Crossbelt sortation system

Abstract: The present application discloses a method and apparatus for conveying parcels on a plurality of transport units (32) moving in a conveying path (30) between an induction station (26) and a discharge station (28). Each transport unit has a driven carrier belt (36) thereon, which is moveable orthogonally to the conveying path. The induction station includes a plurality of tandem driven induction belts (62), extending at an angle to the conveying path. The.discharge station has a plurality of receiving ports (46) positioned along the conveying path. The invention provides a crossbelt sortation system (25) with a transport unit test station (96) that is positioned adjacent to the conveying path. The purpose of the test station is to test movement of the carrier belt associated with individual ones of the transport units passing the test station. Each of the transport units (32) includes a magnet (204a, 204b) that moves in proportion to the linear speed of the carrier belt (36) associated with that transport unit. The test station includes a sensor (200) that senses the magnet of a transport unit passing the test station (96). The sensor includes at least one Hall-effect cell (208a, 208b) and a magnetic antenna (210) coupled with the Hall-effect cell.

Description: This invention relates generally to parcel sortation systems of the type defined in the preamble of claim 1 and, more particularly, to systems which discharge parcels individually supported on transport units to selected receiving ports. The transport units have individual carrier belts, which are operable perpendicular to the conveying path of unit movement in order to discharge the parcel to the selected destination port. Crossbelt sortation systems are known (EP-A-343 613) for their ability to handle parcels of widely varying characteristics. For example, such systems may be used to sort magazines or envelopes at a postal center, frozen food articles, cellophane-wrapped clothing articles, or the like. Crossbelt sortation systems are so widely adaptable because the parcels are loaded onto carrier belts, moveable on transport units orthogonally of the conveying path of the parcels, and discharged from the transport units with the assistance of the carrier belts. In addition to accommodating parcels of varying characteristics, crossbelt sortation systems are capable of being compact because they are able to discharge parcels to closely spaced receiving ports on both sides of the conveying path. Furthermore, parcels may be inducted to the transport units at various separate locations using a plurality of induction stations. One difficultly with crossbelt sortation systems is the relative complexity of the series of transport units, which units create the need for a constant monitoring of the transport units in order to determine when a unit is not property functioning. In order to determine that a transport unit is not functioning, it is known to mount magnets to the drive pulley or idle pulley supporting the carrier belt of each transport unit. As a non-loaded transport unit passes a carrier station, a command is given to the transport unit to operate the belt according to a known velocity profile. A stationary-mounted pickup coil receives an induced voltage from the rotating magnets and control circuitry converts the induced voltage into a speed signal. However, the voltage induced in the pickup coil is sensitive to the speed of magnet movement as well as the distance between the magnet and the coil. Accordingly, such systems are not always reliable and require frequent calibration in order to ensure operability. The object of the present invention is to provide reliable and accurate means to monitor the operation of each transport unit. The present invention provides a crossbelt sortation system as defined in claim 1 with a transport unit test station that is positioned adjacent to the conveying path. The purpose of the test station is to test movement of the carrier belt associated with individual ones of the transport units passing the test station. Each of the transport units includes a magnet that moves in proportion to the linear speed of the carrier belt associated with that transport unit. The test station includes a sensor that senses the magnet of a transport unit passing the test station. The sensor includes at least one magnetic-field sensitive device and a magnetic antenna coupled with the device. In a preferred embodiment, the magnetic antenna is made from a ferromagnetic material and includes a pair of pole shoes that are elongated in the direction of movement of the transport units along the conveying path and are galvanically isolated by the field-sensitive device, which is a Hall effect cell. This arrangement provides a unique interaction between the Hall-effect cell and the pole shoes that provides reliable detection of the movement of the transport unit magnet without excessive sensitivity to either the speed of the magnet movement or the separation distance between the magnet and the sensor. Furthermore, the test station may be made sensitive to the direction of movement of the magnet in order to test not only the velocity profile of the belt but also the correct directional movement of the belt. These and other objects, advantages, and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. Fig. 1 is a top plan view of a crossbelt sortation system, according to the invention; Fig. 2 is an elevation taken along the lines II-II in Fig. 1; Fig. 2a is the same view as Fig. 2, illustrating an alternative flap structure; Fig. 3 is a perspective view of a chain of transport units with portions thereof removed in order to reveal additional details of the mechanical components; Fig. 4 is a block diagram of an electrical control network for the system in Fig. 1; Fig. 5 is a block diagram of an electrical system for propelling transport units; Fig. 6 is a block diagram of an electrical control for transport unit carrier belt activation; Fig. 7 is a plan view of an induction station; Fig. 8a is a perspective view of a test station juxtaposed with a transport unit undergoing tests; Fig. 8b is an enlarged side elevation of the test station sensor and transport unit pulley in Fig. 8a; Fig. 8c is a view taken in the direction 8c-8c in Fig. 8b; Fig. 9 is a signal diagram illustrating carrier belt direction determination for the test station in Figs. 8a-8c; Fig. 10 is a block diagram of an electrical test circuit for the test station in Figs. 8a-8c; Fig. 11 is a speed diagram illustrating the relationship of the output signals of the circuit in Fig. 10 for various carrier belt speeds; Fig. 12 is a block diagram of an alternative electrical test circuit for the test station in Figs. 8a-8c. Referring now specifically to the drawings, and the illustrative embodiments depicted therein, a crossbelt sortation system 25 includes one or more parcel induction stations 26 and one or more discharge stations 28 interconnected by an annular conveying path 30 (Fig. 1). A plurality of transport units 32 move continuously along conveying path 30 (Fig. 3). Each transport unit includes a frame 34 and a carrier belt 36, which is supported on the frame driven by a drive means 38 in a direction orthogonal the motion of transport unit 32 along guide path 30. In the illustrative embodiment, drive means 38 is an electrical motor coupled to a carrier belt drive pulley by a cog belt 41 and capable of driving carrier belt 36 in two opposite directions under the control of a servo drive 101. Transport units 32 may be coupled by a coupling means 40 in order to move in unison in one or more trains along conveying path 30. Transport units 32 are propelled along conveying path 30 by a linear motor 42 whose stator extends along guide path 30. Each transport unit 32 is supported for movement along conveying path 30 by a set of vertical and horizontal guide wheels 44. An insulated bus 45 positioned within conveying path 30 supplies electrical power and data signals to transport units 32 through one or more pick-up shoe assemblies (Fig. 6). Linear motor 42 includes a conductor plate 70 installed on the bottom of each transport unit 32, which form the secondary side of the linear motor (Fig. 5). A plurality of primary side stators 72 are installed on straight track sections at a spacing of approximately 30 transport units. The linear motor primary side stators are controlled by a main invertor 74, which modulate the output frequency in response to a command signal from a sortation control 66. The sorting velocity of the transport units is regulated by sortation control 66 in response to an encoder 76 and a speed reference established in control 66. In the illustrated embodiment, sortation control 66 selects a transport unit speed from among three different velocities (V1, V2, V3) which may be selected from a range that extends from approximately 1 m/sec to 2.5 m/sec. In the illustrated embodiment, linear motor 42 operates at a nominal voltage of 420 AC, 3-phase, at 50/60 Hz. Each discharge station 28 is made up of a plurality of receiving ports 46, which may be all positioned on one side of conveying path 30, or on opposite sides of conveying path 30, depending upon the particular details of the application. In the illustrated embodiment, receiving port 46 includes an inclined chute 48 which is divided by a wall 50 into an upper chute 48a and a lower chute 48b (Fig. 2). A transition plate 52 provides a mechanical interface between transport unit 32 and chute 48. Plate 52 additionally reduces parcel velocity and aerodynamic effects on thin items. A photodetector 54, included with each chute 48, detects chute full conditions. A flap 56 directs parcels from transport unit 32 into either upper chute 48a or lower chute 48b. Flap 56 may be made with sheet metal, or belt or roller conveyor material, and may be either single or double according to the requirements of the application. An alternative flap 56' includes a pair of diverter arms which actuate in opposite directions to selectively direct parcels in the upper chute 48a or lower chute 48b (Fig. 2a). Each chute section 48a and 48b may include a divider 58a, 58b, respectively, which may be selectively erected in order to enable packing personnel to pack an order when the sortation system is assembling the next order and may be operable by a push button, or other suitable means. An indicator 60 may be provided to alert the packer or operator of conditions such as full chute, end-of-batch, shutdown of the sortation system, or the like. A scanner 31 upstream of each discharge station 28 along conveying path 30 (Fig. 1) inputs to sortation control 66 information scanned from each parcel to either identify each parcel or confirm the identification of each parcel (Fig. 4). A reject chute 33 is provided for receipt of parcels whose discharge to a receiving port 46 is aborted. Each induction station 26, which is under the control of an induction control 64, includes a series of individually controlled tandem belts aligned at an angle with conveying path 30 (Fig. 7). The induction station includes, in the order of parcel movement, a coding belt 62a, a buffer belt 62b, a synchronization belt 62c, and a loading belt 62d. As will be set forth in more detail below, coding belt 62a regulates the feeding of parcels to a parcel sensor 68. Coding belt 62a additionally provides a start/stop function to allow an operator to enter item codification and to correct parcel orientation, if incorrect. Parcel sensor 68 determines the length, width, and lateral position of each parcel on induction station 26. Buffer belt 62b receives a parcel from coding belt 62a and retains the parcel until synchronization belt 62c has discharged a prior parcel. Synchronization belt 62c receives a parcel from buffer belt 62b, requests reservation of one or two transport units from sortation control 66, and initiates acceleration of the parcel at the appropriate time. Loading belt 62d receives a parcel from synchronization belt 62c and accelerates the parcel according to a fixed velocity profile until the parcel is loaded onto an available transport unit. A loadability photosensor 37 upstream of each induction station 26, along conveying path 30, identifies or confirms which transport units 32 are not loaded and, therefore, available to be "booked" by the induction station for loading of a particular parcel. A recentering station 39, of the type well known in the art, may be provided downstream of each induction station 26 along the conveying path. Such recentering station verifies, by the use of photosensors or other means, that each parcel is centered on its carrier belt and, if not, the carrier belt is jogged to recenter the parcel. Crossbelt sortation system 25 is controlled by a control system 78 including a supervision system 80 joined with induction control 64 and sortation control 66, utilizing an Ethernet Local Area Network (LAN) 82 (Fig. 4). Each of the supervision system 80, induction station control 64, and sortation control 66 includes a Model 486 personal computer 84 and network interface card 86 for interfacing with network 82, both of which are commercially available from numerous sources. A strict real-time multi-tasking operating system is utilized in induction station control computer 84. Induction control 64 and sortation control 66 each additionally include a serial board 88 to provide serial interface with various devices and a remote interface card 90 to provide interface with a main sortation electrical distribution cabinet 92, remote sortation modules 94, each induction station 26, encoder 76, a cell activation command module, or converter, 100, and a carrier test station 96. Encoder 76, which includes a set of photo-detectors which read a unique series of reflectors on each transport unit 32, provides to sortation control 66 the actual position of each transport unit 32. Based upon this information, sortation control 66 transmits activation commands to the transport units to control actuation of the carrier belts 36 (Fig. 6). The servo drive control 101 and drive means 38 for driving the carrier belt 36 of each transport unit 32 are grouped together in groups of up to eight transport units (only six of which are shown) under the intermediate control of a decoder 102. Decoder 102 is installed on a master transport unit of the group and receives control data over a data bus 106. Power is distributed to the transport units in the group from a power bus 104. Power bus 104 and data bus 106 are portions of insulated bus 45 positioned within conveying path 30 and are interfaced with pickup shoe assemblies 47 mounted on the master transport unit. Based on the actual position of each transport unit sortation as monitored by encoder 76, control 66 produces activation commands. The activation commands are converted by converter 100 from serial format and applied to data bus 106. Deeoder 102 analyzes the data in order to determine commands which are relevant to the group of cells under the control of the particular decoder 102. Deeoder 102 provides information to activate a particular transport unit 32 over output lines 108a, 108b . . . 108n. Decoder 102 transmits digital signals over outputs 108a-108n to the servo drive 101a-108n of the respeetive transport unit 32. Each message conveyed from sorter control 66 to decoder 102 includes the following information: Decoder address, Synchronization byte, Cell activation profile number, Command code. The cell activation profile number is a digital number that defines a velocity profile for the particular transport unit carrier belt. The velocity profile is implemented by servo drive unit 101a-101n according to the synchronization byte. The command code includes a set state or a clear state. The clear state cancels previous commands. Induction control 64 operates the three induction stations 26 illustrated in Fig. 1 through remote I/O modules 90. In addition to controlling the movement of belts 62a-62d, the induction control 64 monitors parcel sensor 68 in order to determine parcel lateral position on the induction belt and calculate parcel dimension. When a parcel is received in induction station 26 on coding or start/stop belt 62a, induction control 64 awaits item codification. The parcel is then transferred to buffer belt 62b while induction control 64 monitors sensor 68 and calculates the parcel position from a lateral edge of the belt, as well as parcel length and parcel width. If another parcel is on synchronization belt 62c awaiting loading onto one or more transport units 32, buffer belt 62b is stopped until the parcel on the synchronization belt is loaded. When a parcel is transferred to synchronization belt 62, the induction control books one or two transport units. depending upon the length of the parcel. While the induction control awaits notification from loadability photosensor 37 that the booked transport unit(s) is (are) approaching the induction station has (have) arrived at a Synchronization Point, shown in Fig. 7, induction control 64 performs calculations in order to establish the location of a loading synchronization point on the basis of the parcel length and position. When the booked cell(s) arrive(s) at the synchronization point, induction control 64 activates synchronization belt 62c, loading belt 62d, and the drive means for the carrier belt. In order to discharge a parcel at discharge station 28 into a chute 48, the carrier belt(s) of the transport unit(s) carrying the parcel is (are) activated at appropriate time(s) in order to discharge the parcel without modifying the speed of the transport unit(s). Carrier test station 96 is provided for the purpose of verifying the complete functionality of each of the transport units 32. Carrier test station 96 tests the functionality of servo drive 101a-101n, drive means 38a-38n, and cog belt 41. Transport unit test station 96 includes a sensor 200 and a test circuit 202, which respond to magnetic fields produced by a pair of bar magnets 204a, 204b positioned within pulley 206 of each transport unit 32 (Figs. 8a-11). Pulley 206 is either the drive pulley or the idler pulley supporting carrier belt 36. In this manner, pulley 206 rotates at a rate that is proportionate to the linear speed of belt 36 under the control of servo drive 101a-101n and drive means 38a-38n. Sensor 200 includes a pair of magnetic-field responsive devices, such as Hall-effect cells 208a, 208b, which are coupled with a magnetic antenna 210. Magnetic antenna 210 includes a first pole shoe 212 and a second pole shoe 214, which are elongated in the direction of movement of carrier unit 32 along conveying path 30. Each pole shoe is made from a ferromagnetic material. Pole shoes 212 and 214 are coupled with Hall-effect cells 208a, 208b in a manner that the pole shoes are galvanically isolated by the Hall-effect cells. As best seen in Fig. 8b, sensor 200 is curved to correspond to the circular profile of pulley 206 such that Hall- effect cells 208a and 208b are radially offset with respect to the rotation of magnets 204a and 204b. Each Hall-effect cell 208a, 208b is connected with a Schmidt Trigger 216a, 216b in order to produce a digital output in response to variation in the input signal caused by the proximity of a magnet 204a, 204b (Fig. 10). The time between variation for one signal cycle is equivalent to the time for the pulley 206 to make a one-half rotation. Therefore, by measuring the signal cycle time, the velocity of the pulley and, hence, carrier belt 36, may be measured. A counter 218 supplied from a clock generator 220 measures the pulley speed. The measurement in counter 218 is stored in a latch 222 and reset for a new calculation. A Read Enable bit (REb) is produced by a monostable multi-vibrator 221 from the output of Schmidt Trigger 216a. The Read Enable bit is supplied as an input to a New Data bit generator 223. New Data bit generator 223 produces a New Data bit (NDb) that is set to zero during data accumulation in order to indicate that the data is not available. A directional bit (Db) outputted by latch 222 has a value corresponding to the direction of rotation of pulley 206. Test circuit 202 is sensitive to the signal transitions illustrated in Fig. 9. If the transition from A - to A + is immediately followed by a transition from B - to B + , the pulley is turning clockwise. If there is, instead, a variation from B + to B - , the sense of rotation is counterclockwise. The rotation direction is determined by a direction identification logic circuit 228. A digital velocity output number is provided on output bus 230. The output signals are optically coupled at 224, as illustrated in Fig. 19, for interface with sortation control I/O card 90. Fig. 20 illustrates the timing sequence between the Read Enable bit (RE b ) and the availability of the New Data bit (ND b ) for various rotational velocities of drive means 38. The carrier test station 96 produces reliable digital data that is not adversely affected by the velocity of bar magnets 204a, 204b and. therefore by the rotational speed of pulley 206. This is accomplished by unique sensor 200, which includes a combination of Hall-effect cells and ferromagnetic pole shoes. This attribute substantially eliminates the requirement for circuit calibration while producing a digital output that is compatible with personal computer and programmable logic control interfaces. Furthermore, carrier test station 96 is capable of determining not only carrier belt velocity but also direction of movement. Although the invention is illustrated with a pair of magnets 204a, 204b, it is only necessary that one magnet be present. The other magnet could be replaced by a counterweight. In an alternative embodiment, a test circuit 202' includes the magnetic-field sensitive devices which are composed of a pair of inductive pick-up coils 208a', 208b'. The rotating magnets 204a, 204b induce a voltage in each coil 208a', 208b', which is integrated by respective integration filters 209a, 209b in order to obtain a square wave signal. The outputs of integration filters 209a, 209b are supplied, respectively, to Schmidt Trigger circuits 216a', 216b' from which the signals are processed as previously described with respect to test circuit 202. Changes and modifications in the specifically described embodiments can be carried out without departing from the invention, which is intended to be limited only by the scope of the appended claims. list of reference numbers 25 crossbelt sortation system 26 induction station 28 discharge station 30 conveying path 31 scanner 32 transport unit 33 reject chute 34 frame 36 carrier belt 37 loadability sensor 38 drive means 39 recentering station 40 coupling means 41 cog belt 42 linear motor 44 guide wheels 45 insulated bus 46 receiving ports 47 pickup shoe assemblies 48 inclined chute 48a upper chute 48b lower chute 50 wall 52 transition plate 54 photodetector 56,56' flap 58a,b divider 60 indicator 62a coding belt 62b buffer belt 62c synchronisation belt 62d loading belt 64 induction control 66 sortation control 68 parcel sensor 70 conductor plate 72 primary side stators 74 main invertor 76 encoder 78 control system 80 supervising system 82 local area network 84 personal computer 86 network interface card 88 serial board 90 remote interface card 92 electrical distrubution cabinet 94 remote sortation modules 96 carrier test station 98 costumer host computer 100 cell activation command module 101 servo drive control 102 decoder 104 power bus 106 data bus 108 output lines 200 sensor 202 test circuit 204a,b bus magnet 206 pulley 208a,b Hall-effect cells 208'a,b inductive pickup coils 209a,b integration filters 210 magnetic antenna 212 first pole shoe 214 second pole shoe 216 Schmidt Trigger 218 counter 220 clock generator 221 monostable multivibrator 222 latch 223 new data bit generator 228 direction identification logic circuit 230 output bus

Claims: A crossbelt sortation system comprising: a plurality of transport units (32) moving in a conveying path (30) between an induction station (26) and a discharge station (28), each transport unit (32) having a driven carrier belt (36) thereon which is moveable orthogonally to the conveying path (30); said discharge station (28) having a plurality of receiving ports (46) positioned along said conveying path (30); said induction station (26) having at least one induction belt (62) extending at an angle to the conveying path (30); characterized by a transport unit test station (96) positioned adjacent said conveying path (30) for testing movement of the carrier belt (36) associated with individual ones of said transport units (32) passing the test station (96), each of said transport units (32) including a magnet (204) that moves in proportion to the linear speed of the carrier belt (36) associated with that transport unit (32) and said test station (96) includes a sensor (200) that senses the magnet (204) of a transport unit (32) passing the test station (96), said sensor (200) including at least one magnetic-field sensitive device and a magnetic antenna coupled with said at least one magnetic-field sensitive device (208). The system in claim 1 wherein each of said transport units (32) further includes a rotatable pulley (206) that rotates with linear movement of the carrier belt (36) associated with that transport unit (32), wherein said magnet (204) is positioned on said pulley (206) for rotating with said pulley (206) at a rotational speed that is a function of the linear speed of the associated carrier belt (36). The system in claim 1 or 2 wherein said magnetic antenna (210) is elongated in the direction of movement of said transport units (32) along said conveying path (30). The system according to any of claims 1 to 3 wherein said magnetic antenna (210) is made from a ferromagnetic material. The system according to any of claims 1 to 4 wherein said antenna (210) includes a pair of pole shoes (212, 214) that are galvanically isolated by said at least one magnetic-field sensitive device (208). The system in claim 5 wherein said pole shoes (212, 214) are elongated in the direction of movement of said transport units (32) along said conveying path (30). The system according to any of claims 1 to 6 comprising a pair of magnetic-field sensitive devices wherein said pair of magnetic-field sensitive devices (208) are offset from each other in the path of movement of said magnet (204) in response to linear movement of the carrier belt (36) associated with that transport unit (32). The system according to any of claims 1 to 7 including a circuit coupled to said magnetic-field sensitive devices (208) for producing an indication of the speed and direction of movement of the carrier belt (36) associated with a transport unit (32) passing said test station (96). The system in claim 8 wherein said indication includes at least one digital word. The system according to any of claims 1 to 9 including a pair of said magnets (204) radially positioned on opposite sides of said pulley (206). The system according to any of claims 1 to 10 wherein said magnetic-field sensitive device is a Hall effect cell (208a, 208b). The system according to any of claims 1 to 10 wherein said magnetic-field sensitive device is an inductive pick-up coil (208'a, 208'b).

Inventors: AFFATICATI ARTEMIO, CEGLIA TEODORO, CERUTTI CALUDIO, AFFATICATI, ARTEMIO, CEGLIA, TEODORO, CERUTTI, CALUDIO
Applicants: MANNESMANN AG, MANNESMANN AKTIENGESELLSCHAFT
Application year: 1995
Main classification: B65G17
IPC codes: B65G43, B61B13, B65G54, B65G17, B65G47