings. 
     In another aspect of the invention, a system embodying features of the invention for grading products comprises a first grader grading products into separate grades of products in individual grade zones and means for forming individual batches of predetermined quantity in each grade zone. A conveyor for advancing batches downstream and receives graded products in batches from means for delivering the separate batches onto the conveyor. Means for diverting the batches from the conveyor to selected destinations divert the batches to a plurality of destinations adjacent to the conveyor downstream of the first grader. 
     Another version of a grading system comprises a grader grading products into separate grades of products in individual grade zones. A sensor system produces sensor signals for determining the quantity of products in the individual grade zones. A controller coupled to the sensor system determines the quantity of products graded in each individual grade zone from the sensor signals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These features and aspects of the invention, as well as its advantages, are better understood by referring to the following description, appended claims, and accompanying drawings, in which: 
         FIG. 1  is an isometric view of a grader usable in a grade-mixing system embodying features of the invention; 
         FIG. 2  is an isometric view of an optical counter used in the grader of  FIG. 1 ; 
         FIG. 3  is a bottom view of a grader as in  FIG. 1  with a different version of optical counter; 
         FIG. 4  is an isometric view of a grader as in  FIG. 3  with a buffer for each grade zone and a batch-forming mechanism; 
         FIG. 5  is an isometric view of a grade-mixing system including two graders as in  FIG. 1 ; 
         FIG. 6  is a side elevation view of the mixing system of  FIG. 5 ; 
         FIG. 7  is a top plan view of the mixing system of  FIG. 5 ; 
         FIG. 8  is a block diagram of a control system in the mixing system of  FIG. 5 ; and 
         FIG. 9  depicts an example flow of batches of graded products in the mixing system of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     One version of a grader usable in a grading system embodying features of the invention is shown in  FIG. 1 . The grader  10  includes a grading section  12  comprising five constant-diameter rollers  14  arrayed in a planar array, shown here as inclined from a higher infeed end  16  to a lower exit end  17 . The rollers are separated by four grading gaps  18  that widen from the infeed end to the exit end to form gauging passages for grading products. The widening gaps are formed by parallel tapered or stepped-diameter rollers or by diverging constant-diameter rollers, such as those illustrated in  FIG. 1 . The ends of the rollers may be fixed in lateral position to define permanent gap widths or may be rotationally and pivotally retained in gap-adjustment mechanisms  20 ,  21  at each end that allow the grading-gap widths at the infeed and exit ends to be adjusted to fine-tune the grading process. The gap-adjustment mechanisms  20 ,  21  may be controlled manually or automatically and may include an analog display providing a visual indication of the grading-gap width or a sensor providing a signal indicative of the gap width. 
     Products to be graded are introduced into a reciprocating or vibrating feed trough  22  that drops the products onto the grading section  12  at the infeed end  16 . The rollers  14  all rotate in the same direction. A fluid spray directed from nozzles in a water pipe  24  lubricates the rollers and helps products slide down the declining grading section in the gaps. When the width of the gap matches the dimension of the product, the product falls through the gap to a bin or a conveyor, such as conveyor belt  26 , below. Dividers  28  divide the conveyor  26  into separate grade zones  30 A,  30 B. The positions of the dividers  28  may be set manually by an operator or automatically by a linear actuator as indicated by arrow  29 . Small products fall into the upstream zone  30 A, and larger products fall into the downstream zone  30 B. The largest products, which are too large to fall through the gap at the exit end  17  of the grading section  12  slide down a chute  32  onto a conveyor belt  34  in a third grade zone  30 C. Thus, the grader shown in  FIG. 1  grades products into three sizes, which can be conveyed laterally away from the grader by conveyor belts. 
     The grader  10  of  FIG. 1  also comprises a sensor system including arrays  35  of optical sensors, each including an emitter  36  and a corresponding detector  37  mounted on cantilevered arms  38 ,  39 , as also shown in  FIG. 2 . The cantilevered arms  38 ,  39  extend from a support  40  with the upper arm  38  above the grading rollers  14  and the lower arm  39  below. The emitters emit light beams  42  that are aligned with each of the gaps  18  across the width of the grader. A product passing along the grading section beneath an emitter  36  interrupts the light beam. The signal from the detector  37  indicates the state of the light beam. When the light beam is interrupted, the state of the detector signal changes. Once the product passes the emitter-detector pair, the light beam&#39;s path is unblocked and the detector&#39;s signal changes state. The signal is routed to a controller ( 82 ,  FIG. 8 ) via signal wires  44  connected to the support. By counting the changes of state of the signal from unblocked to blocked, the controller can count the number of products advancing along each grading gap in the grading section. The optical-sensor array  35 A at the infeed end is used as a counter to count the total number of ungraded products. Another optical-sensor array  35 B is positioned between grade zones  30 A and  30 B to establish the count of the number of products that are advancing to zones  30 B and  30 C. The number of the smallest products falling into zone  30 A is the difference between the accumulated counts of arrays  35 A and  35 B. A third optical-sensor array  35 C at the exit end is used as an optical counter to count the number of the largest-size products falling into the final grade zone  30 C. The number of the products in grade zone  30 B is determined by the difference in the count of the sensor array  35 B and the sensor array  35 C at the exit end. 
     An alternative arrangement of optical sensors used as counters is shown in  FIG. 3 . In this version, an elongated optical array  46  of many pairs of emitters  36  and detectors  37  flank the drop path of the products just below the grading gaps  18 . As products drop through the grading gaps, they interrupt a single light beam or two or more consecutive beams. By processing the changes of states of the detector signals, the controller can determine the number of products falling into each grade zone. 
     A different version of the grader of  FIG. 1  is shown in  FIG. 4 . The grader  48  has the same array  46  of optical-sensor counters as in  FIG. 3 , but is also equipped with three buffers  50 A,  50 B,  50 C corresponding to the three grade zones. Each buffer comprises a pair of angled walls  52  that funnel falling graded products through a restricted opening  54  bounded by a pair of side walls  56 . Vanes  58  are rotated between an open position as shown for the buffers  50 A and  50 C and a closed position for the buffer  50 B. In the open position, the long axis of each vane&#39;s cross section is vertical, which allows product to fall through the openings  54  and onto the conveyor belts  26 ,  34 . When the vanes are closed, the long axis of each vane&#39;s cross section is horizontal and forms a floor atop which falling products accumulate. The controller controls the opening and closing of the vanes to form batches of predetermined quantities on the stationary conveyor in each zone. For example, the vanes in the zone could be closed whenever the count of graded product in that zone accumulates to a predetermined count since the previous batch. Once the vanes are closed, the next batch starts to accumulate in the buffer until the controller starts up the conveyor belt to move the completed batch away. Then the vanes open to drop the accumulated batch and to let subsequently graded products fall to the conveyor belt below. In these examples, the quantity of each batch was determined by head count. As one alternative, the quantity can be determined by weight. Instead of using optical sensors as counters, the grader has a scale  60  or some form of weight sensor beneath the conveying surfaces of the belts  26 ,  34  as a sensor system. A signal corresponding to the weight of product accumulated on the belt in each zone is routed to the controller, which closes the vanes  58  when the batch reaches the predetermined weight, and starts up the belt to convey the batch away from the grader. An impact sensor consisting of a platform mounted on load cells and positioned to support the conveying surface of each belt under the buffers could sense impacts to count or weigh product. By integrating the outputs of the load cells, the controller can determine the accumulated weight of graded product in each zone. Alternatively, by measuring the amplitudes of the impacts of falling products from the load-cell output signals, the controller can determine the number of graded products landing simultaneously on the belt. By counting the number of total impacts and incrementing the count appropriately for higher-amplitude impacts caused by simultaneous impacts, the controller can determine the product count and set the batch size. 
     A mixing system using a grader as in  FIGS. 1-4  is shown in  FIGS. 5-7 . The mixing system  62  includes two graders  10 A,  10 B flanking a trunk conveyor  64 . In this example, each of the graders grades a different product: the grader  10 A grades chicken drummettes, and the grader  10 B grades chicken wing flats. The drummettes and flats are delivered by elevators  66 A,  66 B to infeed troughs  22 A,  22 B of the graders  10 A,  10 B. Each of the graders in this example is set to grade the product into three grades in three zones (from smallest to largest grade): AG 1 , AG 2 , AG 3  (for the drummettes grader  10 A); and BG 1 , BG 2 , BG 3  (for the flats grader  10 B). Conveyor belts  26 ,  34  convey the graded products to the trunk conveyor  64 . Guides  70  above the trunk conveyor  64  funnel the graded products dropping from the belts into the middle of the trunk conveyor. Graded products exiting the trunk conveyor  64  are fed onto a flighted, inclined conveyor  72 , which lifts the graded products up to the level of the tops of open bins  74 . The inclined conveyor  72  dumps the graded products onto a sorting conveyor  76 , which diverts the graded products to specified bins with gates  78  that pivot to a position traversing the sorting conveyor and guide conveyed products off the side and into a selected bin  74 . The gates  78  pivot to a position parallel to the conveying direction  80  along the side of the sorting conveyor to allow products destined for a downstream bin to pass without diversion. Products allowed to pass all the bins flanking the sorting conveyor drop into a bin at the end of the sorting conveyor. Thus, the graded products can be conveyed to seven bins  74  in this example. 
     The two graders  10 A,  10 B include means for forming batches of a predetermined quantity for each of the six graders through the use of buffers and weight sensing or product count. The conveyor belts  26 ,  34  are operated stop-and-go as indexing belts to deliver individual batches of graded products onto the trunk conveyor  64 , which can continuously advance the batches toward the bins. 
     The operation of the system is controlled by the controller  82 , as shown in  FIG. 8 . The controller may be a programmable-logic controller, a personal computer or workstation, or any appropriate programmable device. An operator interface comprising a monitor  84  and an input device, such as a keyboard  86 , allows system settings to be made and the status to be monitored. The controller receives the count signals from all the counters  37  over the optical signal lines  44  or all the weight signals  88  from the scales  60 . The controller  82  controls the starting and stopping of the graders&#39; indexing conveyor belts  26 ,  34  over motor-control lines  90  connected to the belts&#39; drive motors  92  and provides open-close batching signals over vane-control lines  93  to actuators for the buffer vanes  58 . The controller also sends open-close signals  94  to gate actuators  96  that pivot the gates  78  between diverting and passing positions on the sorting conveyor. The controller may control the grading-gap widths, the positions of the grade-zone dividers, or the speed of the trunk conveyor  64 , the elevator  66 , the inclined conveyor  72 , and the sorting conveyor  76  over signal lines  98 . The controller  82  can activate an alarm  101  or display alarm conditions on the monitor  84 . Other sensors  68  sensing the presence of batches at various positions along the conveying system, the grading-gap widths, or the positions of the grade-zone dividers may also send signals to the controller over sensor-signal lines  99  to allow closed-loop control of the transport of batches through the grading system or of the grading-gap or grade-zone settings. 
     The operation of the grading and mixing system is illustrated in  FIG. 9 . In this example, the trunk conveyor  64 , the incline conveyor  72 , and the sorting conveyor  76  are all running at constant speeds in the directions of the arrows  100 . The grader belts  26 ,  34  index batches of graded products of predetermined quantities onto the trunk conveyor from the sides. The grader belts are stopped while they are accumulating graded products. Once the quantity of the batch in each grade zone reaches the predetermined quantity for that batch, the controller closes the buffer and indexes the grader belt forward to load the batch destined for a specific mixing bin  74 . For example, the batch in grade zone BG 2  is denoted in  FIG. 9  as BG 2  M 1  to indicate that it is a batch from grade zone BG 2  destined for mixing bin M 1 . The controller  82  ensures that the batch is loaded onto an open area of the trunk conveyor  74 . Because the controller knows the speeds of the conveyors and their geometries and the times that the grader belts loaded their batches onto the trunk conveyor, the controller can determine the positions of the batches on the trunk conveyor and can control the loading of batches onto the trunk conveyor to avoid collisions. Once the batch is loaded onto the trunk conveyor, the controller stops the indexing grader belt and re-opens the buffer to allow accumulated graded products to drop onto the belt. The batch is loaded onto the trunk belt and conveyed toward the mixing bins. Each batch has a known quantity (count or weight) of a certain grade of products and is associated with a known destination bin. For example, the bin M 4  may require a mixture of 60% large-size drummettes and 40% large-size flats. The controller uses that predetermined mixture setting to set a quantity size for batches of drummettes in grade zone AG 3  and a quantity size for batches of flats in grade zone BG 3 . The designated batches are formed and loaded onto the trunk conveyor. When one of the batches destined for the bin M 4  reaches the bin, the controller pivots the bin&#39;s gate to divert the batch AG 3  M 4  (large-size drummettes) to bin M 4 . The gate is closed to allow the trailing batch AG 2  M 6 , destined for downstream bin M 6  to pass. Then M 4 &#39;s gate is re-opened to the diverting position to guide the BG 3  M 4  batch (large-size flats shown at an earlier time in  FIG. 9  on the incline conveyor) to its destination bin M 4 . Because the controller knows the speeds of the conveyors and their lengths, it can keep a continuously updated map of the traffic on the conveyors. But, for more positive determination of the traffic status, optical sensors, cameras providing visual data, or proximity switches can be positioned along the conveying system to provide the controller with signals indicating the positions of the batches on the conveyors. 
     The controller allows each grade zone to provide batches of different quantities destined for different bins. Thus, the controller runs software processes that: (a) compute the quantities of each grade of products needed to form the selected product mixes; (b) form batches of the computed quantities in each grade zone; (c) load those batches onto the trunk conveyor; (d) assign destination bins to each batch; (e) manage and track traffic flow on the conveyors; and (f) divert the batches to their correct destinations. In this way, the controller automates the mixing of two different graded products into different product mixes. 
     The controller  82  may also provide useful data to operators or dynamically control the operation of grading. The data may be sensor data or data computed from the sensor data or operator settings. One example of useful data is the ratio of the product count to the weight of a batch of graded products. The controller can compute the ratio for each batch from the signals from the counters and the scales. If the ratio lies outside a preset range, the controller can set an alarm or can automatically adjust the gap widths or the positions of the grade-zone dividers. Another example of useful data is the count in each batch in corresponding zones of parallel conveyors within a time window. In grading chicken wings, in which all flats are conveyed to one grader and all drummettes are conveyed to a second grader, the number of drummettes in a grade zone should be more or less the same as the number of flats in the corresponding grade zone. And the gaps and dividers are set up that way. If the cutter that severs the wing tip from the flat is not cutting consistently at the joint, some of the flats will include a portion of a wing tip, which could cause the flat to be graded into too large a grade. So if the counts in corresponding zones from the first grader to the second are not incrementing at more or less the same average rates, an alarm can be sounded or the grader can be automatically adjusted. As another example, if a grader is set to produce batches at the same average rate in all the zones, but one zone is receiving more products than the other zones, the controller can sound an alarm or automatically take corrective action. Thus, the controller can be used to set alarms or automatically adjust grading settings when grading results lie outside alarm limits or set operating ranges. The controller can also display settings, setting ranges and alarm limits, conveyor speeds, batch weights and counts, batching rates, and other information on the monitor that can help operators fine tune the grading process. The controller can use the data it collects and computes to display time series of various grading results to show trends in the grading process that may indicate problems in the grading process. It should be clear that the data presentation, alarm setting, and control functions could be adapted for use with other kinds of graders that grade products into separate grades in individual grade zones. 
     Although the invention has been described with reference to a few specific versions, other versions are possible. For example, any kind of grader equipped with means for forming batches of each grade that contain a selected quantity of graded product could be used in the system. As another example, products could be counted by counters realized as series of limit switches having whisker actuators contacted by the products as they pass along the grading gaps at locations such as those where the optical sensors are located. A camera or other visioning system could also be used as a sensor system to count products falling into each grade zone or to identify the positions of batches on the conveyor. The mixing system may also be used with a single grader or with more than two graders. In the case of more than two graders, the trunk conveyor may have to be lengthened or a number of branch conveyors, each associated with a certain number of graders, may have to be used to feed into a trunk conveyor. And each of the graded batches may be transported to downstream graders if finer grading is required. Besides being useful in mixing batches of graded chicken wings, the grading and mixing system is adaptable to other food products, such as shrimp, fruits, vegetables, and nuts, and to non-food products, as well. So, as these few examples suggest, the scope of the invention is not meant to be limited to the details of the exemplary versions.