Abstract:
A narrow belt conveyor system is provided with a pop-up style diverter comprising a plurality of rows of diverter wheels in which each row raises and lowers independently of any of the other rows. Thus, each row of diverter wheels can be raised before the leading edge of a conveyed article reaches that particular row of diverter wheels and lowered after the trailing edge of the conveyed article has cleared that row. This permits the spacing between the articles to be greatly reduced, greatly increasing the article throughput rate and/or reducing the conveyor speed while achieving the same throughput rate.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of the filing date of the U.S. Provisional Patent Application, Ser. No. 60/812,286, filed Jun. 9, 2006, which is herein incorporated by reference. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    A narrow belt conveyor system is shown in U.S. Pat. No. 6,843,365, which is incorporated herein by reference. Narrow belt conveyor systems utilize a plurality of continuously moving parallel belts for conveying flat-bottomed objects along straight runs. Such a system is shown generally in  FIGS. 1 and 2 , and is generally designated  10 . The system includes multiple belts  15  supported between opposed side frames  16  and  18 . While four belts  15  are shown in  FIGS. 1 and 2 , more or less can be used, as required. The spaces between the belts readily accommodate pop-up transfers and diverters, such as the 90 degree transfer  20  and the 30 degree diverter  22 , to direct conveyed articles to an appropriate destination.. As best seen in  FIG. 1 , the pop-up diverter  22  comprises a plurality of wheels  24  arranged between the spaced belts  15  in three rows to present, when viewed from above, a generally triangular array, 
         [0003]    Efforts are always being made to increase the rate at which items can be handled by a conveyor system, sometimes referred to as the throughput rate. One way to increase the throughput rate is to increase the speed of the conveyor. A second way to increase the throughput rate is to reduce the gap between articles conveyed on the system. However, the extent to which the second way can be utilized has heretofore been limited by the size of the diverter unit. Specifically, and with reference to  FIGS. 1 and 3 , all the diverter wheels of the pop-up diverter are carried on brackets  26  that are typically mounted on a common frame or support member  28  so that they are all raised and lowered in unison. Thus, the minimum spacing or gap between adjacent conveyed articles that pass over the diverter  22  must be greater than the distance across all the rows of wheels  24  that comprise the diverter so that the trailing edge of a first conveyed article completely clears the diverter section before the leading edge of the next conveyed article arrives. As can be appreciated, this puts a lower limit on the space or gap between conveyed articles, thus limiting the extent to which spacing can be reduced to maximize the rate at which articles can be handled by the conveyor. Accordingly, it is an object of the present invention to overcome the limitations inherent in prior art diverter systems to increase the throughput rate of a narrow belt conveyor system. 
       SUMMARY OF THE INVENTION 
       [0004]    This object, as well as others that will become apparent upon reference to the following detailed description and accompanying drawings, are provided by a pop-up style diverter comprising a plurality of rows of diverter wheels in which each row raises and lowers independently of any of the other rows. Thus, each row of diverter wheels can be raised immediately before the leading edge of a conveyed article reaches that particular row of diverter wheels and lowered immediately after the trailing edge of the conveyed article has cleared that row. This permits the gap or spacing between the articles to be greatly reduced, greatly increasing the article throughput rate and/or reducing the conveyor speed while achieving the same throughput rate. 
         [0005]    More specifically, a conveyor system is provided that comprises a plurality of endless narrow belts that support the conveyed articles. A diverter is provided for directing conveyed articles off the narrow belts onto a spur to a first destination in which the diverter comprises a plurality of rotating wheels located between the narrow belts and oriented obliquely to the narrow belts in a plurality of rows. The diverter wheels in each row are mounted so as to be raised and lowered in unison independently of the diverter wheels in any other row. The diverter wheels move from a first position in which the wheels are entirely beneath the upper surface of the narrow belts to a second position in which a portion of the wheel protrudes above the upper surface of the narrow belts so that they can support an article being conveyed over them. 
         [0006]    In another aspect of the invention, a controller is provided for sequentially raising and lowering the rows of wheels so that each row of diverter wheels is raised just before a first item to be diverted passes over that row of wheels and is lowered either after the first item has cleared that row of wheels or just before a second item not to be diverted passes over that row of wheels. 
         [0007]    In another aspect of the invention, a support is provided for each row of wheels and an actuator for each support so as to move the support between the first and second positions. 
         [0008]    In another aspect of the invention, a method for operating a conveyor system that comprises at least one conveyor belt and a diverter comprising at least two rows of diverter wheels, each row of diverter wheels being capable of raising and lowering independently of the other row. In accordance with the method, a first destination code is assigned to each conveyed item that is to be diverted and a second destination code, different from the first, is assigned to each conveyed item that is not to be diverted. The movement of the conveyor belt is measured with an encoder that generates a pulse for each increment of movement of the conveyor. The movement and position of the conveyed items are tracked along the conveyor, and a separate raise signal for each row of diverter wheels is generated to sequentially raise the rows of the diverter wheels when each conveyed item that is assigned the first destination code reaches a predetermined position upstream of each of the rows of diverter wheels. A separate lower signal is generated for each row of diverter wheels to sequentially lower the rows of diverter wheels. 
         [0009]    In keeping with another aspect of the invention, the lower signal is generated when each conveyed item that is assigned the first destination code reaches a predetermined position downstream of each row of diverter wheels. Alternatively, or additionally, a lower signal for each row of diverter wheels may be generated at a specified time after the raise signal for each row has been generated. 
     
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a top view of a prior art narrow belt conveyor system having a 90 degree diverter module and a 30 degree diverter module associated therewith. 
           [0011]      FIG. 2  is a side view of the prior art narrow belt conveyor system of  FIG. 1 . 
           [0012]      FIG. 3  is an enlarged cross-sectional view taken along line  3 - 3  of  FIG. 1  showing a 30 degree diverter as known in the prior art. 
           [0013]      FIG. 4  is a top view of a sequential diverter module in accordance with the present invention. 
           [0014]      FIG. 5  is a side view of the sequential diverter module of  FIG. 4 . 
           [0015]      FIG. 6  is an enlarged plan view of the separate actuators for each of the rows of the diverter wheels for the sequential diverter module of the present invention. 
           [0016]      FIG. 7  is an end view showing a single row of diverter wheels. 
           [0017]      FIG. 8  is a schematic side view showing the relationship between the rows of the diverter wheels and the top of the conveying belts of the associated belts of the narrow belt conveyor system. 
           [0018]      FIGS. 9 ,  10  and  11  are top, end and side views of a single row of diverter rows for use in the present invention. 
           [0019]      FIGS. 12-20  are schematic top views showing the operation of a narrow belt conveyor system having a sequential diverter module according to the present invention. 
           [0020]      FIG. 21  is a schematic diagram of the controller for the sequential diverter module of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Turning to  FIGS. 4-11 , a pop-up diverter module according to the present invention, generally designated  50 , is shown. The diverter module  50  shown is for a “right hand” divert with respect to the direction of travel of the conveyed items. In a “left hand” divert, mirror image versions of the various component parts would be required. 
         [0022]    The diverter module  50  is shown in conjunction with eight narrow conveyor belts  52 , although more or fewer may be used, depending upon the size of the articles to be conveyed. The illustrated diverter module  50  comprises six rows  54 ,  56 ,  58 ,  60 ,  62  and  64  of diverter wheels  66 , each row having seven diverter wheels  66 . Again, more or fewer may be used depending on the user&#39;s requirements The wheels  66  are oriented obliquely with respect to the direction of travel of the narrow belts. In the illustrated embodiment, the diverter wheels are at an angle of 30 degrees with respect to the direction of travel of the belts  52 , although other angles oblique to the direction of travel may be chosen As shown, the wheels  66  of each row are spaced between the sideframe and rightward seven belts  52 . 
         [0023]    As best seen in  FIGS. 9-11 , each of the diverter wheels  66  is mounted to a wheel bracket  68  so as to be freely rotatable. An idler wheel  70  is also rotatably mounted to each wheel bracket  68  Each idler wheel  70  includes two grooves for seating two O-ring drive belts A first drive belt  72  (best seen in  FIG. 11 ) operatively connects an idler wheel  70  to its associated diverter wheel  66 . A second drive belt  74  (best seen in  FIG. 5 ) operatively connects an idler wheel  70  to its associated drive roller  76 . As best seen in  FIGS. 4 and 5 , a separate drive roller  76  is associated with each row  54 - 64  of diverter wheels  66 . The drive rollers  76  are mounted between the side frames of the conveyor system on a stationary axle so that the drive rollers  76  are frictionally engaged by the top sides of the return runs of the belts  52 . Thus, the drive rollers  76  are continuously rotated as long as the belts  52  are moving, and, consequently, the drive rollers  76  continuously rotate their associated idler wheels  70 /diverter wheels  66 . 
         [0024]    In keeping with the invention, each row  54 - 64  of diverter wheels  66  is adapted to be raised and lowered independently of the other rows. To this end, each row of wheel  66  preferably comprises a cross member  78  (best seen in  FIGS. 9-11 ) to which the brackets  68  supporting the diverter wheel  66  are attached. The cross member  78  is pivotally secured between the side frames by a pivot block assembly  80  secured to each of the opposite ends of the cross member  78 . The cross member  78  for each row of diverter wheels  66  has an actuator  82  associated therewith to arcuately pivot the cross member  78  (and thus its associated diverter wheels  66 ) between a first position in which the diverter wheels  66  are entirely beneath the top surface of the belts  52  to let conveyed articles to pass straight through (shown in dotted lines in  FIG. 8 ), and a second position in which the diverter wheels protrude above the belts  52  to redirect or divert the conveyed articles passing over to a spur. As shown, the actuators  82  are piston actuators, with their piston rods operatively connected to the cross member  78 . The pistons are preferably pneumatically or hydraulically controlled. However, other types of actuators, such as servo motors, may be used. 
         [0025]    As best seen in  FIG. 8 , bumper brackets  84  including two rubber ovals are secured to the side frame to limit the pivoting movement of the cross member  78  and to provide for noise reduction, 
         [0026]    With reference to  FIG. 8 , the extent to which the diverter wheel  66  in the various rows of diverter wheels raises above the belt  52  varies depending upon the row. Specifically, the first two rows of diverter wheels  66  protrude a height less than that of rows  3 - 6  to provide for a gradual raising of a conveyed article to the full height. In a preferred embodiment, the diverter wheels  66  in the first row  54  protrude ⅛ inch above the surface of the belts  52 ; the diverter wheels  66  in the second row  54  protrude  1 / 4  inch above the belts  52 ; and the diverter wheels in the third through sixth rows  56 - 64  protrude ⅜ inch above the belts  52 . 
         [0027]    The invention also comprises a system for controlling the diverter  50  Movement of the sortation conveyor belt surface is measured with an incremental encoder, shown in  FIGS. 12-20  as “E”. By way of example, each inch (approximately) of conveyor movement results in one pulse output from the encoder. Since cartons move at the conveyor speed, the encoder output is a direct indication of carton movement on the conveyor. Similar tracking can be done with an absolute encoder. 
         [0028]    Referring to  FIG. 12 , two cartons  90 ,  92  are shown moving on the conveyor. The downstream carton  92  is addressed to a first diverter  94 . The second, upstream carton  90 , is addressed to a second diverter (not shown), which is somewhere downstream of diverter  94 . 
         [0029]    Shown just underneath the conveyor in  FIG. 12  is a data table which keeps track of the destinations of cartons as they move down the conveyor “1” represents the destination of the first (down stream) carton  92 , and “2” represents the destination of the second (upstream) carton  90 . As cartons  92 ,  90  move down the conveyor, the incoming encoder pulses are used to shift the destination data in the data table in a manner synchronous with the carton movement. 
         [0030]    Three rows of diverter wheels for diverter  94  are shown in  FIGS. 12-20  as diagonal slashes  96 , either lowered (thin lines) or raised (bold lines) However, the control sequence as described can be applied to diverters with any number of two or more rows of diverter wheels. In keeping with the invention, each row is individually controlled. One data table position corresponds to each row of diverter wheels. When a value of 1 is moved into one specific data table position, the corresponding row of diverter wheels is given a “raise” signal The row of diverter wheels is raised and stays in the raised position until a “lower” signal is received. When a value not equal to 1 or zero is moved into same data table position, the row of diverter wheels is given a “lower” signal. The row of diverter wheels is then lowered and stays in the lowered position until a “raise” signal is once again received 
         [0031]      FIGS. 12-20  show a sequence of two cartons following each other. The first carton  92  is destined for diverter  1 . As carton  92  it approaches diverter  94 , the three rows of wheels are sequentially raised, based on the data values in the data table, so as to be in the raised position just prior to the leading edge of the carton  92  reaching each row of wheels. The second carton  90  is intended to be conveyed to a destination beyond the diverter  94 . As carton  90  approaches diverter  94 , the three rows of wheels are sequentially lowered, so as to be in the lowered position just prior to the leading edge of the carton  90  reaching each row of wheels Thus the second carton  90  passes diverter  94  without being diverted. 
         [0032]    The diverter wheels can also be lowered based on time, not in place of but in addition to the lowering logic described above. For example, a row of diverter wheels can be lowered if a raise signal has not been received within the previous three seconds. This insures that a row of wheels does not remain in the raised position should there not be any more cartons traveling down the conveyor. 
         [0033]    The diverter of the present invention requires high speed control of the individual rows of diverter wheels. In practice, this requires receiving sensor input signals and triggering outputs with a repeatability of within 10 milliseconds. With reference to  FIG. 21 , a high speed controller  98  is provided for each diverter to handle all diverter control functions, and specifically directing each row of diverter wheels to either raise or lower at the proper time to affect a divert. 
         [0034]    A sortation controller  100  is used to control the entire conveyor system The controller  100  determines the destinations of all products introduced to the conveyor system, and tracks the movement of the product as it is conveyed along the conveyor system. The sortation controller  100  receives inputs from photosensors  102  and encoders, and operates motor drives and the controller  98 . 
         [0035]    The sortation controller  100  communicates to the individual diverter controllers  98  over a bus network, such as “DeviceNet,” available from Rockwell Automation. The sortation controller  100  signals a specific controller  98  when a product on the conveyor is within a specified short distance of the divert position associated with the controller  98 . The controller  98  then creates a time window, which is a fixed time period during which an induct photosensor is armed to look for approaching conveyed product. If the product&#39;s leading edge blocks the induct photosensor within the time window, the controller  98  then takes over tracking of the product, activating or deactivating the actuators  104  associated with the controller  98  as required to raise and lower the six rows of divert wheels in the required timing sequence 
         [0036]    If the product&#39;s leading edge blocks the induct photosensor when there is no time window present, the controller  98  will then cause the deactivating of the actuators associated with the controller  98  as required to lower the rows of diverter wheels in the required timing sequence. 
         [0037]    Accordingly, a diverter system and method of operation has been provided that fully meets the objects of the present invention. While the invention has been described in terms of a preferred embodiment, there is no intent to limit it to the same. For example, while the diverter rollers in the described embodiment are pivoted in an arcuate motion between their lowered and raised positions, the diverter rollers could be mounted so as to move linearly along, e.g., a track between their lowered and raised positions Thus, the scope of the invention is defined by the following claims.