Abstract:
A document transfer buffer device for holding temporarily a document between an upstream document feeding device and a downstream envelope inserter has a transporting device for moving the document from the upstream document feeding device to the envelope inserter and an envelope holding device for temporarily holding the document in a holding location between the upstream document feeding device and the envelope inserter and a controlling program that selectively activates the transporting device and the temporary holding device and is responsive to the upstream feeding device and the envelope inserter possible error conditions that initiate document holding and releasing situations.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention pertains generally to a system for temporarily halting the flow of one or more incoming mail pieces into an envelope inserter apparatus. More particularly, the subject invention relates to a document buffer system having a controlling program that is utilized in connection with a document interface feeding device, an envelope inserter, and documents being transferred through the interface feeding device into the inserter, wherein one or more of the incoming documents may be temporarily halted, within the interface feeding device, before entry into the envelope inserter and buffered or cued in known order until the controlling program directs any cued documents to once again enter the envelope inserter. 
   2. Description of Related Art 
   Traditionally, when a series of document packets (often one or more pages in a billing statement for goods and/or services provided) are delivered by a transport device to an envelope inserter and an error is detected in the process there were three solutions: 1) the transporter is stopped, with the accompanied stoppage in production until the problem is resolved; 2) the transporter continues running, the envelopes filled, and the error is resolved later; and 3) the transporter continues to run with the problem document packets diverted out of the production process. However, there are two significant problems with the traditional solutions: 1) reduced productivity and 2) reduced quality. For whatever reason the inserter stops (there are many and they often occur about every minute, during the average process), the negative results are the same. All document packets that are in transition (frequently, from one to four) stack up either in the inserter track of in a diverter tray. After an operator rectifies the inserter error, the operator must remove the document packet(s), manually separate then from each other, insure that each document packet is complete and correct, and hand place them back into the track one at a time while cycling the inserter between them. Clearly, this corrective action is time consuming and can significantly increase the time to complete a job (often as much as a 30% increase). Also, human intervention of document packet production always increases the chance of making significant quality errors. The operator can inadvertently make several different errors; not separating two document packets that may have nested when stacked will result in two document packets mailed in the same envelope, mixing sheets from one document packet with another when separating them will result in incomplete or incorrect mailed document packets placing document packets in the track in the wrong sequential order will result in improper insert matching, or placing document packets in the track in the wrong orientation will result in undeliverable mail. Plainly, many difficulties existed in the prior error-resolution processes. 
   Several mechanisms already exist to divert of buffer the flow of documents during document transfers in numerous specific settings, but these mechanisms do not make obvious, teach, suggest, or imply in any manner the subject invention. 
   U.S. Pat. No. 3,948,564 discloses a fluid bearing apparatus and method that utilizes a selective turntable diverter structure to temporarily store identical items in a buffer station. The buffer station merely maintains a ready pool of identical items to supply the needs of an associated apparatus. No item sequence information is recorded or needed with this device. 
   Described in U.S. Pat. No. 4,544,146 is an insertion machine with control signals stored on searchable medium. Envelopes are printed with desired information and utilized (buffered and flipped) with an inserter and associated inserter stations. 
   A control signal buffer for use in an inserter system is related in U.S. Pat. No. 4,707,790. An information control buffer, no physical item is buffered, is provided in which control information from the supervisory controller to the sheet inserter system is buffered so that synchronicity is achieved between the transfer of batches of documents from a web of incoming documents and what is actually inserted into designated envelopes. 
   A communication network and protocol for real-time control of mailing machine operations is disclosed in U.S. Pat. No. 5,003,538. Information buffers within microprocessors are utilized to facilitate the transfer of controlling information to operate a traditional mailing machine. 
   U.S. Pat. No. 5,029,832 presents an in-line rotary inserter for use with an envelope inserting machine. A number of diverter stations are disposed ahead of the envelope inserting station for diversion of envelopes and inserts and ahead of the inserted envelope stacking assembly to divert inserted envelopes during normal operation and detected error situations. Upon detection of an error situation, the subject invention halts incoming statements before any envelopes are encountered. 
   U.S. Pat. Nos. 5,503,388 and 5,538,140 disclose a buffered stacker that selectively diverts horizontally disposed documents from a main conveying path, then stacks and transports the documents to replaceable receiving containers. This system directly diverts the selected documents away from the conveying path and does not allow any selected documents to reenter the main conveying path. 
   Described in U.S. Pat. No. 5,613,669 relates a control process for use in the production of printed products and means for performing the process. In the sequential assembly of multi-page document sets a controller, using a camera/detector, is utilized to scan and analyze each incoming page to determine if the correct page has been delivered and, if not, to direct corrective actions. 
   U.S. Pat. No. 5,816,715 outlines an interfacing mechanical buffer that allows two streams of materials to be united, even if the rates of flow of the materials from each of the two streams differ. To merge two streams of documents, each traveling at different speeds, one stream is slowed by having a mechanical buffer receive the documents and then release them in a first-in-first-out order. The mechanical buffer comprises a matched set of four helical-shaped screws that receive a incoming document, rotate to receive additional documents, and permit discharge of the received documents in order of their entrance to the buffer. 
   U.S. Pat. Nos. 5,826,869 and 6,131,053 present a high throughput document-processing machine having a dynamic speed control. The device merely directs the flow accumulated sets of documents from a first transport pathway to a second transport pathway if a jam is detected in the first pathway. 
   A transporter buffer and inserter method are disclosed in U.S. Pat. No. 5,860,504. A plurality of sensors detect positions of items in a transfer system and stop the items at predetermined locations based upon when the items should enter a receiving area. 
   The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant&#39;s acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully submitted, however, that none of these patents teaches or renders obvious, singly or when considered in combination, applicant&#39;s claimed invention. 
   BRIEF SUMMARY OF THE INVENTION 
   An aspect of the invention is to provide an information and physical mailing piece buffer to temporarily store at least one mailing piece or document packet and associated information in the event that an error is detected in relation to an inserter that is to receive the mailing piece or document packet for insertion into a mailing envelope. 
   Another aspect of the invention is to disclose a buffer system, utilized prior to an envelope inserter apparatus, for temporarily halting and holding, upon detection of a processing error, one or more incoming mailing pieces or document pieces and then releasing the held incoming mailing pieces or document packages upon resolving the difficulty that generated the halting error. 
   A still further aspect of the invention is to relate a computer program controlled document interface feeding device, utilized immediately prior to an envelope inserter, and with documents being transferred through the interface feeding device into the inserter, wherein if an error is detected in the processing of the incoming documents, one or more of the incoming documents may be temporarily halted and held within the interface feeding device, before entry into the envelope inserter and buffered or cued in known order until the controlling program processes the detected error and the error situation is remedied and then directs any cued documents to once again enter the envelope inserter. 
   The computer controlled subject transporter comprises a supporting frame having a plurality of lower and upper pulleys and belts along the general configuration of a conveyor. Document packets (often mailing pieces) enter the subject transporter either directly or indirectly from the output of a folder, or the like, and are contained between the upper and lower pulleys and belts and passively gripped. The belts are driven by an encoder controlled motor actively linked to the inserter. Along the document packet travel path, under the belts, are computer controlled gates for stopping individual document packets that can each be activated independently. Activation is often by associated pneumatic cylinders of electric solenoids. When activated, each gate moves into the document packet pathway and blocks the movement of the document packet. Since the belts only grip the document packet passively, the belts slip on the document packet for a short duration until the belts cease movement, as directed by the controlling computer. When the error is corrected each gate may be disengaged to permit normal transport. 
   The general software logic utilized by the controlling computer system detects that the downstream equipment (usually the inserter) is not able to receive a document packet it will determine to “buffer” or halt and hold delivery of the document packet, then it will determine to buffer additional document packets until the upstream equipment can be stopped. As the incoming document packets enter the subject transporter buffer, the first document packet proceeds to the last buffer gate (the furthest downstream) and is held. The following document packet proceeds to the second to last buffer gate and is held, continuing until all of the buffer gates are filled. Once the last statement is buffered, the subject transport belts stop. After the errors are remedied and the inserter is “armed” to begin processing, the system controller is directed to resume production, the inserter cycles to the ready position. The transport belts start movement and the buffer releases the first document packet which is delivered into the insert track. The inserter cycles once more and the buffer releases the second document packet. This continues for all subsequent document packets. Once the subject buffer is empty of held document packets the system begins normal operation automatically. Document packet detection sensors are located in the document packet travel path to indicate the presence or absence of a statement at each subject gate. Each sensor insures that a document packet has arrived at the appropriate gate, as expected, that document packets have not slipped past a gate while buffered, that document packets have not been removed while buffered, and that document packets have departed, as expected. If any of these difficulties occur, the system controller notifies the operator of the condition. 
   Advantages of the subject invention include, but are not limited to, increased productivity and enhanced quality. If the downstream equipment (the inserter) is not ready to receive document packets (such as the inserter has stopped for a jam), the document packets that have been sent to the inserter (perhaps from a collator and/or folder) continue to be transported toward the inserter. The subject buffer fills up with the incoming document packets and the system stops. After the operator rectifies the inserter stop reason, the operator can begin document packet production without regard to those document packets in the subject buffer. The system automatically delivers the document packets cued in the buffer one at a time into the inserter track with the assurance that no two document packets are nested together, no sheets are mixed up with another document packet, document packets maintain their original sequence order, and document packets are in the proper orientation (i.e. face down, top way, or whatever proper orientation is required). With the assurance of these actions, there is a guarantee that the quality issues have been eliminated (two document packets mailed in the same envelope, incomplete document packets mailed, improper insert matching, or undeliverable mail). Also, the entire time that this process is taking place automatically, the operator is available to attend to other system needs, such as restocking inserter hoppers and unloading completed mail pieces into the mailing trays. By doing so, the operator will be more efficient and can complete the job assignment is a shorter time. 
   Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
       FIG. 1  is a perspective view of the subject device. 
       FIG. 2  is a cut-away side view of the subject device showing all four gates in the lowered or retracted positions. 
       FIG. 3  is a cut-away side view of the subject device showing one gate in the up or extended position and the other three gates in the lowered or retracted positions. 
       FIG. 4  is a cut-away side view of the subject device shown from the opposite side as seen in  FIGS. 2 and 3 . 
       FIG. 5  is a state transition diagram for the controlling software utilized in the subject invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus and software diagram generally shown in  FIG. 1  through  FIG. 5 . It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein. 
   It should be appreciated that a conventional envelope inserter apparatus is utilized in conjunction with the subject buffer invention. The envelope insertion operation is generally carried out by conventional inserter apparatus which provides for the collecting or assembling of several sheets of mail materials together into packets, and the insertion of the assembled packets into envelopes to produce a mailing piece. In standard inserter devices, a stream of opened envelopes is generally conveyed past an inserter arm by a conveyor system. Individual inserts are obtained from insert hoppers and added to billing statements (comprised of one or more pages of listed charges for a service rendered and other relevant information) or other items to form the packets, and the assembled packets are sequentially directed by conveyor means to the inserter arm. The inserter arm then inserts or stuffs each packet of mail materials into an opened envelope by pushing the packet with pusher members or pusher fingers. The filled or stuffed envelopes are then generally directed to an envelope sealing operation. The inserter and pre- and post-processing equipment are controlled by a system computer programmed to coordinate mailing piece assembly and to monitor the entire system for errors in assemble and processing. 
   The controlling computer programming halts the envelope insertion process when an unsuitable occurrence or error is detected at some specific point in the overall process of the document packet or mailing piece assembly. Usually, a document interface feeding device delivers a document packet of mailing items, like billing statements, from a printer, folder, collator, or other device or combination of devices to the envelope inserter. Document packets are transferred through the interface feeding device into the inserter, if the process is interrupted or if an error is detected in the processing of the incoming documents, one or more of the incoming document packets may be temporarily halted, within the subject buffer, before entry into the envelope inserter and buffered or cued in known order until the controlling program processes the detected error and the error situation is remedied (usually by diverting the incoming document packet(s) to a separate hand-processing area) and then directs any cued document packets to once again enter the envelope inserter. 
   Specifically, as seen in  FIG. 1-4 , the subject buffer device  5  comprises a supporting frame generally having two opposing side walls  10  and  15 . The side walls  10  and  15  are secured to one another by any suitable standard means such as the illustrated cross-support members  11  and  12 . 
   Extending between and secured to the side walls  10  and  15  are a plurality of rotating cylinders or pulleys that support and drive a series of transport belts. Pulleys  20 ,  25 ,  30 , and  35  generate a lower transport belt path to support and drive the lower transport belts  36 ,  37 , and  38 . Pulleys  40 ,  45 ,  50 , and  25  generate a first upper transport belt path to support and drive first upper transport belts  51  and  52 . Pulleys  55 ,  60 ,  65 , and  30  generate a second upper transport belt path to support and drive second upper transport belts  61  and  62 . In combination, these pulleys and belts configure a conveyor system to move documents packets into the inserter. In  FIGS. 1-4  each document packet enters the subject device from the right and is moved to the left as the pulleys and belts rotate to transport the document packets. Document packets (often mailing pieces) enter the subject transporter (from the right in the illustrations) either directly or indirectly from the output of a folder, or the like, and are contained between the upper and lower pulleys and belts and passively gripped (gripped with enough force for movement, but not enough force to damage the document packets as the belts slide over them should the packets be temporarily halted upon detection of an error). The pulleys/belts are driven by an encoder controlled motor  70  or motors actively linked to operational timing of the inserter. 
   Along and below the document packet travel path are computer controlled gates  75 ,  80 ,  85 , and  90  for stopping, when stop-errors are detected, individual document packets at separate specific locations in the travel path. Although other equivalent methods may be utilized to move a gate into and out of the document packet travel path, preferably each gate  75 ,  80 ,  85 , and  90  pivots about a rotational axis  76 ,  81 ,  86 , and  91  into the document packet path to block transfer of a document packet and pivots out of the path to release a document packet. Each gate  75 ,  80 ,  85 , and  90  comprises an elongated plate with suitably positioned notches to accommodate passage of the belts when the gate is pivoted into the document packet path to block a desired document packet. 
   Each gate  75 ,  80 ,  85 , and  90  may be independently activated and pivoted into the path to block passage of a document packet or independently deactivated and pivoted away from the path to release a document packet to travel towards or into the inserter. Activation is often by associated pneumatic cylinders or electric solenoids that are suitably interfaced to the controlling computer system for activation or deactivation. Specifically shown in  FIG. 4 , compressed air cylinders  100 ,  105 ,  110 ,  115  are utilized to pivot gates  75 ,  80 ,  85 , and  90 , respectively, into and out of the path. When activated, each gate  75 ,  80 ,  85 , and  90  moves into the document packet pathway and blocks the movement of the document packet. Since the belts  36 ,  51 , and  61  only grip the document packet passively (“passively” meaning with a minimal force sufficient for path movement purposes), the belts slip on the document packet for a short duration until the belts cease movement, as directed by the controlling computer. Specifically, as seen in  FIG. 3 , only one gate  90  was activated to pivot about point  91  and into the document packet path to block the document docket. Clearly, one or more gates  75 ,  80 ,  85 , and  90  may be activated if the situation arises. When the error that produced activation of a gate is remedied or corrected, each gate  75 ,  80 ,  85 , and  90  may be disengaged by a command of the controlling computer to pivot down and out of the path to permit normal transport of a document packet, as seen in  FIG. 2 . 
   To detect if document packets are actually stopped and present behind any or all of the various gates  75 ,  80 ,  85 , and  90  or that the document packet path areas behind the various gates  75 ,  80 ,  85 , and  90  are open and free of document packets, suitable sensors are utilized and appropriately interfaced with the controlling computer system. Although other equivalent types of sensors are contemplated to be within the realm of this disclosure, a preferred sensor configuration is a paired light emitter and light receiver sensor  200 ,  205 ,  210 , and  215 . If a document packet is present the light between the emitter and receiver is blocked and the controlling system so notes and if no document packet is present the light passes from the emitter to the receiver and, again, the controlling system so notes. 
   Specifically, as illustrate the  FIG. 5  state transition diagram, the subject buffer device utilizes controlling software that interfaces with the controlling system of the associated inserter. When predetermined errors of various types are detected by the controlling system the subject buffer software is activated to control delivery of document packets to the inserter. 
   For purposes of clarity and by way of example and not by way of limitation, the control logic of the subject buffer gate device is specified by the behavior of a single buffer gate and in terms of the document packet specifically being a billing statement (usually for service provided or products purchased) generated by a suitable device upstream from the subject buffer device. Multiple instances of the same control program are activated, one for each buffer gate (four such gates  75 ,  80 ,  85 , and  90  are illustrated in  FIGS. 1-4 ). 
   A state transition diagram (shown in  FIG. 5 ) is employed to specify the control logic of the subject buffer gate program. An explanation is provided below for the state transition diagram in general and provides specific examples to assist in fully understanding the state transition diagram for the subject buffer gate program. Before describing the subject state transition diagram, it is deemed appropriate to identify and describe the events the subject control program detects and the actions the control program takes. In addition, it is appropriate to list the states the control program occupies and the conditions (data values) the program can access. To fully specify the behavior of the subject program the state transition diagram utilizes four elements: 1) events, 2) actions, 3) states, and 4) conditions. 
   1) Events 
   The subject buffer gate program responds to the following events: 
   
     
       
             
           
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               EVENTS RESPONDED TO BY THE SUBJECT PROGRAM 
             
           
        
         
             
               Event 
               Means of detection 
             
             
                 
             
             
               Initialization 
               This event is common to all control programs and 
             
             
                 
               represents the start of the program. 
             
             
               Statement Message 
               The statement message is a software signal sent by a 
             
             
                 
               device upstream from the gate to indicate that a 
             
             
                 
               statement has been sent. 
             
             
               Statement Arrival 
               The statement arrival event is provided by an 
             
             
                 
               encoder system that signals the program when the 
             
             
                 
               transport has reached the position corresponding 
             
             
                 
               to the arrival of a statement at the gate. 
             
             
               Transport Start 
               This software signal is provided by the system 
             
             
                 
               management software when the transport starts. 
             
             
               Transport Stop 
               This software signal is provided by the system 
             
             
                 
               management software when the transport stops. 
             
             
               Downstream Ready 
               This software signal is sent by a device 
             
             
                 
               downstream from the gate when it is able to receive 
             
             
                 
               a statement. For example, when an inserter is 
             
             
                 
               enabled and has an empty slot in its input section 
             
             
                 
               it sends this signal to the buffer gate closest to the 
             
             
                 
               inserter. In addition, each buffer gate sends this 
             
             
                 
               information to the adjacent upstream buffer gate 
             
             
                 
               when it has released a statement and can now 
             
             
                 
               receive a statement. 
             
             
               Downstream 
               This software signal is sent by the device 
             
             
               Stopped 
               downstream from the gate when it is not able to 
             
             
                 
               receive a statement. For example when the 
             
             
                 
               inserter jams and has a statement in its input section 
             
             
                 
               it sends this signal to the buffer gate closest to 
             
             
                 
               the inserter. In addition each buffer gate sends 
             
             
                 
               this information to the adjacent upstream buffer 
             
             
                 
               gate when it is holding a statement. 
             
             
               Sensor Poll Clear 
               This software signal is sent by a standard polling 
             
             
                 
               thread that monitors the state of the sensor at the 
             
             
                 
               buffer gate when the sensor transitions from 
             
             
                 
               blocked to clear. 
             
             
               Path Error 
               This software signal is sent by various external 
             
             
                 
               programs for various possible reasons. The signal 
             
             
                 
               indicates that the identity or reliability of material 
             
             
                 
               on the transport is no longer certain. 
             
             
                 
             
           
        
       
     
   
   2) Actions 
   The subject buffer gate control program takes the following actions. 
   
     
       
             
           
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               ACTIONS TAKEN BY THE SUBJECT PROGRAM 
             
           
        
         
             
               Action 
               Means of actuation 
             
             
                 
             
             
               Open Gate 
               Switch the gate so that each statement is allowed to pass. 
             
             
               Close Gate 
               Switch the gate so that a statement is held at the gate. 
             
             
               Send Statement 
               Send a software signal to a downstream device to 
             
             
               Message 
               indicate that a statement has been released. 
             
             
               Send Ready 
               Send a software signal to an upstream device to indicate 
             
             
               Message 
               that the gate can now receive a statement. 
             
             
               Send Stopped 
               Send a software signal to an upstream device to indicate 
             
             
               Message 
               that the gate cannot receive a statement because it is 
             
             
                 
               already holding one. 
             
             
               Display Error 
               Display an error message and stop the insertion system so 
             
             
                 
               that the operator can correct an error. 
             
             
                 
             
           
        
       
     
   
   3) States 
   The subject buffer gate program is always in one of the following states: 
   
     
       
             
           
             
             
           
         
             
               TABLE 3 
             
           
           
             
                 
             
             
               STATES IN WHICH THE SUBJECT PROGRAM ALWAYS EXISTS 
             
           
        
         
             
               State 
               Conceptual description 
             
             
                 
             
             
               Inactive 
               The transport is stopped and the buffer gate sensor is clear. 
             
             
               Ready 
               The transport is running, the gate is open, and no 
             
             
                 
               statements are expected from an upstream device. 
             
             
               Waiting 
               The transport is running, the gate is open, and a statement 
             
             
                 
               is expected from an upstream device but has not yet arrived. 
             
             
               Holding 
               The transport is running and a known statement is being 
             
             
                 
               held at the gate. 
             
             
               Stopped 
               The transport is stopped and a known statement is being 
             
             
                 
               held at the gate. 
             
             
               Faulted 
               The transport is stopped and unsuitable/unmailable material 
             
             
                 
               is held at the gate. 
             
             
                 
             
           
        
       
     
   
   4) Conditions 
   The subject buffer gate program can determine the following conditions at any point in time. 
   
     
       
             
           
             
             
           
         
             
               TABLE 4 
             
           
           
             
                 
             
             
               CONDITIONS DETERMINED BY THE SUBJECT PROGRAM 
             
           
        
         
             
               Condition 
               Means of accessing/maintaining the data 
             
             
                 
             
             
               Sensor 
               The buffer gate program can directly read the state of the 
             
             
               Blocked/Clear 
               gate sensor at any time. 
             
             
               Downstream 
               The buffer gate program records the most recent message 
             
             
               Ready/Stopped 
               from a downstream device to indicate whether it is 
             
             
                 
               currently ready or stopped. 
             
             
                 
             
           
        
       
     
   
   State Transition Diagram—Background (see  FIG. 5 ) 
   The subject control program responds to events by taking actions. The specific action taken in response to an event is determined by the state of the program at the time the event occurs and may also depend on the value of one or more conditions. In addition to taking the indicated action, the program also changes its state. The state transition diagram, shown in  FIG. 5 , documents the system&#39;s behavior as transition arrowed-lines leading from one state to another. Each transition arrowed-line represents an event and may also contain an action. Further, if a transition arrowed-line behavior depends on any condition the transition arrowed-line shows a required value for the condition. To determine the response of the system to a sequence of events the transition arrowed-line of interest is “followed” to observe what action is taken in response to each event. 
   The Buffer Gate Program and State Transition Diagram (see  FIG. 5 ) 
   To clarify the meaning of the state transition diagram seen in  FIG. 5 , behavior examples for the subject buffer gate program are provided. 
   The following tables (Tables 5-8) show example scenarios handled by the subject program. In each scenario a hypothetical sequence of events occurs. Each table shows the action taken in response to each event. The “State” column shows the state of the system at the time the event occurs. (Note that the state of the system on one row is the result of the transition occurring on the previous row.) 
   Throughout each example sequence the action can be determined from the state transition diagram,  FIG. 5 , as follows. First, find the rectangle on the diagram corresponding the state (remembering that the subject program is always in one of the six listed states in Table 3, above). Then examine the arrows leading out of the rectangle and find the one labeled with the event that has occurred. The bold-underlined text indicates the action taken in response to the event. 
   Note that the same event will trigger a different action in different states. For example, in Sequence 1 the transport start event triggers a Send Ready Message action when the state was Inactive. However, when the state was Stopped the Transport Start triggered no action. 
   Finally note that in each state only a subset of the list of events has an outbound transition. This is because in each state some events are ignored by the program or simply can not occur. For example, when the buffer gate is in the Faulted state a Downstream Ready message is ignored. In the Waiting state the system does not poll the sensor so the Sensor Poll Clear event can not occur. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 5 
             
           
           
             
                 
             
             
               SEQUENCE 1 - NORMAL 
             
           
        
         
             
               State 
               Event 
               Response (Action) 
             
             
                 
             
             
               None - program 
               Initialization 
               (none) 
             
             
               not activated 
             
             
               Inactive 
               Transport Start 
               Send Ready Message 
             
             
               Ready 
               Transport Stop 
               (none) 
             
             
               Inactive 
               Transport Start 
               Send Ready Message 
             
             
               Ready 
               Statement Message 
               (none) 
             
             
               Waiting 
               Statement Arrival 
               Send Statement Message 
             
             
                 
               [Downstream Ready, 
             
             
                 
               Sensor Blocked] 
             
             
               Ready 
               Statement Message 
               (none) 
             
             
               Waiting 
               Statement Arrival 
               Close Gate 
             
             
                 
               [Downstream Stopped, 
             
             
                 
               Sensor Blocked] 
             
             
               Holding 
               Transport Stop 
               (none) 
             
             
               Stopped 
               Transport Start 
               (none) 
             
             
               Holding 
               Downstream Ready 
               Open Gate, Send Statement 
             
             
                 
                 
               Message, Send Ready 
             
             
                 
                 
               Message 
             
             
               Ready 
             
             
                 
             
           
        
       
     
   
   For Sequence 2, 
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 6 
             
           
           
             
                 
             
             
               SEQUENCE 2 - STATEMENT FAILS TO ARRIVE AT GATE 
             
           
        
         
             
                 
               State 
               Event 
               Response (Action) 
             
             
                 
                 
             
             
                 
               Ready 
               Statement Message 
               (none) 
             
             
                 
               Waiting 
               Statement Arrival 
               Display Error 
             
             
                 
                 
               [Downstream Ready, Sensor 
             
             
                 
                 
               Clear] 
             
             
                 
               Inactive 
             
             
                 
                 
             
           
        
       
     
   
   For Sequence 3, 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 7 
             
           
           
             
                 
             
             
               SEQUENCE 3 - STATEMENT REMOVED FROM GATE 
             
           
        
         
             
               State 
               Event 
               Response (Action) 
             
             
                 
             
             
               Ready 
               Statement Message 
               (none) 
             
             
               Waiting 
               Statement Arrival 
               Send Statement Message 
             
             
                 
               [Downstream Ready, Sensor 
             
             
                 
               Blocked] 
             
             
               Ready 
               Statement Message 
               (none) 
             
             
               Waiting 
               Statement Arrival 
               Close Gate 
             
             
                 
               [Downstream Stopped, 
             
             
                 
               Sensor Blocked] 
             
             
               Holding 
               Sensor Poll Clear 
               Display Error 
             
             
               Inactive 
             
             
                 
             
           
        
       
     
   
   For Sequence 4, 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 8 
             
           
           
             
                 
             
             
               SEQUENCE 4 - GATE CONTENTS UNKNOWN 
             
           
        
         
             
               State 
               Event 
               Response (Action) 
             
             
                 
             
             
               Ready 
               Statement Message 
               (none) 
             
             
               Waiting 
               Statement Arrival 
               Send Statement Message 
             
             
                 
               [Downstream Ready, Sensor 
             
             
                 
               Blocked] 
             
             
               Ready 
               Statement Message 
               (none) 
             
             
               Waiting 
               Statement Arrival 
               Close Gate 
             
             
                 
               [Downstream Stopped, 
             
             
                 
               Sensor Blocked] 
             
             
               Holding 
               Path Error 
               (none) 
             
             
               Faulted 
               Sensor Poll Clear 
               (none) 
             
             
               Inactive 
             
             
                 
             
           
        
       
     
   
   Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”