Abstract:
A motorized drive roller conveyor includes an upstream zone and a downstream zone, with each zone having a drive roller, an idler roller that is driven by the drive roller, and a sensor. The upstream zone and the downstream zone are controlled by a card, which measures a gap between a first item on the conveyor and a second item on the conveyor by beginning a counter when a trailing edge of the first item passes the sensor of the upstream zone and stopping the counter when a leading edge of the second item passes the sensor of the upstream zone to generate a counter value. If the first item is stopped in the downstream zone, the card of the upstream zone causes the drive roller of the upstream zone to advance the second item into the downstream zone for a distance derived from the counter value before stopping the transportation of the second item.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
       [0001]    The present invention relates generally to a networked motorized drive roller conveyor. 
         [0002]    Conventional conveyor control systems utilize a central Programmable Logic Controller (“PLC”) mounted in a central control panel. This type of system requires control devices, e.g., photo-eyes, solenoid valves, and motor starters, to be terminated at the main control panel. A typical control system utilizing a PLC requires several hundred to several thousand feet of control wiring, which requires significant time, labor and money to route and terminate the wiring. In addition, the PLC requires specialized knowledge, e.g., knowledge of ladder logic, and familiarity with the many different interface requirements unique to each manufacturer&#39;s product. Moreover, since there is a central controller, response time with respect to the control devices may be increased because the single processor must account for all operations occurring within the system. 
         [0003]    A Motorized Drive Roller (“MDR”) is a conveyor roller with an integrated motor. An MDR is typically configured to drive a plurality of idler rollers, usually by way of urethane belts or chains. The MDR and idler rollers thus define a zone. There is typically one MDR per zone. 
         [0004]    For conveyor systems that utilize MDR technology, networked motor controllers are frequently used to handle basic transport, diversion, and accumulation tasks to move items through a conveyor system. These motor controllers are mounted in close proximity to the MDR rollers and directly interface with the product sensors associated with each MDR. An MDR conveyor system has many advantages over other conveyor technologies, such as lower power consumption, noise reduction, and a decreased need for maintenance. 
         [0005]    Unlike conventional control systems, modular distributed controls don&#39;t require hundreds to thousands of feet of wiring from a centralized PLC to each device in the system. With controls located near the control devices, wiring and wiring labor may be reduced. This shortens the time to complete implementation and provides a parallel control capability that minimizes response time issues common to conventional PLC based systems. Because the system is not limited by the speed of a central processor in a PLC, the system can grow without worry of overtaxing a centralized controller. Testing and start-up time is also reduced, as various segments of the system can be installed and tested independent of other segments. It is common practice in existing conveyor systems that use MDR roller conveyor along with associated motor controllers to utilize smaller, localized PLC&#39;s distributed throughout the system to handle conveyor operations such as diverting, bar code scanning, RFID communication, label applications, etc. These peripherals typically communicate serially (RS232 or RS485) or via a network protocol such as Ethernet. Having multiple PLCs in this environment creates other undesirable issues as single point diagnostics are difficult to implement. 
         [0006]    The networked, distributed control system of the present invention provides localized controls for various operations, e.g., diverting, bar code scanning, RFID transactions, labeling, etc. The inventive control system can also handle the basic MDR conveyor drive and accumulation responsibilities, which greatly reduces the wiring needed for the system, implementation time, and cost while maintaining a centralized diagnostic capability. Additional capability to allow localized programming as well as status and diagnostics capability are additional benefits of the inventive control system. Eliminating the need for PLCs and associated ladder logic is a further benefit of the inventive design because it reduces the complexity of installation, operation and modification of the control system and corresponding conveyor system. 
         [0007]    As noted above, MDR conveyor systems have many advantages over other conveyor technologies, such as lower power consumption, noise reduction, and less maintenance. However, prior to the present invention, MDR systems lacked the ability to control the size of gaps between items on the conveyor system. Prior art systems are also limited to transporting “Items” that are shorter in length than a single “Zone”. 
         [0008]    Existing technology is typically marketed as “Zero pressure Accumulation” conveyor technology, as items on the conveyor are allowed to accumulate with one item per zone. As such, with control technology currently marketed, items accumulate with varying gaps between items, based on the length of the items. 
         [0009]    In accordance with one aspect of the inventive conveyor control system, a gap control arrangement is used to control gaps between items on the conveyor system. The elimination of gaps between items on the conveyor system is desirable, in that gaps reduce the number of items that can be accumulated on the conveyor, providing lower accumulation efficiency. Thus, reducing or even eliminating gaps between items helps to maximize the accumulation efficiency of the conveyor system. The gap control system incorporates the use of MDR technology and its desirable attributes while at the same time providing the operator with the ability to control the size of the gaps between items on the conveyor system. 
         [0010]    In one embodiment of the invention, a networked motorized drive roller conveyor includes a plurality of motorized drive roller assemblies, where each assembly comprises a zone. The conveyor has a plurality of networked cards, with each card controlling a pair of adjacent zones. The conveyor further has a plurality of sensors for detecting items on the conveyor, with each sensor corresponding to a zone. For a pair of adjacent zones, the corresponding networked card measures a gap between consecutive items on the conveyor by beginning a counter when a trailing edge of a first item passes the sensor of an upstream zone within the pair of zones, and stopping the counter when a leading edge of the second item passes the sensor of the upstream zone within the pair of zones, to generate a counter value. If the first item is stopped in the downstream zone, the networked card causes the motorized drive roller assembly of the upstream zone to move the item into the downstream zone a distance derived from the counter value before stopping the movement of the second item. 
         [0011]    In another embodiment of the invention, a motorized drive roller conveyor includes an upstream zone and a downstream zone. Each zone has a drive roller, an idler roller that is driven by the drive roller, and a sensor. A card controls the upstream zone and the downstream zone. The card measures a gap between a first item on the conveyor and a second item on the conveyor by beginning a counter when a trailing edge of the first item passes the sensor of the upstream zone and stopping the counter when a leading edge of the second item passes the sensor of the upstream zone to generate a counter value. If the first item is stopped in the downstream zone, the card of the upstream zone causes the drive roller of the upstream zone to advance the second item into the downstream zone for a distance derived from the counter value before stopping the movement of the second item. 
         [0012]    In yet another embodiment of the invention, a method for controlling a gap between items on a motorized drive roller conveyor includes the steps of (a) detecting a trailing edge of a first item at a predetermined location in a first zone on a conveyor system; (b) beginning a counter once the trailing edge of the first item passes the predetermined location; (c) stopping the counter upon the first occurrence of the following: (i) a leading edge of a second item is detected at the predetermined location, or (ii) the first item is stopped in a downstream zone adjacent the first zone; and (d) generating a counter value. 
         [0013]    These and other aspects and advantages of the present invention will be made apparent from the following description taken together with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    An exemplary embodiment of the invention is illustrated in the accompanying drawings in which like reference numerals represent like parts throughout. 
           [0015]    In the drawings: 
           [0016]      FIG. 1  is an isometric view of a networked MDR conveyor in accordance with the present invention; 
           [0017]      FIG. 2  is schematic of a card used in connection with the networked MDR conveyor of the present invention; 
           [0018]      FIG. 3  is a representation of a physical embodiment of a card used in connection with the networked MDR conveyor of the present invention; 
           [0019]      FIG. 4  is another isometric view of the networked MDR conveyor of  FIG. 1 ; 
           [0020]      FIG. 5  is a schematic side elevation view of a networked MDR conveyor of the present invention; 
           [0021]      FIG. 6  is an enlarged partial isometric view of the networked MDR conveyor of  FIG. 1 ; 
           [0022]      FIG. 7  is a side view of the networked MDR conveyor of  FIG. 1  illustrating gaps between items on the conveyor; 
           [0023]      FIG. 8  is a top view of the networked MDR conveyor of  FIG. 1 ; 
           [0024]      FIG. 9  is a side isometric view of a second embodiment of a networked MDR conveyor accordance with the present invention; 
           [0025]      FIG. 10  is an enlarged partial side isometric view of the networked MDR conveyor of  FIG. 9 ; 
           [0026]      FIGS. 11A-11G  are schematic views of various conveyor configurations that may be integrated into a networked MDR conveyor in accordance with the present invention; and 
           [0027]      FIG. 12  is a flow chart illustrating a method of determining the size of a gap between items in the networked MDR conveyor in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  shows a portion of the conveyor system  10  of the present invention that incorporates control cards  20  in accordance with the present invention. Generally speaking, a number of items  11  are supported on the conveyor  10 , which includes a plurality of rollers  13 , including MDRs and corresponding idler rollers. The conveyor system  10  further includes a plurality of sensors  14  that detect items  11  as the items  11  move along the conveyor system  10 . The conveyor system  10  is divided into zones  15 . Each zone  15  is defined between adjacent sensors  14 . Additionally, each zone  15  corresponds with an MDR/idler roller assembly. In the inventive system, each zone  15  is shorter than the length of the respective items  11  being conveyed by the conveyor system  10 . 
         [0029]      FIGS. 2 and 3  illustrate a networked, distributed MDR control card  20  with local control capabilities. Accordingly, the inventive card  20  eliminates the need for a central PLC and reduces and/or eliminates the need for wiring associated with a system using a PLC. As a result, implementation and installation costs of a conveyor control system  10  incorporating the MDR control cards  20  of the present invention may also be reduced while, at the same time, providing a more efficient installation and implementation process. Still further, the card  20  of the present information is programmable, and therefore is able to be reprogrammed depending on its desired utilization. 
         [0030]    In the illustrated embodiment, the card  20  contains drivers  22 , e.g., on a microprocessor, for one or more MDR rollers, which preferably feature a dual brushless motor. More specifically, for zero-pressure accumulation mode of operation, e.g., one in which the items on the conveyor are not intended to contact one another, each card  20  will service two zones  15 . In other words, the card  20  will contain drivers for respective MDR rollers in adjacent zones  15 . The drivers are adapted to support any variation of MDR roller, e.g. commonly available MDR rollers, e.g., those ranging from 22 watts to 50 watts, may be used. 
         [0031]    The card  20  of the present invention includes a plurality of Inputs and Outputs (“I/O”)  23  for interfacing with various components that are typically utilized in conveyor assemblies, e.g., limit switches, solenoid valves, motor contactors, alarms/buzzers, and status beacons. 
         [0032]    The card  20  further includes a plurality of photo sensor input jacks  24  that connect with sensors  14 , which, as discussed above, detect items  11  that move along the conveyor system  10 . For example, four such jacks  24  are shown on the block diagram in  FIG. 2 ; see also,  FIG. 3 . The card  20  also includes one or more network jacks  25  to provide network communications capabilities for connection to a supervisory control computer (e.g., a personal computer or industrial computing device). The illustrated embodiment incorporates a CAN network using Can-Open or Device-Net protocols, although Ethernet or serial communications could also be utilized. In this arrangement, any card  20  in the conveyor system  10  can communicate over the network to any other card  20  attached to the network or to a supervisory control element, such as a PC or industrial controller. Accordingly, system-wide changes, e.g., relating to product volume, conveyor speed. etc., can be implemented using any card  20  on the network. 
         [0033]    The card  20  further includes a serial I/O port  26  to facilitate communications with external peripheral devices such as bar code scanners, RFID reader/writer devices, label applicators, in motion weigh scales, or other serial devices. 
         [0034]    The card  20  may also feature an operator interface display  27 . For example, the display may include button switches for interfacing with the module, a high intensity beacon for fault and error notification, and a display element that provides textual and/or graphical information to the operator. An operator interface display allows parameters such as roller speed, acceleration and deceleration rates, delays, etc. to be set locally from any card  20 , rather than from a central point such as a PLC. 
         [0035]    In this description, the term “card” is used to describe item  20 , which controls operation of adjacent zones in conveyor system  10 . It is understood that the term “card” is used for convenience, and that item  20  may be any satisfactory control, device that includes the features and functionality to connect to the sensors and drive rollers of the adjacent zones of conveyor system  10  and to control their operation. The term “card” is not intended to denote any particular structural or physical characteristics of the control device. 
         [0036]    The inventive conveyor system  10  improves upon existing designs by entirely eliminating the need for a PLC controller for normal conveyor operations. The conveyor system  10  allows additional functions to be implemented seamlessly without the need for PLCs or any knowledge of ladder logic on the part of the operator or system installer. 
         [0037]      FIG. 11  shows typical configurations that are included in conveyor systems. While typically controlled by a PLC, in the inventive conveyor system  10  these operations are controlled locally by any one or group of cards  20  in the conveyor system  10 . Such typical configurations include but are not limited to the following examples. For example,  FIG. 11A  shows a zone accumulator and  FIG. 11B  shows a back-to-back accumulator. 
         [0038]    One configuration is an interface with an in-motion weigh scale as shown in  FIG. 11C , which allows items  11  to be singulated and transported singly over an in-motion weigh scale. An identification device, such as a bar code scantier or RFID device, is connected directly to a card  20  and provides the method of identification of the item  11 . The weight of the item  11  is compared locally, i.e., at a card  20 , with an expected result and a decision is made locally, i.e., at a card  20 , to allow the item  11  to continue along the conveyor system  10  or to be diverted off to a second conveyor in the event the weight of the item  11  is not within a defined tolerance. The I/O  23  on the card  20  will be utilized to communicate with the in-motion weigh scale. 
         [0039]    Another type of configuration is an interface with a label applicator or “print and apply” label applicator as shown in  FIG. 11D . This configuration allows items  11  to be singulated and transported singly past a labeler, such as an in-motion labeler, static label only, or “print and apply” labeler. An identification device, e.g., a bar code scanner or RFID device, is connected directly to the card  20  and provides the method of identification of the item  11 . The information required on the label is determined locally on the card  20 . The label is printed (if necessary) and applied and then the item  11  is passed on to the next conveyor zone  15 . The I/O  23  on the card  20  will be utilized to communicate with the printer/applicator. 
         [0040]    Another type of configuration is a 90 degree transfer as shown in  FIG. 11E . This pre-programmed operation will facilitate an item  11  transfer from one conveyor zone  15  to another completing a 90 degree right angle transfer. A corresponding card  20  processes the timing required to ensure that the item  11  is completely transferred prior to initiating the next transfer of an item. The card  20  further processes any additional input/output required to signal the transfer device. 
         [0041]    Yet another configuration is a “+” transfer as shown in  FIG. 11F . This pre-programmed operation will facilitate an item transfer from one conveyor zone to one of three possible divert points. An identification device, e.g., a bar code scanner or RFID, is connected directly to a corresponding card  20  and provides the method of identification of the item  11 . The desired divert location is determined locally on the card  20  and the item  11  is either allowed to continue on or is diverted to one of two other conveyors completing a 90 degree right angle transfer. The card  20  processes the timing required to ensure that the item  11  is completely transferred prior to initiating the next decision relating to a subsequent item transfer. The card  20  further processes any additional input/output required to signal the transfer device. 
         [0042]    Another configuration is a “T” transfer as shown in  FIG. 11G . This pre-programmed operation facilitates an item transfer from one conveyor zone to one of two possible divert points. An identification device, e.g., a bar code scanner or RFID, is connected directly to a corresponding card  20  and provides the method of identification of the item  11 . The desired divert location is determined locally on the card  20  and the item  11  is either allowed to continue on or is diverted to another conveyor completing a 90 degree right angle transfer. The card  20  processes the timing required to ensure that the item  11  is completely transferred prior to initiating the next decision relating to a subsequent item transfer. The card  20  further processes any additional input/output required to signal the transfer device. 
         [0043]    The illustrated embodiment includes either a display on the card  20  or a touch screen type interface on a personal computer or industrial computing device. The touch screen allows a setup operator to easily drag and drop the aforementioned pre-programmed operations to each card  20 , with no knowledge of programming ladder logic or other programming required. The interface also allows parameters such as speed, timing, direction, etc. to be easily communicated to the individual cards  20  via the network. 
         [0044]    The illustrated embodiment of the conveyor system  10  also has the ability to retain a backup of each card  20  in the system, should a replacement he required because of a card failure. The parameters and standard code blocks can simply be downloaded to the card  20 , greatly minimizing downtime in the event of a card failure. 
         [0045]    As discussed above, it is not desirable to have gaps  30  between items  11  on a conveyor system  10 . The gap control system of the present invention uses MDR rollers in conjunction with cards  20  and sensors  14  to control the gaps  30  between items  11 . As shown in  FIG. 5 , for example, in the illustrated embodiment, any item  11  being conveyed is greater in length “L” (measured longitudinally along the direction of flow of the conveyor) than the distance “d” between the zone sensors  14 . The sensors  14  are preferably photo-eye type sensors, but any type of sensor capable of determining the presence of an item  11  could be used, including, but not limited to, proximity sensors, limit switches, strain gauges, weight measurement devices, imagers, or ultrasonic sensors. 
         [0046]    Depending on the nature of the items  11  being conveyed, the size of the zones  15  may be smaller than the arrangement shown in  FIG. 1 . Accordingly, the spacing of sensors  14  may be varied to accommodate items  11  of various sizes. Referring to  FIG. 6 , items  11  of length “L” must be greater than distance “d,” the distance between sensors (and also the length of the zone), in other words, the length of zone  15 , in order to effectively eliminate gaps between items. Alternatively, where the item length “L” is less than distance “d,” in some circumstances it may not be possible to effectively eliminate the gap between an upstream item and a stopped downstream item depending upon the location at which the downstream item is stopped within the downstream zone. The zone length can be varied as desired depending on the size of the items to be conveyed. Thus, the zone length may be greater than the item length or less than the item length as desired. 
         [0047]      FIGS. 4-8  show one embodiment of the conveyor system  10  featuring the gap control system of the present invention.  FIGS. 9-10  show a second embodiment of a conveyor system  10  featuring the inventive gap control system. 
         [0048]    The illustrated embodiment uses brushless DC motors integrated within the MDRs. These motors provide feedback as to the position of the roller, e.g., via Hall effect sensors that are integral with the motor itself. The inventive gap control system utilizes the feedback from the Hall effect sensors to dynamically determine the length of the gap  30  between items  11  that are transported on the conveyor system  10 . 
         [0049]    More specifically, as an item  11  passes a sensor  14 , the sensor  14  transitions from blocked (i.e., when the item  11  is triggering the sensor  14 ) to unblocked (i.e., when the item  11  is not triggering the sensor  14 ). Accordingly, as an item  11  passes a sensor  14 , a counter is initiated within a microprocessor  28  on the card  20 . The counter counts the number of pulses received by the Hall effect sensor within an MDR until a subsequent item  11  blocks the sensor  14 . In other words, the counter records the number of pulses received from the MDR while no item  11  was being transported by the MDR, which is a measure of the gap  30  between consecutive items  11 . A counter value is calculated and maintained for every sensor  14  in the conveyor system by corresponding cards  20 . Thus, as a downstream item  11  approaches a blocked zone  15 , the corresponding counter value is used to continue to transport an item  11  the requisite number of pulses, i.e., the number of pulses stored in the counter value, in order to close the gap  30 . This effectively transports the item  11  right up to the stopped item  11 , barely touching it, providing zero pressure accumulation as desired. 
         [0050]    In addition to the scenario discussed above, i.e., wherein a sensor  14  detects a second item  11  after a first item  11  has passed the sensor  14 , there is another scenario in which the counter may be stopped. Specifically, the second scenario occurs when an item  11  that has passed a particular sensor  14  is stopped on the conveyor system  10  before a second item  11  is detected by the particular sensor  14 . In other words, the item  11  is stopped before the second item  11  reaches the particular sensor  14 . Thus, when the item  11  has been stopped, the card  20  corresponding to the downstream zone  15  in which the item  11  is stopped communicates with the card  20  corresponding to the adjacent upstream zone  15 , which then stops the counter. Accordingly, the counter value represents the distance between the end of the stopped, downstream item  11  and the sensor  14  in the adjacent, upstream zone  15 . Thus, the cards  20  communicate with one another such that a subsequent item  11  is moved up to the stopped item  11 , thus closing the gap  30  between the two items. 
         [0051]    The illustrated embodiment also allows the counter value to be converted to a known distance, such that the counter value could be modified to allow the user to select a desired gap distance between items  11  so that items  11  do not touch, but have a minimal gap  30 . 
         [0052]    The present invention further includes a method for determining a gap  30  between items  11  on a conveyor system  10 . Generally speaking, as shown in  FIG. 12 , the method includes the steps of (a) detecting a first edge of a first item at a predetermined location on a conveyor system; (b) detecting a second edge of the first item at the predetermined location on the conveyor system; (c) beginning a counter once the second edge of the first item passes the predetermined location on the conveyor system; (d) stopping the counter once a first edge of a second item is detected at the predetermined location; and (e) generating a counter value based upon the counter data. Accordingly, the counter value represents a gap  30  between adjacent items  11  on a conveyor system  10 . 
         [0053]    Additional steps of the method may include using the counter value to eliminate the gap  30  between the items  11 . For example, the counter value may be used to rotate an MDR a corresponding number of rotations in order to close the gap  30  between the adjacent items  11  in the event that the downstream item.  11  has been stopped on the conveyor system. Moreover, the counter value may be adjusted or converted to a predetermined value so that the size of the gap remains fixed if a gap (preferably minimal) between items  11  is desired. 
         [0054]    The method may also include steps to stop the counter when an item has been stopped in a downstream zone. For example, the method may include the steps of (a) detecting a first edge of a first item at a predetermined location on a conveyor system; (b) detecting a second edge of the first item at the predetermined location on the conveyor system; (c) beginning a counter once the second edge of the first item passes the predetermined location on the conveyor system; (d) stopping the counter When the item has been stopped on the conveyor system; and (e) generating a counter value based upon the counter data. Further steps may include using the counter data to rotate an. MDR a corresponding amount of rotations in order to close the gap  30  between the adjacent items  11 . 
         [0055]    Various alternatives and modifications are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.