Paper sheet folding device
BACKGROUND OF THE INVENTION AND PRIOR ART 
     The present invention relates to a paper sheet folding device and more particularly to such a device adapted to fold a packet of several paper sheets at one time. 
     A typical construction of such a paper sheet folding device of the prior art is disclosed, for example, by Japanese Utility Model Registration No. 1592186 (Utility Model Publication No. 59-29007). This device comprises a paper feeder mechanism, a folding plate provided with an adjustably movable stopper and a pair of folding rollers. The paper sheet is fed by the paper feeder mechanism to the folding plate in such manner that the forward end thereof comes in contact with the stopper of said folding plate to be flexed, then the flexed portion of the paper sheet is grasped between the folding rollers to fold the paper sheet. 
     The device of the prior art as has been described above cannot be used to fold a packet of paper sheets because its paper feeder mechanism is not adapted to feed the packet of several paper sheets at once and also because a folding deviation tends to occur between each pair of adjacent paper sheets within each packet when the latter is folded at once. This deviation occurs since a location along which each paper sheet is folded depends upon factors such as the degree of paper sheet flexure and the timing of the paper sheet being grasped by the folding rollers. Thus, this device is certainly suitable for continuously handling a plurality of paper sheets having the same size one by one, but inconvenient when it is desired to fold a packet of paper sheets at once into a predetermined size, as when several letter sheets are folded to be inserted into each envelope. Accordingly, it has been a usual practice to manually fold each packet of letter sheets for insertion into each envelope. However, such a manual operation is extremely troublesome and inconvenient in that the size of each sheet after being folded cannot be uniform within each packet. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome the above-mentioned disadvantages of the prior art by the provision of an improved paper sheet folding device permitting a packet of several paper sheets to be effectively folded at one time into a predetermined size. 
     To achieve the object as set forth above, the device constructed in accordance with the present invention comprises a support member, a pair of folding rollers, delivery means, and a member to drive the delivery means. The support member includes an element adapted to position a paper sheet or a packet of paper sheets along one end. The folding rollers are disposed so that they are closely adjacent to one side of the paper sheet or the packet of paper sheets at a position of the fold to be formed. The delivery means is disposed on the opposite side to the folding rollers, i.e., closely adjacent to the packet on the other side thereof so that said delivery means is movable towards the folding rollers. The driving member is adapted to drive the delivery means towards a position adjacent a line along which the pair of folding rollers come in contact with each other. 
     With the paper sheet folding device constructed in accordance with the present invention as briefly described above, the delivery means is actuated to forcibly flex a paper sheet or a packet of paper sheet towards the contact line of both folding rollers a portion of the paper sheet or packet thus flexed is grasped between the folding rollers so as to fold the paper sheet or the packet of paper sheets. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view illustrating a central part of a triple-folder incorporated with one embodiment of the paper sheet folding apparatus according to the present invention; 
     FIG. 2 is a schematic side view illustrating a drive mechanism of said triple-folder; and 
     FIG. 3 is a schematic side view illustrating a drive mechanism as seen from the opposite side with respect to FIG. 2 but inverted for a better understanding. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to FIG. 1, a support member or folding plate 10 is shown consisting of a pair of partitions which define therebetween a thin and planar space used to set a paper sheet or a packet of paper sheets. This support member 10 is divided into an upper portion and a lower portion at a position corresponding to a line along which the packet is folded in a manner as will be described later. The division is achieved by a pair of openings 12, 14 extending through the associated partitions and defined by respective pairs of edges extending perpendicularly to a plane of the drawing (longitudinally of folding rollers as will be described later). The partitions defining the upper portion of the support member 10 are upwardly flared to form an inlet 16 of paper sheets and downwardly converged to form an inclined planar region 18. The partitions defining the lower portion of the support member 10 are upwardly flared to form a guide region 20 and downwardly converged to form an inclined planar region 22 in alignment with said inclined planar region 18. The lower inclined planar region 22 is provided with a threaded stopper 24 which is adjustably and slidably fixed in a known manner at a desired position so that the forward end of the paper sheet or the packet bears against the stopper 24 and thereby the paper sheet or the packet is aligned and positioned. This stopper 24 includes a sheet detector element 26 using a microswitch or a photosensor. 
     Adjacent the opening 12, there are provided outside the support member 10 a pair of folding rollers, i.e., a driven roller 30 and a follower roller 32, which are mounted on axes extending longitudinally of the opening 12, respectively, and rotatably driven by drive means associated with said axes as will be described later. Adjacent the other opening 14, there is provided outside the support member 10 a small roller serving as delivery means 34 mounted on a free axis also extending longitudinally of the openings 12, 14 for movement towards the folding rollers 30, 32 and adapted to be driven by a driving device associated with said axis in the direction of said movement. On the side of the folding rollers 30, 32 opposite to the support member 10, there is provided a downwardly inclined folding plate 36 of the arrangement as previously mentioned in connection with the prior art and this folding plate 36 also includes a threaded stopper 38 which is adapted to be adjustably and slidably fixed at a desired position in a known manner. A pair of folding rollers associated with the folding plate 36 comprise said driven roller 30 and a follower roller 40 operatively associated therewith. 
     Referring to FIG. 2, an output shaft of an electric motor (not shown) carries a gear 52 coupled via a reduction gear train to a gear 64a which is integral with the driven roller 30. The reduction gear train comprises a large gear 56 coupled via a timing belt 54 to the output gear 52, a small gear 58 coaxial and integral with said large gear 56, and another large gear 62 which is coupled via another timing belt 60 to said small gear 58 and coaxially integral with said gear 64a. The gear 64a is engaged with a gear 66a integral with the follower roller 32, on one side, and with a gear 68a integral with the follower roller 40, on the other side. The gears 66a, 68a are biased by spring members 70a, 72a, respectively, towards the gear 64a. A slot 76a is formed in a housing wall adjacent the drive mechanism to support a shaft 74 for the delivery means or small roller 34. The slot 76a spans both openings 12, 14 of said support member 10 as seen in the side view, permitting an operative movement of the shaft 74 and, therefore, the small roller 34. Adjacent the slot 76a, there is provided a lever 80a adapted to rock around its lower shaft 78 which is integral with said lever 80a. The lever 80a is driven in a manner as will be described later so that said lever 80a may drive the shaft 74 for the small roller 34 using a cutaway 82a formed in its upper portion. The lever 80a is normally biased leftwards as seen in the drawing under an action of a spring 86a suspended between a spring hanger 84a mounted on the housing wall and an upper end of the lever 80a. 
     Referring to FIG. 3, also on this side, a gear 64b integral with the driven roller 30 is engaged with gears 66b, 68b which are integral with the follower rollers 32, 40, respectively. The gears 66b, 68b are biased respectively by springs 70b, 72b into engagement with said gear 64b so as to assure a reliable operation of the folder. A slot 76b is formed in the housing wall to support the shaft 74 for the small roller 34. A lever 80b is provided adjacent this slot 76b. The lever 80b is adapted to rock around an integral lower shaft 78. The lever 80b also includes a cutaway 82b adapted to bear against the shaft 74 under a biasing effect of a spring 86b suspended between a spring hanger 84b mounted on the housing wall and an upper end of said lever 80b. In regard to these aspects, the arrangement of the drive mechanism on this side is in symmetrical relationship with that on the side as shown by FIG. 2. 
     A small gear 88 is coaxially integral with the gear 64b which is, in turn, integral with the driven roller 30. The gear 88 is engaged with a large gear 90 located adjacent the center on this side. A cam 92 is coaxially integral with the large gear 90 and engaged with a roller 94 projecting from the lever 80b. The cam 92 is shown to be in engagement with the roller 94 in the largest diameter region (x) of said cam, urging the lever 80b to its limit position on the right hand in the figure. Therefore, the shaft 74 and the small roller 34 are moved from the driven roller 30 under the influence of gravity of said small roller 34. When the cam 92 is engaged in its smallest diameter region (y) with the roller 94, the lever 80b is released and rotated leftwards in the drawing under the action of the spring 86b and the small roller 34 is urged by the shaft 74 against the driven roller 30. While the cam 92 is engaged in its intermediate diameter region (z) with the roller 94, the lever 80b is maintained at a position slightly rightward with respect to the position at which the lever 80b is maintained when the cam 92 is engaged in its smallest diameter region (y) with the roller 94. During engagement of the intermediate diameter region (z), the small roller 34 is maintained freely spaced from the driven roller 30 under the influence of gravity of said small roller 34. 
     On the opposite side of the lever 80b to the cam 92, there is provided a microswitch 96 including a switch pin (not shown) projecting towards the lever 80b. The drive motor (not shown) continues to operate independently of the position of the microswitch 96 so long as said paper sheet sensor element 26 senses the presence of paper sheets. While the element 26 senses the absence of paper sheets, the drive motor continues to operate so long as the switch pin of the microswitch is kept projecting and is deenergized upon retraction of said switch pin. 
     To perform actual operation of paper sheet folding with the triple folder constructed as has been described above, both the stoppers 24, 38 may be position-adjusted, if desired, according to the sheet size and the folding format in the initial state of the folder. (The respective figures correspond to this initial state) Thereafter, a single paper sheet or a packet of paper sheets may be introduced through the inlet 16 into the support member 10. When the paper sheets bear at their forward ends against the stopper 24 and are thereby properly positioned, the sheet sensor element 26 senses the presence of the paper sheets, actuating the drive motor. Simultaneously, the cam 92 is rotated counterclockwise in the drawing to release the lever 80b and, in consequence, said lever 80b and the lever 80a are rotated under the effect of the associated springs 86b, 86a so as to move the shaft 74 for the small roller 34 leftwards in the drawing along the slots 76a, 76b. 
     Such operation as mentioned above causes, in the central portion of the folder, the small roller 34 to move from the opening 14 to the opening 12 of the support member 10 to forcibly flex the paper sheet or the packet of paper sheets within the support member 10 from the rear side of the packet towards the pair of folding rollers 30, 32. As a result, a flexed portion of the paper sheet or the packet is grasped between the folding rollers 30, 32 and fed towards the folding plate 36 while the paper sheet or the packet is folded between said folding rollers. The upper and lower edges of the opening 12 serve as guide elements for effective flexure of the paper sheet or the packet. The small roller 34 continues to be rotated with the packet held between said small roller 34 and the roller 30 under the effect of the springs 86a, 86b, so long as the cam 92 is engaged at its smallest diameter region (y) with the roller 94. 
     The cam 92 continuously rotates to be engaged at its intermediate diameter region (z) with the roller 94 and during such transition the paper sheet or the packet of paper sheets has been folded on the side of the folding plate 36 in the manner as previously mentioned in connection with the paper sheet folding apparatus of prior art. More specifically, the paper sheet or the packet of paper sheets introduced into the folding plate 36 bears at its forward end corresponding to the fold which has been formed by the rollers 30, 32 against the stopper 38 provided within the folding plate 36. The rollers 30, 32 continue to feed the paper so as to flex the paper in the vicinity of the folding rollers 30, 40, and a flexed portion of the paper sheet or the packet of paper sheets is grasped between these folding rollers 30, 40 to form another fold. Finally, the paper sheet or the packet of paper sheets is folded in a desired threefold configuration and discharged out of the system. Even when the packet of paper sheets is being folded, the occurrence of the folding deviation is negligible, since, within the folding plate 36, the packet of paper sheets has already been folded on the precedent stage and the fold formed on this precedent stage constrains the packet against any significant relative displacement of the paper sheets. 
     The cam 92 is rotated as the above-mentioned folding process progresses, and comes in engagement at its largest diameter region (x) with the roller 94 again as the paper sheet or the packet of paper sheets is discharged out of the system. Thereupon, the lever 80b is rotated to the right and back to its initial position as shown in the drawing. In this position, the rear side of the lever 80b depresses the switch pin of the microswitch 96 to deenergize the drive motor. 
     Although the support member 10 as well as the folding plate 36 have been illustrated to include the respective stoppers 24, 38 in the above-mentioned, embodiment, the triple-folder exclusively used to fold paper sheet(s) of a fixed size into a predetermined form would require neither of these stoppers. The delivery means adapted to forcibly flex paper sheet(s) has been illustrated in the form of a small roller, but this delivery means may also be in the form of blade-like means having a thin edge along its forward end. Furthermore, the starting of the drive motor may be achieved not by the paper sheet sensor element 26 but by manipulating a separate switch button. In this case, the switch button continues to be depressed until rotation of the lever 80b releases the switch pin of the microswitch 96 to project and thereby automatically actuate the drive motor. 
     With the paper sheet folding apparatus according to the present invention, the delivery means forcibly flexes paper sheet(s) perpendicularly to the plane of paper sheet(s) to start the folding process, so that even a packet of several paper sheets can be correctly folded without any significant folding deviation.