Patent Publication Number: US-6663104-B2

Title: Method and system for aligning moving sheets

Description:
TECHNICAL FIELD 
     The present invention relates to an envelope inserting machine and, more particularly, to a method and device for aligning enclosure materials, which are released from enclosure feeders and collated into a stack to be inserted into an envelope for mailing. 
     BACKGROUND OF THE INVENTION 
     In an inserting machine for mass mailing, there is a gathering section where enclosure material is gathered before it is inserted into an envelope at an envelope insertion area. The gathering section is sometimes referred to as a chassis subsystem, which includes a gathering transport with pusher fingers rigidly attached to a conveyor belt and a plurality of enclosure feeders mounted above the transport. If the enclosure material contains many documents, these documents must be separately fed from different enclosure feeders. 
     Inserting machines are well-known. For example, U.S. Pat. No. 4,501,417 (Foster et al.) discloses an inserter feeder assembly for feeding enclosures; U.S. Pat. No. 4,753,429 (Irvine et al.) discloses a collating station; and U.S. Pat. No, 5,660,030 (Auerbach et al.) discloses an envelope inserter station wherein envelopes are separately provided to an envelope supporting deck where envelopes are spread open so as to allow enclosure materials to be stuffed into the envelopes. 
     An exemplary inserting machine is shown in FIG.  1 . As shown, an inserting machine  10  typically includes a gathering section  12  an envelope feeder/inserter station  14 . The gathering section  12  includes a plurality of enclosure feeders  20  for separately releasing documents  100 . The released documents are pushed toward the envelope feeder/inserter station  14  by a plurality of pusher fingers  30 , which are attached to an endless chain  32  for movement. As shown, the document  100  released by a respective enclosure feeder  20  lands on a tray  24  and then pushed off the tray  24  by an approaching pusher finger  30  onto a deck  40 . As the pusher fingers  30  move forward, they collect more released documents  100 . When the released documents  100 , pushed by the pusher fingers  30 , reach the envelope feeder/inserter station  14 , they are collated into a stack (collation)  110  comprising of a plural of sheets. Thus, the gathering section  12  can also be referred to as a sheet collator. The envelope feeder/inserter station  14  includes an envelope feeder  22  positioned above an envelope insertion area  16  for releasing one envelope  200  at a time so that the stack  110  can be inserted in the released envelope  200  (see FIG.  2 ). Usually, the enclosure feeders  20  are arranged and aligned such that the released documents  100  are supposed to line up with each other when are collated into a stack  110 . However, when a document  100  is released onto the tray  24 , as shown in FIG. 2, it may not land at a designated position. It may be skewed to one side or another. Thus, even though the trailing edge of the document, where the document is pushed by the pusher finger, can be automatically aligned with the trailing edge of other documents in the stack, the side edges of the document may not be aligned with the side edges of the other documents in the stack. This may cause a problem when the stack is inserted into the envelope. 
     Thus, it is advantageous and desirable to provide a method and system for aligning the documents in a stack prior to the insertion of the documents into an envelope. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to align the side edges of a plurality of sheets in a moving stack or collation. The object can be achieved by providing a pair of alignment devices positioned at opposite side of the moving stack to push the side edges of the sheets toward a center line of the deck of a gathering section in an inserting machine. 
     Accordingly, the first aspect of the present invention is an alignment system for aligning a stack having a stack width and containing a plurality of sheets, each sheet having a leading edge and two opposing side edges defining a sheet width smaller than the stack width, wherein the stack is moved along a path in a moving direction toward a downstream end. The alignment system comprising: a pair of alignment devices located at opposite sides of a center line of the path near the downstream end for pushing the opposing side edges of the sheets toward the center line, wherein each alignment device comprises a cam having an outer surface with at least one section thereof having a non-constant radius, and wherein the outer surfaces face each other to define a gate having a gate width, and a mechanism to cause the cams to rotate synchronously with respect to each other in opposite directions to change the gate width such that the gate width is greater than the stack width when the leading edge of the sheets moves into the gate, and the gate width is reduced after the leading edge has passed the gate until the gate width is substantially equal to the sheet width so as to cause the side edges of the sheets in the stack to be aligned with each other. 
     Preferably, each of the cams is mounted on a shaft, and the alignment system further comprises a mechanism to relocate the shafts relative to each other to adjust the gate width according to the sheet width. 
     Preferably, the outer surface of the cams is spiral in shape. It is also possible that the outer surface of the cams is circular in shape and each cam is rotated about an off-centered axis. It is also possible that each of the cams comprises a first circular disk rotatably mounted on a second circular disk and the cam is caused to rotate about the center of the second circular disk, wherein the outer surface of the cams is the circumference of the first circular disk. Alternatively, each cam is caused to rotate about a rotational axis and the outer surface of each cam comprises two spiral surface sections symmetrically arranged about the rotational axis. 
     Preferably, the sheets are moved at a constant sheet velocity by a moving means, and the cams are operatively linked to the moving means for rotation in synchronism with the movement of the sheets. It is also preferred that the cams are rotated at a constant angular velocity defining a tangential velocity at a point on the outer surface and the tangential velocity is substantially equal to the sheet velocity when the gate width is substantially equal to the sheet width. 
     According to the second aspect of the present invention, a method of aligning sheets in a moving stack having a stack width, wherein each of the sheets has a leading edge and two opposing side edges defining a sheet width smaller than the stack width, and the stack is moved along a path in a moving direction toward a downstream end, the method comprising the steps of: 
     providing a pair of alignment devices located at opposite sides of a center line of the path near the downstream end for pushing the opposing side edges of the sheets toward the center line, wherein each of the alignment device comprises a cam having an outer surface with at least one section thereof having a non-constant radius, and wherein the outer surfaces face each other to define a gate having a gate width; 
     causing the cams to rotate synchronously with respect to each other in opposite directions to change the gate width such that the gate width is greater than the stack width when the leading edge of the sheets moves into the gate, and the gate width is reduced after the leading edge has passed the gate until the gate width is substantially equal to the sheet width so as to cause the side edges of the sheets in the stack to be aligned with each other. 
     Preferably, the sheets are moved at a constant sheet velocity by a moving means and the cams are operatively linked to the moving means for rotation in synchronism with the movement of the sheets, and wherein the cams are rotated in a constant angular velocity. 
     According to the third aspect of the present invention, a sheet collation apparatus having an upstream end and a downstream end, the sheet collation apparatus comprises: 
     a moving mechanism to move a plurality of sheets in a moving path from the upstream end toward the downstream end, wherein each sheet has a leading edge and two opposing side-edges defining a sheet width; 
     means, located along the moving path, for collating the sheets into a stack having a stack width greater the sheet width; 
     a pair of alignment devices located at opposite sides of a center line of the path near the downstream end for pushing the opposing side edges of the sheets in the stack toward the center line, wherein each alignment device comprises a cam having an outer surface with at least a section thereof having a non-constant radius, and wherein the outer surfaces face each other to define a gate having a gate width, and a mechanism to cause the cams to rotate synchronously with respect to each other in opposite directions to change the gate width such that the gate width is greater than the stack width of the sheets when the leading edge moves into the gate, and the gate width is reduced after the leading edge has passed the gate until the gate width is substantially equal to the sheet width so as to cause the side edges of the sheets defining the stack to be aligned with each other. 
     The present invention will become apparent upon reading the description taken in conjunction with FIGS. 3 a - 6 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic representation illustrating a prior art inserting machine. 
     FIG. 2 is a diagrammatic representation illustrating part of the prior art inserting machine as shown in FIG.  1 . 
     FIG. 3 is a diagrammatic representation illustrating the location of the alignment system, according to the present invention, in relation to envelope feeder/inserter station in an inserting machine. 
     FIG. 4 is a diagrammatic representation illustrating the alignment system, according to the present invention. 
     FIG. 5 a  is a diagrammatic representation illustrating the alignment system, when the leading edge of a stack of sheets is moved into the aligning position of the alignment system. 
     FIG. 5 b  is a diagrammatic representation illustrating the alignment system, according to the present invention, when the stack is about halfway through the aligning position of the alignment system. 
     FIG. 5 c  is a diagrammatic representation illustrating the alignment system, according to the present invention, when the stack is almost moved through the aligning position of the alignment system. 
     FIG. 5 d  is a diagrammatic representation illustrating the alignment system, according to the present invention, when the trailing edge of the stack has reached the aligning position of the alignment system. 
     FIG. 5 e  is a diagrammatic representation illustrating the alignment system, according to the present invention, when the stack is completely off the alignment system and a following stack is approaching the aligning position. 
     FIG. 6 a  is a diagrammatic representation illustrating the alignment system having an adjusting mechanism to accommodate the width of sheets. 
     FIG. 6 b  is a diagrammatic representation illustrating the alignment system being used to aligned a stack of sheets with a greater width. 
     FIG. 7 a  is a diagrammatic representation illustrating the preferred embodiment of the cam used in the alignment system, according to the present invention. 
     FIG. 7 b  is a diagrammatic representation illustrating a variation of the cam used in the alignment system, according to the present invention. 
     FIG. 7 c  is a diagrammatic representation illustrating another embodiment of the cam used in the alignment system, according to the present invention. 
     FIG. 7 d  is a diagrammatic representation illustrating yet another embodiment of the cam used in the alignment system, according to the present invention. 
     FIG. 7 e  is a diagrammatic representation illustrating still another embodiment of the cam used in the alignment system, according to the present invention. 
     FIG. 7 f  is a diagrammatic representation illustrating a further embodiment of the cam used in the alignment system, according to the present invention. 
     FIG. 7 g  is a diagrammatic representation illustrating yet another embodiment of the cam used in the alignment system, according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 3 shows the location of the alignment system in relation to the sheet collation section  12  in an inserting machine  10 . The alignment system, according to the present invention is denoted by reference numeral  50 . As shown the alignment system  50  is located in the downstream end. Preferably, the alignment system  50  is linked to the endless chain  32  with coupling mechanism  60 ,  62  so that the alignment system  50  is caused to operate in synchronism with the pusher fingers  30 . 
     FIG. 4 illustrates the arrangement of the alignment system  50  in relation to a moving path of the stacks  110  in the sheet collation section  12 . The moving path is represented by a center line  202 . As shown, each stack  110  is pushed by a pair of pusher fingers  30  toward the downstream end of the collation section  12  with a moving speed V along a moving direction represented by arrow  130 . The separation between adjacent stacks  110  is referred to as a pitch, P. The leading edge and the trailing edge of each are denoted by reference numeral  102  and  104 , respectively. The width of the stack  20  is denoted by SW, which is greater than the width W of the sheets. It should be noted that the width of one stack may be slightly different from the width of another stack. However, the stack width in a typical inserting machine, in general, does not various significantly. The alignment system  50  comprises a pair of cams,  70  and  70 ′, separately mounted on shafts  72  and  72 ′ for rotation. The cams  70  and  70 ′ are positioned at opposite sides of the center line  202 , which is parallel to the moving direction  130 . As shown in FIG. 4, the cams  70  and  70 ′ are caused to rotate synchronously with each other but in opposite directions  140 ,  140 ′. The outer surfaces S and S′ of the cam  70  and  70 ′ face each other to define a gate  52  having a gate width GW. Because the radius curvature of outer surfaces S and S′ varies from one section to another, the gate width GW also varies from one time to another as the cams  70 ,  70 ′ rotate. It is arranged such that when a stack  110  approaches the gate  52 , the gate width GW is sufficiently greater than the stack width SW. When the stack is moving through the gate, the GW is reduced in order to align the sheets in the stack, as shown in FIGS. 5 a - 5   d . However, it is preferred that the gate width GW is not smaller than W while the stack is moving through the gate  52 . After the trailing edge  104  of a stack has passed the gate  52 , the gate width GW can be smaller or greater than, or equal to W. 
     As shown in FIG. 3, it is preferable to link the alignment system  50  to the endless chain  30  for motion. As such, the rotating motion of the cams  70  and  70 ′ can be synchronized with the moving speed V of the pusher fingers  30 . With the cam design as shown in FIG. 4, the cams  70  and  70 ′ are required to rotation by 360 degrees in a time period t=P/V, or the angular velocity of the cams  70  and  70 ′ is equal to 2πV/P. 
     FIGS. 5 a - 5   e  illustrate the principle of sheet alignment method, according to the present invention. As shown in these figures, two stacks  20  and  20 ′ each having three sheets  100 ,  100 ′ and  100 ″ are moved by two sets of pusher fingers  30  toward the downstream ends. The width of the stack  20  is slightly greater than that of the stack  20 ′, but these widths are substantially equal a typical stack width CW. FIG. 5 a  shows when the leading edge  102  of the stack  20  just reaches the gate  52  defmed by the facing outer surfaces S and S′ of the cams  70  and  70 ′. The left side edges of the sheets  100 ,  100 ′ and  100 ″ are denoted by reference numerals  108 ,  108 ′ and  108 ″ respectively. Only the right side edge  106  of the top sheet  100  can be seen in FIG. 5 a . The width of the sheets  100 ,  100 ′ and  100 ″ is denoted by W. As shown, because the gate width GW at this point is sufficiently greater than the stack width SW, the outer surface S of the cam  70  does not touch any of the left side edges  108 ,  108 ′ and  108 ″, and the outer surface S′ of the cam  70 ′ does not touch the right edge  106 . 
     As the cams rotate, the radius of the outer surface S and S′ increases. According, the gate width GW is reduced. After the cams have rotated a quarter turn (from the positions as shown in FIG. 5 a ), the outer surface S of the cam  70  touches the left side-edge  108 ″ of the bottom sheet  100 ″, while the outer surface S′ of the cam  70 ′ touches the right side-edge  106  of the top sheet  100 , as shown in FIG. 5 b.  As the cams rotate further and the gate width GW is reduced further, the outer surface S of the cam  70  pushes the left side-edge  108 ″ of the bottom sheet  100 ″ toward the center line  202 , causing the bottom sheet  100 ″ to move toward the right. At the same time, the outer surface S′ of the cam  70 ′ pushes the right side-edge  106  of the top sheet  100  toward the center line  202 , causing the top sheet  100  to move to the left thereby reducing the stack width to SW′, as shown in FIG. 5 c . At some point during the passage of the stack  20  through the gate  52 , the gate width GW, as defined by points q 1  and q 1 ′ on the outer surfaces S and S′ at this instant, becomes substantially equal to the width W of the sheets  100 ,  100 ′ and  100 ″. The side-edges of the sheets are caused by the outer surfaces S and S′ to align with each other, as shown in FIG. 5 d.  The stack is thus aligned. After that alignment point, the radius of the outer surfaces S and S′ can either remain the same or decrease, until the trailing edge  104  of the stack  20  has passed the gate  52 . The cams  70  and  70 ′, as shown in FIGS. 4-5 c,  are designed such that the radius of the outer surfaces S and S′ remains the same after the alignment of the stack is completed. Accordingly, even after the stack  20  has moved further toward the downstream end, as shown in FIG. 5 e,  the gate width GW is the same as the gate width as shown in FIG. 5 d.  At this instant, the gate width GW is defined by points q 2  and q 2 ′ on the outer surfaces S and S′. This means that the radius R, or the distance from the rotation axis of the cam  70  ( 70 ′) to the outer surface S (S′), is the same from point q 1  (q 1 ′) to point q 2  (q 2 ′), as shown in FIG. 7 a . Accordingly, the tangential velocity of the outer surface S from point q 1  to q 2  is constant. Ideally, the tangential velocity of the outer surface S or S′ from q 1  or q 1 ′ to q 2  or q 2 ′, respectively, is equal to V to avoid slippage. Thus, it is preferred that the radius R (from q 1  to q 2  and from q 1 ′ to q 2 ′) be equal to P/2π. In practice, if the contact between the cams and the side-edges of the sheets in the stack is brief, the tangential velocity of the outer surface S and S′ at the alignment point can be smaller or greater than V. Accordingly, R can be smaller or greater than P/2π. 
     It is preferred that the gate width GW can be adjusted to accommodate sheets of different widths. As shown in FIGS. 6 a  and  6   b,  the rotation shafts  72 ,  72 ′ are mounted to adjustment mechanisms  80 ,  80 ′, respectively, so that they can be relocated to align a narrower stack  20 N, or a wider stack  20 W. The center portion of the stack is supported by a center deck as the stack is pushed by a pair of pusher fingers  30 . 
     FIGS. 7 a - 7   g  shows examples of different cam designs. In FIG. 7 a,  a larger section of the outer surface S has a constant radius R, which is defined as the distance from the rotation axis O to a point on the outer surface S. As shown in FIG. 7 a,  from point q 1  to point q 2 , the radius R is constant. In FIG. 7 b,  the surface section between point q 1  and q 2  is very smaller, as compared to the other section of the outer surface S. The cam, as shown in FIG. 7 a  and  7   b,  having a spiral shape. The cam as shown in FIG. 7 c  is a circular surface with an off-centered rotation axis O. In FIG. 7 d,  the cam is basically one circular disk (with center O′) mounted on another circular disk (with rotation axis O). The cams as shown in FIGS. 7 a - 7   d  are designed to rotate 360 degrees in a time period t=P/V (see FIG.  4 ). The cams as shown in FIGS. 7 e  and  7   g  are designed to rotate 180 degrees in a time period t=P/V. 
     It should be noted that the present invention has been described in conjunction with a sheet collator, wherein a plurality of the sheets are collated into a stack, and a pair of alignment devices positioned on opposite sides of the stack to align the sheets in the stack. The present invention can also be used to align a single sheet, or an item with a substantially constant width, such as an envelope. In a sheet collator as shown in FIGS. 4-5 e,  the distance P between two adjacent stacks is constant and thus it is possible to link the cams to the endless chain to engage the cams in constant and continuous rotating motion. However, in a machine where the stacks are moving in a sporadic manner, it is possible that the cams are caused to rotate differently. For example, the cams can be caused to make a complete cycle to align a stack and pause to wait for the next stack. The cams can be triggered to start the next cycle by one or more sensors that detect the arrival of the next stack. 
     Thus, 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.