CONVEYOR SYSTEM WITH DIVERTING TRACK NETWORK

Abstract: A diverting assembly for diverting articles from a conveying surface (1) includes a plurality of movable pushers (14) that are associated with the conveying surface (1) and adapted move transversely across the conveying surface (1). A plurality of diverting tracks (40, 50) are configured to guide selected ones of the movable pushers (14) across the conveying surface (1). A plurality of diverters (25a, 25i) are adapted to selectively divert at least one movable pusher (14) along the diverting tracks (40, 50) when activated into a diverting state. A controller (60) selects a subset of at least two diverters from the plurality of diverters and activates them into the diverting state. The subset includes first and second diverters (25a, 25c) which are separated from each other by at least one intermediate diverter (25b) which is not activated into the diverting state. The activation of the diverters may be simultaneous, or the downstream diverter (25a) may be activated prior to the upstream diverter (25c) being activated.

Description: CONVEYOR SYSTEM WITH DIVERTING TRACK NETWORK CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of commonly assigned application serial no. 09/606,610 filed June 29, 2000. BACKGROUND OF THE INVENTION This invention relates generally to conveyor diverting systems, and, more particularly, to conveyor diverting systems having an endless conveying surface composed of multiple surface members, each one or group of adjacent ones mounted with a laterally movable shoe capable of diverting articles from the conveyor by pushing laterally against the articles as they move down the conveyor. Such lateral pushing thereby diverts a package, such as from the main conveyor to an adjacent branch conveyor, or other receiving structure. Conveyor diverting systems using a moving conveying surface consisting of a plurality of parallel surface members, the conveying surface being propelled, such as by being mounted to endless chains, have been known for a number of years. Such diverting systems utilize a diverter shoe movably mounted on one or more surface members for lateral movement with respect to the conveying surface under the guidance of a track network. The track network is located generally under the conveying surface and guides the diverter shoes via pins descending from the diverter shoes and engaging the track network. Diverters in the track network selectively transfer guidance of each diverter shoe from a track running in the direction of the movement of the conveying surface to a diagonal track, or plurality of diagonal tracks, in order to cause lateral movement of the diverter shoes. An example of a diverting gate used to selectively transfer guidance of diverter shoes between tracks is disclosed in U. S. Pat. No. 5,409,095, issued to Hoshi et al., and U.S. Pat. No. 5,039,912, issued to Cotter. In order to avoid wasted spacing between variable-length packages, such diverting systems may include manual or automatic measuring means at an infeed point to cause the diverter gate associated with the selected branch conveyor to divert a selected number of shoes corresponding in general to the length of the package. Exemplary of this type of conveyor are U.S. Pat. No. 3,361 ,247, issued to James N. Lauzon et al. and U.S. Pat. No.4,738,347, issued to Brouwer, and commonly assigned with the present invention. With increased demands for the number of packages to be conveyed by such conveying systems, the inter-package spacing distance has become a critical factor in the design of conveying systems. Decreasing the spacing between packages on the conveyor allows a greater throughput of packages by the conveyor. Conversely, providing more space between the packages results in a diminished efficiency and throughput. A specific minimum inter-package spacing is required in this system as a result of the rotation of the diverted package as it is initially diverted. Because of this rotation, additional inter-package spacing is required to avoid conflict between the diverting package and a closely trailing package. This rotation pushes the trailing corner of the package adjacent the branch conveyor back a distance, which can be estimated using the width (W) of the package and the acute angle (α) which is formed by the intersection of the material flow on the main conveyor and the diverter shoe diagonal guide track. Using these two variables and assuming that the package rotates about the trailing comer opposite the branch conveyors, it will be observed that: A = Wsin α where A is the distance the trailing corner adjacent the branch conveyor is pushed back by the package's rotation. It is, therefore, necessary with this system that packages to be diverted are not spaced closer together than the distance Wsin α. By way of example, if a diverting branch is oriented at about 20° with packages 16 inches in width, an inter package distance of approximately 5.5 inches is necessary. If the package is 24 inches long, this results in the need for approximately 23% more empty space on the conveyor. A hypothetical system that could divert packages without any significant space between packages could thus produce a 23% increase in package throughput without any increase in conveyor speed. The high desirability of such a system is thus clear. Prior methods of diverting packages that addresses the problem of reducing the required inter-package spacing, is described in commonly assigned U.S. Pat. No. 5,165,515, issued to Michael L. Nitschke et al., which is commonly assigned with the present application. This system increases throughput by not rotating the diverted packages. This non-rotation is accomplished by using a plurality of generally parallel diverting tracks oriented diagonally with respect to the direction of conveyor movement, instead of a single diverting track. Each track has its own diverting gate which is actuated to divert the movement of the diverting shoes from the direction of the conveyor to the lateral diverting direction. By simultaneously activating more than a single diverting gate, a group of diverting shoes corresponding to the measured package length can be moved laterally across the conveyor surface. This group of shoes acts along nearly the entire length of the package to be diverted and, therefore, causes no rotation of the package. Without rotation of the package, the inter-package spacing requirement is reduced to a minimum. However, this technique is not without difficulties. The deliberate non-rotation of the packages means the packages will enter the branch conveyor still aligned parallel to the main conveyor, but oriented generally diagonally with respect to the branch conveyor (i.e., their lengthwise sides are not parallel to the direction of motion of the branch conveyor). This orientation significantly increases the necessary width of the branch conveyors, resulting in an increase in cost and a reduction in the spacing on branch conveyors. Still another method of diverting packages which reduces the required inter- package spacing, is described in commonly assigned U.S. Pat. No. 5,927,465, issued to Shearer, Jr. With this system, an automatic controller oversees the operation of the diverting gates to determine which diverting gates are to be actuated and for how long, depending upon the measured length of the packages on the conveyor. Once the length of the package is determined, the controller determines whether a package will be diverted using one diverting gate or two (or more) diverting gates. For certain situations, such as long packages, a single diverter is activated and as many diverting shoes are diverted as necessary to divert the package through the single diverting gate. Packages diverted in this manner are rotated, with the trailing corner of the package moving in an initial rearward direction. Other packages are diverted with two or more gates in a manner that the packages are initially diverted out of line with other packages without substantially rotating the packages, in the same manner as in Nitschke et al. '515 Patent. After the initial diverting, the package is then rotated prior to discharge to the spur. This has the advantage of the Nitschke et al. '515 Patent of not requiring increased gaps between packages but eliminates the disadvantage of increased spur size. However, some of the packages, such as long packages, are still diverted using conventional techniques and increased gaps must be provided at both ends of such packages. It will thus be observed that there exists a need for a conveyor diverting system that can divert packages with little or no inter-package spacing, and ensure that packages diverted to the branch conveyor are properly aligned, all while keeping costs to a minimum. SUMMARY OF THE INVENTION The present invention provides a sortation system which achieves efficiency gains through reduction of the inter-package spacing. These efficiency gains are especially desirable because they can be achieved without the extra power consumption, noise, and wear that results from increasing the conveyor speed. According to one aspect of the present invention, a diverting assembly for diverting articles from a conveying surface of a conveyor is provided in a sortation system. The diverting assembly includes a plurality of movable pushers, a set of at least three diverting tracks, a set of at least three diverters, and a controller. The plurality of movable pushers are associated with the conveying surface and are adapted to be movable transversely across the conveying surface. The diverting tracks are configured to guide selected ones of the movable pushers across the conveying surface. Each of the diverters are adapted to selectively divert at least one movable pusher along one of the diverting tracks when the diverter is activated into a diverting state. When an article is to be diverted from the conveying surface, the controller is adapted to select a subset of at least two diverters from the set of at least three diverters and activate the subset into the diverting state. The subset of diverters includes a first and a second diverter which are separated from each other by at least one intermediate diverter which is not activated into the diverting state. According to another aspect of the present invention, a method for diverting articles from a conveyor having a conveying surface is provided. The method includes providing a plurality of movable pushers which are associated with the conveying surface and which are adapted to be movable transversely across the conveying surface. A set of at least three diverting tracks and at least three diverters are also provided. The tracks are configured to guide selected ones of the movable pushers across the conveying surface. The diverters are each adapted to selectively divert at least one movable pusher along one of the diverting tracks when the diverter is activated into a diverting state. The length of an article to be diverted is also determined, and a subset of at least two diverters from the set of at least three diverters is selected based upon the determined length of the article to be diverted. The subset of diverters includes a first and a second diverter which are separated from each other by at least one intermediate diverter. The first and second diverters are activated into the diverting state while at least one intermediate diverter is maintained in a nondiverting state. According to still another aspect of the present invention, a diverting assembly for diverting articles from a conveying surface of a conveyor is provided. The diverting assembly includes a plurality of movable pushers, a plurality of diverting tracks, and a plurality of diverters. The movable pushers are associated with the conveying surface and adapted to be movable transversely across the conveying surface. The diverting tracks are configured to guide selected ones of the movable pushers across the conveying surface. Each of the diverters are adapted to selectively divert at least one of the movable pushers along one of the diverting tracks when the diverter is activated into a diverting state. A controller is also provided for selecting at least two diverters from the plurality of diverters. The controller first activates a downstream one of the selected diverters into the diverting state and subsequently activates an upstream one of the selected diverters into the diverting state. According to still further aspects of the present invention, the selection of which diverters to activate may be based upon the length of an article to be diverted. The activation of the diverters may occur such that one diverter is activated when the leading edge of the article to be diverted is adjacent that diverter, and the other diverter is activated when the trailing edge of the article to be diverted is adjacent that other diverter. The diverters that are activated may be activated simultaneously, nonsimultaneously, or a combination thereof. The diverting tracks may also be shaped such that an article to be diverted is initially pushed with a nonrotational force by the movable pushers and then subsequently pushed with a rotational force by the movable pushers. The methods and devices of the present invention provide an efficient method for diverting articles onto a branch conveyor or other structure. These and other objects, advantages, and features of this invention will become apparent upon review of the following specification when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a divert assembly for a conveyor system according to one aspect of the invention; FIG. 2 is a top plan view of the conveyor system of FIG. 1 , with a center portion of the conveying surface removed to illustrate the underlying structure; FIG. 3 is the same view as FIG. 2 of an alternative preferred embodiment thereof; FIG. 4 is the same view as FIG. 2 of another alternative preferred embodiment thereof; FIG. 4a is the same view as FIG. 2 of yet another alternative preferred embodiment thereof; FIG. 5 is the same view as FIG. 2 of still another alternative preferred embodiment thereof; FIG. 6 is a diagram of a single package in various stages of divert, along a downstream track and an upstream track; FIG. 7 is a diagram of a single package in various stages of divert, along a pair of downstream tracks; FIG. 8 is a flow chart of a method for diverting a package according to the invention;. FIG. 9 is a top plan view of a divert assembly according to still another aspect of the present invention; and FIG. 10 is a flowchart of a method for diverting an article according to the divert assembly of FIG. 9. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to the drawings and the illustrative embodiments therein, a conveying system 10 includes a main conveyor 9 and a plurality of branch conveyors 5, of which only one is shown. Although the invention is illustrated for use with a unidirectional divert conveyor which diverts articles to one lateral side of the conveying surface, it should be understood that its principles may also be used with a bi-directional divert conveyor which diverts articles selectively to either lateral side of the conveyor surface. Branch conveyor 5 is positioned adjacent to main conveyor 9, and at an angle, as is conventional. The arrows illustrate the direction of conveyance for both main conveyor 9 and branch conveyor 5. A conveying surface 1 of main conveyor 9 is defined by a series of surface members 13 which define a product conveying surface. The lengthwise direction of surface members 13 is oriented perpendicular to the direction of movement of main conveyor 9. Surface members 13 are supported on either side by side members 2 and 3. The details of the conveying surface are disclosed in U.S. Pat. No. 5,127,510, issued to Cotter et al., the disclosure of which is hereby incorporated herein by reference and will not be repeated. A series of movable pushers, or diverting shoes, 14 are located along main conveyor 9, opposite branch conveyor 5 and proximate to side member 2. When diverting shoes 14 are not being utilized to displace an article off main conveyor 9 and onto branch conveyor 5, they travel in sequence along a shoe guideway 8, adjacent the longitudinally extending guide track 12. Guide track 12 prevents diverting shoes 14 from moving transversely across main conveyor 9 except at the point along main conveyor 9 at which diverters 25a through 25i are located, or along similar points where a branch conveyor connects to main conveyor 9. Diverters 25a through 25i can be seen attached along side member 2 of main conveyor 9, and in the path of diverting shoes 14. Diverters 25a through 25i may be of the type disclosed in commonly assigned U.S. Pat. No. 5,038,912, issued to Cotter or of the type disclosed in U.S. Pat. No. 5,409,095, issued to Hoshi et al., or of the type disclosed in commonly assigned patent application serial no. , filed April 23, 2001 by Veit et al for a sortation system diverter switch ( attorney docket RAP04 P-615A) the disclosures of which are hereby incorporated herein by reference. With reference to FIG. 2, a section of conveying surface 1 has been removed from the central portion of main conveyor 9 to illustrate the structure of a diverting track network 30. Diverting track network 30 includes a plurality of first, or upstream diverting tracks 40, and one or more second, or downstream, diverting tracks 50. Although there are seven upstream diverting tracks 40 and two downstream diverting tracks 50 illustrated in FIG. 2, it is within the spirit and scope of the invention to have any number of upstream diverting tracks 40 and downstream diverting tracks 50. In general, diverting tracks 40, 50 span the maximum article length to be transported by conveyor system 10, as will be discussed in detail hereinbelow. Downstream diverting tracks 50 traverse substantially the entire conveying surface 1 at a preselected angle to the direction of movement of main conveyor 9. Each downstream diverting track 50 may be generally straight or linear throughout its length. Each upstream diverting track 40 terminates partway across conveying surface 1 , at a location that generally relates to the width of the package stream conveyed by conveyor 10. In the illustrated embodiment, each diverting track 40 includes a linear, or first section 42 which is generally parallel to downstream diverting tracks 50, and a second section 44 projecting from the end of first section 42, and extending downstream at an obtuse angle to first section 42. Each second section 44 of upstream diverting tracks 40 is operably coupled to the second section 44 of the adjacent upstream diverting track 40. Second section 44 of the upstream diverting track 40 adjacent to, and immediately upstream of, first downstream diverting track 50a is operably connected to downstream diverting track 50a, a preselected distance below end 54. Upstream diverting tracks 40 may be integrally formed with second section 44 bent to achieve the preselected angle. Alternatively, second section 44 may be a separate member, operably coupled to first section 42 by any means commonly employed in the art. Collectively, second sections 44 form an upwardly curved path, toward side member 3, as they approach downstream diverting track 50a. Downwardly depending portions of diverting shoes 14 are diverted to specific upstream diverting tracks 40a through 40g, and downstream diverting tracks 50a and 50b by a dedicated diverter 25a through 25i. Diverters 25a through 25i are electrically actuated, for example, by shoe divert solenoids, in electrical connection with a divert control module 26 as disclosed in Cotter '192 or by magnetic attraction of a portion of the diverting shoe as disclosed in Hoshi et al. '095. It will be recognized by those with ordinary skill in the art that diverters 25a through 25i may be controlled by any means commonly recognized in the art without departing from the spirit and scope of the invention. The number of upstream diverting tracks 40 utilized in conveyor system 10 is dictated by the maximum length of a package to be handled by the conveyor system. Preferably, the distance between downstream diverting track 50b and upstream diverting track 40a farthest upstream is approximately equal to, or greater than, the maximum length of packages to be diverted along conveyor system 10. The longitudinal spacing between upstream diverting tracks 40 and downstream diverting tracks 50 may be substantially equal to the longitudinal distance of a single surface member 13, so that each diverting shoe 14 positioned over upstream diverting tracks 40 and downstream diverting tracks 50 may be selectively actuated by the associated diverter 25a through 25i. Alternatively, the longitudinal spacing between upstream diverting tracks 40 and downstream diverting tracks 50 may be some multiple, such as twice the width of a surface member 13, such that every other diverting shoe 14 may be selectively actuated when positioned over diverting tracks 40, 50 without departing from the scope of the invention. Conveyor system 10 is equipped with at least one sensor 58, operably connected to a control system 60, to thereby determine the length of each package being transported along conveyor system 10. Sensor 58 may be any sensor commonly used in the art, and is positioned in proximity to, or along main conveyor 9, upstream of diverting track network 30 or upstream of main conveyor 9. Control system 60 is in electrical communication with divert control module 26. When a particular package 70 is to be diverted onto branch conveyor 5, a signal is sent from control system 60 to divert control module 26 to thereby cause the selective actuation of diverter 25a, and at least one of diverters 25b through 25i to thereby divert at least two diverting shoes 14. One diverting shoe will be diverted along a downstream diverting track, preferably track 50b, and one along another track thereof, such as the other downstream diverting track 50a, or an upstream diverting track 40. Specifically, the divert control module 26 will effect actuation of diverter 25a farthest downstream along main conveyor 9, which corresponds to downstream diverting track 50b, and the leading end 68 of package 70 to be diverted. Simultaneously, control divert module 26 will actuate a diverter 25b through 25i along a downstream diverting track 50a or along a particular upstream diverting track 40, whichever is most proximate to the trailing end 69 of package 70. Consequently, diverting shoes 14 will be diverted along downstream diverting track 50b, and along downstream diverting track 50a, or a particular upstream diverting track 40. This will effect non-rotational movement of package 70 out of line with other packages traveling along conveyor surface 9. If the upstream one of diverting shoes 14 is diverted to an upstream diverting track 40, the particular diverting shoe 14 urges trailing end 69 of package 70 and contacts second section 44. Subsequent movement of diverting shoe 14 along second section 44 imparts a rotational force upon package 70 to thereby orient leading end 68 of package 70 in a direction substantially orthogonal to the direction of movement of branch conveyor 5. The lateral speed of the diverting shoes actuated along downstream diverting track 50b and on an upstream diverting track 40 will be substantially equal while the diverting shoe traveling along upstream diverting track 40 is located in linear section 42. Once the diverting shoe engages second section 44, however, the lateral speed of the diverting shoe traveling along downstream diverting track 50b increases compared to the lateral speed of the diverting shoe traveling on successive second sections 44. This difference in lateral speed rotates leading edge 68 of package 70 towards branch conveyor 5. Once diverting shoe 14, travelling on successive second sections 44, converges into downstream diverting track 50b, the rotational movement of package 70 ceases, and it is thereafter diverted in a direction substantially parallel to the direction of main conveyor 9. The degree of rotation of package 70 may be degrees less than or equal to the angle V, formed at the intersection of main conveyor 9 and branch conveyor 5. Preferably, the degree of rotation of package 70 is substantially equal to the angle V, formed at the intersection of main conveyor 9 and branch conveyor 5. As conveyor system 10, illustrated in FIGS. 1 and 2, depicts a pair of downstream diverting tracks 50a and 50b, if a package 70 to be diverted has a length less than the distance between diverters 25a and 25b, the package will be diverted by the actuation of diverters 25a and 25b to thereby divert a pair of diverting shoes 14 along downstream diverting tracks 50a and 50b. Packages of this length will be transported substantially parallel to the direction of movement of main conveyor 9 and will not experience a rotational force. For packages having a length greater than the distance between diverters 25a and 25b, control system 60 will cause the simultaneous diversion of a diverting shoe along the farthest downstream diverting track 50, and at least one along an upstream diverting track 40. With respect to FIG. 3, conveyor system 10 is shown having only one downstream diverting track 50. In this embodiment, packages of any length will be moved laterally without rotation out of line with other packages traveling along conveyor's surface 9 and will experience a rotational force as it is further diverted, toward the branch conveyor 5 because, in all instances, a diverting shoe will be diverted along both downstream diverting track 50, and at least one upstream diverting track 40. Turning now to FIG. 4, in an alternative preferred embodiment, each upstream diverting track 40 has a second section 44 which, rather than being coupled to an adjacent second section 44 of an adjacent upstream diverting track 40, are each separately connected to a downstream diverting track 50. In all other aspects, conveyor system 10' is structurally and functionally similar to conveyor system 10. Individual attachment of second section 44 to downstream diverting track 50 reduces the noise produced by conveyor system 10' by minimizing the number of mechanical gaps that a diverting shoe 14 must traverse as it is diverting a package toward branch conveyor 5. FIG. 4a shows another preferred alternative embodiment with the same configuration as FIG. 4, but only one downstream diverting track 50. It will be recognized that in the embodiments of FIGS. 4 and 4a, each second section 44 of upstream diverting tracks 40 may be curved upwards towards downstream diverting track 50 as are the second sections 44 depicted in FIGS. 1 and 2. Referring now to FIG. 5, conveyor system 10" illustrates an embodiment wherein once initially diverted in a substantially parallel direction, the package experiences a continuous rotational force until it is discharged onto branch conveyor 5. This is achieved by each second section 44 of upstream diverting tracks 40 being operably connected to a second section 44 of an adjacent upstream diverting track 40. The second section 44 of the upstream diverting track 40, positioned adjacent to downstream diverting track 50, is operably connected to downstream diverting track 50, proximate to end 54. Consequently, once the diverting shoes 14 are diverted along downstream diverting track 50 and a particular upstream diverting track 40, package 70 will be urged towards branch conveyor 5, but will not begin to rotate until a diverting shoe contacts second section 44 of upstream diverting track 40. Thereafter, package 70 will continue to rotate until being discharged onto branch conveyor 5. In all other aspects, conveyor system 10" is structurally and functionally similar to conveyor system 10. FIG. 6 illustrates the diversional sequence of a package being diverted by diverting track network 30. As can be seen, the package will travel in a substantially parallel to the direction of travel of main conveyor 9, indicated by the directional arrow, as the package is diverted out of line with other packages traveling along conveying surface 1 , until a rotational force is subsequently imparted upon the package as a diverting shoe 14 contacts second section 44, and continues travel therealong. FIG. 7 illustrates the diversional sequence of a package being diverted by downstream diverting track 50a and 50b of diverting track network 30. As can be seen, the package being diverted will travel in a substantially parallel direction of travel of main conveyor 9, throughout the length of main conveyor 9, until it is discharged onto a branch conveyor. Turning now to FIG. 8, there is shown a diagrammatic representation of the control sequence necessary to divert a package according to the present invention. The control sequence includes determining at 72 the length of a package to be diverted. Thereafter, once the package is positioned over the farthest downstream diverting track 50, the diverting associated with the farthest downstream diverting track 50 and at least one diverting gate associated with an upstream diverting track 40, are simultaneously diverted at 74. The choice of which upstream diverting gate is to be activated along with the downstream diverting gate is dictated by the length of the package to be diverted. Specifically, the upstream diverting gate most proximate to the trailing end of the package will be actuated. Although the invention is illustrated with two shoes diverting each package, it could be implemented with three or more shoes diverting each package. Preferably, to the extent the article to be diverted exceeds the length of two pushers, it is diverted using trailing and leading diverters which are separated by at least one intermediate diverter which is not activated into the diverting state. Where the article does not exceed the length of two pushers, two adjacent diverters may be used to divert the article. The invention is not intended to be limited by the configuration of the diverting shoe 14, the surface members 13 or diverters 25a-25i. In another embodiment of the present invention, a modified control system 60' can be implemented that is different from the control system 60 described previously herein (FIGS. 9-10). Instead of having the control system simultaneously activate two or more diverters 25, control system 60' can delay the activation of the upstream diverter 25 for a variable length of time. This delay may be especially useful to accommodate widely varying lengths of articles without having to install as many diverters 25 and their associated diverting tracks 40 as the maximum length of packages would require in FIGS. 1-7. For example, if the maximum expected article length is three feet, and each diverter 25 can be spaced apart 4 inches, then a total of nine diverters 25 and their associated diverting tracks could be accommodated in the diverting area. However, nine diverters and diverting tracks may be undesirably expensive. In order to still be able to accommodate three foot long articles, a lesser number of diverters and diverting tracks could be used and spaced in a more compact area, such as a two foot area. In such a situation, control system 60' would activate the downstream diverter when the leading edge of the article was adjacent this downstream diverter. If the article were three feet long, the trailing edge of the article would not be adjacent the most upstream diverter at this time because the most upstream diverter is only two feet away from the downstream diverter. The activation of the most upstream diverter is therefore delayed until sufficient time has passed for the article's trailing edge to have moved adjacent the most upstream diverter. At that moment, the most upstream diverter is activated by control system 60'. The delay between the time the downstream diverter is activated and the time the upstream diverter is activated is dependent upon the speed of the conveyor as well as the length of the article being diverted relative to the distance between the upstream and downstream diverters. An example of an article 70a being diverted by control system 60' is depicted in FIG. 9. Article 70a has a length greater than the distance between the most downstream diverter 25a and the most upstream diverter 25d. When the leading edge of article 70a was adjacent downstream diverter 25a, the trailing edge of article 70a was still upstream of upstream diverter 25d. At that amount controller 60' therefore only activated diverter 25a into a diverting state. Controller 60' delayed activating diverter 25d into the diverting state until the trailing edge of article 70a had traveled sufficiently far so as to reach, or be adjacent to, diverter 25d. The control logic followed by controller 60' in carrying out this divert is depicted in FIG. 10. Controller 60' first determines at block 76 when the leading edge of the article to be diverted is adjacent the most downstream diverter. At that movement, controller 60' activates the downstream diverter in block 78. At block 80, controller 60' also determines if the trailing edge of the article is adjacent any diverters and, if so, activates the diverter adjacent the trailing edge at block 82. Where the trailing edge of the article is adjacent an upstream diverter at the same time the leading edge is adjacent the downstream diverter, the activation of the upstream and downstream diverters in blocks 78 and 82 occurs substantially simultaneously. If, at block 80, it is determined that the trailing edge of the article is not adjacent any upstream diverter, this is due to the article being longer than the length of the diverter array, such as article 70a. In this case, control passes to block 84 where controller 60' waits until the trailing edge of the article arrives at a location adjacent the most upstream diverter. Controller 60' then activates the most upstream diverter at block 86 and control returns to block 76 for the next article to be diverted. As noted, control system 60' determines whether to activate diverters simultaneously or non-simultaneously based on the length of the article. By choosing between non-simultaneous and simultaneous diverter activation, control system 60' allows the conveying system 10 to divert articles that exceed the maximum distance between the furthest downstream diverter 25 and the furthest upstream diverter 25 in a particular diverting area. While the non-simultaneous diverting of pusher shoes will result in the article experiencing an initial rotational force, such rotation may be acceptable in order to limit the expenses by reducing the number of diverters and their associated diverting tracks. Control system 60' may be used with any of the diverting track configurations depicted in the attached drawings, or still other configurations, including configurations in which the diverting tracks are completely parallel with each other, or configurations in which one or more of the upstream diverting tracks do not terminate partway across the conveying surface. Also, while control system 60' is depicted in FIG. 9 as being used in conjunction with four diverters 25 and four diverting tracks 40 or 50, it will be understood that more or fewer diverters and diverting tracks could be used with controller 60'. In determining whether an article's leading or trailing edge is adjacent a diverter, one or more sensors, such as a photo-eyes or other conventional sensors, may be used. Such sensors can be plated an any known location and may be used in combination with other sensors, such as encoders that measure the movement of the conveying surface, to determine an articles position and/or length. Having described the invention in connection with certain specific embodiments thereof, it is to be understood that the description is meant to be interpreted as illustrative only, and that various modifications may also be made by those skilled in the art without departing from the spirit and scope of the invention as expressed in the accompanying claims.

Claims: What is claimed is: 1. A sortation system including a conveying surface and a plurality of diverting assemblies spaced along said conveying surface, each of said diverting assemblies for selectively laterally displacing an article on said conveying surface, at least one of said diverting assemblies comprising: a plurality of movable pushers associated with the conveying surface and adapted to be movable transversely across the conveying surface; a set of at least three diverting tracks configured to guide selected ones of said movable pushers across the conveying surface; a set of at least three diverters, each said diverter adapted to selectively divert at least one movable pusher along one of said diverting tracks when said diverter is activated into a diverting state; and a controller adapted to select, when an article is to be diverted from the conveying surface, a subset of at least two diverters from said set of at least three diverters and activate said subset of diverters into the diverting state, said subset of diverters including a first and second diverter which are separated from each other by at least one intermediate diverter which is not activated into said diverting state. 2. The assembly of claim 1 further including a sensor for determining the location of a trailing and leading edge of an article to be diverted, said controller further adapted to select said subset of diverters based upon the determined location of the trailing and leading edges of the article to be diverted. 3. The assembly of claim 1 wherein said controller is further adapted to substantially simultaneously activate all of said diverters in said subset of diverters into the diverting state. 4. The assembly of claim 1 wherein said controller is further adapted to occasionally activate all of said diverters in said subset of diverters into the diverting state substantially simultaneously and occasionally activate all of said diverters in said subset of diverters into the diverting state non-simultaneously. 5. The assembly of claim 1 wherein said controller is. further adapted to divert only a single movable pusher along each diverting track in which a diverter has been activated into the diverting state. 6. The assembly of claim 1 further including at least a fourth diverter and at least a fourth diverting track. 7. The assembly of claim 1 wherein said at least three diverting tracks include at least a first diverting track having a first shape and at least a second diverting track having a second shape different from said first shape. 8. The assembly of claim 1 wherein said at least three diverting tracks are shaped such that an article to be diverted is initially displaced with a non-rotational force by said movable pushers and subsequently displaced with a rotational force by said movable pushers. 9. The assembly of claim 1 wherein at least two of said set of at least three diverting tracks converge. 10. The assembly of claim 1 wherein each of said diverting tracks in said set of at least three diverting tracks includes a first and a second section, said first sections being parallel to each other and oriented at a first angle, said second sections being parallel to each other and oriented at a second angle, said second angle being different from said first angle. 11. The assembly of claim 1 wherein said set of at least three diverting tracks includes an upstream-most diverting track into which a plurality of said diverting tracks merge. 12. The assembly of claim 11 further including a downstream diverting track which does not merge with any other diverting tracks. 13. A sortation system including a conveying surface and a plurality of diverting assemblies spaced along said conveying surface, each of said diverting assemblies for selectively laterally displacing an article on said conveying surface, at least one of said diverting assemblies comprising: a plurality of movable pushers associated with the conveying surface and adapted to be movable transversely across the conveying surface; a set of at least three diverting tracks configured to guide selected ones of said movable pushers across the conveying surface; a set of at least three diverters, each said diverter adapted to selectively divert at least one movable pusher along one of said diverting tracks when said diverter is activated into a diverting state; a sensor for determining the length of an article to be diverted; and a controller adapted to select, when an article is to be diverted from the conveying surface, a subset of at least two diverters from said set of at least three diverters and activate said subset of diverters into the diverting state, said subset of diverters including a first and second diverter which are separated from each other by at least one intermediate diverter which is not activated into said diverting state, said subset of diverters being selected by said controller based upon the determined length of the article to be diverted. 14. The assembly of claim 13 wherein said controller is further adapted to select said subset of diverters based upon a determined location of a trailing and a leading edge of the article to be diverted. 15. The assembly of claim 13 wherein said controller is further adapted to simultaneously activate all of said diverters in said subset of diverters into the diverting state. 16. The assembly of claim 13 wherein said controller is further adapted to occasionally activate all of said diverters in said subset of diverters into the diverting state simultaneously and occasionally activate all of said diverters in said subset of diverters into the diverting state non-simultaneously. 17. The assembly of claim 13 wherein said controller is further adapted to divert only a single movable pusher along each diverting track in which a diverter has been activated into the diverting state. 18. The assembly of claim 13 further including at least a fourth diverter and at least a fourth diverting track. 19. The assembly of claim 13 wherein said at least three diverting tracks include at least a first diverting track having a first shape and at least a second diverting track having a second shape different from said first shape. 20. The assembly of claim 13 wherein said at least three diverting tracks are shaped such that an article to be diverted is initially pushed with a non-rotational force by said movable pushers and subsequently pushed with a rotational force by said movable pushers. 21. A method for laterally displacing an article on a conveying surface of a conveyor: providing a plurality of movable pushers associated with the conveying surface and adapted to be movable transversely across the conveying surface; providing a set of at least three diverting tracks configured to guide selected ones of said movable pushers across the conveying surface; providing a set of at least three diverters, each said diverter adapted to selectively divert at least one movable pusher along one of said diverting tracks when said diverter is activated into a diverting state; determining a length of an article to be diverted; at least occasionally selecting a subset of at least two diverters from said at least three diverters based upon the determined length of the article to be diverted, said subset of diverters including a first and second diverter which are separated from each other by at least one intermediate diverter; and activating said first and said second diverters in said subset of diverters into the diverting state while maintaining said at least one intermediate diverter in a non-diverting state. 22. The method of claim 21 further including activating said first and said second diverters substantially simultaneously. 23. The method of claim 21 further including activating said first and said second diverters substantially simultaneously when diverting some articles and substantially non- simultaneously when diverting other articles. 24. The method of claim 23 wherein said first and said second diverters are activated substantially simultaneously when an article to be diverted is less than a predetermined length and said first and said second diverters are activated substantially non- simultaneously when an article to be diverted is greater than or equal to the predetermined length. 25. The method of claim 24 wherein when said first and said second diverters are activated substantially non-simultaneously, a downstream one of said first and second diverters is activated first followed by an upstream one of said first and second diverters. 26. The method of claim 21 further including determining a location of a leading and trailing edge of an article to be diverted, activating said first diverter into said diverting state when the leading edge of the article to be diverted is adjacent said diverter, and activating said second diverter into said diverting state when the trailing edge of the article to be diverted is adjacent said diverter. 27. The method of claim 21 further including providing at least four diverting tracks and at least four diverters. 28. A diverting assembly for diverting articles from a conveying surface of a conveyor comprising: a plurality of movable pushers associated with the conveying surface and adapted to be movable transversely across the conveying surface; a plurality of diverting tracks configured to guide selected ones of said movable pushers across the conveying surface; a plurality of diverters, each said diverter adapted to selectively divert at least one movable pusher along one of said diverting tracks when said diverter is activated into a diverting state; and a controller for selecting at least two diverters from said plurality of diverters, said controller first activating a downstream one of said selected diverters into the diverting state and subsequently activating an upstream one of said selected diverters into the diverting state. 29. The assembly of claim 28 further including a sensor for measuring a length of the article to be diverted wherein said at least two diverters are spaced apart by a distance that is less than the measured length of the article to be diverted. 30. The assembly of claim 28 wherein said plurality of diverting tracks includes at least one diverting track having a first shape and at least one diverting track having a second shape different from said first shape. 31. The assembly of claim 28 wherein said controller is further adapted to activate said downstream diverter when a leading edge of the article to be diverted is adjacent said downstream diverter, and to activate said upstream diverter when a trailing edge of the article to be diverted is adjacent said upstream diverter. 32. The assembly of claim 28 including at least three diverting tracks and at least three diverters, said controller being adapted to select and activate two diverters which are separated from each other by at least one intermediate diverter which is not activated into the diverting state. 33. The assembly of claim 28 wherein said controller is further adapted to activate both said downstream and said upstream diverters only for a length of time sufficient to cause only a single one of said movable pushers to be diverted by each of said downstream and upstream diverters when diverting a single article. 34. A method for diverting articles from a conveying surface of a conveyor comprising: providing a plurality of movable pushers associated with the conveying surface and adapted to be movable transversely across the conveying surface; providing a plurality of diverting tracks configured to guide selected ones of said . movable pushers across the conveying surface; providing a plurality of diverters, each said diverter adapted to selectively divert at least one movable pusher along one of said diverting tracks when said diverter is activated into a diverting state; and selecting at least two diverters from said plurality of diverters; first activating a downstream one of said selected diverters into the diverting state; and subsequently activating an upstream one of said selected diverters into the diverting state. 35. The method of claim 34 further including measuring a length of the article to be diverted and selecting said at least two diverters such that they are spaced apart by a distance less than the length of the article to be diverted. 36. The method of claim 34 further including activating said downstream diverter when a leading edge of the article to be diverted is adjacent said downstream diverter, and activating said upstream diverter when a trailing edge of the article to be diverted is adjacent said upstream diverter. 37. The method of claim 34 including selecting and activating two diverters which are separated from each other by at least one intermediate diverter which is not activated into the diverting state. 38. The method of claim 34 further including activating both said downstream and said upstream diverters only for a length of time sufficient to cause only a single one of said movable pushers to be diverted by each of said downstream and upstream diverters when diverting a single article.

Inventors: SHEARER JAMES T JR, VEIT FRANK W, SHEARER, JAMES, T., JR., VEIT, FRANK, W.
Applicants: ATECS MANNESMANN AG
Application year: 2001
Main classification: B65G47
IPC codes: B65G17, B65G47