Abstract:
A batch sheet feeder has an upstream first conveyor section arranged to convey sheets singly in a downstream direction to a downstream second conveyor section. The second conveyor section has an upper second conveying section and a lower second conveying section forming a gap therebetween. The gap is largest at an upstream end of the second conveyor section and diminishes in size toward a downstream end of the second conveyor section. A gate positioned proximate the downstream end of the second conveyor section selectively blocks sheets fed along the second conveyor section. In another embodiment, the sheet feeder has a sheet conveyor, sheet sensor, and visual attribute sensor. The visual attribute sensor has a field of view covering an area of the conveyor at a certain downstream location so as to sense an area of any sheet on the conveyor at this downstream location. The visual attribute sensor can compare a sensed area of a sheet at the downstream location with a stored visual attribute. In this way, where the sheets of a batch are different, the visual attribute sensor can be used to verify that a sheet of a batch has visual characteristics matching those of the expected sheet at that ordinal position in the batch. This assists in ensuring a batch is not faulty. In a related method of verifying batches of sheets, for each sheet at a given ordinal position in each batch a visual attribute measure for at least an area of the sheet is obtained. A comparison is made of the visual attribute measure with a stored visual attribute measure. Each batch is selectively verified based on this comparison.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a sheet feeder particularly useful in feeding batches of sheets and to a method of verifying batches of sheets.  
         BACKGROUND OF THE INVENTION  
         [0002]    In known batch sheet feeders, sheets may be fed singly from a stack through parallel belts and counted while they are transported through the parallel belts. The sheets are then either fed individually to a target (e.g., a box between flights of a downstream conveyor) so as to be stacked in batches directly on the target, or fed and stacked onto some sort of drop table (e.g., a reciprocating table) to be dropped vertically onto or into their target as a batch.  
           [0003]    One drawback with singly feeding sheets to the target is that the target area must not move or be obstructed during the entire time that a given batch is being fed. By stacking the batch on a drop table, this problem is avoided in that the entire batch is dropped to the target together as one group. However, the speed at which the batch drops is fixed (by gravity) and the feeding of sheets to the table must halt for the time it takes the drop table to open, the product to drop and the table to return to its ready position. Another drawback is that the target must be able to accept the product from the top. With both approaches, a further difficulty in stacking the sheets is in controlling the trailing edge of a sheet so that the next sheet does not crash into it. This difficulty increases with the speed of feeding.  
           [0004]    While known batch sheet feeders count sheets to ensure there is a proper number of sheets in each batch, in many applications the sheets of a batch are printed differently. Thus, each sheet of a batch may be unique in the batch. In such applications, another problem is ensuring that each batch has a proper set of sheets. Another drawback with the noted types of batch sheet feeder is that they have no mechanism to address this problem.  
           [0005]    This invention seeks to provide a batch sheet feeder that avoids at least one of these drawbacks.  
         SUMMARY OF INVENTION  
         [0006]    According to the present invention, there is provided a batch sheet feeder comprising: an upstream first conveyor section arranged to convey sheets singly in a downstream direction to a downstream second conveyor section; said second conveyor section comprised of an upper second conveying section and a lower second conveying section forming a gap therebetween, said gap being largest at an upstream end of said second conveyor section and diminishing in size toward a downstream end of said second conveyor section; and a gate positioned proximate said downstream end of said second conveyor section for selectively blocking sheets from exiting said second conveyor section.  
           [0007]    According to another aspect of the invention, there is provided a batch sheet feeder, comprising: a lower endless conveyor; an upper endless conveyor arranged with respect to said lower conveyor so as to form a sheet feed path between said lower conveyor and said upper conveyor for feeding sheets in a downstream direction; said lower conveyor substantially paralleling said upper conveyor along an upstream first section, said lower conveyor jogging away from said upper conveyor at an upstream end of a downstream second section so as to form a gap between said lower conveyor and said upper conveyor at said second section that is larger than any gap between said lower conveyor and said upper conveyor at said first section.  
           [0008]    According to a further aspect of the invention, there is provided a sheet feeder, comprising: a sheet conveyor; a sheet sensor; a visual attribute sensor having a field of view covering an area of said conveyor at a certain downstream location so as to sense an area of any sheet on said conveyor at said downstream location, said visual attribute sensor for comparing a sensed area of a sheet at said downstream location with a stored visual attribute.  
           [0009]    According to another aspect of the present invention, there is provided a method of verifying batches of sheets, comprising: for each sheet at a given sheet position in each batch of sheets: obtaining a visual attribute for at least an area of said each sheet; comparing said visual attribute with a stored visual attribute; and selectively verifying said each batch based on said comparing.  
           [0010]    According to a further aspect of the invention, there is provided a method of verifying batches of sheets, comprising: conveying sheets in a sheet conveyor; sensing sheets with a sheet sensor; sensing a visual attribute with a visual attribute sensor having a field of view covering an area of said conveyor at a certain downstream location so as to sense an area of any sheet on said conveyor at said downstream location; verifying batches of sheets at a processor receiving an output from said visual attribute sensor and said sheet sensor.  
           [0011]    Other features and advantages of the invention will be apparent after reviewing the description in conjunction with the accompanying drawings. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0012]    In the figures which illustrate example embodiments of the invention,  
         [0013]    [0013]FIG. 1 is a perspective view of a sheet feeder made in accordance with this invention,  
         [0014]    [0014]FIGS. 2 and 2 a  are schematic side views of FIG. 1,  
         [0015]    [0015]FIG. 3 is a perspective end view of a portion of the feeder of FIG. 1,  
         [0016]    [0016]FIG. 4 is a schematic side view of another embodiment of this invention,  
         [0017]    [0017]FIG. 5 is a schematic side view of yet another embodiment of this invention, and  
         [0018]    [0018]FIG. 6 is a schematic side view of a further embodiment of this invention.  
     
    
     DETAILED DESCRIPTION  
       [0019]    Referencing FIGS. 1 and 2, sheet handling apparatus  10  comprises an in-feed sheet feeder  12 , a batch sheet feeder  14 , and a downstream target, such as boxes  15  between flights of flight conveyor  16 .  
         [0020]    The in-feed sheet feeder may be of any type that will feed sheets singly to batch sheet feeder  14 . As illustrated, in-feed sheet feeder  12  has a stack  18  of sheets  20  supported by sheet guides  22  arranged such that the bottom sheet contacts a feed belt  23 . A motor  26  is provided to rotate a feed wheel  24 . If feed belt  23  is circulating, rotation of wheel  24  through an arc will feed a single sheet downstream. Such an in-feed sheet feeder  12  is further described in U.S. Pat. No. 4,651,983 to Long, the contents of which are incorporated by reference herein.  
         [0021]    The batch sheet feeder  14  feeds sheets in a downstream direction D from the in-feed sheet feeder  12  to conveyor  16 . The batch sheet feeder  14  has a lower endless conveyor  30  and an upper endless conveyor  32  forming a sheet feed path between them. The conveyors  30 ,  32  are driven by a motor  28 . Motor  28  also drives feed belt  23 . As is apparent from FIGS. 1 and 3, each of these conveyors comprises a plurality of endless belts  30 B,  32 B. The lower conveyor  30  substantially parallels the upper conveyor  32  along an upstream first section  34 . The lower conveyor  30  then wraps around separating support rolls  36 ,  38  to jog away from the upper conveyor  32 . The separating support rolls are mounted on a base  37 , as is a backstop  66 ; the base allows the downstream position of the separating support rolls (and the backstop) to be adjusted. The separating support rolls define an upstream end of a downstream second section  40  of the batch sheet feeder. With this arrangement, any gap between the upper  32  and lower  30  conveyors at the first section  34  is smaller than the gap  42  between these conveyors at the upstream end of the second section  40 .  
         [0022]    The upstream end of the lower  30  and upper  32  conveyors is supported by in-feed support rolls  44 ,  46 , respectively. The downstream end of these conveyors is supported by exit rolls  54 ,  56 , respectively. Exit rolls  56 ,  58  are mounted so that their spacing can be adjusted to some extent by screws  57 ,  59 . However, any gap between the exit rolls  54 ,  56  should be significantly smaller than gap  42  at the upstream end of second section  40 . In consequence, the gap  42  between the lower  30  and upper  32  conveyors is largest at the upstream end of the second section  40  and reduces in size toward the downstream end of the second section  40 .  
         [0023]    An adjustable support roll  60  bears against the upper conveyor  32  at the second section  40 . The adjustable support roll may be adjusted in a direction toward or away from the lower conveyor  30  in order to selectively adjust the size of the gap  42  between the lower  30  and upper  32  conveyors.  
         [0024]    Separating support roll  38  is upstream of separating support roll  36 . The lower conveyor  30  wraps around a downstream side of separating support roll  36  and around an upstream side of separating support roll  38  so as to form an “S” shape in the downstream conveyor. (In the right hand side view of FIG. 2, this appears as a backwards “S” shape.)  
         [0025]    A retractable gate  62  is positioned proximate the downstream end of the second section  40  to selectively block sheets from exiting the batch sheet feeder  14 . A pneumatic valve  74  provides air pressure to reciprocate the gate. The gate depends from a bracket  72  and a guide  70  (FIG. 3) maintains the gate  62  in its proper orientation. Side sheet guides  73  (FIG. 3) are provided upstream of the gate  62 .  
         [0026]    With reference to FIG. 3, each of the exit rolls  54 ,  56  may be an undulating roll. These undulating rolls parallel each other with the peaks  76  of the upper undulating exit roll  56  aligned with the troughs  78  of the lower undulating roll  54 . The peaks of each undulating roll have gently sloped crowns  80 . Each belt  30 B,  32 B of the conveyors  30 ,  32  wraps around one of these crowns. However, in order to accommodate gate  62 , no belt wraps around the central peak of the upper undulating exit roll  56 . This configuration of the exit rolls  54 ,  56  allows the lower conveyor to project to, or above, the level of the upper conveyor at the exit rolls  54 ,  56 . Thus, optionally, there may be no gap at all between the lower and upper conveyors at the exit rolls. Furthermore, with this arrangement, the belts self-centre on the crowns  80  of the peaks  76 . Optionally, in-feed support rolls  44 ,  46  may be similarly configured undulating rolls.  
         [0027]    A visual attribute sensor  82  and a sheet sensor  86  are positioned along the first section  34  of the batch sheet feeder. The visual attribute sensor may be a colour sensor of the type that, when prompted, memorises the colour currently within its field of view. After memorising a colour, the colour sensor outputs a “match” signal whenever it is subsequently prompted to sense the colour within its field of view and the colour it sees is the same as the memorised colour. A suitable colour sensor operating in this fashion is the CZ-K series RGB digital fiberoptic sensor manufactured by Keyence Corporation of Japan. The visual attribute sensor has a mount  84  that allows its traverse and downstream position to be adjusted. A batch sensor  88  is positioned along the second section  40  of the batch sheet feeder.  
         [0028]    A processor  90  receives an output signal from each of sheet sensor  86  and batch sensor  88 . The processor is also coupled for communication with visual attribute sensor  82 . The processor outputs control signals to each of motors  26  and  28  and pneumatic valve  74 . The processor also receives batch demand signals on control line  92 .  
         [0029]    Sheet handling apparatus  10  may be operated with visual attribute sensor  82  active or inactive. It is assumed first that processor  90  is loaded with an indication visual attribute sensor is inactive. The processor is also loaded with an indication of the number of sheets that are to be in each batch and a stack  18  of sheets  20  is loaded into sheet guides  22 . The downstream position of base  37  is then adjusted so that the length of gap  42  between backstop  66  and gate  62  is sufficient to accommodate the length of the sheets  20  that are in stack  18 .  
         [0030]    The processor  90  may then accumulate a first batch of sheets at the second section  40  of batch sheet feeder  14 . To do so, the processor ensures gate  62  is blocking the exit of the batch sheet feeder by sending an appropriate activation signal to the pneumatic valve  74 . The processor then activates motor  28  in order to circulate conveyors  30  and  32  (and feed belt  23 ) and motor  26  to rotate feed wheel  24  in order to feed sheets singly between the conveyors  30 ,  32 . The conveyors  30 ,  32  entrain the sheets and move them in the downstream direction D toward the gate  62 . As sheets  20  pass sheet-sensor  86 , “sheet sensed” signals are sent to the processor. This allows the processor to keep track of the number of sheets that have been fed. After this number reaches the previously loaded number of intended sheets in each batch, the processor stops motors  26  and  28 .  
         [0031]    As each fed sheet passes separating support roll  36 , it drops into the gap  42  between the upper  32  and lower  30  conveyors and then continues downstream until stopped by gate  62 . Adjustable support roll  60  creates a bend in upper conveyor  32 . This causes sheets feeding past support roll  60  to bend—as illustrated by sheet  20 B in FIG. 2 a . Once the trailing edge of a bent sheet enters gap  42 , the sheet naturally begins to straighten out to lose its bend; this urges the trailing edge of the sheet downwardly, thereby reducing the risk of the next upstream sheet crashing into the trailing edge of the straightening sheet. Because of the enlarged gap between the upper and lower conveyors in the second section  40 , the frictional contact of the lowermost and uppermost sheets accumulated in section  40  with respective conveyors  30  and  32  is reduced sufficiently to avoid bruising or spindling the sheets. Adjustable support roll  60  may be adjusted in accordance with the size of a batch: the larger the batch, the larger the gap  42  so as to control the frictional force on the uppermost sheet accumulated in section  40 . Additionally, the spacing between exit rolls  56 ,  58  can also be adjusted in accordance with the size of the batch to control the frictional forces on the batch.  
         [0032]    Backstop  66  precludes the possibility of the trailing edge of a sheet becoming entrained in the short upstream run of the lower conveyor  30  as it loops back from roll  36  to roll  38 .  
         [0033]    Once an entire batch is in gap  42  and the processor has stopped motors  26  and  28  (thereby stopping the conveyors  30 ,  32 ), the processor causes the gate  62  to be retracted. Optionally, the processor may then control motor  28  to move conveyors  30 ,  32  slowly in order to advance the accumulated batch sufficiently so that the batch is between the exit rolls  54 ,  56 , whereupon the processor again stops the conveyors  30 ,  32 . (A rotary encoder associated with motor  28  can be used to allow the processor to know how far it has advanced the batch.) In this situation, the front of the batch is tightly held between the exit rolls  54 ,  56  (but the trailing edge of the batch has not passed batch sensor  88 ).  
         [0034]    When the processor  90  receives a batch demand signal on line  92 , it activates motors  26  and  28  to again begins circulating conveyors  30  and  32  so that the batch exits to conveyor  16  through the exit rolls  54 ,  56 . In this regard, with the upper surface of the lower conveyor belts  30 B positioned below the lower surface of the upper conveyor belts  32 B, the sheets in the batch will be forced to assume an undulated shape as they pass through the exit rolls. This enhances the frictional engagement of the batch of sheets with the conveyor belts  30 B,  32 B and thereby assists in ensuring proper feeding. (Where in-feed support rolls  44 ,  46  are similarly configured, in-fed sheets may also be forced to assume an undulated shape that enhances frictional engagement and thereby assists in ensuring proper feeding.)  
         [0035]    When the trailing edge of a batch passes batch sensor  88 , the batch sensor signals processor  90 . This prompts the processor to extend gate  62  to again block the feed path. With both motors  26  and  28  activated, a new batch is accumulated in the second section  40  of the batch sheet feeder. The operation then repeats as aforedescribed.  
         [0036]    The adjustment mechanism for adjustable support roll  60  may be a manually operated mechanism or an actuator controlled by processor  90 . In the latter case, where the ready position of a batch (i.e., the rest position of the batch while a demand signal is awaited) is such that the trailing edge of the batch is upstream of roll  60 , once a batch reaches the ready position, the processor may lower roll  60  to engage the batch more securely. This will allow a batch to be more securely ejected. On the batch has been ejected, the processor would retract roll  60  back to a position for accumulation of the next batch.  
         [0037]    Optionally, two adjustable support rolls (not shown) may be provided at the downstream position of gate  62 , one on either side of the gate. If these additional rolls are provided, they may remain in a retracted position while gate  62  blocks the feed path, but may extend to push the conveyor belts  30 B or  32 B with which they are associated closer together when gate  62  is retracted. These two adjustable support rolls may therefore assist in ensuring that the batch is positively fed to the exit rolls  54 ,  56  after the gate has been retracted. Also, if the feeder is equipped with these additional adjustable support rolls, the spacing between the exit rolls  54 ,  56  may be increased. The increased spacing between the exit rolls helps ensure that the exit rolls are not so tightly spaced as to jam a developing batch against the gate with a force that will spindle sheets in the batch.  
         [0038]    In the special case where the processor is loaded with an indication that a batch comprises only a single sheet, the processor can permanently raise gate  62  and, where it can control the position of roll  60  through an actuator, can lower roll  60  so that the conveyors  30 ,  32  beneath the roll will pinch a single sheet. The operation of feeder  14  would also differ in that processor would simply operate motors  26  and  28  until batch sensor  88  is interrupted by a single sheet. Thereafter, on receipt of a demand signal, the sheet interrupting the batch sensor would be ejected and feeding would resume until the next sheet interrupted the batch sensor  88 .  
         [0039]    Optionally, motors  26  and  28  could be replaced by a single motor with an appropriate drive train to obtain a desired speed ratio between (slower moving) feed wheel  24  and conveyors  30 ,  32 .  
         [0040]    Optionally, the flight conveyor  16  could move substantially in downstream direction D, rather than transversely to this downstream direction as is shown in FIG. 1. For example, with reference to FIG. 4, a conveyor  116  conveys target boxes  115  in a target downstream direction DT. Target downstream direction DT crosses downstream direction D at a batch insertion station where a batch  120  is inserted into an open top of a box  115 . In this regard, conveyor  116  may operate continuously and the batch sheet feeder  14  controlled so that it ejects batches at a speed matched to that of the conveyor  116 . As a further example, with reference to FIG. 5, a batch deflector  225  is added to the output end of batch sheet feeder  14 . A conveyor  216  conveys boxes  215  in a downstream direction DT that crosses downstream direction D at a batch insertion station. The batch sheet feeder  14  is controlled so that a batch is projected with sufficient speed to be inserted into the open top of a box  215  as it passes. Again, the speed of feeding batches may be controlled to match that of a continuously operating conveyor. Unlike drop table batch sheet feeders, there is no requirement to feed to a target only from directly above; also, the speed of feeding may be greater than what can be achieved by gravity. And unlike batch feeders that stack a batch directly on to a target, there is no need to stop the target while the batch is fed. It will be apparent that, in fact, if desired, batch sheet feeder  14  may feed batches at high speed. This allows the batch sheet feeder  14  to place batches onto, or into, targets that continuously move past the exit rolls  56 ,  58 . Further, these targets may move in, or substantially in, the downstream direction D of the batch sheet feeder  14 .  
         [0041]    [0041]FIG. 6 illustrates an alternate arrangement for the batch sheet feeder. Turning to FIG. 5 wherein like parts have been given like reference numerals, batch sheet feeder  214  differs from batch sheet feeder  14  of FIGS.  1  to  5  in that the downstream second section  40  is separate from the upstream first section  34 . More particularly, the upstream section  34  is defined by conveyors  130 ,  132  which ride on rolls  44 ,  250 , and  46 ,  252 , respectively. And the downstream section  40  is defined by conveyors  230 ,  232  which ride on rolls  270 ,  54 , and  272 ,  56 , respectively. A suitable drive train may operatively couple the conveyors of the upstream section with those of the downstream section. With separate upstream  34  and downstream  40  sections, batch sheet feeder  214  omits the separating rolls  36 ,  38  of FIGS.  1  to  4  and so the length of the downstream section  40  is not readily adjustable. In other respects, the batch sheet feeder  214  operates in the same manner as batch sheet feeder  14  of FIGS.  1  to  5  with sheets feeding singly along the upstream section and dropping into gap  42  and accumulating as a batch.  
         [0042]    In the batch sheet feeder  214  of FIG. 6, the upper conveyor  132  could be replaced with a stationary sheet guide.  
         [0043]    Where the sheets of a batch are visually different, the visual attribute sensor  86  may be used to help ensure each batch is properly constituted. For example, each sheet of a batch may have a different pattern of colours. This could occur where, for example, each sheet of a batch is a different advertisement. For such batches, the visual attribute sensor  86  could be the aforedescribed colour sensor.  
         [0044]    Typically, sheets of a batch are printed such that each batch has the same set of sheets (e.g., the same set of advertisements) in the same order. To verify such batches, an area of one sheet (the “target” sheet) of a model batch is selected that is coloured distinctly from the same area of all other sheets of the batch. The target sheet will have a certain ordinal position in the batch. The processor  90  is then prompted to advance sheets of the first batch until the target sheet from the first batch (i.e., the sheet in the first batch that is at the certain ordinal position) is at a given downstream position. Colour sensor  82  is then moved in its mount  85  so that its field of view is aligned with the selected area of the target sheet; the colour sensor is then locked in its mount in that position. With the selected area of the target sheet within the field of view of the colour sensor, the colour sensor is prompted to memorise the colour(s) of that area of the target sheet. The processor is also prompted to memorise the ordinal position of the target sheet in the batch.  
         [0045]    Conveniently, the sheet sensor  82  sends a signal to processor  90  each time it senses (a leading or trailing) edge of a sheet (such that the processor counts one sheet after receiving two consecutive signals from sheet sensor  82 ). In such case, the given downstream location of the target sheet can be defined as the position at which the sheet sensor  86  senses the leading edge of the target sheet.  
         [0046]    After the processor has memorised the noted parameters (of colour and ordinal position), whenever a batch is fed, the processor monitors for the leading edge of the target sheet (i.e., the sheet at the memorised ordinal position) in the batch and prompts sensor  82  to capture the colour of the selected area of that sheet. Provided the target sheet is, in fact, the intended sheet, the colour sensor will output a “match” signal. On the other hand, if the target sheet is not the intended sheet, the colour of the target sheet at the selected area will not match the memorised colour. In consequence, the processor will not receive the expected “match” signal. This will cause the processor to flag the current batch as faulty so that appropriate action can be taken.  
         [0047]    While the example visual attribute sensor  82  is a colour sensor, other visual attribute sensors may be used. For example, the visual attribute sensor may be a visual pattern sensor for sensing the visual pattern within its field of view in addition to, or instead of, the colour. For example, the sensor could include a camera (such as a CCD camera) and output a “match” signal only when the (coloured) pattern within the field of view of the camera matched a memorised pattern. Alternatively, where the sheets included bar codes, the visual attribute sensor could be a bar code reader. Also, instead of the visual attribute sensor being a separate component, the sensor could be a combination of a visual sensor, such as a camera (at the location of sensor  86 ) and the processor  90 . That is, the processor could process signals from a camera in order to store an initial (coloured) pattern and compare it with a current pattern.  
         [0048]    Optionally, a visual attribute of more than one sheet, or indeed of all sheets, of a batch may be memorised and used as a metric of comparison with corresponding sheets of future batches to identify faulty batches. As a further option, the last sheet in each batch may be provided with a visible end-of-batch indicia positioned so that it will be in the field of view of the visual attribute sensor as this last sheet passes the sensor. In such instance, the processor learns from the sensor that the last sheet of a batch has been fed. Consequently, there is no need for the processor to be pre-loaded with the batch size and, indeed, this size may change from batch to batch.  
         [0049]    Adjustable support roll  60  could be replaced with an adjustable support abutment having a low friction surface that makes sliding contact with the upper conveyor  32 .  
         [0050]    Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.