Abstract:
The present invention reveals an automated sorting device capable of receiving articles from an input source, correctly choosing among which of many output destinations to direct the articles, and transferring those articles without slowing the sorting process. To accomplish its purpose, a sorting conveyor is pivoted at its receiving end about both a horizontal axis and a vertical axis. The sorting conveyor is cradled within a vertically moveable carriage which, in turn, is mounted within a horizontally moveable frame. The frame is driven horizontally and the carriage driven vertically to align the conveyor&#39;s output end with each output destination. In a preferred embodiment, tracks attached to a support structure stabilize the frame and a controller positions the frame and carriage in response to destination indicia associated with each article to be sorted.

Description:
TECHNICAL FIELD 
     The present invention relates to the automatic sorting of articles bound for different geographical locations and more particularly relates to a modular automatic sorting device, intended for installation within an existing sorting system, which receives articles from a feed conveyor and transfers them to an appropriate output conveyor under programmed control. 
     BACKGROUND ART 
     Daily, package delivery companies collect millions of packages from thousands of locations scattered over large geographical areas and transport them to sorting facilities for processing. After processing, the packages are carried to an equally large number of scattered destinations. To meet the rigorous schedules of today&#39;s business environment, while providing accurate deliveries of packages whose final destinations are literally everywhere in the world, sorting facilities are equipped with automated transfer systems whenever possible. These transfer systems must be fast, durable, easy to repair or replace, and provide gentle but accurate handling of each package. 
     Initially, laborers employed throughout the sorting facility comprised the sorting process; that is, they had to grab, lift, carry and place packages from one sorting station to another. Such use of labor produced an exceedingly slow and inefficient system that was plagued with human injury. While extensive use of labor has diminished as new and large sorting facilities are equipped with automated sorting and transfer systems, the sorting processes at old and small facilities often still rely on laborers at critical stations that require decisions regarding package placement. For example, at some old and small sorting facilities, conveyors typically feed packages to a cluster of laborers who must individually chose a package, pick it up, read the zip code or foreign address, then place the package on an output belt or into a chute associated with the packages&#39; destination. This process is repeated in successively finer steps until the package is loaded onto a delivery vehicle assigned to a limited geographic area. 
     Those critical stations which are not automated remain burdened with the problems of manual labor and continue to be the source of delays and errors in an otherwise efficient process. Retrofitting these critical stations with automated devices is one solution taught by the automated sorting systems found in new facilities. For example, it is known to position a feed conveyor so that articles may be received from a single input source and transferred to a single output destination. In addition, it is known to adjust the feed conveyor so that articles may be transferred to additional output destinations. To accomplish the latter, an operator typically positions the feed conveyor between the input and desired output destination before loading articles onto the conveyor. However, such systems require an operator, are not readily adaptable to existing sorting systems, occupy a large amount of space, include complex mechanisms that are relatively difficult to repair, and are unable to move as fast as the existing automated transfer process. 
     U.S. Pat. No. 4,813,526 (Belanger) discloses a mobile conveyor unit that requires an operator to manipulate each change in destination; that is, swing laterally, raise or lower, and extend or retract the conveyor so articles can be transferred from one position to another. This transfer system is built with two conveyors and a large frame on a curved track that guides the sub-frame side to side while the transfer conveyor, pivoting about a horizontal axis at its entry end, moves up and down by means of hydraulic cylinders. 
     Similarly, U.S. Pat. No. 2,212,702 (Scott) describes a portable conveyor unit that requires an operator to position the frame then align the main conveyor by pivoting its entry end about a horizontal axis. The main conveyor extends from the horizontal axis, through a pair of upright posts, and terminates at an unsupported free end. The conveyor itself is raised and lower by cables and a winch, but has no provision for lateral movement once the frame is set in place. After the conveyor is positioned vertically, a safety rod is inserted through both the posts and conveyor to provide additional support for the conveyor while in its fixed position. 
     The transfer system disclosed in U.S. Pat. No. 5,090,549 (Thiel) is built of a series of conveyor sections which include a section that pivots about a horizontal axis for vertical movement and about a vertical axis for horizontal movement. 
     U.S. Pat. No. 1,753,036 (Williamson) discloses a manually powered letter sorter with a conveyor that can be raised or lowered and swung laterally between three positions in order to line up with a specific pigeonhole. The conveyor is aligned manually through the manipulation of levers and plungers. 
     While prior art teaches alignment of a feed conveyor between the input source and output destination, to achieve the desired alignment such devices require an operator to stop the apparatus, physically maneuver the feed conveyor as required, then restart the device before continuing the transfer process. Because each alignment requires shut-down, physical manipulation of the conveyor or conveyor controls, and start-up, these devices are incapable of rapid response to destination changes. 
     Portability, a strength in some prior art devices, is also a flaw when considering adoption into an existing process. For example, the drivable chassis of Belanger (&#39;526) and bulky supporting structure of Scott (&#39;702) prohibit integration within an enclosed structure of limited space. The Thiel (&#39;549) apparatus, even if scaled down, is so large and complicated that it appears entirely restricted to outdoor use. 
     The primary thrust of the prior art devices, that include powered mechanisms for changing the orientation of a conveyor, is transferring as opposed to sorting articles. Such devices are capable of some degree of flexibility to provide alignment between input source and output destination, but are limited by lack of responsiveness. On the other hand, the manually operated Williamson (&#39;036) device incorporates sorting capabilities but is limited by the cantilever conveyor design to very light and small articles, and is slow because it lacks automation. 
     Thus, existing transfer systems require an operator; are complex both mechanically and electrically; are by their nature large, bulky, slow and noisy; require significant maintenance; are not suitable for application in existing sorting facilities; and, where they do provide a means for sorting are slow and limited to very small and light articles. Accordingly, there has long existed a need in the art for a device that both transfers and sorts, does not require an operator, is simple in construction, requires little maintenance, is suitable for applicable in existing processes, provides a high throughput of sorted items per occupied floor space, and operates at a speed compatible with other automated devices in an automated process. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to cure the process problems and prior art inadequacies noted above by replacing laborers at critical stations with an automatic sorting device capable of receiving articles from an input source such as a feed conveyor, correctly choosing which of many output destinations to direct the articles, and transferring those articles without slowing the existing automated system. 
     In accordance with the invention, these objectives are accomplished by providing a device for automatically distributing articles, comprising: a sorting conveyor mounted to a pivot at its receiving end; a frame including a carriage that cradles the sorting conveyor between its receiving and output ends; an array of output destinations; means for moving the frame along a linear path from side to side in front of the array; and a controller capable of positioning the frame and carriage so the sorting conveyor is aligned to transfer the article from the input conveyor to the output destinations. In the preferred embodiment for operation, the sorting conveyor receiving end is pivoted about a horizontal and vertical axis so that the output end can be elevated or lowered by the carriage to mate with output conveyors on at least three levels, and swung laterally by the frame to mate with output conveyors on at least four positions on each level. 
     The alignment of the sorting conveyor from the pivot to the desired output conveyor within the array preferably is accomplished by a translating frame and carriage assembly. Preferably, the frame is in contact with fixed upper and lower toothed rails, located a convenient distance in front of the array center and perpendicular to the feed conveyor, driven by toothed wheel and tire assemblies connected by a drive belt configuration and reversible servo-motor. The vertical legs of the frame guide a carriage which is raised or lowered by another reversible servo-motor and drive belt configuration. The sorting conveyor rests within the carriage and follows passively in response to the position of either frame or carriage. Horizontal translation of the frame in combination with vertical positioning of the carriage provides the range of motion necessary to align the sorting conveyor output end to any of twelve output conveyors in the output array. 
     In practice, the frame and carriage are directed by destination information affixed to the article and input to a programmed logic controller by an optical reader. A shaft encoder on the feed conveyor can track the article while photocells at the output conveyors confirm the article has been discharged onto the proper output conveyor. 
     While the above describes the preferred embodiment, variations and alternative embodiments are readily apparent. For example, though the sorting module is intended as a retrofit, it is suitable for new systems; any number of sources may replace the feed conveyor as the source of articles; a chute or other method of conveyance may replace the sorting conveyor; any number of different wheel and surface combinations may support, guide, or drive the frame; and, any number of receptacles may replace the output conveyors as destinations. Finally, by reversing the direction of all the conveyors, the sorting device may be effectively employed as a collecting device. Normally, the final destination for a package within the sorting facility is a delivery vehicle such as a truck. Such collecting devices would contribute to an efficient sorting system by accepting pre-sorted articles from stations throughout the sorting facility and directing them to their respective delivery vehicles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the sorting device. 
     FIG. 2 shows a top diagrammatic view of the sorting device embodying the present invention. 
     FIG. 3 shows a side diagrammatic view of the sorting device embodying the present invention. 
     FIG. 4 is a front elevation view of the sorting device. 
     FIG. 5 is an end elevation view of the upper wheel assembly and track of FIG. 4, taken along section line ‘ 5 — 5 ’ of FIG.  4 . 
     FIG. 6 is an end elevation view of the lower wheel assembly and track of FIG. 4, taken along section line ‘ 6 — 6 ’ of FIG.  4 . 
     FIG. 7 is a longitudinal cross-section view of the sorting conveyor assembly. 
     FIG. 8 is a block diagram outlining operation of the sorting system under control of a digital controller. 
    
    
     DETAILED DESCRIPTION 
     Referring now in more detail to the drawings, in which like numerals refer to like parts throughout the several views, FIG. 1 shows a modular automatic sorting device  10  embodying the present invention. One or more sorting devices  10  may be incorporated in an existing sorting system  1  between a feed conveyor  11  and an output array  12 . The feed conveyor  11  transfers articles to be sorted, such as parcels P, in the direction of arrows A. The sorting device  10  receives parcels P from a output end  11   a  of the feed conveyor  11 . Prior to transfer, the parcels&#39; destination within the output array  12  is relayed to the sorting device  10 . In a manner described in detail below, a sorting conveyor  15  of the sorting device  10  transfers parcels P by acting as a conduit between the feed conveyor output end  11   a  to a receiving end  13   a  of a pre-selected array conveyor  13  within the output array  12 . It will be understood that one or all of the output destinations may be chutes, receptacles, or the like, rather than conveyors; and, more or less than twelve output destinations may exist. Also, the present invention can be used with many different types of feed conveyors, such as belt and powered roller variations. 
     Referring now to FIG. 4, a sub-assembly of the sorting device  10 , necessary to provide horizontal alignment between the feed conveyor output end  11   a  and array conveyor receiving end  13   a , is a translating frame  21  which supports the sorting conveyor  15 . Rectangular in shape, the translating frame  21  is formed by two opposite vertical legs  22  connected by an upper horizontal end brace  23  and a lower horizontal end brace  24 . An intermediate horizontal cross brace  25  bridges the vertical legs  22  a short distance above the lower end brace  24 . Referring now to FIGS. 5 and 6, the vertical legs  22  extend beyond the end braces  23  and  24  to form yokes  26  and  26   a , respectively, located just beyond each upper and lower corner of the frame perimeter. Ratably mounted within the yokes  26  and  26   a  are toothed wheels  41  and  41   a , respectively, as well as a pair of high friction wheels  42  flanking each toothed wheel  41 , and a pair of high friction wheels  42   a  flanking each toothed wheel  41   a . The wheels  42  and  42   a  may be surrounded by coatings or tires made of rubber or a high friction polymer. Extruded solid or hollow structural metal, or other suitably strong materials, may be utilized to construct the frame, yokes and accompanying bracing with connections made in a known manner. 
     To both support and guide the translating frame  21 , an upper toothed track  31  is mounted on an upper structural surface  32  and a lower toothed track  31   a  is mounted on a lower structural surface  34 . The teeth of the tracks  31  and  31   a  are of such size and spacing that they smoothly engage, tooth face to tooth flank, with toothed wheels  41  and  41   a  respectively. The toothed tracks  31  and  31   a  are respectively mounted to the surfaces  32  and  34 , each of which extend beyond the width of the toothed tracks  31  and  31   a  sufficiently to provide a pair of high friction surfaces for engaging the wheels  42  and  42   a  with adequate traction. Extruded solid or hollow structural metal, or other suitably strong materials, may be used to construct the toothed tracks and adjacent surfaces with connections made in a known manner. Referring now to FIGS. 2 and 3, the preferred form reveals the upper toothed track  31  and lower toothed track  31   a  are positioned to form straight lines directly in front of and approximately parallel to the face of the output array  12 , and thus approximately at right angles to the feed conveyor  11 . 
     The toothed wheel  41  of each upper yoke  26  is sandwiched between the two tire wheels  42  and connected to a spur assembly driven gear  43  through an axle (not shown). The toothed wheels  41  are in constant contact with the upper toothed track  31 , and the tire wheels  42  are in constant contact with the structural surface  32 . 
     The spur assembly driven gear  43  is permanently engaged to a spur assembly drive gear  44  which in turn is rigidly affixed to an upper driven notched pulley  45 . The upper notched pulley  45  is belted by a long notched drive belt  46  which is looped and powered in a fashion described in detail below. For the frame  21  to be driven horizontally along the tracks, the upper toothed wheels  41  and tire wheels  42  must rotate at the same time and speed but in the opposite direction to the lower toothed wheels  41   a  and tire wheels  42   a . When rotated by the long notched drive belt  46 , the upper pulley  45  and drive gear  44  follow and rotate in the same direction. However, the driven gear  43 , in conjunction with the drive gear  44 , reverses the direction of rotation imparted to the tires wheels  42  and toothed wheels  41 ; that is, they rotate in a direction opposite to the drive belt  46 . 
     Referring now to FIG. 6, located within each lower yoke  26   a  the lower wheel assembly comprised of the toothed wheel  41   a  sandwiched between two tire wheels  42   a  is connected by an axle (not shown) to a lower inside notched pulley  51  which is rigidly affixed to a lower outside notched pulley  52 . The toothed wheel  41   a  is in constant contact with the lower toothed track  31   a , and the tire wheels  42   a  are in constant contact with the structural surface  34 . The outside notched pulley  52  is belted by the long notched drive belt  46  and the inside notched pulley  51  is belted by a short notched drive belt  53  which, referring now to FIG. 4, is looped to a wheel drive reversible servo-motor  54  mounted on the lower end brace  24 . 
     When rotated by the servo-motor  54 , the short notched drive belt  53  turns the inside notched pulley  51 , outside notched pulley  52 , toothed wheel  41   a  and tire wheels  42   a  as well as the long notched drive belt  46  that is looped to the upper driven notched pulley  45 , all in the same direction. The spur assembly drive gear  44  follows the notched pulley  45  but, in concert with the driven gear  43  reverses the direction of rotation. Accordingly, the upper toothed wheels  41  and tire wheels  42  are driven simultaneously along the toothed track  31  and adjacent surface  32 , as the lower toothed wheel  41   a  and tire wheels  42   a  are driven in the same direction along the toothed track  31   a  and adjacent surface  34 . Linear motion of the translating frame  21  moves the sorting conveyor  15 , described in detail below, between the positions shown in dashed lines in FIG.  2 . As shown, the receiving ends  13   a  of the array conveyors preferably form an arc so that the sorting conveyor  15  can be positioned closely to each array conveyor  13  as the sorting conveyor pivots about its input end. 
     Referring again to FIG. 4, another sub-assembly of the sorting device  10 , necessary to provide vertical alignment between the feed conveyor output end  11   a  and array conveyor receiving end  13   a , is a carriage  61 . The preferred embodiment reveals the carriage  61  is mounted within the translating frame  21  by sleeves  62  fitted to encase the respective vertical leg  22 , the sleeves and legs being separated only by a friction reducing surface or lubricant (not shown). At identical locations from the bottom end of both sleeves  62 , a rounded-top sorting conveyor support  63  is attached between the sleeves  62  with connections made in a known manner. The sleeves  62 , together with the sorting conveyor support  63 , form a channel shaped cradle that is raised and lowered within the translating frame  21  in a fashion described in detail below. 
     Attached to the outside face of each sleeve  62  in a known manner is a medium length notched drive belt  64  and  64   a . Each drive belts  64  and  64   a  loop an inside notched pulley  65  and  65   a  at one end and a smooth idler pulley  66  and  66   a  at the opposite end. The inside notched pulley  65  and  65   a  is rigidly affixed to an outside notched pulley  67  and  67   a  which in turn is belted by a short notched drive belt  68  and  68   a . For the carriage  61  to be driven vertically within the frame  21 , the medium notched drive belts  64  and  64   a  must rotate at the same time and speed but in opposite directions. This is accomplished by the short notched drive belt  68  being looped at an end opposite the pulley  67  to a carriage servo-motor notched pulley  69  and rotated by a carriage reversible servo-motor  70  mounted on the horizontal cross brace  25 . In similar fashion, the short notched drive belt  68   a  is looped at an opposite end to a notched pulley  71 , also mounted on the horizontal cross base  25 , and rigidly affixed to a spur assembly driven gear  72  (not shown). The driven gear  72  is permanently engaged with the spur assembly drive gear  73  (not shown) which is mounted on the servo-motor  70  axle (not shown) directly behind the notched pulley  69 . 
     When directed, the servo-motor  70  rotates the notched pulley  69  which drives the short notched drive belt  68 , the outside notched pulley  67  and inside notched pulley  65 , the medium notched drive belt  64 , and smooth idler pulley  66  all in the same direction. Simultaneously, the servo-motor  70  rotates the spur assembly driver gear  72  which, in concert with the driven gear  72  reverses the direction of rotation for notched pulley  71 , short notched drive belt  68   a , outside notched pulley  67   a  and inside pulley  65   a , the medium notched drive belt  64   a , and smooth idler pulley  66   a . Accordingly, the sleeves  62  are raised and lowered simultaneously along the vertical legs  22  by drive belts  64  and  64   a  rotating in opposite directions. The resulting vertical motion of the carriage  61  moves the sorting conveyor  15  between the positions shown in FIG.  3 . 
     Referring now to FIG. 7, another sub-assembly of the sorting device  10 , necessary to actually transport the parcels P from the feed conveyor  11  to the array conveyor  13 , is the sorting conveyor  15 . The preferred embodiment shows a sorting conveyor frame  82  formed of suitably strong material similar to the translating frame  21  and carriage  61 , sheathed along both sides and attached with connections made in a known manner. An endless conveyor belt  83  is mounted over an end roller  84 , located at the sorting conveyor receiving end  85 , rests on a plurality of idler rollers  86  mounted the length of the conveyor frame  82 , and passes around a motorized end roller  87  to define the sorting conveyor output end  88 . Along the bottom of the conveyor frame  82  are mounted a plurality of idler rollers  86  which support the return side of the conveyor belt  83 , and a pair of conveyor runners  89  with low friction surface. As shown in FIG. 4, attached to the conveyor support  63  and located between the two conveyor runners  89  are two directional guideposts  90 . 
     The sorting conveyor frame  82  is pivotally mounted at the receiving end  85  about a horizontal axis  101  to a support yoke  102 . The yoke  102  is pivotally mounted at a pivot joint  103  to provide rotation about a vertical axis with respect to a support frame  105 . The sorting conveyor  15  extends from the yoke  102  to a position within the carriage  61 , between the sleeves  62  with the conveyor runners  89  resting directly on the sorting conveyor support  63 . The conveyor support  63  is of sufficient width to provide a sliding fit or slight gap  104  between each side of the sorting conveyor frame  82  and the adjacent sleeve  62 ; that is, the conveyor support  63  is long enough to permit the conveyor frame  82  an unrestricted range of motion when the sorting conveyor is aligned with the outermost array conveyors  13  of the output array  12 . This configuration, where the conveyor receiving end  85  is supported about a horizontal axis  101  and vertical axis  103 , and where the conveyor frame  82  is supported by the conveyor runners  89  so that the conveyor output end  88  is cantilevered out beyond the translating frame  21 , permits the directional guideposts  90  to direct the sorting conveyor frame  82  as the frame  21  is driven horizontally and the carriage  61  is driven vertically to mate the conveyor output end  88  with the pre-selected array conveyor receiving section  13   a.    
     The output array  12  is a matrix of output destinations that is formed by array conveyors  13  three rows high and four columns wide, positioned and shaped so that each array conveyor receiving end  13   a  can mate with the sorting conveyor output end  88 . Each array conveyor receiving end  13   a  accepts parcels P from the sorting conveyor output end  88  and transports the parcels P to the next step of the sorting system. In the preferred embodiment, the array conveyors  13  are continuously moving. Output destinations may include chutes, receptacles or the like and be more or less than twelve in arrays of varying configurations. 
     Referring now to FIG. 1, triangular beam photocells  111  are positioned astride the feed conveyor output end section  11   a  just upstream of the entrance to the sorting device  10 , to provide a signal indicating a parcel P is entering the sorting device. At each array conveyor  13 , an exit confirmation photocell  112  is positioned adjacent to where parcels leave the sorting conveyor belt  83 . The photocells  112  are retro-reflective photocells that provide a signal when a parcel passes. 
     Referring to the block diagram of FIG. 8, the operation of the sorting device  10  is automated through the use of a digital controller, such as a programmable logic controller  113  (PLC), or a general purpose computer having an appropriate microprocessor. The PLC may receive input signals from an optical reader  114  that reads barcode or two-dimensional symbols (such as MaxiCode symbols) on labels on the parcels. Such a symbol may contain address information which allows the PLC to determine, in a well known manner, which is the correct array conveyor  13  to receive the parcel. The PLC may also receive information about the parcel directly from sensors  115 , such as a scale or a device for measuring the dimensions of the parcel P. A set of rotary belt encoders  116  are positioned to measure the displacement of the feed conveyor  11  and the output of these encoders  116  is input to the PLC. Parcel information may also be manually entered at a keyboard  117 . The PLC, in response to these input signals, sends control signals to the wheel drive servo-motor  54  and carriage servo-motor  70  which move the respective frame drive and carriage drive elements. 
     In operation of a sorting system  1  that incorporates a sorting device  10 , parcels are placed on the feed conveyor  11 . The PLC receives input from the rotary belt encoders  116  associated with the conveyor  11 , and from the optical reader  114  or an alternative label reader or manual input device. The optical reader or other input device is used to acquire destination data about each package as the package is placed onto the sorting system. Any bar codes or other symbols on a parcel are detected and decoded. Destination information may be embedded in a dense code, or may be stored in a database location the address of which is contained in a bar code. Furthermore, textual address information on the parcel label can be analyzed using OCR techniques. 
     When a package is imaged at the reader  114 , the current count of the encoder  116  is obtained. The rotary encoder device  116  allows the PLC to track how far the feed conveyor  11  has traveled since any particular package was placed onto the feed conveyor. The photocells  111  inform the PLC when a parcel leaves the feed conveyor output end  11   a  and enters the sorting conveyor receiving end  85 . 
     A suitable optical reader system for imaging labels is shown in U.S. Pat. Nos. 5,291,564; 5,308,960; 5,327,171; and 5,430,282 which are incorporated herein by reference. Systems for locating and decoding bar codes and the MaxiCode dense code symbology are described in U.S. Pat. Nos. 4,874,936; 4,896,029; 5,438,188; 5,412,196; 5,412,197; 5,343,028; 5,352,878; 5,404,003; 5,384,451 and PCT Publication No. WO 95/34043. 
     A record for each package stored in the PLC memory may contain the parcel identification, destination address, and package characteristics. In addition, a description of the contents of the parcel, its dimensions and weight, or a code indicating the contents are fragile or hazardous or have some other special status, may be stored. 
     Once the destination information for the parcel is known, the PLC looks in an appropriate part of its memory for the proper array conveyor  13  corresponding to the parcel&#39;s destination. Preferably, this information is stored in fields of a record already created for the parcel. 
     In a known manner, the PLC  113  determines when a parcel P is approaching the sorting device  10  and to which array conveyor  13  the parcel should be transferred. The PLC reads the encoder counts and photocell  111  signals as the parcel travels, and compares this position information to the discharge location information stored in memory. The belts of the sorting conveyor  15  and the array conveyors  13  preferably are continually in motion. When the PLC receives signals indicating that the parcel has reached the sorting conveyor receiving end  85 , the PLC sends control signals to the wheel drive servo-motor  54  and carriage drive servo-motor  70  instructing the servo-motors to position the translating frame  21  and carriage  61  as required to align the sorting conveyor output end  88  to mate with the appropriate array conveyor receiving end  13   a . It will be understood that the PLC need store only four positions for the servo-motor  54  and three positions for the servo-motor  70  corresponding to alignment of the twelve conveyors  13  within the output array  12 , but these position requirements would change if a different number of array conveyors were provided in the array. 
     Those skilled in the art should understand that the programs, processes, methods, etc. described herein are not related or limited to any particular computer or apparatus. Rather, various types of general purpose machines may be used with programs constructed in accordance with the teaching described herein. Similarly, it may prove advantageous to construct specialized apparatus to perform the method steps described herein by way of dedicated computer systems with hard-wired logic or programs stored in nonvolatile memory, such as read only memory. 
     From the foregoing description, it is seen that an automatic sorting device embodying the present invention, and specifically the novelty of a passively following sorting conveyor cradled by a carriage mounted within a transversing frame, is of appropriate scale, speed and flexibility to perform within an existing automated sorting system, provide a high throughput of parcels to be sorted, does not require an operator, is simple both mechanically and electrically, is quickly constructed, and requires little maintenance. 
     While the present invention in its various aspects has been described in detail with regard to preferred embodiments thereof, it should be understood that variations, modifications and enhancements can be made to the disclosed apparatus and procedures without departing from the spirit and scope of the present invention as defined in the appended claims.