Abstract:
A singulator includes a mechanism for actuating a portion of a conveyor to remove one item at a time from the conveyor end, a detection system, a control system that actuates the conveyor to remove items from the conveyor one at a time based on the item positions according to a scheme of: ( 1 ) selecting a first item, ( 2 ) actuating a portion of the conveyor underlying the first item between the first item and the end of the conveyor; ( 3 ) actuating a portion of the conveyor underlying the second item between the second item and the exit end of the conveyor when a gap between the trailing edge of the first item for removal and a leading edge of a second item for removal reaches a predetermined size; and ( 4 ) repeating steps ( 1 )-( 3 ) for additional items until all items in the group have exited the conveyor.

Description:
RELATED APPLICATIONS  
       [0001]    This application is a conversion of provisional application Ser. No. 60/200663, filed Apr. 28, 2000, the disclosure of which is incorporated herein by reference for all purposes. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to an apparatus, system and method of organizing a disordered stream of articles into an ordered stream of single items spaced from each other for subsequent processing.  
         BACKGROUND OF THE INVENTION  
         [0003]    In high volume product handling operations, such as mail handling and similar processing, large quantities of items such as boxes, parcels packages or parts often varying widely in size, must be inducted into a sorter system. Typically, a feeder system for use in such processing areas takes a disordered stream of items fed to it on a conveyor and inducts the items onto a sorter system. The feeder system ideally should perform several functions. To the maximum extent possible, the feeder should singulate disordered items in order to present the articles to downstream processing equipment, such as a sorter, one at a time with some minimum specified spacing or separation between product items. The feeder system must also provide for the reading of destination information from the item so that the control system for the sort can track it through the system and sort it correctly. In the U.S., scannable bar codes are used for this purpose in automated systems. A third important function is intercepting and removing items which are non-machinable because they are too large, too heavy or the like from the system for special handling.  
           [0004]    Singulation is an essential first step in the handling and sorting of product items such as boxes, parcels or soft packages. Material singulation as used herein means the generation of a flow of discrete pieces of material having no two pieces abreast, stacked, or having a gap or lineal (in the direction of flow) separation less than some minimum value. In other words, singulation is a process whereby a randomly input stream of items moving on a conveyor system is separated into a stream of single items spaced from each other so that a downstream process can readily perform operations on each item one at a time. Mixed item streams are a particular challenge in that a mixed material stream may include packages that vary greatly in size and may be piled at random one upon another, forming agglomerates of packages that are difficult to detect and separate.  
           [0005]    Presently, singulation is accomplished in two ways, by manual manipulation of material on bulk conveying lines and with mechanical singulators that rely on the mechanical characteristics of the material being singulated to generate an output stream in which the probability that each piece is singulated is high. While manual operations can be relatively effective, they are costly; and high throughput, either continuous or in bursts, can exceed an individual&#39;s capacity, resulting in “doubles” or “multiples” (unsingulated output). Conventional mechanical singulation schemes vary widely in method, throughput, and error rates, but tend to be large (requiring a large amount of floor space) and subject to high error rates when handling material at the margins of the mechanical material specifications for which they are designed and/or tuned. They too tend to degrade in performance when they encounter heavy bursts of material flow.  
           [0006]    According to one previously proposed method for singulation of mail, an inclined ramp with holes for applying suction is provided. Letters are allowed to slide down the ramp and then suction is applied to hold them in place on the slide. The suction is then selectively released in order to release one item at a time. See Interim Report For Phase I, U.S. Postal Service Contract 104230-85-H-0002, Apr. 5, 1985, ElectroCom Automation, Inc.,pages 3-10 to 3-13. This method provide one form of singulation, but is of doubtful utility for larger items that maybe difficult to hold effectively using suction and that may tend to tumble down a slide, possibly evading the effect of suction and leaving the singulator prematurely. The system according to the present invention addresses these difficulties.  
         SUMMARY OF THE INVENTION  
         [0007]    The selective advance intelligent singulator of the invention provides a means of generating a stream of single pieces of discrete material, such as cartons, from a single layer bulk flow, accumulation, or batch containing one or more of said pieces. It is used to convert a bulk material flow or batch to a stream of single items with controlled spacing on a conveying device such as may be needed for some process such as reading or sorting. It accomplishes accurate separation of a wide spectrum of pieces using knowledge of material boundaries acquired by various means, computer processing using a straightforward algorithm, and a suitable conveying mechanism to selectively pull material piece-by-piece from a single layered, bulk accumulation of pieces, i.e. with an intelligent process.  
           [0008]    In one aspect, the invention provides a singulator including a conveyor for carrying a group of items from an entry end towards an exit end and an item detection system, such as a vision system, that captures image information associated with pieces of material along with the position of the pieces. The singulator includes a mechanism for selectively advancing selected items while retarding the advance of other items so that the forward motion of selected lead items can be controlled independently of the remaining pieces. A control system controls the operation of the conveyor or conveyor(s) and the mechanism for actuating the conveyor or conveyors in a manner effective to remove pieces from a group of pieces one at a time based upon the position of the piece or piece(s) and image information captured by the detection system.  
           [0009]    Pieces are advanced in accordance with a removal scheme including the steps of: ( 1 ) selecting a first item for removal; ( 2 ) actuating one or more conveyors or conveyor sections underlying the selected piece and between the first item and the exit end of the conveyor in order to transport the first item to the exit end of the singulator at a velocity relative to the following pieces sufficient to create a gap between the first piece and the next piece where the following piece may have a velocity between zero and the exit velocity; (c) actuating one or more conveyors or conveyor sections underlying the next piece to be removed and between the next item to be removed and the exit end of the conveyor in order to transport the first item to the exit end of the singulator at a velocity relative to the following pieces sufficient to create a gap between that piece and the following piece; and (d) repeating step (c) for additional items.  
           [0010]    A control system utilizes image and item position information derived from the detection system and the removal scheme to control operation of the conveyor and the mechanism for selectively advancing and retarding pieces so that the pieces exit from the singulator one at a time.  
           [0011]    The conveyors or conveyor sections may comprise an array of independently controlled rotary carriers such as belts or rollers that allow movement of a velocity boundary across the singulator. The conveyor may also comprise one or more sliding conveyors or conveyor sections with extendable belts that also allow for movement of a velocity boundary across the singulator.  
           [0012]    The principle advantage of the selective advance intelligent singulator is its capacity to reliably singulate bulk material in a number of embodiments adaptable to the throughput, material mix, cost, and other requirements of a particular encompassing system design. A selective advance intelligent singulator provides an accurate means of automating the singulation function in a compact machine capable of handling a wide spectrum of material without risk of increased error rates or otherwise degraded performance as flow fluctuates. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements, and:  
         [0014]    FIGS.  1 - 6  are partial schematic flow diagrams illustrating the flow of items in a batch mode embodiment of the invention;  
         [0015]    FIGS.  7 - 12  are partial schematic flow diagrams illustrating the flow of items in a continuous mode embodiment of the invention according to the invention;  
         [0016]    [0016]FIG. 13 is a partial side view of a raised belt conveyor according to an aspect of the invention;  
         [0017]    [0017]FIG. 13A is a partial top view of a raised belt conveyor according to an aspect of the invention;  
         [0018]    [0018]FIG. 14 is a partial side view of a cam apparatus for use in connection with a conveyor according to the invention;  
         [0019]    [0019]FIG. 15 is a partial schematic of a belt type conveyor apparatus according to the invention;  
         [0020]    [0020]FIG. 16 is a partial side view of a first alternative belt type conveyor apparatus according to the invention;  
         [0021]    [0021]FIG. 17 is a partial side view of a second alternative belt type conveyor apparatus according to the invention;  
         [0022]    [0022]FIG. 18 is a partial side view of a roller type conveyor apparatus according to the invention;  
         [0023]    [0023]FIG. 19 is a partial cross-section of a multiple speed conveyor drive apparatus according to the invention;  
         [0024]    [0024]FIG. 20 is a partial side view of a dual velocity belt type conveyor according to the invention;  
         [0025]    [0025]FIG. 21 is a partial side view of a dual velocity roller conveyor for use in connection with the invention;  
         [0026]    [0026]FIG. 22 is a partial side view of a extendable belt type conveyor apparatus according to the invention; and  
         [0027]    [0027]FIG. 23 is a schematic illustration of one embodiment of a control system for use in connection with the invention.  
     
    
     DETAILED DESCRIPTION  
       [0028]    A selective advance intelligent singulator according to the invention accomplishes accurate, wide-spectrum separation of pieces by using precise knowledge of material boundaries acquired by various means, computer processing, and a suitable mechanism to selectively pull material piece-by-piece from a single-layered, bulk accumulation of pieces. Knowledge of material boundaries and the mechanism which pulls material from a bulk accumulation can be accomplished by various means.  
         [0029]    In one embodiment, the system uses a camera to generate image information for the bulk material immediately upstream from the singulator. Another embodiment uses an array of vertical distance measuring devices to accomplish the same objective. Yet another embodiment uses an array of physical presence and/or pressure sensing devices over which the material is conveyed to accomplish the same objective. This information is transformed via suitable algorithms into boundary information for each individual piece. Alternatively, in some situations the material may be placed in a known configuration immediately upstream from or directly onto the singulator. In this case it is possible to use data from the emplacing system, a data base, or both to generate boundary information.  
         [0030]    One class of embodiments of the selective advance intelligent singulator processes bulk material in batches. In embodiments of this type, piece boundary information is acquired for a batch of material as it is moved onto the singulator. The singulator then holds all pieces except those that can be immediately released as singulated pieces gapped (spaced lineally) at least a specified distance apart. These pieces are conveyed forward immediately, and as soon as the distance from the trailing boundary of the moving pieces equals/exceeds the minimum gap, one or more additional pieces is released. This process continues until the batch is exhausted, at which time a new batch is positioned on the singulator. Specific embodiments in this class of embodiments use different conveying means to move a batch of material onto the singulator and to hold and release individual pieces.  
         [0031]    In one embodiment of a batch process according to the invention a set of narrow belts is used to move accumulated material onto the singulator. The belts are decelerated to a low velocity or a full stop when the singulator is full, at which time a matrix of support mechanisms interleaved among the belts rises beneath all pieces or all pieces except those that can be immediately released, while the belts begin again to move forward.  
         [0032]    As the released pieces, riding on the belts, move forward, supports are dropped (retracted) under successive additional pieces as required to achieve the desired gap, allowing them to be carried forward by the belts until the trailing piece wholly on the singulator begins moving forward. At this point, material accumulated upstream also begins moving forward refilling the singulator and beginning the next batch cycle. An apparatus suitable for practicing this mode of the invention is disclosed in copending application Ser. No. 540,371, filed Mar. 31, 2000, assigned to Siemens ElectroCom L.P., the disclosure of which is incorporated herein for all purposes.  
         [0033]    FIGS.  1 - 6  schematically illustrate an apparatus  10  and the steps for batch singulation in accordance with the invention. A stream of pieces  1 - 9  are conveyed via infeed conveyor  12  at entry velocity V e  onto singulator  14 . Pieces  1 - 9  are conveyed from the singulator with takeaway conveyor  16  at exit velocity V x . The velocity boundary between V e  and V x  is schematically represented by line  18 .  
         [0034]    As shown in FIG. 1, in step  1  of the process, accumulated pieces of material are moved fully onto the singulator  14 . Conveying means  20  on the singulator such as belts or rollers move the accumulated batch of pieces  1 - 9  at entry velocity V e  until the singulator  14  is full or near full. V e  then drops to zero.  
         [0035]    In FIG. 2, the boundary between entry and exit velocities of the conveying means on the singulator has been extended forward to the trailing edge of the first piece selected for advancement. The selected piece accelerates to exit velocity and moves forward away from the remainder of the stationary batch of accumulated items.  
         [0036]    Turning to FIG. 3, the first selected piece moves forward with no change in the velocity boundary  18  until the gap between its trailing edge and the leading edge of the second selected piece reaches a specified minimum value (minimum gap). V e  remains zero.  
         [0037]    When, as shown in FIG. 4, the minimum gap is achieved between the first and second pieces,  1  and  2 , respectively, the velocity boundary of the singulator&#39;s conveying means is again extended, this time to the trailing edge of the second selected piece.  
         [0038]    As shown in FIG. 5, the first and second selected pieces move forward, with no change in the velocity boundary, until the gap between the trailing edge of the second selected piece and the leading edge of the third selected piece, pieces  2  and  3 , respectively, reaches the specified minimum value.  
         [0039]    Next, as shown in FIG. 6, when the minimum gap between the second and third pieces is attained, the velocity boundary  18  of the singulator&#39;s conveying means is again adjusted, this time to the trailing edge of the next selected piece. The process of extending the velocity boundary and waiting, if necessary, until the minimum gap is attained, is repeated until the last piece filly positioned on the singulator  14  has begun to move at exit velocity V x . At this point V e  again becomes a non-zero, positive value, moving the next accumulation of pieces onto the singulator and beginning the next batch cycle. In the special case wherein an incoming stream of pieces which has already been singulated and wherein the required gap is present between all of the pieces, there is no necessity for batch processing as described above as long as at any instant the boundary information for individual pieces is known and processed for all pieces on the singulator and in a zone upstream from the singulator. In this case no batch of material is defined and V e  remains constant. In such a case there is no reason internal to the singulator  14  for V e  ever to be less than V x  so that a piece of material enters and exits the singulator  14  with no change in velocity.  
         [0040]    Another class of embodiments of the selective advance intelligent singulator processes bulk material continuously. In embodiments of this type, piece boundary information is acquired for some predefined distance upstream from the forward most unsingulated piece. Bulk material is advanced onto the singulator at a controlled entry velocity less than or equal to singulator exit velocity until the trailing edge of the piece identified as next to be singulated is fully on the active portion of the singulator. At this point, the selected piece is moved at exit velocity until the required gap between it and the following piece is attained. Entry velocity is adjusted to ensure that the gap can be achieved and to ensure that, as long as the input rate can equal or exceed the output rate, the next piece is always available for extraction (transfer to exit velocity) at the time needed to achieve the desired gap. Note that this means that the ratio of entry velocity to exit velocity is variable.  
         [0041]    One continuous process embodiment uses a discrete matrix of rollers or belts, each of which can be independently engaged to one of two drive mechanisms. One drive mechanism moves at a varying rate so as to move the belts or rollers engaged to it at entry velocity. The other drive mechanism moves at a constant rate so as to move belts or rollers engaged to it at exit velocity. In this embodiment, the individual belts or rollers in the matrix are selectively engaged to the appropriate drives so as to advance the bulk material onto the singulator at entry velocity until the trailing edge of the piece identified as next to be singulated is fully on it. At this point, the belts or rollers under the selected piece and extending downstream to the end of the singulator are engaged to the exit velocity drives. The speed of the entry velocity drive is varied to ensure that, if possible, the trailing edge of the next piece will be fully on the singulator when the required gap between this and the following piece is attained. When two conditions are met: 1) the minimum gap has been achieved, and 2) the trailing edge of the next piece is fully on the singulator; the belts or rollers then under the second piece are engaged to the exit velocity drive mechanism. This process is then repeated for each successive piece. An example of how continuous processing embodiments work is given in FIGS.  7 - 12 .  
         [0042]    Another class of embodiments of the selective advance intelligent singulator of the invention is a variant of the preceding continuous mode embodiment. In embodiments of this type, although the entry velocity varies over time, the exit velocity varies with it such that there is a fixed ratio between the entry velocity and the exit velocity. Bulk material is advanced onto the singulator at a controlled entry velocity until the trailing edge of the piece identified as next to be singulated is fully on the active portion of the singulator. At this point, the selected piece is moved at exit velocity until the required gap between it and the following piece is attained. Entry velocity is adjusted to insure that the gap can be achieved and to ensure that, as long as the input rate can equal or exceed the output rate, the next piece is always available for extraction (transfer to exit velocity) at the time needed to achieve the desired gap. One continuous process embodiment uses a matrix of rollers or belts, each of which can be made to move at one of two velocity ratios with respect to a common drive mechanism. The drive mechanism moves at a varying rate so as to move the belts or rollers engaged to it at the entry ratio to properly move material onto the singulator. Selectively coupling rollers or belts to move at the higher velocity ratio permits pulling a gap between the currently selected item and the next to be singulated. At the downstream end of the singulator, a conveying mechanism with a velocity equal to or greater than the higher singulator velocity receives and transports the singulated material.  
         [0043]    As in the previously described embodiment, the individual belts or rollers in the matrix are selectively engaged to the appropriate drives so as to advance the bulk material onto the singulator at entry velocity until the trailing edge of the piece identified as next to be singulated is fully on it. At this point, the belts or rollers under the selected piece and extending downstream to the end of the singulator are engaged to the exit velocity drives. The speed of the entry velocity drive is varied to ensure that, if possible, the trailing edge of the next piece will be fully on the singulator when the required gap between this and the following piece is attained. When two conditions are met: 1) the minimum gap has been achieved, and 2) the trailing edge of the next piece is fully on the singulator; the belts or rollers then under the second piece are engaged to the exit velocity drive mechanism. This process is then repeated for each successive piece. In principle, fixed-ratio continuous processing embodiments work as shown in FIGS.  7 - 12  though successful design of such embodiments are more sensitive to belt speeds, singulator length, and material arrival rates and sizes.  
         [0044]    FIGS.  7 - 12  schematically illustrate an apparatus  30  and the steps for continuous singulation in accordance with the invention. A stream of pieces  1 - 9  are conveyed via infeed conveyor  32  at entry velocity V e  onto singulator  34 . Pieces  1 - 9  are conveyed from the singulator with takeaway conveyor  36  at exit velocity V x . The velocity boundary between V e  and V x  is schematically represented by line  38 .  
         [0045]    Turning now to FIG. 7, accumulated material, e.g. pieces  1 - 9 , are moved partially onto singulator  34 . Conveying means  20  on the singulator such as belts or rollers move the accumulated batch of material at entry velocity V e  until at least one piece is fully on the singulator  34 , in other words until the trailing edge of at least one piece is on the active portion of the singulator. V e  is controlled at or less than V x .  
         [0046]    As shown in FIG. 8, the boundary between entry and exit velocities of the conveying means on the singulator is extended forward to the trailing edge of the first piece selected. The selected piece is accelerated to V x  and moves forward. V e  may be varied between zero to V x , but if the gap between piece  1  and  2  is less than the specified minimum gap, as illustrated, V e  is reduced to less than V x  after the location of the trailing edge of the second selected piece is known.  
         [0047]    As shown in FIG. 9, the first selected piece moves forward while the velocity boundary  38  follows it until the gap between its trailing edge and the leading edge of the second selected piece reaches a specified minimum value. V e  must be controlled and varied between zero and V x  as required to expeditiously achieve two objectives. First, the gap between the first and second pieces,  1  and  2 , respectively, needs to be opened to the specified minimum gap. Second, the second piece needs to be advanced until its trailing edge is fully on the singulator  34 .  
         [0048]    Referring now to FIG. 10, when the minimum gap between the first and second piece,  1  and  2  respectively, is achieved, the velocity boundary  38  of the singulator&#39;s conveying means  40  is again extended, this time to the trailing edge of the second selected piece.  
         [0049]    As illustrated in FIG. 11, the first and second pieces,  1  and  2 , respectively, move forward while the velocity boundary moves with their trailing edges until the gap between the trailing edge of the second selected piece and the leading edge of the third selected piece reaches a specified minimum value. Again, V e  is varied between zero and V x  as required to open the gap between the second and third pieces,  2  and  3  respectively, and to advance the third piece until its trailing edge is fully on the singulator  34 .  
         [0050]    Turning to FIG. 12, when the minimum gap between pieces two and three is attained, the velocity boundary of the singulator&#39;s conveying means is again extended, this time to the trailing edge of the third selected piece. The process of extending the velocity boundary, then simultaneously opening a gap and moving the next piece fully onto the singulator  34  continues indefinitely. In the special case of an incoming stream of pieces that are already singulated, e.g. have the required minimum gap between the pieces, the singulator responds by moving the velocity boundary to the trailing edge of each piece as soon as it is fully on the singulator  34 . In this case there is no reason internal to the singulator for V e  ever to be less than V x  so that a piece of material enters and exits the singulator  34  with no change in velocity.  
         [0051]    The output corresponding to maximum throughput of a batch mode embodiment of the selective advance intelligent singulator approximates a stream consisting of groups of pieces spaced at the desired gap, with the spacing between groups determined by the specific entry and exit belt velocities and other design details and criterial of the singulator and its system context. The output corresponding to maximum throughput of a continuous mode embodiment of the selective advance intelligent singulator approximates a continuous stream of pieces spaced at the desired gap, assuming the design of the system context does not limit the availability or input velocity of bulk material. Thus, maximum throughput of a batch embodiment is a function of exit velocity, gap length, and the gap between groups imposed by the cyclic deceleration of incoming material while the maximum throughput of a variable ratio continuous embodiment is a function of exit velocity and gap length only. The maximum throughput of a fixed ratio continuous embodiment is also a function of arrival and takeaway rates, material density (pieces per unit area of conveying surface), and singulator length.  
         [0052]    Thus, the selective advance intelligent singulator according to the invention reliably singulates bulk material in a number of embodiments adaptable to the throughput, material mix, cost, and other requirements of a particular encompassing system design. The following descriptions of specific embodiments of the conveying surface of the singulator illustrate the range of potential design options. Note that all continuous mode embodiments can be either fixed- or variable-ratio except those specifically designated as fixed-ratio. Actuation means can in general be electrical or pneumatic bi-position actuators at each “point” or a motor-driven mechanical assembly that controls a whole (longitudinal) column of “points”. Also disclosed are a number of different means (FIGS.  15 - 20 ) for coupling or (clutching) the driven belt or roller to its driver.  
         [0053]    Referring now to FIG. 13 and  13 A, a raised belt continuous mode apparatus  60  corresponding to one embodiment of the conveying means  20  is disclosed. In embodiments of this type, narrow slider belts  62 , supported by a flat, low-friction surface, and driven at one velocity, either entry velocity V e  or exit velocity V x , are interleaved with narrow belts  64 , such as elastic “O” belts, driven at the other velocity. The second set of belts  64  are wrapped in serpentine fashion around pairs of rollers  66  as shown in FIG. 13. The upper surface of a serpentine belt is normally slightly below that of the slider belts  62 . Engagement of the serpentine belt with the bottom surface of conveyed material is achieved by raising a selected roller pair so that the upper surface  78  of belt  64  is raised slightly above the surface of the adjacent slider belts  62 . In the illustrated embodiment, columns  70  are each provided with an inclined face  72  that is engaged by an inclined surface  76  of cam member  74  as the member is advanced, raising the column. This raises the pair of rollers  66  associated with the column  70  until the upper surface of belt  64  is above the adjacent slider belts  62 . Actuating the cam member  74  to raise roller pairs  66  can be achieved by electrical means, such as a solenoid  80 , a pneumatic or hydraulic cylinder, a motor using a screw-type drive or other mechanical means. As best shown in FIG. 13A, the velocity boundary using a raised belt embodiment may be moved by raising a pair or pair(s) of rollers  66 , each corresponding to longitudinal column or column(s) n consisting of m roller pairs. Thus, only n actuators are required as opposed to m×n, where m represents the number of lateral rows of columns.  
         [0054]    [0054]FIG. 14 illustrates an alternate cam member  82  for use in connection with the embodiment illustrate in FIG. 13 is illustrated. As shown, cam members  84 ( a )- 84 ( c ) are arranged along the length of tube  86 , each tube corresponding to a successive column or columns  70  and each cam member corresponding to a row. As will be appreciated, as the tube  86  is rotated in the direction indicated by arrow  88 , cams  84 ( a )- 84 ( c ) will successively engage corresponding columns, raising the corresponding roller pair or pairs. As will also be appreciated, when the tubes  86  are rotated through 360° to the location designated by arrows  90 , to the cams  84 ( a )- 84 ( c ) will simultaneously disengage allowing all of the columns corresponding to belt  64  to lower at one time. Tubes  86  may be actuated and rotated with an electric solenoid or motor, a hydraulic or pneumatic cylinder or other mechanical or electrical devices, depending upon the application.  
         [0055]    [0055]FIG. 15 illustrates a locally-clutched belt continuous mode apparatus  100  corresponding to another embodiment of conveying means  20 . In this embodiment, the bed or upper surface of the singulator  34  is populated with an array or matrix of short belts  108 . Each belt  108  is wrapped around two idler rollers  102  that the conveyed material, and two clutched drive rollers,  104  and  106 . Each of the drive rollers  104  and  106  is mounted on a shaft,  110  and  112 , respectively, rotating at a speed associated with either entry or exit velocity. Clutches  114  and  116  corresponding to drive rollers  104  and  106  are selectively engaged or disengaged to cause the belt to move at the appropriate velocity. For example drive roller  104  may be configured to operate at a constant velocity where as drive roller  106  maybe configured to operate at a controlled speed. The drive for each belt  108  is intelligently selected, either constant velocity or controlled velocity, to move one or more parcels downstream at the constant velocity while retarding others as required to achieve a downstream flow of single pieces separated by a controlled minimum gap as discussed in connection with FIGS.  7 - 12 . As used herein, the terms “intelligence” and “intelligently” refers generally to the use of a means of capturing and generating image information for pieces such as a camera or vision system or an array of physical measuring devices such as photocells, pressure sensors, and similar devices, information that is transformed via suitable algorithms into boundary information for individual piece and subsequently used by a computer or microprocessor to control the operation of discrete elements such as apparatus  100 .  
         [0056]    [0056]FIG. 16 shows a three-roller locally driven belt continuous mode apparatus  120 , comprising another alternative embodiment of conveying means  20 , is shown. In this embodiment, the singulator bed is populated with an array of short belts  122  that support conveyed material. Each belt  122  is wrapped around two idler rollers  124  that support the weight of the conveyed material and a third idler roller  126  well below the surface of the bed. As shown, idler rollers  124  and  126  are mounted on a frame  132 . Frame  132  is in turn pivotable around drive engagement pivot pin  134 . A solenoid  136  or similar actuator is coupled to a lower section of frame  132  in order to selectively pivot the frame. Drive rollers  128  and  130  are mounted adjacent to lower idler roller  126  and are operated at rotational speeds corresponding to entry velocity V e  and exit velocity V x , respectively.  
         [0057]    As will be appreciated, actuator  136  may selectively pivot frame  132  causing belt  122  to be engaged by either of drive rollers  128  and  130 , surfaces of which are moving at either entry velocity or exit velocity, where the belt wraps around idler roller  126 . Thus, the drive for each belt  122  maybe intelligently selected, corresponding to either entry velocity V e  or exit velocity V x , to move one or more parcels downstream while retarding others as required to achieve a downstream flow of single pieces separated by a controlled minimum gap as discussed in connection with FIGS.  7 - 12   
         [0058]    [0058]FIG. 17 illustrates a two-roller locally driven belt continuous mode apparatus corresponding to yet another embodiment of conveying means  20 . The apparatus  150  is in all respects similar to the apparatus shown in FIG. 16 with the exception that the third idler belt  126  of apparatus  120  is omitted. Instead, each belt  122  is wrapped around two idler rollers  124  that support the weight of the conveyed material. Where belt  122  wraps around each of the idler rollers  124  the belt may be selectively engaged either of drive rollers  128  and  130  whose surfaces is moving at entry velocity V e  and exit velocity V x , respectively, by means of actuator  136  pivoting frame  132 .  
         [0059]    [0059]FIG. 18 illustrates a locally driven roller continuous mode apparatus  150  corresponding to an additional embodiment of conveying means  20 . In this embodiment, the bed of the singulator is populated with an array of rollers  152  that support conveyed material. Each roller  152  is moveable for engagement with either drive roller  128  whose surface is moving at entry velocity V e  or with a drive roller  128 , whose surface is moving at exit velocity V x . Thus, the drive for each locally driven roller apparatus  160  may be intelligently selected, corresponding to either entry velocity V e  or exit velocity V x , to move one or more parcels downstream while retarding others as required to achieve a downstream flow of single pieces separated by a controlled minimum gap as discussed in connection with FIGS.  7 - 12 .  
         [0060]    [0060]FIGS. 19 and 19A illustrate a drive  170  for a fixed ratio belt continuous apparatus. In this embodiment a planetary mechanism, gear or friction engaged, and two clutches in a drive roller are used to generate two velocities from a single drive shaft. The planetary drive includes drive shaft  178 , frame  182 , an outer rotational element (gear or roller)  172 , a clutch engagement element  174 , clutch pads  190 , an inner rotational element (gear or roller)  188  coupled to drive shaft  178 , middle rotational elements (gears or rollers)  186  and a planetary middle rotational element (axles and dual speed roller). An actuator such as a solenoid or hydraulic or pneumatic cylinder  180  actuates the clutch for engagement between the outer planetary element and the middle element for shaft velocity or between the outer planetary element to the frame for low velocity as shown in FIG. 19A.  
         [0061]    [0061]FIG. 20 illustrates a fixed-ratio belt continuous apparatus that is yet another embodiment of conveying means  20  for use in connection with the singulator of the invention. Conveying belt  202  passes over a pair of idler rollers  204  and dual-velocity drive roller  206 , all of which are mounted in a roller/belt frame  210 . Dual-velocity drive roller  206  includes a drive shaft  212  for coupling the drive roller to a two-speed drive, such as the planetary drive illustrated in FIGS. 19 and 19A In this embodiment, planetary mechanism  170  (gear or friction engaged) is used to generate two velocities from a single drive shaft. Thus, each fixed-ratio belt apparatus  170  maybe intelligently driven at one of the two speeds corresponding to the outputs of the planetary drive  170  by means of actuator  180 , to move one or more parcels downstream while retarding others as required to achieve a downstream flow of single pieces separated by a controlled minimum gap.  
         [0062]    [0062]FIG. 21 illustrates a fixed ratio roller continuous apparatus  220  corresponding to a further embodiment of conveying means  20 . The apparatus includes a dual-velocity drive roller  222  mounted in a supporting structure  206 . The drive roller  222  includes a drive shaft  204  that maybe coupled to a two-speed drive such as the planetary apparatus illustrated in FIGS. 19 and 19A and operated in the same fashion described above in connection with the fixed-ratio belt apparatus  200  illustrated in FIG. 20.  
         [0063]    Turning now to FIG. 22, there is illustrated a sliding boundary continuous conveying apparatus  230  for use as an embodiment of conveying means  20 . As shown, the apparatus  230  includes extendable belts  232  and  234  operating at entry velocity V e , and exit velocity V x , respectively. As will be appreciated, embodiments of the invention using this type of conveying means are based not on an array of discrete points (FIG. 23), but on a set of long, narrow columnar structures that support two narrow in-line belts, one driven at entry velocity and the other at exit velocity.  
         [0064]    Each of belts  232  and  234  pass around boundary idler rollers  252 , end rollers  254  that maybe drive rollers, and through a series of tension rollers  237  and idler rollers  235  in a serpentine path. Tension rollers are  237  are mounted in a moveable frame  236  that is spring-loaded by spring  238  to allow for take up and let out of the belts  232  and  234  as the boundary support  250  is moved longitudinally by means of screw drive  246 . Each of belts  232  and  234  is supported by a slider belt support  240  which as shown includes overlapping sections  242  and  244  that may be moved relative to each other by screw drive  246 . Screw drive  246  is actuated by screw drive motor  248  which in turn is intelligently controlled to vary the position of boundary support  250  that in turn moves the boundary  18  (FIG. 7) so as to move one or more selected pieces downstream in the manner discussed in connection with FIGS.  7 - 12  to achieve a downstream flow of single pieces separated by a controlled minimum gap.  
         [0065]    [0065]FIG. 23 schematically illustrates a control system  270  for use in connection with the selective advance intelligent singulator. As shown, a feed conveyor  272  upstream of singulator  274  is equipped with image information capturing devices (detection system) such as one or more cameras  280 , and /or vertical and/or horizontal sensors  282  and/or an array of pressure sensing devices  284 , as desired. These or similar devices are utilized to capture image information corresponding to a stream of disordered pieces of material to be singulated.  
         [0066]    The captured image information is transmitted to a computer or microprocessor  286  where the information is interpreted and/or transformed through the use of preprogrammed algorithms. Alternatively, this data collection means by be replaced by the use of pallet layer placement information in conjunction with a data base.  
         [0067]    As shown, singulator  274  is represented as an array of discreet points or locations  278 , each of which correspond to a conveying means  20 . The devices illustrated in FIGS.  14 - 21 , and discussed in connection therewith may be advantagegeously utilized at each of the locations  278  as conveying means. Multiple devices of the type shown in FIGS. 13 and 22 may also be utilized as conveying means  20  in a similar fashion, however; it will be appreciated that these devices would be more accurately represented by longitudinally extending columns or zones.  
         [0068]    Each conveying means  20  positioned at locations  278  may be discretely and intelligently controlled by microprocessor  286  so as to vary the boundary velocity  18  (FIGS. 1 and 7) across the singulator  274  and transform a disorganized stream of material into an orderly flow of single pieces separated by a controlled minimum gap as discussed in connection with FIGS.  1 - 12 . Additional cameras  280  and/or sensors  282 ,  284  may also be used in connection with the singulator  274  to monitor and control the operation of the system. It will also be appreciated that while various belt and roller conveying devices have been disclosed in connection with the invention, it is contemplated that other material transporting devices may also be used, as well as variations of the belt and roller devices disclosed herein.  
         [0069]    While the invention has been described in reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various rearrangements of parts, modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description.