Abstract:
In a booklet maker or sheet folder wherein one or more sheets are pushed through a nip formed by a pair of crease rolls, a pair of flexible gate members cover the nip while sheets to be folded are being loaded. When the sheets are pushed through the nip, the flexible gate members are displaced, allowing the nip to receive the sheets. Following feeding of the sheets, the flexible gate members spring back to a closed position.

Description:
TECHNICAL FIELD  
       [0001]     The present disclosure relates to automated booklet makers, in which sheets forming a booklet are folded by passing through a pair of crease rolls.  
       BACKGROUND  
       [0002]     Booklet makers are well-known devices for forming folded booklets which are stapled along the crease thereof. It is becoming common to include booklet makers in conjunction with office-range copiers and printers (as used herein, a “copier” will be considered a type of “printer”). In basic form, a booklet maker includes a slot for accumulating signature sheets, as would be produced by a printer. The accumulated sheets, forming the pages of a booklet, are positioned within the stack so that a stapler mechanism and complementary anvil can staple the stack precisely along the intended crease line. In one embodiment, the creased and stapled sheet sets are then pushed, by a blade, completely through crease rolls, to form the final main fold in the finished booklet. The finished booklets are then accumulated in a tray downstream of the crease rolls.  
       PRIOR ART  
       [0003]     U.S. Pat. No. 5,316,280 shows an example of a current practical booklet maker design.  
         [0004]     A multifunction finisher module marketed by Xerox® Corporation as of the filing hereof includes a metal door disposed upstream of the crease rolls of a booklet maker. When sheets to be folded are being loaded into the booklet maker, the door is in a position to prevent sheets from accidentally approaching the nip. Only when the sheets are all loaded into the booklet maker, ready for folding, is the door opened, such as by a servomotor, exposing the nip of the crease rolls.  
       SUMMARY  
       [0005]     According to one aspect, there is provided an apparatus for folding sheets, comprising a first crease roll and a second crease roll, arranged to form a nip therebetween. A first flexible gate member is disposed upstream of the nip along a process direction, the gate member covering the nip. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a simplified elevational view of a finisher module as would be used with a mid-range copier or printer.  
         [0007]      FIGS. 2 and 3  show crease rolls, as would be used in a finisher module, with associated flexible gate members. 
     
    
     DETAILED DESCRIPTION  
       [0008]      FIG. 1  is a simplified elevational view of a “finisher module,” generally indicated as  100 , including a booklet maker, as would be used with an office-range digital printer. Printed signature sheets from the printer  99  are accepted in an entry port  102 . Depending on the specific design of finisher module  100 , there may be numerous paths such as  104  and numerous output trays  106  for print sheets, corresponding to different desired actions, such as stapling, hole-punching and C- or Z-folding. It is to be understood that the various rollers and other devices which contact and handle sheets within finisher module  100  are driven by various motors, solenoids and other electromechanical devices (not shown), under a control system, such as including a microprocessor (not shown), within the finisher module  100 , printer  99 , or elsewhere, in a manner generally familiar in the art. For present purposes what is of interest is the booklet maker generally indicated as  110 .  
         [0009]     Booklet maker  110  defines a “slot” which is here indicated as  112 . Slot  112  accumulates signature sheets (sheets each having four page images thereon, for eventual folding into pages of the booklet) from the printer  99 . Each sheet is held within slot  112  at a level where a stapler  114  can staple the sheets along a midline of the signatures, the midline corresponding to the eventual crease of the finished booklet. In order to hold sheets of a given size at the desired level relative to the stapler  114 , there is provided at the bottom of slot  112  an elevator  116 , which forms the “floor” of the slot  112  on which the edges of the accumulating sheets rest before they are stapled. The elevator  116  is placed at different locations along slot  112  depending on the size of the incoming sheets.  
         [0010]     As printed signature sheets are output from printer  99 , elevator  116  is positioned so that the trailing edge of the output sheets (which would be at the top of slot  112 ) are disposed above crease rolls  10 ,  12 . When all of the necessary sheets to form a desired booklet are accumulated in slot  112 , elevator  116  is moved from its first position to a second position where the midpoint of the sheets are adjacent the stapler  114 . Stapler  114  is activated to place one or more staples along the midpoint of the sheets, where the booklet will eventually be folded.  
         [0011]     After the stapling, elevator  116  is moved from its second position to a third position, where the midpoint of the sheets are adjacent a blade  14  and a nip formed by crease rolls  10  and  12 . The action of blade  14  and crease rolls  10  and  12  performs the final folding, and sharp creasing, of the sheets into the finished booklet. Blade  14  contacts the sheet set along the stapled midpoint thereof, and bends the sheet set toward the nip of crease rolls  10  and  12 , which draw all the sheets in and form a sharp crease. The creased and stapled sheet sets are then drawn, by the rotation of crease rolls  10  and  12 , completely through the nip, to form the final main fold in the finished booklet. The finished booklets are then conducted along path  122  and collected in a tray  124 .  
         [0012]     Of particular interest to the present disclosure is a mechanism associated with the crease rolls  10  and  12 , which are shown in  FIGS. 2 and 3 . As shown in the Figures, crease rolls  10  and  12  generally contact each other along longitudes thereof, shown as nip  16 . When a set of sheets is caused to be creased as described above, the folded set of sheets is first pushed toward nip  16  by motion of blade  14 , and then the folded sheets are drawn through nip  16  by frictional engagement with the crease rolls  10  and  12 .  FIG. 2  shows blade  14  in a first, withdrawn position, where sheets such as S to be folded into a booklet are loaded in slot  112 , upstream of the nip  16  along a process direction.  FIG. 3  shows blade  14  in a second, operative position, where the sheets such as S are pushed toward nip  16  to be creased and folded by crease rolls  10 ,  12 .  
         [0013]     Also shown in  FIGS. 2 and 3  are a first flexible gate member  20 , and a second flexible gate member  22 . The gate members  20 ,  22  are disposed to effectively cover the nip  16  when the blade  14  is in its withdrawn position, as in  FIG. 2 , such as while slot  112  is being loaded with sheets to be stapled and folded. The gate members  20 ,  22  thus prevent the sheets such as S from accidentally approaching nip  16  until all the necessary sheets are loaded into slot  112 .  
         [0014]      FIG. 3  shows the flexible gate members  20 ,  22  after the blade  14  has moved to its operative position and pushed sheets such as S toward nip  16 . The motion of the blade  14  and the sheets such as S displaces the flexible gate members  20 ,  22  so that nip  16  is exposed to accept the sheets for creasing and folding. After the sheets are fed through nip  16 , blade  14  is returned to its withdrawn position, as in  FIG. 2 , and the flexible gate members  20 ,  22  return to the covering position shown in  FIG. 2 , by their own resilient properties.  
         [0015]     In this embodiment, both flexible gate members  20 ,  22  are stationarily anchored within the booklet maker relative to the nip  16 , as opposed to a prior-art design, in which a metal door is selectably moved away from nip  16  by a servomotor or electromagnet. Thus, the embodiment represents a significant cost savings over the prior art.  
         [0016]     The flexible gate members  20 ,  22  are each substantially made of a flexible, resilient material which can provide the necessary “spring back” once the flexible gate members  20 ,  22  are displaced by sheets riding on blade  14 . One possible material for flexible gate members  20 ,  22  is DuPont® Mylar®. In an alternate embodiment, relatively rigid, door-like gate members can be provided, which are springably mounted within the booklet maker; in such a case, the flexible quality of the gate members is provided by the mountings and not by the members themselves, but the practical effect would be the same as in the above embodiment.  
         [0017]     As will be noticed in  FIG. 2 , a portion of the first flexible gate member  20  overlaps a portion of the second flexible gate member  22 , to be in front of the second flexible gate member  22  along the process direction. This small overlap helps in preventing sheets such as S entering slot  112  from getting caught in any gap between flexible gate members  20 ,  22 . To ensure that the overlap is maintained every time the flexible gate members  20 ,  22  snap back after the blade  14  returns to its withdrawn position as in  FIG. 2 , the first flexible gate member  20  is effectively stiffer than the second flexible gate member  22 . The extra stiffness can be provided by making first flexible gate member  20  thicker that second flexible gate member  22 .