Patent Publication Number: US-11390464-B1

Title: Chain slack adjustment mechanism for mail sortation systems

Description:
1. TECHNICAL FIELD 
     The present application relates to sortation conveyor systems, in particular, the chain tensioning on shoe sorter transports used in such sortation conveyor systems for sorting mail, such as letters, flats, parcels, trays, and polybags along sorter conveyor systems in parcel sorting machines. 
     2. DESCRIPTION OF RELATED ART 
     Machines for automatically sorting items such as mail, parcels and trays, into one of an array of selected bins, bags, tubs, cardboard containers, or compartments, are common. Typically, such sorting machines have a feed mechanism that inducts articles one-at-a-time onto belts and/or onto conveyors. Sensing components along the travel path monitor and track the movement of the articles. Belts and/or conveyors feed items onto a transport which has multiple slats, driven by chains, that transport each item down the sorter&#39;s length. When an item has reached an identified discharge location, control electronics command diverting gate assemblies or other redirecting mechanisms to discharge the item from the transport slats into a specific destination compartment or bin. 
     Conventional chain driven sortation systems use two chains spanning between a motor driven axle with chain sprockets on one end of the machine, and a second non-powered idler axle also with chain sprockets. These axels are usually solid and span across the full width of the transport. The chains must remain in tension between the driven and idler axles for the sorter to safely carry the parcel transport slats and otherwise function properly. The solid drive axle to solid idler axle arrangement used in parallel chain driven systems, such as used in parcel sorting systems, significantly contributes to chain wear. This type of wear is due to typical uneven parcel weight loading on the chain driven slats, which causes a diagonal torqueing action of the chains against the sprockets. This twisting motion of the chains against the sprockets significantly aggravates chain wear, which in turn accelerates the need for chain length adjustment. 
     Due to such wear, along with normal wear and tear, the chains increase in length such that the chains must be manually shortened to eliminate excessive chain slack by removing slats and chain links from the chains on both sides of the sorter. Manually shortening these chains is a very time consuming process, which causes a loss of the sorter&#39;s production time and the associated loss of considerable item processing profits. Although great strides have been made in the area of chain driven sortation systems, significant shortcomings remain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed a characteristic of the system of the present application is set forth herein. However, the system itself, as well as a preferred mode of use, along with further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a conventional item sortation conveyor system. 
         FIG. 2  is a simplified perspective view of the item sortation conveyor system of  FIG. 1 . 
         FIG. 3  is a side view of the item sortation conveyor system of  FIG. 1 . 
         FIG. 4  is an enlarged perspective view of the idler axle and sprocket assembly of the item sortation conveyor system of  FIG. 2 . 
         FIG. 5  is a simplified perspective view of a mail sortation system having a chain slack adjustment mechanism according to the preferred embodiment of the present application. 
         FIG. 6  is a side view of the mail sortation system of  FIG. 5 . 
         FIG. 7  is an enlarged perspective view of a split idler axle assembly of the mail sortation system of  FIG. 5 . 
         FIG. 8  is an exploded view of the chain slack adjustment mechanism of  FIG. 7 . 
         FIG. 9  is an enlarged partial exploded detail view of certain components of the chain slack adjustment mechanism of  FIG. 8 . 
         FIG. 10  is another enlarged partial exploded detail view of certain components of the chain slack adjustment mechanism of  FIG. 8 . 
         FIG. 11A  is an enlarged side view of the chain slack adjustment mechanism of the mail sortation system of  FIG. 5 . 
         FIGS. 11B and 11C  are enlarged side views of the chain slack adjustment mechanism of the mail sortation system of  FIG. 5 , in which certain components have been shown with cross-hatched lines to illustrate the movement of the chain slack adjustment mechanism. 
     
    
    
     While the system of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the method to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, combinations, and alternatives falling within the spirit and scope of the present application. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Illustrative embodiments of the chain slack adjustment mechanism for mail sortation systems of the present application are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     Reference may be made herein to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms, to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. 
     Referring now to  FIGS. 1-4  in the drawings, a conventional chain and slat sortation conveyor system  100  is shown. As shown in  FIG. 1 , sortation conveyor system  100  is logically divided into three parts—a front section  101 , a middle section  103 , and an end section  105 . A longitudinal conveyor  110  extends through each of sections  101 ,  103 , and  105 . Front section  101  includes an idler axle  106  having chain sprockets  107  and other related carrier assemblies. Middle section  103  includes multiple discharge containers  115 . End section  105  includes a chain drive motor  109 , a drive axle  112 , drive chain sprockets  116 , and one or more separate exit conveyors  118  for items that do not get sorted. Conveyor  110  travels from left to right, as shown in  FIGS. 1 and 2 , between front section  101  and rear section  105 . Conveyor  110  includes multiple slats  111  that extend transversely across conveyor  110 . Slats  111  are configured to carry block-shaped shoes  117 . Shoes  117  slide along corresponding slats  111  and push items off of slats  111  and into discharge containers  115  according to preprogrammed instructions from a control system  122 . It will be appreciated that control system  122  includes multiple sensors, controllers, actuators, etc. Chains  124  located on both sides of conveyor  110  are driven by chain drive motor  109 , drive axle  112 , and drive chain sprockets  116 ; and are guided by a drive chain return guide  126 . 
     In operation, various items are received onto slats  111  of conveyor  110  at first section  101 . Then, the items traverse along the conveyor  110  through middle section  103 . Then, at the appropriate time, control system  122  activates shoes  117  causing the items to be discharged into the appropriate discharge containers  115 . 
     As shown in  FIGS. 2 and 3 , chain slack accumulates at the bottom return path just below drive axle  112  at the rear of conveyor system  100 . The slack in chain  124  is guided by chain return guide  126 . Excessive chain wear eventually requires both chains  124  to be replaced. Chains  124  are large, heavy, specially made for the application and are very expensive in chain cost, labor to replace them, and system down time production losses during replacement. Therefore, reducing chain wear becomes a major cost avoidance issue for economical sorter operation. 
     Chain slack  203  at the rear module accumulates from chain wear. Chain return guide  126  directs the chain slack back into a chain return channel under conveyor  110 . If chain slack  203  becomes excessive, chain  124  and slats  111  could snag on chain return guide  126 , causing catastrophic damage to conveyor system  100 . An excessive chain slack sensor is commonly provided at the apex of chain slack  203  to halt conveyor system  100  if the acceptable chain slack length is exceeded. When the chain slack is in excess of the acceptable length, chains  124  must be split, slats and chain links removed, and the chains joined back together before sorter operation can continue. 
     Referring now specifically to  FIG. 4  in the drawings, a partial close-up perspective view from inside front section  101  is illustrated. The following description pertains to one side of the idler axle assembly, with the other side being a mirror image. An axle carrier assembly  501  mounts directly to a sorter frame  502  with mounting hardware  407 . Idler axle  212 , an axle bearing  406 , and idler gear  108  are mounted to axle carrier assembly  410  with an axle-bearing hub  403 . The axle and sprocket assemblies are free to rotate, being supported by bearings  406  in the axle-bearing hub  403 . The horizontal axle assembly centerline, with relationship to the entire sorter, is shown by the indicated dashed plane  409 . 
     Referring now to  FIGS. 5-7  in the drawings, a mail sortation system  500  having a chain slack adjustment mechanism  501  according to the present application is illustrated. In system  500 , there is no chain slack loop. This is accomplished by the chain slack being adjusted out of the system by increasing the distance between idler axles  1211  (see  FIG. 6 ) and driven axle  1214 , until no slack remains, by actuating chain slack adjustment mechanism  501 . Chain slack adjustment mechanism  501  provides a method to adjust the chain slack out of the system. Chain slack adjustment assembly  501  also provides spring tension on idler axle assembly to absorb minor shocks to chains  520  due to the inertial forces caused by the starting and stopping of conveyor system  500 , and the placement and subsequent removal of asymmetrically loaded heavy articles on slats  522 . 
     In the conveyor systems of the present application, no chain slack return guides are required at the rear of the sorter, as the chain slack has been eliminated. As is shown, the single shaft front idler axle  106  of the prior-art conveyor  100  has been replaced by two short independent (stub) idler axles  1211 , one on each side, with each stub idler axle  1211  being coupled to and adjusted by chain slack adjustment mechanisms  501 . By incorporating independent stub idler axles  1211  as a part of chain slack adjustment mechanism  501 , chain wear is significantly reduced, chain life is extended, and the need for chain length adjustments is reduced. This configuration improves chain dynamics, because each chain  520  may be independently adjusted and tensioned to prevent uneven chain wear caused by uneven side-to-side slat loading during normal sorter operation. 
     Another novel feature of chain slack adjustment mechanism  501  is that by using two separate independent stub idler axles  1211 , chains  520  are free to accommodate the unequal torque forces generated due to uneven item weight distribution across slats  522  down the length of conveyor system  500 . Chain slack adjustment mechanisms  501  may be selectively moved towards the front end of sortation system  500  to provide adjustment of chain slack, by increasing the distance between the stub idler axles  1211  and drive axle  1214 . An idler gear  1207  is attached to each stub idler axle  1211  and rotates therewith. Each stub idler axle  1211  is supported by an axle bearing  1406 , which is retained by an axle bearing hub  1403 , each of which in turn is mounted to an idler axle carrier assembly  1501 . Each idler axle carrier assembly  1501  is configured to slide front-to-back inside a captured channel having a longitudinal slot for receiving guide pins  1703  from idler axle assembly  1501 . By using two stub idler axles  1211 , the left and right side conveyor chains  520  are decoupled. This allows the left and right side chains  520  to skew relative to each other in reaction to typical differential loading across conveyor slats  522 . This resulting chain skewing action is absorbed by the chain slack adjustment springs  1616  and the idler axle carrier slide assembly  1603  (see  FIG. 8 ). By preventing the common chain binding caused with the prior-art design, a significant reduction in chain wear results, dramatically increasing the time before a system shutdown is required for slat and chain link removal, reducing costly sorter down time. 
     Referring now also to  FIG. 8  in the drawings, an exploded perspective view of chain slack adjustment mechanism  501  is illustrated. A slide assembly  1603  is shown captured by retaining slide rails  1605 . One outer stub idler axle  1211  and an axle-bearing hub  1403  are mounted to movable slide assembly  1603 . Stub idler axle  1211  passes through adjustment slide assembly  1603  to mount to idler gear  1207  and an inside axle bearing  1607  and an inner axle bearing hub  1403 . Inner axle bearing hub  1403  is mounted to sliding idler axle assembly  1501 , which is retained by guide pins  1703  (see  FIG. 9 ) captured by guides mounted to the inside of conveyor frame  1503  (see  FIG. 7 ). An adjustment rod assembly  1611  is fastened to an adjustment slide  1620  using a bulkhead plate  1617  (see  FIG. 9 ). Adjustment rod assembly  1611  includes bulkhead plate  1617 , a spring  1616  with end caps  1618 , and an adjusting nut  1622 . 
     Referring now also to  FIG. 9  in the drawings, certain moving components of chain slack adjustment mechanism  501  are illustrated. All components shown in  FIG. 9  move toward the left when adjusting nut  1622  on adjustment rod assembly  1611  is tightened. Adjustment rod assembly  1611  is fastened to chain slack adjusting slide assembly at the bulkhead plate  1617 . An adjusting slide assembly  1603  is coupled to sliding idler axle carrier assembly  1501 . Sliding inner axle support assembly  1501  is maintained level in a back-to-front orientation by guide pins  1703  riding inside pin retainers  1503  (see  FIG. 7 ). Stub idler axle  1211  passes through and is supported by outer bearing  1607 , which is captured by outer bearing hub  1405 . Stub idler axle  1211  also passes through inner bearing  1406 , which is captured and supported by inner axle bearing hub  1403 . 
     Referring now also to  FIG. 10  in the drawings, a slide assembly adjustable stop  1901  is illustrated. Adjustable stop  1901  prevents excessive rearward travel of slide assembly  1603  (see  FIG. 8 ). Adjustable stop  1901  is preferably a threaded adjustment bolt  1911  having a knurled end cap  1903 . Adjustable stop  1901  threads into an adjustable stop bracket  1905 . Adjustment bolt  1911  is screwed in or out of a threaded portion of bracket  1905 , as required for optimum positioning. A lock screw  1907  threads into a threaded nut  1909  on bracket  1905  to lock adjustment bolt  1627  into the desired position. 
     Referring now also to  FIGS. 11A-11C  in the drawings, the operation of chain slack adjustment mechanism  501  is illustrated. Covers  1601  cover bracket chain slack adjustment mechanism  501  for personnel protection from the moving chains. Idler axle bearing retainer assembly  1405  is mounted to and moves with the adjustment slide assembly  1603  in a back-to-front direction. Adjustment slide assembly  1603  is captured and guided by channeled guide rails  1605  mounted above and below adjustment slide assembly  1603 . Channeled guide rails  1605  keep adjustment slide assembly  1603  flush to the sorter frame and allow adjustment slide assembly  1603  to only move in a back-to-front direction. Bulkhead plate  1617  is fastened to channeled guide rails  1605  to provide a frame mounted surface that adjustment slide assembly  1603  can be pulled forward using threaded pull rod assembly  1611  with tension spring  1616 , end caps  1618 , and adjustment nut  1622 . If the chain slack exceeds the tension range of tension spring  1616 , tension spring  1616  will move adjusting nut end cap  1618  to move away from bulkhead plate  1617 , thereby triggering a position sensor  1623  that signals a control system programmable logic controller (PLC) that a chain slack adjustment is needed. A ruler  1627  can be included as a guide referencing the adjustment nut end cap position to view the relative amount of accumulated chain length increase since the last chain slack adjustment. 
     Slide assembly  1603  is mounted between two retaining rails  1605 , which permits slide assembly  1603  to move left-to-right as shown in the figures. Idler gear  1207 , stub idler axle  1211 , and inner and outer axle bearings are all mounted to and move with slide assembly  1603 . Adjustment rod  1611  and spring assembly  1616  are adjusted to compress spring assembly  1616  against the stationary bulkhead  1617  to pull slide assembly  1603  to the left. By pulling slide assembly  1603  to the left, stub idler axle  1211  and idler gear  1207  are also pulled to the left, thereby creating tension on chain  520  to remove any accumulated chain slack (see  FIG. 5 ). If the chain slack eventually becomes excessive causing tension rod assembly  1611  to shift towards the left, sensor  1623  signals an indication to the control system that spring tension assembly  1616  requires adjustment. Slide assembly stop rod  1627  is adjustable to limit the rearward travel of slide assembly  1627 . Thus, chain slack adjustment mechanism requires minimal maintenance, even for continuous duty operation with heavy parcel loads; automatically notifies the control system when adjustment is required; removes the highly troublesome chain slack accumulation at the rear motor driven end; and significantly reduces long-term chain wear and elongation resulting in significant operational savings due to reduced down time and maintenance costs. 
     Although chain slack adjustment mechanism  501  is preferably driven by the force of tension spring  1616 , it will be appreciated that chain slack adjustment mechanism  501  may be driven and/or powered by other means, such as pneumatic, hydraulic, and/or electromagnetic systems. Such alternative systems may be controlled by the control system. 
     In  FIGS. 11B and 11C , slide assembly  1603  of chain slack adjustment mechanism  501  has been shown in cross-hatched lines to show the movement of slide assembly  1603  due to chain wear. The shaded slide is pulled towards the left by tightening the adjustment nut, compressing the tension spring and added tension against the chain. By pulling slide assembly  1603  towards the left, the distance between drive axle  1214  and stub idler axles  1211  is increased, thereby removing the chain slack. The compressed spring  1616  provides tension on slide assembly  1603  to allow for moderate chain wear before manual chain slack adjustment is required by tightening the adjusting nut. The manual chain slack adjustment can be made while the conveyor system  500  is running, eliminating the need to do a time consuming and costly sorter shutdown. 
     Although the foregoing embodiments refer to removing the slack from the chains in chain-driven mail sortation systems, it will be appreciated that the slack removal mechanisms of the present application may also be used to remove the slack from belts in belt-driven mail sortation systems. 
     The particular embodiments disclosed above are illustrative only, as the application may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered, combined, and/or modified, and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the claims below. It is apparent that a system with significant advantages has been described and illustrated. Although the system of the present application is shown in a limited number of forms, it is not limited to just these forms but is amenable to various changes and modifications without departing from the spirit thereof.