Abstract:
A system and method for performing a right angle transfer and for aligning stuffed envelopes in a high speed mail processing inserter system, whereby unwanted timing variation in the aligning process is lessened by using a moving vertical aligning belt as the aligning wall against which envelopes are impacted and aligned.

Description:
TECHNICAL FIELD 
     The present invention relates to an aligning module in a high speed mass mail processing and inserting system. The aligning module ensures that the edges of envelopes, or other articles, in the output subsystem are consistently registered along a plane parallel to a transport direction. Proper registration helps to ensure that an envelope is properly aligned for future processing of the envelope, such as for performing a sealing operation, or for applying postage indicia. 
     BACKGROUND OF THE INVENTION 
     Inserter systems such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Additional, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series and 9 series inserter systems available from Pitney Bowes Inc. of Stamford Conn. 
     In many respects the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation. 
     Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes. 
     An inserter system may typically include a right angle transfer module to perform a 90-degree change of direction of documents flowing through the inserter system. The right angle transfer module allows for different configurations of modules in an inserter system and provides flexibility in designing a system footprint to fit a floor plan. Such a right angle transfer module is typically located after the envelope-stuffing module, and before the final output modules. Right angle transfer modules are well known in the art, and may take many different forms. 
     During processing, envelopes will preferably remain a regulated distance from each other as they a transported through the system. Also, envelopes typically lie horizontally, with their edges perpendicular and parallel to the transport path, and have a uniform position relative to the sides of the transport path during processing. Predictable positioning of envelopes helps the processing modules perform their respective functions. For example, if an envelope enters a postage-printing module crooked, it is less likely that a proper postage mark will be printed. For these reasons it is important to ensure that envelopes do not lie askew on the transport path, or at varying distances from the sides of the transport path. 
     For this purpose, envelopes, or other documents, are typically urged against an aligning wall along the transport path so that an edge of the envelope will register against the aligning wall thereby straightening the envelope and putting it at a uniform position relative to the sides of the transport path. This aligning function may be incorporated into a right angle transfer module, whereby a document may impact against an aligning wall as part of performing a 90-degree change of direction. 
     Typically the envelope edge that is urged against the aligning wall is the bottom edge, opposite from the top flapped edge of the envelope. Thus after coming into contact with the aligning wall and being “squared up,” the envelope travels along the transport path with the left or right edge of the envelope as the leading edge. 
     The action of impacting the bottom edge of the envelope against the aligning wall may also serve the purpose of settling the stuffed collation of documents towards the bottom of the envelope. By settling the collation to the bottom of the envelope it is more likely that no documents will protrude above the top edge of the envelope, and that the envelope flap can be closed and sealed successfully. 
     Current mail processing machines are often required to process up to 18,000 pieces of mail an hour. Such a high processing speed may require envelopes in an output subsystem to have a velocity as fast as 85 inches per second (ips) for processing. At such a high rate of speed, system modules, such as those for sealing envelopes and putting postage on envelopes, have very little time in which to perform their functions. If spacing is not maintained between envelopes the modules may not have time to perform their functions, envelopes may overlap, and jams and other errors may occur. 
     For example, if the space between contiguous envelopes has been shortened, a subsequent envelope may arrive at the postage metering device before the meter has had time to reset, or perhaps even before the previous envelope has left. As a result, the meter will not be able to perform its function on the subsequent envelope before a subsequent envelope arrives. As a result, the whole system may be forced to a halt. At such high speeds there is very little tolerance for variation in the spacing between envelopes. 
     Other potential problems resulting from excess variation in distance between envelopes include decreased reliability in diverting mechanisms used to divert misprocessed mail pieces, and decreased reliability in the output stacking device. Each of these devices have a minimum allowable distance between envelopes that may not be met when unwanted variation occurs while envelopes travel at 85 ips. 
     Jam detection within the aligning module itself may become difficult to manage. Jam detection is based on theoretical envelope arrival and departure times detected by tracking sensors along the envelope path. Variability in the aligner module will force the introduction of wide margins of error in the tracking algorithm, particularly for start and stop transport conditions, making jam detection less reliable for this module. 
     The conventional aligner system described above presents a problem for such a high-speed system because it inherently introduces undesirable variation that can contribute to a failure. As envelopes in a high speed mailing system impact the conventional aligner wall, the impact causes the envelopes to decelerate in a manner that may cause the gap between envelopes to vary as much as +/−30 ms. While such a variation might not be significant in slower machines, this variation can be too much for the close tolerances in current high speed inserter machines. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the problems of the conventional art by providing a deterministic aligner. The aligner is incorporated into a right angle transfer module, whereby an envelope (or other document) to be aligned impacts with an aligner wall during a 90 degree change in direction. A deterministic aligner avoids the uncontrollable variation in envelope position inherent in conventional aligners. Such a deterministic aligner is characterized by having an aligner wall that comprises a vertical moving belt against which envelopes impact. Such an aligner belt preferably moves at the same speed and in the same direction as the desired down stream flow path for the envelopes. It has been found that the impact of an envelope with an aligner wall comprising a moving vertical aligner belt does not cause the same non-deterministic behavior that was undesirable in conventional aligners. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a non-deterministic aligner system. 
     FIG. 2 is a top view of a deterministic aligner system using an aligner belt. 
     FIG. 3 is a view of rollers used in the aligner system. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 depicts a non-deterministic aligner system that does not utilize the aligner belt  40  (FIG. 2) of the preferred embodiment of the invention. FIG. 1 will be used to illustrate the disadvantages of not using an aligner belt as part of the registration wall. 
     Transported envelopes are introduced into the aligner system at an input section  10 . Input section  10  may typically include a belt  11  on which envelopes are carried from a prior module into the aligner system. Initially the envelopes travel in the direction designated “Y,” toward aligner wall  20 . 
     From belt  11 , a transported envelope will be captured by a redirecting transport which, for example, may be comprised of three roller pairs  12 . The redirecting transport changes the direction of transport by 45 degrees in the “X” direction. As seen in FIG. 3, each of roller pairs  12  are “hard-nipped” and include an upper biased idler roller  13  and a corresponding lower driven roller  14 . A normal force is applied by the upper biased rollers  13  which are coupled to a supporting shaft  15  extending from a mounting plate  16 . Each idler roller  13  is rotatably mounted on a pivotal lever arm  17 . A torsion spring is mounted on each shaft  15  and is attached at one end to shaft  15  and at the other end to lever arm  17  so as to bias each idler roller  13  downward against the corresponding lower driven rollers  14 . 
     After having its direction changed by 45 degrees by the redirecting transport, a transported envelope travels to registration wall  20  and aligner rollers  30 , as depicted in FIG.  1 . Upon impact with the registration wall  20 , the envelope can no longer travel in the Y direction. Aligner rollers  30 , working in conjunction with registration wall  20 , cause a transported envelope to travel in the output path direction (designated “X” in FIGS.  1  and  2 ), while at the same time being urged firmly against the registration wall. Aligner rollers  30  are oriented at an angle of 25 degrees relative to the X direction to drive transported envelopes in the flow direction X and against the registration wall. 
     As can be seen in FIG. 3, aligner rollers  30  are “soft-nipped” and each include a roller pair having an upper biased idler roller  31  and a corresponding lower driven roller  32 . The lower driven rollers  32  are angled at twenty-five degrees from transport direction X, and drive in both the X direction and in the Y direction, towards the registration wall  20 . Preferably each idler roller  31  has a spherical configuration and extends partially downward through a circumferential opening formed in a housing  33 . Each housing  33  extends downward from a mounting plate  34 . Within each housing is a spring  35  that is biased between the top surface portion of the spherical roller  31  and the top wall of mounting plate  34  so as to provide the normal force against the corresponding lower driven roller  32 . One of skill in the art will recognize that the arrangement of aligner rollers  30  depicted in the Figures is but one example from a range of aligner transports that may be used in connection with the present invention. 
     In operation, in order to meet the speed requirements of modern inserter systems, stuffed envelopes are transported and processed through the system at 85 inches per second (ips). Thus, when an envelope initially enters the input section  10  of the aligner system it is traveling at 85 ips in the Y direction. For further processing, it is desired that the envelope do a right angle turn as depicted in FIG.  1  and end up traveling in the X direction at 85 ips, with as little variable acceleration and deceleration as possible in between. 
     To achieve this result, roller pairs  12  in the redirecting transport have a surface speed having velocity vectors of 85 ips in both the X direction and in the Y direction. Accordingly, the combined velocity vector of roller pairs  12  is 120 ips at their 45-degree angle. Therefore, an envelope captured by the hard-nipped roller pairs  12  undergoes acceleration in the X direction to 85 ips while continuing in the Y direction at 85 ips. 
     When the envelope reaches aligner rollers  30 , it is desirable to maintain the envelope&#39;s velocity vector of 85 ips in the X direction. Taking into account the 25-degree angle of the rollers towards the Y direction, the surface velocity of aligner rollers  30  is 94 ips (X: 85 ips, Y: 40 ips). The velocity vector of aligner rollers  30  in the Y direction urges the envelopes against the registration wall and achieves alignment of the envelopes. 
     Ideally, the 85 ips transport velocity in the X direction achieved by the hard-nipped rollers  12  is maintained by the soft nipped rollers  30 , and even spacing between subsequent envelopes is maintained. However, it has been observed that upon the impact of an envelope with the registration wall  20  the reactionary force of the registration wall  20  decelerates the envelope in a non-deterministic manner that can disrupt the spacing between envelopes. 
     The reactionary force will include a component opposite the X-direction. This force will depend on the normal force between the registration wall  20  and the envelope and the coefficient of friction (μ) between the envelope and the wall  20 . The reactionary force in the X direction, R X , is the product of the coefficient of friction, μ, and the normal force of the aligner wall on the envelope in the Y direction, R y . In equation form, the force balance is: R x =μR y . 
     The deceleration of an envelope resulting from the impact will also depend on the positioning of the envelope, the angle of the impact, and the coefficient of restitution. For example, an envelope could impact the wall with its bottom edge, or instead, the leading or trailing corner could impact first. Each of these uncontrollable varying circumstances could result in different reactionary forces being exerted on the envelope opposite the X direction. As a result of the varying reactionary forces from the impact of the envelopes with the registration wall  20 , the spacing between envelopes can vary as much as +/−30 ms. 
     With reference to FIG. 2, registration wall  20  can comprise a high coefficient of friction vertical aligner belt  40  to eliminate such unwanted variation in impact reactionary forces. Aligner belt  40  moves at the desired speed of the envelope in the X direction, e.g. at 85 ips for the example above. Because the aligner belt  40  is moving at the same speed as the envelope in the X direction, there is no reactionary force relative to the X direction resulting from the impact of the envelope with the belt. Even if one of the envelope corners first impacts the aligner belt  40 , the resulting translation of the envelope in the X direction is constant. The component of the aligner rollers  30  in the Y direction will continue to urge the envelope to register its bottom edge against the aligner belt  40  as the registration wall. 
     Aligner belt  40  is preferably made from a rubber material having a high coefficient of friction, preferably greater than 1. The aligner belt  40  is thicker than a typical timing belt to help absorb the energy of impact of the envelope, thereby reducing the likelihood of bounce and promoting consistent translation in the X direction. In this preferred embodiment, the rubber belt is approximately ⅛ inch thick, but may vary in a range from {fraction (1/16)} to ¼ inch thick. 
     In the preferred embodiment, the aligner belt  40  is electronically geared to the aligning rollers  30  to provide consistent translation during starting and stopping conditions. The aligner belt  40  may be physically geared to the aligning rollers  30 , or they may be controlled in a manner so as to accelerate and decelerate at the same rate when starting and stopping. 
     Although the invention has been described with respect to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the spirit and scope of this invention.