Abstract:
In a mailpiece stacking system, a pressure pad is used to direct incoming mailpieces from a mailing machine used with the system onto a feed deck, where the mailpieces are stacked against a stacking wall in the system. To properly handle mailpieces including window envelopes, the length of the pressure pad is selected in accordance with the invention such that it effectively deflects each mailpiece to land beyond the window part of any window envelope preceding thereto on the feed deck. Advantageously, the risk of having the mailpiece getting caught by an edge of the window part, resulting in a congestion, is avoided. In addition, among other things, a catch nub is included in the pressure pad for hooking onto a stub shaft mounted on the frame of the system. The nub hooks onto the stub shaft when the pressure pad is raised to allow it to stay in the raised position. Moreover, to effectively attach the stacking system to the mailing machine, the stacking system provides thereunder a hook having a C-shaped opening. The hook is used to be slidably engaged with a support knob underneath the mailing machine through the opening. The resulting engagement aligns the mailing machine with the stacking system to allow proper feeding of the mailpieces from the mailing machine to the stacking system, notwithstanding the vibrations occasioned by the operation of the mailing machine and the stacking system.

Description:
FIELD OF THE INVENTION 
     The present invention relates to stacking systems and methods, and more particularly to systems and methods for stacking mailpieces processed by a postage meter or franking machine. 
     BACKGROUND OF THE INVENTION 
     Use of a postage meter to frank postage on mailpieces is ubiquitous. A stacking system is often used to efficiently assemble the mailpieces after they are processed by the postage meter. One such stacking system is disclosed in U.S. Pat. No. 5,615,995, issued Apr. 1, 1997 to Nobile et al. (hereinafter “the Nobile patent”), which is hereby incorporated by reference. 
     Specifically, the Nobile stacking system uses a pressure pad to direct mailpieces received from the postage meter onto a set of conveyance belts in the system to cause consecutive mailpieces to be arranged in a shingled overlapped relationship. The pressure pad is also used to exert force on the mailpieces to ensure feeding contact between the mailpieces and the conveyance belts. The conveyance belts transport the shingled mailpieces toward a stacking wall against which the mailpieces are pushed upwardly to form a stack. 
     SUMMARY OF THE INVENTION 
     Although it is advantageous to use a pressure pad in a stacking system, e.g., the Nobile stacking system, to help assemble mailpieces, it has been recognized that a prior art pressure pad actually causes problems in certain applications. One such problem arises when the prior art pressure pad is used in a stacking system collecting mailpieces that include window enveloped mailpieces, hereinafter simply referred to as “window envelopes.” In particular, in assembling a stream of mailpieces, the prior art pressure pad deflects each mailpiece at such a sharp angle that its leading edge would land on the window part of any window envelope preceding the mailpiece. Consequently, the mailpiece gets caught by an edge of the window of the window envelope as the mailpiece and the window envelope are being pushed against the stacking wall. The mailpiece that gets caught invariably causes a congestion in the midstream of the mailpieces to be assembled, resulting in a disheveled pile at best. A prolonged congestion causes spilling of the succeeding mailpieces over the stacking system. Some of the mailpieces may even be deflected at the congestion off the stacking system, especially when the stacking system operates at a high speed. Disadvantageously, using the stacking system with the prior art pressure pad, the mailpieces to be assembled may get lost because of the spillover and/or deflection. 
     Thus, in accordance with the invention, the length of a pressure pad is selected such that the end thereof extends past the leading window edge of a deflected window envelope as it lands on the conveyance belts. As such, the leading edge of a succeeding mailpiece deflected by the pressure pad would land beyond the leading window edge of the window envelope, thereby effectively averting any unwanted congestion described above. 
     Another problem with the prior art pressure pad is that it causes mailpieces to be unevenly distributed by the conveyance belts. This problem stems from the fact that the prior art pressure pad comes in contact with the mailpieces on the conveyance belts too soon, before the last mailpiece deflected by the pressure pad fully settles on the conveyance belts. 
     Thus, in accordance with an aspect of the invention, a friction causing connector, e.g., a washer having coarse surfaces, is applied to the connection of the pressure pad to the stacking system for delaying the pressure pad from contacting the mailpieces until after the last deflected mailpiece fully settles on the conveyance belts. 
     It has also been recognized that a mailpiece stacking system, when used with a postage meter, normally needs to be manually attached to a mailing machine incorporating the postage meter. Such an attachment needs to be simple and convenient, without having to lift the mailing machine, which is significantly heavy. At the same time, the attachment needs to afford proper alignment of the stacking system with the mailing machine to allow efficient feeding of mailpieces from the mailing machine to the stacking system. In addition, such an alignment needs to withstand vibrations caused by the operation of the stacking system and the mailing machine. 
     Thus, in accordance with another aspect of the invention, a connector is provided underneath the stacking system for attaching it to the mailing machine. The connector, e.g., a hook having a C-shaped opening, is used to slidably and snugly hook onto a support knob on the underside of the mailing machine through the opening. Advantageously, using the inventive arrangement, the stacking system can be attached to, and thereby aligned with, the mailing machine on the same support surface without having to lift the mailing machine. Because of the tight fit of the hook onto the support knob, the risk of the stacking system and the mailing machine becoming misaligned due to vibrations occasioned by their operation is reduced. 
     Many mailing machines provide the option of printing out postage marked labels for putting onto bulk size mailpieces that are too large to be processed by the machines. When a prior art stacking system, e.g., the Nobile stacking system, is used with such mailing machines generating the postage marked labels, the pressure pad therein would peel the labels off their backing upon contacting the labels. Thus, it may be desirable to operate the stacking system with the pressure pad being raised when labels are generated, thereby preventing the pressure pad from contacting the labels. 
     Thus, in accordance with yet another aspect of the present invention, the pressure pad provides a catch nub for engaging with a stub shaft, mounted on the frame of the stacking system, when the pressure pad is raised to maintain its raised position. Preferably, the catch nub has a gradual angular surface such that it can be easily disengaged from the stub shaft with a mild downward force on the pressure pad. Accordingly, the pressure pad can readily be returned to the normal operative position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing, 
     FIG. 1 is a perspective view of a stacking system in accordance with the invention for use with a typical mailing machine; 
     FIG. 2A provides a cross-sectional view of the stacking system of FIG. 1 taken from its inlet, where mailpieces enter; 
     FIG. 2B illustrates a mechanism for receiving mailpieces at the inlet of the stacking system; 
     FIG. 3 illustrates the range of pivotal movement of the pressure pad in accordance with the invention; 
     FIG. 4A provides a top view of the stacking system processing a window envelope; 
     FIG. 4B illustrates a relationship between the pressure pad and the window envelope in accordance with the invention; 
     FIG. 5A illustrates the connection of the pressure pad to the stacking system; 
     FIG. 5B provides a side view of the pressure pad; 
     FIG. 5C illustrates an interaction at the connection between the pressure pad and the stacking system; and 
     FIG. 6 illustrates a mechanism whereby the stacking system is attached to the mailing machine, in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates stacking system  10  embodying the principles of the invention for assembling mailpieces processed by mailing machine  15  of conventional design. Mailing machine  15  includes postage meter  20  and feed base  25 . In a conventional manner, mailpieces to be processed are fed by feed rollers  30  and  35  along feed deck  40  on feed base  25  through postage meter  20  for printing appropriate postage marks on the mailpieces as evidence of payment of postage. It should be noted that mailing machine  15  is shown for illustration purposes only, and that other mail processing machines, of various sizes and models, may be used in its place with stacking system  10 . 
     As shown in FIG. 1, stacking system  10  comprises elongate frame  45  on which operable components of stacking system  10  are mounted. Mailpieces are ejected seriatim from outlet  50  of mailing machine  15  into inlet  55  of stacking system  10 . In accordance with an aspect of the invention, guide wheels  60  and  62  (guide wheel  62  shown in FIG. 2A but not in FIG. 1) are used to receive and align the incoming mailpieces onto upper feed deck portion  65  through tongue  70  into the nip between feed roller  75  and pressure roller  80 . 
     The mailpieces are pulled by feed roller  75  from upper feed deck portion  65  through the nip between feed roller  75  and pressure roller  80 . Parallel conveyance belts  90 ,  92 , and  94  extend over the length of lower feed deck portion  85  for receiving the mailpieces that emerge from the nip between rollers  75  and  80 . Conveyance belts  90 ,  92 , and  94  transport the mailpieces from upstream to downstream in direction A toward stacking wall  100 . Pressure pad  105 , pivotally connected to housing portion  110  of frame  45 , extends along a portion of conveyance belts  90 ,  92 , and  94 . Pressure pad  105  controllably deflects mailpieces exiting the nip between rollers  75  and  80  down onto conveyance belts  90 ,  92 , and  94 . Pressure pad  105  also exerts generally vertical force on the mailpieces disposed on conveyance belts  90 ,  92 , and  94  to effectively urge the mailpieces into contact with conveyance belts  90 ,  92 , and  94  to be transported thereby. Stacking wall  100  is disposed at the downstream end of feed deck portion  85  against which the mailpieces are stacked in a generally upward angle. For accommodating mailpieces of different size and thickness, stacking wall  100  may be pivotally and/or laterally movable. 
     FIG. 2A provides a view of inlet  55  of stacking system  10  taken from the line  2   a — 2   a  of FIG.  1 . FIG. 2B is a cross-sectional view through housing portion  110  over feed deck portion  65  of stacking system  10  taken from the line  2   b — 2   b  of FIG.  2 A. Guide wheels  60  and  62  are disposed on opposite sides across inlet  55  and biased downwardly to exert force onto an incoming mailpiece to ensure proper horizontal alignment of the incoming mailpiece as described before. 
     Feed roller  75  and pressure roller  80  are arranged in a driving engagement where feed roller  75  pulls the incoming mailpiece forward. Feed roller  75  is driven by a drive mechanism of conventional design, which is housed within frame  45 . It is important to note that a mailpiece ejected from mailing machine  15  maintains a propagation speed, and the circumferencial speed, rω, of roller  75  as driven is higher than such a propagation speed to create a pull on the mailpiece, where r and ω represent the radius and the angular velocity of roller  75 , respectively. Multiple projections (a representative one of which is denoted  117  in FIGS. 2B and 3) extend outward in the radial direction slightly beyond the periphery of feed roller  75 . Such projections are used to forcibly urge the trailing edge of the mailpiece downwardly towards conveyance belts  90 ,  92 , and  94  as the mailpiece exits from the nip between rollers  75  and  80 . 
     In order to accommodate oversize mailpieces, it is preferable to incorporate three conveyance belts  90 ,  92 , and  94  parallel to one another, as shown in FIG.  1 . It is important that the upstream end of conveyance belts  90 ,  92 , and  94  extend to the point where the leading edge of a mailpiece exits the nip between rollers  75  and  80 . This ensures that the leading edge of the mailpiece lands on conveyance belts  90 ,  92 , and  94 . The downstream end of conveyance belts  90 ,  92 , and  94  terminates close to stacking wall  100  to ensure that mailpieces lying on conveyance belts  90 ,  92 , and  94  are fully transported up to stacking wall  100 . Conveyance belts  90 ,  92 , and  94  are also driven by the aforementioned drive mechanism. The linear velocity of conveyance belts  90 ,  92 , and  94  is considerably less than that of a mailpiece exiting the nip between rollers  75  and  80  so that mailpieces landing on conveyance belts  90 ,  92 , and  94  would form a shingled overlapped relationship with one another. 
     To further ensure that the mailpieces land on conveyance belts  90 ,  92 , and  94  in a shingled overlapped relationship, it is necessary to prevent mailpieces from being transported by belts  90 ,  92 , and  94  too far downstream before a succeeding mailpiece reaches belts  90 ,  92 , and  94 . To that end, an optical switch is used for controlling the drive mechanism driving roller  75  and belts  90 ,  92 ,  94 . The drive mechanism is activated only when mailpieces are being ejected from mailing machine  15 , triggering the optical switch. 
     FIGS. 2A and 2B show the optical switch, comprising tongue  70 , light generator  120 , and optical sensor  122 . Light generator  120  and optical sensor  122  are hidden under the surface of feed deck portion  65 . Light generator  120  faces optical sensor  122  across opening  125  such that an optical beam generated by light generator  120  would be received by optical sensor  122 , provided that the optical beam is not blocked. In fact, when the optical switch is in the normal “off” position, such a light beam is blocked by tongue  70 . The latter, made of opaque plastic material, is pivotally connected to housing portion  110  and extends therefrom down into opening  125 . Such a pivotal connection allows tongue  70  to pivot between a light-blocking position, corresponding to the “off” position of the optical switch (shown in solid lines in FIG.  2 B), and a non-light-blocking position, corresponding to the “on” position of the optical switch (shown in dash-dotted lines). Tongue  70  is normally biased towards the light-blocking position. During operation, the leading edge of a mailpiece ejected from mailing machine  15  pushes tongue  70 , thereby unblocking the beam from generator  120  to sensor  122 . As soon as sensor  122  detects the beam across opening  125 , the optical switch causes the drive mechanism to be activated. 
     Tongue  70  is urged back to the light-blocking position as the trailing edge of the last mailpiece is no longer in contact with tongue  70 . Accordingly, the drive mechanism is deactivated by the optical switch at the end of a predetermined delay period after tongue  70  returns to the light-blocking position. Deactivating the drive mechanism at the end of the aforementioned delay period ensures that proper spacing of the shingled overlapped relationship between consecutive mailpieces is maintained, independent of the rate at which mailpieces are ejected from mailing machine  15 . It should be noted that due to the design that light generator  120  and sensor  122  are hidden from the surface of feed deck portion  65 , interference by ambient light with, or blockage by dust of, the light beam in the optical switch is desirably averted. 
     Referring to FIG. 3, pressure pad  105  is pivotally connected to housing portion  110  of frame  45 . This allows pressure pad  105  to pivot between the normal operative position, shown in solid lines, and the raised position, shown in dash lines, for reasons set forth below. When pressure pad  105  is in the normal operative position, it is disposed at an angle to the plane of conveyance belts  90 ,  92 , and  94  (shown in FIG.  1 ). Pad  105  intercepts mailpieces exiting from the nip between rollers  75  and  80  and controllably deflects the leading edges of the mailpieces downwardly toward conveyance belts  90 ,  92 , and  94 . 
     It has been recognized that a prior art pressure pad presents substantial problems when it is used to direct mailpieces which include window envelopes in the stacking system, e.g. system  10 . In particular, in assembling a stream of mailpieces, the prior art pressure pad deflects each mailpiece at such a sharp angle that its leading edge would land on the window part of any window envelope preceding to the mailpiece. Consequently, the mailpiece gets caught by an edge of the window of the window envelope as the mailpiece and the window envelope are being pushed up against stacking wall  100 . The mailpiece that gets caught invariably causes a congestion in the midstream of the mailpieces to be assembled, resulting in a disheveled pile at best. A prolonged congestion causes spilling of the succeeding mailpieces over stacking system  10 . Some of the mailpieces may even be deflected at the congestion off stacking system  10  especially when system  10  operates at a high speed. Disadvantageously, using stacking system  10  with the prior art pressure pad, the mailpieces to be assembled may get lost because of the spillover and/or deflection. 
     In accordance with the invention, a pressure pad, e.g., pressure pad  105 , of a selected length is used. FIG. 4A is a top view of stacking system  10  showing the position of window envelope  140  after it is deflected by pad  105  onto feed deck portion  85 . The length of pressure pad  105  is selected such that the end thereof, denoted  142 , extends past leading window edge  145  of window envelope  140 . Thus, shown in FIG. 4B, which provides a view taken from line  4   b — 4   b  of FIG. 4A, projection  147  of pressure pad  105  onto feed deck portion  85  extends beyond leading window edge  145  of window envelope  140  in accordance with the invention. As such, the leading edge of the succeeding mailpiece deflected by pad  105  would land beyond leading window edge  145 , thereby effectively averting any unwanted congestion described above. 
     In addition, it has been recognized that the prior art pressure pad causes mailpieces to be unevenly distributed by conveyance belts  90 ,  92 , and  94 , stemming from the fact that the prior art pressure pad comes in contact with the mailpieces too soon, before the last mailpiece ejected from roller  75  fully settles on portion  85 . Referring to FIGS. 3,  5 A,  5 B, and  5 C, in accordance with the invention, a friction-causing connector, e.g., washer  147  having coarse surfaces, is connected between housing portion  110  and at least one of connecting members  150  and  155  of pressure pad  105  to increase, by a controllable amount, the friction of the pivotal connection of pressure pad  105  to housing portion  110 . As a mailpiece impacts pressure pad  105  and is deflected thereby onto portion  85 , pad  105  is temporarily pushed up to form a small gap between its end  142  and the shingled mailpieces already on portion  85 . The increased friction caused by washer  147  delays pressure pad  105  from landing back on the mailpieces until after the just deflected mailpiece has substantially settled on portion  85 , thereby allowing the mailpieces to align properly and correcting the uneven distribution described above. 
     The mechanism for controllably urging pressure pad  105  against mailpieces on portion  85 , which involves interactions between protruding arm  160 , stub shaft  162 , a torsion spring (not shown), and finger button  165  (shown in FIGS.  1  and  3 ), is fully described in the Nobile patent, and its description is thus omitted here. It is sometimes desirable to operate stacking system  10  with pressure pad  105  being raised (shown in a dash line position in FIG.  3 ). One such occasion is when stacking system  10  is fed with postage labels generated by mailing machine  15 . Many mailing machines provide the option of printing postage marks on labels for putting onto bulk size mailpieces which are too large to be processed by the machines. When a prior art stacking system, e.g., the Nobile stacking system, is used with such mailing machines generating the postage marked labels, the pressure pad therein would peel the labels off their backing upon contacting the labels. Thus, it may be desirable to operate the stacking system with the pressure pad being raised when labels are being generated, thereby preventing the pressure pad from contacting the labels. 
     In accordance with the invention, protruding arm  160 , as shown in FIG. 5B, provides pointed nub  167  to form a serrated surface on arm  160 . FIG. 5C shows a side view of a pivotal connection of pressure pad  105  to housing portion  110 , with both the solid line operative position and dash line raised position of pad  105  shown. When pad  105  is in the raised position, protruding arm  160  extends over and around stub shaft  162  to engage pointed nub  167  with stub shaft  162 , thereby maintaining the raised position. It should be noted that pointed nub  167  has a selected sharpness so that nub  167  can readily be disengaged from stub shaft  162  to return pressure pad  105  to the operative position. 
     It has also been recognized that a mailpiece stacking system, e.g., system  10 , typically needs to be manually attached to a mailing machine, e.g., machine  15 , to process mailpieces. However, such an attachment needs to be simple and convenient, without having to lift mailing machine  15 , which is significantly heavy. At the same time, the attachment needs to afford proper alignment of stacking system  10  with the mailing machine  15  to allow efficient feeding of mailpieces from machine  15  to system  10 . In addition, such an alignment needs to withstand vibrations caused by the operation of system  10  and machine  15 . 
     Referring to FIG. 6, foot stand  170  in accordance with the invention is placed underneath stacking system  10  for attaching system  10  to mailing machine  15  by its base  25 . Stand  170  provides holes  172  and  174  for accommodating support knobs  180  and  182  of stacking system  10 , respectively. In accordance with the invention, stand  170  also provides a connector, e.g., hook  185  having a C-shaped opening, at the inlet end of stacking system  10 . Hook  185  is used to engage with support knob  190  located at the outlet end of mailing machine  15 . Operatively, stacking system  10  is put on top of stand  170  by coinciding holes  172  and  174  with support knobs  180  and  182 , respectively. By pushing the inlet end of stacking system  10  towards the outlet end of mailing machine  15  on the same support surface until hook  185  snugly hooks onto support knob  190  through the C-shaped opening, system  10  is attachably aligned with machine  15 . Advantageously, using the inventive arrangement, stacking system  10  can be attached to, and thereby aligned with, mailing machine  15  on the same support surface without having to lift machine  15 . Because of the tight fit of hook  185  onto support knob  190 , the risk of system  10  and machine  15  becoming misaligned due to vibrations occasioned by their operation is reduced. In an alternative embodiment, holes  195  and  200  accommodate the support knobs of a riser unit (not shown) that can be put between stacking system  10  and stand  170 . This riser unit would allow stacking system  10  to be evenly connected to a taller mailing machine. 
     The foregoing merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise numerous other arrangements which embody the principles of the invention and are thus within its spirit and scope.