Patent Publication Number: US-6666324-B2

Title: System and method for reorienting flat articles

Description:
FIELD OF THE INVENTION 
     This invention relates generally to mail handling systems, and, more particularly to a system for reorienting a moving stream of generally flat articles. 
     BACKGROUND OF THE INVENTION 
     In the field of automated mail processing, there are numerous inventions and machines designed to handle uniformly dimensioned articles, typically known as first class mail, ranging in size from post cards to business letter envelopes. There are, however, a limited number of machines designed to automate the processing of larger flat articles otherwise known as “mail flats,” which may be up to fifteen inches square and one and a quarter inches thick. 
     Current practices in automated mail handling include the placement of batches of flat mail, or mail flats, into feeders, which separate the individual pieces and expel those pieces in a serial stream having a vertical orientation and a predetermined periodicity or pitch between the leading edges of adjacent pieces. The mail flats in this vertically oriented stream are then reoriented and placed on a horizontal conveyor with another predetermined periodicity, for the purpose of further handling and processing. This reorientation process can be particularly challenging for several reasons. 
     One challenge to the reorientation process is the handling of magazines and newspapers. Magazines must be automatically handled by their bound edge, and newspapers must be handled along their final fold. This requirement is critical to achieving any sort of speed in the automatic handling process. For this reason, these articles are placed in the feeder bin with the bound edge or final fold facing downward and are expelled from the feeder in this orientation. Later, when magazines and newspapers are placed on the horizontal conveyor, they must have their bound edge or final fold facing forward for proper handling. Therefore, the reorientation step must be performed so that the bottom edge of the vertically oriented mail flats becomes the leading edge of the horizontally oriented mail flats. 
     Space constraints are another challenge in the reorientation process. Input feeders typically have maximum height, ergonomic limitations to allow an operator to conveniently and safely place stacks of mail into the feeder. The horizontal output conveyors typically have minimum height requirements for receiving the mail flats because of similar constraints in removing objects. Therefore, the reorientation apparatus is limited in the amount of height that it can use for the reorientation process. The height restriction is further aggravated by the size and nature of the mail flats to be handled. As mentioned, such mail flats may be up to 15 inches by 15 inches, with thicknesses up to 1_inches. Automatically reorienting a stiff 15×15×1.25 inch parcel is much more challenging than reorienting a flexible magazine. 
     Mail processing machinery also needs to operate at a sufficient throughput, commonly measured as “pieces per hour” (pph), that is economically viable for the mail handling agency to sacrifice the electrical power and space requirements as well as justify the capital expenditure. The machinery must also have sufficient throughput and accuracy to justify replacement of manual labor. 
     A common method of handling mail is from a horizontally oriented conveyor. The horizontal conveyor affords the easiest means for handling mail flats. Also, various other devices, such as scanners, cameras and sorters, have already been designed to work with such conveyors. A key hurdle in designing systems is how to achieve high throughput without adjacent pieces colliding with each other. U.S. Pat. No. 5,860,504 discloses machinery that places mail flats on a horizontal conveyor using multiple input feeders, which individually sense open spaces on the horizontal conveyors and then deliver their individual pieces to the sensed openings. The mail flats being handled have already been reoriented for proper placement on the horizontal conveyor. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention provides a system for reorienting flat articles in a serial stream including a conveyor mechanism for receiving a horizontally moving, serial input stream of substantially vertically oriented flat articles, which each have a downwardly oriented primary edge, and having a diverter gate for laterally directing the flat articles alternately between two separate output paths. A separate pocket is coupled to each separate output path for impeding horizontal movement of each flat article and for positively engaging and accelerating each flat article in the direction of its primary edge. A separate channel is coupled to each pocket to deliver the substantially horizontally oriented flat articles from each pocket. 
     In a refinement of the above invention, each separate output path of the conveyor mechanism is adapted for imparting rotational movement to each flat article therein. 
     In a separate refinement, each pocket includes a drive mechanism to pressure flat articles on opposing flat sides to positively engage and accelerate the flat articles. In this manner, a control system may be used to control at least one of the pockets for causing flat articles to be delivered from both channels at regular intervals. 
     In a further separate refinement, each channel includes a driven conveyor having a lower, flexible belt conveyor to support flat articles along the entire length of the channel and an upper, flexible belt conveyor adapted to place force on the lower, flexible belt conveyor and flat articles in the channel. 
     The method of the present invention covers reorienting flat articles in a serial stream, including the steps of: receiving a horizontally moving, serial input stream of substantially vertically oriented, flat articles each having a downwardly oriented primary edge; laterally diverting the flat articles in the serial input stream, alternately between a pair of separate paths; impeding horizontal movement of each flat article in each separate path; accelerating each flat article with impeded horizontal movement in the direction of its primary edge; and delivering substantially horizontally oriented flat articles from each separate path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustratively described and shown in reference to the appended drawings in which: 
     FIG. 1 is a perspective view of a system constructed in accordance with an embodiment of the present invention; 
     FIG. 2 is an enlarged and partially exposed view of a portion of the system of FIG. 1; 
     FIG. 3 is a partial top view of the system of FIG. 1; 
     FIG. 4 is an exposed perspective view of a drop pocket section in accordance with the embodiment of FIG. 1; 
     FIG. 5 is a rotated perspective view of the drop pocket section of FIG. 4; and 
     FIG. 6 is a functional block diagram of the system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The embodiments described herein are directed to the handling of mail flats. However, these embodiments may also be used for handling other similar flat articles which might not fall within the definition of mail flats. 
     A mail flat handling system  10  is illustratively shown in FIG.  1  and generally includes an input port  12  for receiving a horizontally moving input stream of vertically oriented mail flats  11 , a conveyor mechanism  14  for handling the vertically oriented mail flats  11 , a drop pocket section  16  and a horizontally oriented output port  18 . Mail flats  11 , having a downwardly oriented primary edge  13 , are conveyed from input port  12  and through conveyor mechanism  14 , by a multiplicity of vertically mounted conveyor belts  20  which engage the vertically oriented mail flats on opposing sides. Conveyor belts  20  are mounted on various vertically mounted rollers  22 , and rollers  22  are in turn mounted on various fixed and biased position axles  24 , all in accordance with practices known in the art. The biased position axles  24   a  are used in a known manner to maintain lateral pressure from the conveyor bands  20  on opposing sides of the mail flats  11  while compensating for the various allowed thicknesses for such mail flats. Conveyor belts  20  are typically driven by a motor located below the deck  37  of conveyor mechanism  14 . Several conveyor belts  20 , that are normally used in mechanism  14  are missing from FIGS. 1 and 2 for purposes of clarity, but their form, fit and function would be obvious to someone skilled in the art based upon the current disclosure. 
     A particular aspect of conveyor mechanism  14  is that it includes a diverter gate  30  for laterally dividing or splitting the input stream of mail flats alternately between two output paths  32  and  34 . In this manner, sequential mail flats in the input stream, are diverted into or split between the paths  32 ,  34 . These alternate paths  32 ,  34  each lead to a separate drop pocket  42 ,  44 , respectively, of drop pocket section  16 . 
     FIG. 2 shows an enlarged view of diverter gate  30  and the corresponding portion of the conveyor mechanism  14 . Gate  30  generally includes a diverter vane  36  mounted to the drive shaft of a rotary solenoid  38 . Diverter vane  36  is located in the mail stream above conveyor deck  37  while rotary solenoid  38  is mounted below deck  37  and connected to vane  36  through a hole in deck  37 . The upper end of vane  36  is rotationally mounted in a strut  35 . Also affixed to the drive shaft of rotary solenoid  38  is a limiter  39  for defining the range of motion of vane  36 . The control of diverter vane  36  may be accomplished by any suitable mechanism such as the rotary solenoid  38  or by any suitable compressed air device. Rotary solenoids are commercially available, and the current solenoid  38  includes a spring return which is sufficient for purposes of the present system. In operation, diverter vane  36  is spring biased to divert mail flats into one of the two paths  32 ,  34  and then electrically flipped to divert alternating mail flats into the other path. 
     Conveyor mechanism  14  may also incorporate various forms of peripheral devices, such as scanners, cameras and bar code printers, for processing the mail flats. Such peripheral devices may be mounted on either side of the mail stream, and even on both sides in cases where the address label may be oriented in either direction. Conveyor mechanism  14  shows a space  33  in FIG. 1 where a peripheral device may be mounted to access the mail flats  11 . In the space  33 , the conveyor belts  20  are not present on the right hand side of the input path, to allow unrestricted access to the mail flats by a peripheral device. Also shown are two sets of biased position rollers, with each set mounted on a biased position axle  24   a . In this manner, axles  24   a  are movable to compensate for various thicknesses of the mail flats, while the right hand side of each mail flat passes the same location for consistent access by a peripheral device. FIG. 2 shows an additional biased position axle  24   a , which is spring biased towards a similar opposed axle (not shown). This combination of biased position axles  24   a  can be used for providing overall tension to conveyor belts  20 , as well as for providing appropriate lateral pressure to individual mail flats of different sizes. 
     The process of reorienting, or changing the direction of travel of the mail flats is accomplished by the use of drop pockets  42 ,  44 . Drop pockets  42 ,  44  first decelerate or impede the relative lateral or horizontal movement of the mail flats and then accelerate the mail flats in their relative vertical or longitudinal direction. As shown in FIG. 1, the present embodiment avoids collisions between mail flats and apparatus jams which can result from this process of deceleration and acceleration, by spitting the input mail stream between two or more separate paths  32 ,  34 , and drop pockets  42 ,  44 . This approach enables the system  10  to function at the high throughput rates-available from contemporary feeders while still avoiding collisions between adjacent mail flats. Although the use of more than two separate paths is possible, the use of only two paths is preferable for the purpose of reducing size, cost and complexity of the system  10 . 
     FIG. 3 shows an enlarged top view of drop pocket  42  including the coupling of conveyor belts  20  thereto. The longest end  21  of conveyor belts  20  is shown mounted on an inclined or slanted axle  45  mounted on drop pocket  42 . As also shown in FIG. 4, axle  45  is at an angle of approximately ten (10) degrees from the vertical orientation of the input mail stream. Individual mail flats exit from between opposing conveyor belts  20  as indicated by arrow  46 . Because of the speed at which the mail flats are traveling and the angle of axle  45 , the mail flats are rotationally accelerated and imparted with rotational movement in the counterclockwise direction relative to their direction of travel. This action begins the reorientation of the mail flats. In this manner, the end  21  of belts  20  with the inclined axle  45  and the associated rollers form an inclined element  45   a  which rotationally accelerates mail flats using their own horizontal movement into drop pockets  42 ,  44 . 
     FIG. 4 shows an exposed view of drop pocket section  16 , detailing the mechanism for each drop pocket  42 ,  44 . The description herein of “drop” pockets is intended to be taken illustratively as various pocket type devices may be used. Drop pockets  42 ,  44  are constructed from matching components which bear the same reference numbers for both drop pockets. Mail flats entering each drop pocket  42 ,  44  are received by a flat member or slider plate  50  and a trap door  51 , under bias from a driven belt  52 . 
     In the present embodiment, slider plate  50  is inclined at an angle of approximately twenty (20) degrees from the vertical causing each mail flat to be held against driven belt  52  by a portion of its own weight. This angle can generally have a wide range of values. In one embodiment, the range is from ten to thirty degrees. The angle of slider plate  50  thus defines initial rotation of the mail flats in the reorientation process. As mentioned in reference to FIG. 3, inclined element  45   a  imparts a counter-clockwise rotation to the mail flats due to their horizontal velocity, which generally causes the mail flats to rotate to the full angle of slider plate  50  and impact thereon. This rotation enhances the overall height efficiency of the reorientation process. 
     Each mail flat impacts the side apparatus plate  56  and any potential bounce back of the mail flats from plate  56  is affected by driven belt  52 , which is constantly running and biasing the mail flat towards plate  56 . In this manner, the overall horizontal movement of mail flats is impeded or blocked and the justification of the mail flats within each drop pocket is maintained with a certain consistency. 
     As mentioned, mail flats within each drop pocket are also supported by a trap door  51 . The position of trap door  51  may be manipulated by any suitable means as represented by actuator  59 . Commercially available actuators may be used, such as a dual action, compressed air unit. 
     An optical sensor  54 , or beam of light (BOL), senses the presence of each mail flat as it obscures the opening  57  in slider plate  50 . This sensing causes a pinch roller actuator  58  to move a pinch roller  60  against the sensed mail flat and thereby positively engage the sensed mail flat against an opposing pinch roller  62 . Actuator  58  causes pinch roller  60  to press against and engage one side of the sensed mail flat. This pressure is typically transmitted through the mail flat pressing the other side thereof against opposing pinch roller  62 . 
     Pinch rollers  60 ,  62  are then used in conjunction with the opening of trap door  51  to positively accelerate the engaged mail flat in a direction perpendicular to its relatively lateral path of entry into the drop pocket. In one embodiment, pinch rollers  60 ,  62  are both driven to best control acceleration of the mail. This location of pinch rollers  60 ,  62  provides positive engagement of mail flats, as well as acceleration thereof, under a high degree of control over the mail flats and thus enables system  10  to operate at a high throughput. Alternatively, only a single driven roller may be used in conjunction with a second, free roller resulting in an apparatus with less performance. Actuator  58  may be formed by any suitable mechanism. In the present embodiment, actuator  58  is a dual action, compressed air driven slider, which allows direct, positive control over the location of pinch roller  60 . 
     Pinch rollers  60 ,  62  accelerate each mail flat substantially downwardly in the direction of its downwardly oriented primary edge. The specific angle at which mail flats are accelerated from the pockets can vary significantly depending upon the design of the pocket used. Thus, all useable pockets may not be termed “drop” pockets. 
     Mail flats are thus accelerated from drop pockets  42 ,  44  into an effective curved path channel  64  defined by upper and lower, flexible belt conveyors  70 ,  72 , respectively. Each effective curved path channel  64  includes a relatively higher, substantially vertically oriented input port  65  located adjacent trap door  51  and a relatively lower, substantially horizontally oriented output at port  18 . Lower, flexible belt conveyor  72  forms one side of the effective curved path channel  64  from input to output and functions to drive and support mail flats within channel  64 . 
     Upper, flexible belt conveyor  70  includes a supported driven axle  73 , a ganged pair of free axles  75  and a plurality of flexible conveyor belts  77  engaging the driven and free axles. Ganged axles  75  may optionally be replaced by a single axle. Ganged axles  75  are supported from the driven axle  73  and kept parallel thereto by a pair of struts  79 . Struts  79  do not receive or transmit rotational force with any of the axles  73 ,  75 . Instead, struts  79  merely maintain the axles  73 ,  75  in a parallel relationship. In this manner, the location of ganged axles  75  is free to move angularly with respect to driven axle  73 . This free movement allows a portion of the weight of ganged axles  75  and struts  79  to exert force upon lower conveyor  72  and thereby provide tension to the belts of lower conveyor  72 . In this manner, free axles  75  are adapted to exert force on lower conveyor  72  and any mail flats located between lower conveyor  72  and ganged axles  75 . The force created by axles  75  is not intended to be limited to the weight of ganged axles  75 , but may also be created by any suitable means, such as a spring bias. 
     Channel  64  and conveyors  70 ,  72  are aided by an optional, fixed skid plate  74  to support heavier mail flats. Although the various sections of the conveyors  70 ,  72  appear straight and skid plate  74  may be flat, the multiple belts of conveyors  70 ,  72 , as well as the positioning of conveyor  70 , are designed to be flexible to fully engage and accommodate mail flats which may be both thick and stiff, and the overall effect of path  64  is that of a curved path from the slider plate  50  to the horizontal orientation represented by conveyor platform  76 . The degree of curvature is not intended to be limited by the present embodiment but is loosely defined in each specific apparatus by the degree of initial rotation achieved in the pockets as well as the final degree of horizontal orientation necessary at output port  18 . Platform  76  is shown in FIG. 4 without the normal drive belts that would be suspended between rollers  78 ,  78   a.    
     In operation, the upper and lower conveyors  70 ,  72  run at the same speed and also at the speed used by conveyors interfacing with output port  18 . Engagement of the mail flats by both upper and lower conveyors  70 ,  72  insures that the mail flats have the proper velocity after acceleration by pinch rollers  60 ,  62  and any affects from gravity and friction. Proper acceleration is also enhanced by the spacing of upper conveyor  70  from the trap door  51 . This spacing avoids engagement of larger mail flats between upper and lower conveyors  70 ,  72  while pinch rollers  60 ,  62  are still moving such larger mail flats from the drop pockets. This allows greater control of the speed and timing (or position) of mail flats by the pinch rollers  60 ,  62 . 
     FIG. 5 shows the back side of drop pocket section  16 , on which are mounted many of the drive components used by section  16 . Again, identical components for each drop pocket are identified with the same reference number. Driven belt  52 , as shown with respect to FIGS. 4 5 , is moved by a constantly driven motor  90  coupled by a drive belt  92 , all of which are mounted from the back apparatus plate  56 . Each pair of pinch rollers  60 ,  62  are driven by a single servo motor  94  coupled to pinch rollers  60 ,  62  by a pair of drive belts  96 ,  98 , respectively. To achieve rotation of pinch rollers  60 ,  62  in opposite directions, a circular cross-section drive belt  98  is used with a half twist, which twist is not present in belt  96 . Also, proper tension is maintained on belt  96  by generally locating it in a direction perpendicular to the direction of movement of pinch roller  60 . 
     A single drive belt  100  is also shown powering the conveyors  70 ,  72  of both drop pockets  42 ,  44  through their respective driven axles  73 ,  101 . The speed of upper and lower conveyors  70 ,  72  is intended to be a predetermined constant which matches the speed of any horizontal conveyor located to receive mail flats from output port  18 . Because the mail flats are only held on the conveyor by weight and friction, the velocity of mail flats delivered by system  10  should match the speed of any recipient belt to avoid any disruptive acceleration to the mail flats. Drive belt  100  is driven through a toothed gear  102 , which is intended to be coupled, along with rollers  78  through toothed gear  104  to the receiving horizontal conveyor (not shown). Belt  100  may alternatively be driven by separate motor  106  of FIG.  4  and its drive shaft  107 . 
     FIG. 6 shows a functional block diagram of the system  10  in connection with a control system  110 , which general includes a computer  112 , a compressed air source  114  and a valve system  116  for controlling delivery of the compressed air. Horizontal conveyor  14  and drop pocket section  16  are shown as functional blocks with the associated actuators, motors and sensors attached thereto. Horizontal conveyor  14  has a peripheral device  118 , a conveyor drive motor  120  for conveyor belts  20 , and a diverter gate actuator  122  attached thereto. Drop pocket section  16  representatively shows drop pockets  42  and  44 , along with trap door actuator  59 , pinch roller actuator  58 , pinch roller servo motor  94 , driven belt motor  90  and beam of light sensor  54  attached to drop pocket  42 . Each of the components so attached to drop pocket  42  would be duplicated for drop pocket  44 , but are not shown here for purposes of clarity. Various other sensors (not shown) may also be used in conjunction with the current embodiment in ways known to persons skilled in the art. One example would be extra beam of light sensors for monitoring the progress of mail flats through system  10 . Also computer  112  may be dedicated to the operation of system  10  or it may be a part of a larger process control computer. 
     In operation, computer  112  normally keeps conveyor drive motor  120  and driven belt motor  90  constantly running. Computer control of these motors allows emergency shut down and might even be used to provide speed control. During operation, peripheral device  118  might be used to determine the precise position of mail flats to enable computer  112  to provide precise control of diverter gate actuator  122 . As mentioned, diverter gate actuator  122  may take the form of rotary solenoid  38 , as taught, or the form of a compressed air actuator. As with all of the compressed air actuators, computer  112  provides control signals to valve section  116  to control the delivery of compressed air. 
     Next, mail flats entering each of drop pockets  42 ,  44  trigger the BOL sensor  57 , which is monitored by computer  112 . Computer  112  responsively directs compressed air to pinch roller actuator  58  causing pinch roller  60  to be pressed against and engage one side of the sensed mail flat. In conjunction with this engagement, computer  112  sends air pressure to actuator  59  to open trap door  51 . After an appropriate delay, computer  112  energizes pinch roller servo motor  94 . 
     One control aspect resides in the delay used by computer  112  to activate the pinch roller servo motor  94  to drive mail flats from each drop pocket. A certain nominal delay may be used to allow the engagement of each mail flat and the opening of trap door  51 . An additional delay is also used for the drop pocket  42 , which is located closest to the output port  18 . The closer orientation of drop pocket  42  to output port  18  means that the mail flats travel a shorter distance, and correspondingly, the respective curved path channel  64  is shorter. In order to run the upper and lower conveyors  70 ,  72  at the predetermined output speed and output mail flats with a constant pitch, compensation is needed for the shorter effective curved path channel  64  of drop pocket  42 . 
     This compensation takes the form of controlling movement of alternating mail flats from the serial input stream and results in providing a combined delivery of mail flats from both paths at regular intervals. One method for controlling this movement includes providing an uneven or alternating pitch to the mail flats in the input stream and according adjusting the response of diverter gate  30 . 
     Another method for controlling movement of alternating mail flats includes delaying the acceleration of mail flats from at least one drop pocket  42 . This alternate method simplifies the control interface with the input feeder and makes the current system more compatible with different input feeders. In this manner, delaying the acceleration of mail flats in drop pocket  42  enables delivery of the mail flats alternately from both drop pockets to the output port  18  with the same pitch and the appropriate velocity. 
     A further aspect of controlling the acceleration of mail flats is the use of servo motors  94 , which have a rotational position that is sensed and coupled back to computer  112 . Computer  112  may responsively control the drive current coupled to each servo motor  94  to provide a specific velocity profile (acceleration, maximum speed, and total drive time) and thereby control the acceleration of each mail flat by pinch rollers  60 ,  62 . Again, this control is enhanced by the separation of upper conveyor  70  form its respective drop pocket. 
     Various modifications and changes may be made by persons skilled in the art to the embodiments described above without departing from the scope of the invention as defined in the appended claims. The present invention is not intended to be limited to the handling of mail flats and may be applied to other similar flat articles. The present invention is also not intended to be limited to the particular conveyor mechanism  14  described above, and may be practiced by any similarly functioning mechanism. It is further possible to practice the present invention using varying degrees of mail flat rotation initiated by the conveyor mechanism  14 . The present embodiment is also illustrated utilizing a dual path, however more paths may also be used.