Abstract:
A hole punch has a punching unit with a rotatable punch for punching a hole through a paper sheet, a die which is rotatable in synchronism with the punch and a paper transporting device for transporting the paper sheet from an upstream side to a downstream side generally in a specified direction of paper transportation. The transporting device includes a paper supplying device and a paper discharging device respectively on the upstream and downstream side of the punching unit for supplying and discharging the paper sheet towards and away from the punching unit. The paper supplying device has a clamping device for clamping the paper sheet at a distance x 1  away from the punching position where a hole is punched by the punch. The paper discharging device has another clamping device at a distance x 2  away from the punching position. At least one of the distances x 1  and x 2  is made smaller than the distance of the first hole punched through the paper sheet by the punching unit from the front edge of the paper sheet. There is a guide member for a side edge of the paper sheet to slide along as the paper sheet is transported. Oblique clamping devices on the upstream side of the punching unit serve to apply an oblique force on the paper sheet with respect to the direction of paper transportation and to press the paper sheet onto the guide member.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a hole puncher for a sheet of paper. This invention relates in particular to such a hole puncher capable of improving the quality of the punched holes.  
           [0002]    Prior art methods of punching holes include the method of using a rotary punch as partially described in Japanese Patent Publication Tokkai 2000-42994, the method of using a press punch as partially described in Japanese Patent Publication Tokkai 10-7307 and the so-called rotary punch method for punching a hole while causing a punch and a die to rotate through gears. When such methods are used, it is commonly done to align a plurality of punches perpendicularly to the direction in which paper sheets are transported such that a plurality of holes can be punched simultaneously. With such a prior art method, the size of the punch unit can be reduced only within a limited extent because it is comprised of a plurality of punches and the number of holes to be punched at the same time was fixed according to the number of punches in the punch unit.  
           [0003]    In view of the above, it has been attempted to use a punch unit including only one punch and to repeat the punching operation several times while each paper sheet is passed by such that the size of the punch unit can be reduced or to punch a plurality of holes in the direction of transportation of the paper sheet by means of a single punch unit at a fixed position. In such a case, however, the punched hole can be easily torn and burrs are likely to result because the paper sheets tend to flutter. Variations also tend to be large in the position of the punched holes and hence a mechanism is needed for keeping the distance of the hole constant from an edge parallel to the direction of motion of the paper sheet. In summary, it has been difficult to maintain a high quality of punched holes.  
         SUMMARY OF THE INVENTION  
         [0004]    It is therefore an object of this invention to provide a hole puncher and a method of punching holes in paper sheets capable of improving the quality of punched holes.  
           [0005]    A hole puncher according to this invention comprises a punching unit having a rotatable punch for punching a hole through a paper sheet and means for transporting the paper sheet to and from the punching unit. In one aspect of the invention, the hole puncher is characterized in that the paper sheet is prevented from fluttering by means of rollers for transporting the paper sheet positioned appropriately closely to where the punching takes place.  
           [0006]    Explained more in detail, the part of the means for transporting the paper sheet that supplies it to the punching unit may be referred to as a paper supplying device and the part that discharges it from the punching unit may be referred to as the paper discharging device. Both the paper supplying device and the paper discharging device include clamping members such as rollers for clamping the paper sheet in between. Let x 1  and x 2  respectively represent the distance between the punching position where a hole is punched by the punching unit and the position of the clamping members of the paper supplying device and the paper discharging device closest to the punching unit.  
           [0007]    Furthermore, let T 1  be the distance between the position of the first hole punched through the paper sheet by the punch and the front edge of this paper sheet which reaches the punching unit first as the paper sheet is transported to it by the paper supplying means. According to the invention, the hole puncher is characterized wherein least one of x 1  and x 2  is less than T 1 .  
           [0008]    The invention may be characterized alternatively wherein at least one selected from the paper supplying device and the paper discharging device has a clamping device such as rollers disposed away from the punching position by a distance which is less than T 1 .  
           [0009]    The paper transporting means may be controlled such that the speed of transportation by the paper discharging device is greater than that by the paper supplying device and the force of clamping by the paper discharging device may be controlled to be less than that by the paper supplying device so as to suppress the fluttering of the paper sheet as it is punched.  
           [0010]    The hole puncher of this invention may be further characterized in that the rotatable punch is provided with a holder member which may be made of an elastic material for clamping and holding the paper sheet while a hole is punched therethrough and that there is also provided a die which is rotatable in synchronism with the punch. In order to prevent the paper sheet from becoming folded as it is punched, the contact surface of the holder member is made shorter than the die both in the direction of paper transportation and in the perpendicular direction. The opposite surface of the holder member not contacting the paper sheet need not be made smaller than the die because such a surface will not contact the paper sheet and hence will not function to cause the paper sheet to become folded.  
           [0011]    In another aspect of the invention, the hole puncher may be characterized as having a guide member extending in the direction of the paper transportation. Some of the aforementioned means for transporting the paper sheet may be referred to as an oblique clamping devices which may include a cylindrically shaped roller with its shaft oriented not exactly perpendicularly to the direction of paper transportation, or that of the guide member, but obliquely by making a specified angle with the perpendicular direction such that a force in a direction transverse to the direction of paper transportation will be exerted on the paper sheet and the paper sheet will be thereby pushed towards the guide member and its side edge will slide against it as the paper sheet is transported to the punching unit.  
           [0012]    The hole puncher of this invention is further characterized as also including a straight transportation device which may include rollers with shafts extending exactly perpendicularly to the direction of paper transportation, or the guide member, for transporting the paper sheet straight in the direction of the paper transportation. This is disposed closer to the punching unit than any of the other paper transporting devices including the aforementioned oblique clamping devices such that the paper sheet, having been pushed towards the guide member, is caused to reach the punching unit by moving straight in the direction of paper transportation.  
           [0013]    It is preferable that the distance of paper transportation along the specified direction of paper transportation be longer than the length of any paper sheet intended to be used on this hole puncher such that the transverse position of even a paper sheet with the longest admissible length can be corrected towards the guide member and holes can be punched at a position at a specified distance from its side edge.  
           [0014]    With a hole puncher designed as described above according to this invention, a hole can be punched reliably through a paper sheet at an intended position without causing the paper sheet to flutter such that a hole can be punched neatly without unwanted burrs. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a schematic side view of a paper processing apparatus incorporating this invention.  
         [0016]    [0016]FIG. 2 is a front view of the paper processing apparatus of FIG. 1 taken in the direction of arrow S in FIG. 1.  
         [0017]    [0017]FIGS. 3A and 3B, together referred to as FIG. 3, are each a drawing for showing a design for the oblique rollers.  
         [0018]    [0018]FIG. 4 is a schematic side view of the hole punching unit of the paper processing apparatus shown in FIG. 1.  
         [0019]    [0019]FIG. 5 is a diagonal external view of the punch unit of FIG. 1.  
         [0020]    [0020]FIG. 6 is a diagonal view of the punch of FIG. 5.  
         [0021]    [0021]FIG. 7 is another diagonal view of the punch unit of FIG. 1.  
         [0022]    [0022]FIG. 8 is a block diagram of the paper processing apparatus of FIG. 1.  
         [0023]    [0023]FIG. 9 is a detailed side view of the punch unit.  
         [0024]    [0024]FIGS. 10A and 10B, together referred to as FIG. 10, are plan views of paper sheets of different sizes each having three holes punched therein.  
         [0025]    [0025]FIG. 11 is a flowchart for the operation of the paper processing apparatus of FIG. 1.  
         [0026]    [0026]FIGS. 12A, 12B and  12 C, together referred to as FIG. 12, show the punching operation by the punch and the die of the punch unit, respectively showing the moment when the punching is about to start, the time of punching and the moment at the end of the punching operation.  
         [0027]    [0027]FIG. 13 is a detailed flowchart for Step S 3  in the flowchart of FIG. 11.  
         [0028]    [0028]FIG. 14 is a diagram for showing the speed of rotation of the punch in the punch unit of FIG. 7.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    The invention is described next by way of examples. FIG. 1 shows an image forming apparatus  1  and the general structure of a paper processing apparatus  2  making use of a hole puncher according to this invention.  
         [0030]    The image forming apparatus  1  may be a printer, a copier or a facsimile machine. Sheets of paper printed thereby are adapted to be discharged therefrom by means of its discharge rollers  11  towards the paper processing apparatus  2 . A paper sheet discharged through these discharge rollers  11  and received by the paper processing apparatus  2  through its paper receiving opening  12  is shown in FIG. 2 and indicated as P max  (for a large size sheet) or P min  (for a small size sheet) and is adapted to be received with its side edge guided along a guide plate  61  extending in the direction of its transportation. For the convenience of disclosure, FIG. 1 shows the image forming apparatus  1  and the paper processing apparatus as if they were separated. In actual operations, however, they are intended to be attached to each other.  
         [0031]    The paper processing apparatus  2  not only has the paper receiving inlet  12  but also includes a hole punching unit  13  for transporting a paper sheet from the paper receiving inlet  12  and punching holes in it, a motion reversing unit  14  for reversing the direction of motion of the paper sheet, a tray  15  for receiving discharged paper sheets, sensors for detecting paper sheets and rollers for transporting each paper sheet. The sensors include a reversion sensor  21 , a discharge sensor  22  and a tray sensor  23 , each serving to detect a paper sheet being transported along a transportation path where it is installed. The rollers include oblique rollers  41 - 43 , transportation rollers  44 ,  45  and  47 - 49 , and reversion rollers  46  and discharge rollers  50 , each set of rollers consisting of a driver roller (with letter “a” following a numerical indicator) and a follower roller (with letter “b” or “c” following a numerical indicator). Each driver roller is driven by a corresponding motor controlled by a control unit (shown at  142  in FIG. 8) and is made of a highly frictional material such as rubber. Each follower roller is for being pressed against a corresponding one of the driver rollers so as to sandwich a paper sheet in between with a specified pressure and is made of a less frictional material such as a plastic material.  
         [0032]    The hole punching unit  13  is comprised of a punch unit  31  and a series of oblique rollers  41 - 43  and transportation rollers  44  disposed sequentially along a paper transportation path defined between the paper receiving inlet  12  and the punch unit  31 .  
         [0033]    The motion reversing unit  14  is comprised of a transportation roller  45  (consisting of a transportation driver roller  45   a  and transportation follower rollers  45   b  and  45   c ) and a reversion roller  46  (consisting of a semicircular reversion driver roller  46   a  and a reversion follower roller  46   b ). Transportation rollers  47 - 49  (each consisting of a driver roller  47   a ,  48   a  or  49   a  and a follower roller  47   b ,  48   b  or  49   c ) and a discharge roller  50  (consisting of a discharge driver roller  50   a  and a discharge follower roller  50   b ) are sequentially disposed between the motion reversing unit  14  to the tray  15 .  
         [0034]    A paper sheet discharged from the discharge roller  11  of the image forming apparatus  1  is first received through the paper receiving inlet  12  by the oblique roller  41  of the hole punching unit  13  and is then transported to the punch unit  31  by the oblique rollers  42  and  43  and the transportation rollers  44 . Holes are then punched therein by the punch unit  31  (as will be described in detail below) and the punched paper sheet is then transported to the motion reversing unit  14 .  
         [0035]    Inside the motion reversing unit  14 , the paper sheet is moved downward in the downstream direction by means of the transportation driver and follower rollers  45   a  and  45   b . When a specified length of time has passed after the back edge of the paper sheet is detected by the reversion sensor  21  disposed between the hole punching unit  13  and the motion reversing unit  14  the back edge of the paper sheet has passed the position between the transportation driver and follower rollers  45   a  and  45   b , a stopper (not shown) controlling the rotation of the shaft of the reversion driver roller  46   a  is removed by means of a solenoid (shown at  143  in FIG. 8) such that the reversion driver roller  46   a  begins to rotate.  
         [0036]    As explained above, the reversion driver roller  46   a  is semicircularly shaped. As the paper sheet is transported to the reversion driver and follower rollers  46   a  and  46   b  and until its back edge passes their position, the reversion driver roller  46   a  has its straight peripheral portion facing the transportation path and hence does not interfere with the passage of the paper sheet. When the solenoid  143  causes the shaft of the reversion driver roller  46   a  to rotate, the reversion driver roller  46   a  has its arcuate peripheral portion facing the transportation path to cause the paper sheet to be transported in the downstream direction towards the transportation driver and follower rollers  45   a  and  45   c.    
         [0037]    Thereafter, the paper sheet is transported further in the downstream direction by means of the transportation driver and follower rollers  46   a  and  46   c , By these operations of the motion reversing unit  14 , the direction of transportation of the paper sheet is reversed, or its back edge and front edge are reversed. As a result, the top surface of the paper sheet on which an image was formed by the image forming apparatus  1  is now a back surface. The paper sheet is thereafter transported sequentially by means of the transportation rollers  47 - 49  and discharged to the tray  15  by means of the discharge rollers  50 . Right before the discharge rollers  50  is a discharge sensor  22 . As the back edge of the paper sheet being discharged is detected by the discharge sensor  22 , the transportation of the next paper sheet is started.  
         [0038]    Since each paper sheet is flipped over inside the motion reversing unit  14 , paper sheets which are discharged from the image forming apparatus  1  sequentially are piled up in the tray  15  without reversing the sequence. The tray  15  is mobile in the vertical direction by means of a belt (not shown) and a tray motor (shown at  144  in FIG. 8) and moves downward when the top surface of the paper sheets piled up in the tray  15  is detected by the tray sensor  23 .  
         [0039]    [0039]FIG. 2 is referenced next to explain the manner of transporting paper sheets inside the hole punching unit  13 . P min  indicates a paper sheet with a shortest length L min  that can be handled by the paper processing apparatus  2 . P max  indicates a paper sheet with a longest length L max  that can be handled by the paper processing apparatus  2 . In what follows, FIG. 2 will be explained with reference to a paper sheet P with length L such that L min  L L max .  
         [0040]    During the time interval from the moment when the back edge of the paper sheet P leaves the discharge rollers  11  of the image forming apparatus  1  until it enters the transportation rollers  44 , the paper sheets P is transported by the oblique rollers  41 - 43  so as to move along the guide plate  61 . As explained above, each set of the oblique rollers  41 - 43  consists of a driver roller  41   a ,  42   a  or  43   a  and a follower roller  41   b ,  42   b  or  43   b . Since all these oblique rollers  41 - 43  are structured alike, the oblique rollers  41  will be described in detail next with reference to FIG. 3.  
         [0041]    The oblique follower roller  41   b  may be set obliquely, with a small angle θ (such as 7.5°) from the direction of transportation of the paper sheets, as shown in FIG. 3A. The corresponding driver roller  41   a  is set normally, parallel to the direction of transportation. Thus, the paper sheet P in between is pressed onto the obliquely set follower roller  41   b  as it is driven by the driver roller  41   a . In other words, the paper sheet P is transported by the principal force F 1  in the direction of transportation by being pressed against the driver roller  41   a  but since the follower roller  41   b  is tilted, there is a perpendicular (or transverse) component of force F 2 , and the motion of the paper sheet P is corrected towards the guide plate  61 . The perpendicular force component F 2  can be obtained from the tilt angle θ, the pressure load and the friction force of the follower roller  41   b  and the friction force of the driver roller  41   a . Alternatively, the follower roller  41   a  may be formed conically, as shown in FIG. 3B so as to be thinner in the direction toward the guide plate  61  such that a principal force F 1  in the direction of transportation and a perpendicular component F 2  as shown in FIG. 3A will result on the paper sheet sandwiched between the driver roller  41   a  and the follower roller  41   b.    
         [0042]    Thus, the horizontal position of the paper sheet P is corrected toward the guide plate  61  from the moment when its back edge passes the discharge rollers  11  of the image forming apparatus  1  by means of the oblique follower rollers  41   b ,  42   b  and  43   b  positioned at an angle θ. As a result, the paper sheet P comes to be accurately aligned such that the positions where holes are to be punched will be accurately set at a constant specified distance from the guide plate  61 .  
         [0043]    The paper sheet P, now thus aligned, is transported by the transportation rollers  44  towards the punch unit  31  affixed in the hole punching unit  13 . The transportation follower roller  44   b  is set so as to transport the paper sheet P in the direction of transportation such that the positions of the holes to be punched will not be affected by the oblique follower rollers  41   b ,  42   b  and  43   b  or the transverse motion of the paper sheet caused thereby.  
         [0044]    In FIG. 4, the distance L 0  indicates the distance along the transportation path between the discharge rollers  11  of the image forming apparatus  1  and the transportation rollers  44   a  and  44   b . From the moment when the back edge of the paper sheet P leaves the discharge rollers  11  of the image forming apparatus  1  until its front edge reaches the transportation rollers  44   a  and  44   b , the paper sheet P is transported only by means of the oblique rollers  41 ,  42  and  43 . In other words, the transverse position of the paper sheet P is corrected such that its side edge will travel along the guide plate  61  only over this distance of L 0 .  
         [0045]    If the length L of the paper sheet P is longer than L 0 , this means that its front edge will be already between the transportation rollers  44   a  and  44   b  before its back edge is released from the discharge rollers  11  of the image forming apparatus  1  and hence that there is no range over the travel path of the paper sheet, that is, no distance over which the paper sheet P will be driven only by the oblique rollers  41 ,  42  and  43 . In such a situation, the paper sheet P has no chance to have its transverse position corrected so as to come to travel against the guide plate  61 . Thus, the distance L 0  must be selected to be at least greater than L. In reality, L 0  must be greater than L by an extra distance required for making the positional correction. This extra distance depends on factors such as the tilting angle θ, pressure load and friction of the oblique follower rollers  41   b ,  42   b  and  43   b . With such extra distance taken into consideration, L 0  must be made greater than L max , the length of the longest paper sheet P max  intended to be handled by the paper processing apparatus  2 . With L 0  thus made sufficiently long, paper sheets of any length intended for the paper processing apparatus  2  can be adjusted reliably so as to end up traveling along the guide plate  61  by means only of the oblique rollers  41 ,  42  and  43 .  
         [0046]    [0046]FIG. 5 is referenced next to explain the structure of the punch unit  31  comprised of a first box element  101  and a second box element  102 . A punch  103 , a paper sensor  105 , a die  106  and a paper guide  107  are disposed on the side of the first box element  101  facing the paper transportation path. A punch drive motor  108  is disposed so as to be surrounded by the first and second box elements  101  and  102 . As shown more in detail in FIG. 6, the punch  103  is provided with a holder member  104  made of rubber for pressing the paper sheet down when a hole is being punched therein. The clamping member  104  may alternatively be made of sponge, or a member using a spring to be made elastic may be used for obtaining a similar effect.  
         [0047]    The paper sensor  105  is a sensor of either the transmission type of the reflection type for obtaining data on the position of the paper sheet as a hole is punched therethrough. After the paper sensor  105  detects the front edge of the paper sheet and after a specified length of time depending on the size of the paper sheet and the number of holes to be punched has passed, the punch driver motor  108  causes the punch  103  and the die  106  to be rotated so as to complete a punching operation as the paper sheet is transported along the paper guide  107 .  
         [0048]    As shown more in detail in FIG. 7, the punch driver motor  108  of the punch unit  31  has a pulley  121  attached to it, and the motion of the punch driver motor  108  is communicated therefrom to a second pulley  122  through a belt  128  and from there further to a gear  123  connected to a shaft  126 . Another gear  125  is attached to this shaft  126 , and the gear  125  engages with still another gear  124  having another shaft  127 . Shaft  126  is connected to the die  106  and shaft  127  is connected to the punch  103 . Thus, the motion of the punch driver motor  108  is communicated to gear  124  through the pulleys  121  and  122  and the gear  125  such that the die  106  and the punch  103  are both rotated in a mutually correlated manner to carry out the punching process. In other words, the die  106  is in synchronism with the punch  103 , and the die  106  and the punch  103  rotate in mutually opposite directions. The gear  123  serves also as an encoder. A notch is provided on the periphery of its flange, and its angular position is detected by a position sensor  109 . The angular positions at which the punch  103  and the die  106  are stopped can thus be kept constant.  
         [0049]    The control system for the paper processing apparatus  2  is explained with reference to the block diagram shown in FIG. 8. Its central processing unit (CPU)  141  serves to control the operation of the paper processing apparatus  2  as a whole on the basis of commands received from the image forming apparatus  1  or signals received from the reversion sensor  21 , the discharge sensor  22 , the tray sensor  23 . the paper sensor  105  and the position sensor  109 .  
         [0050]    The control system includes a roller controller  142  serving to control the rotary motions of all of the driver rollers (the oblique driver rollers  41   a ,  42   a  and  43   a , the transportation driver rollers  44   a ,  45   a ,  47   a ,  48   a  and  49   a , reversion driver roller  46   a  and the discharge driver roller  50   a ) on the basis of the control from the CPU  141 .  
         [0051]    Next, the operations of the punch unit  31  are explained more in detail with reference to FIGS. 9 and 10. As shown in FIG. 9, a paper sheet P is delivered to the punch unit  31  between the transportation driver and follower rollers  44   a  and  44   b  in the direction indicated by arrow Y and passed between the transportation driver and follower rollers  45   a  and  45   b . The hole position (or the punching position) H is the position where a hole is punched in the paper P by means of the die  106  and the punch  103 . The distance from the contact position between the transportation driver and follower rollers  44   a  and  44   b  to the hole position H is defined as x 1  and the distance from the hole position H to the contact position between the transportation driver and follower rollers  45   a  and  45   b  is defined as x 2 .  
         [0052]    [0052]FIGS. 10A and 10B respectively show a paper sheet P min  and P max  with the aforementioned minimum and maximum length L min  and L max  that can be processed by the paper processing apparatus  2 , each having three holes punched therein by the punch unit  31 . In both FIGS. 10A and 10B, pitch P 1  indicates the distance between the first and second holes and pitch P 2  indicates the distance between the second the third holes punched in the paper sheet P min  or P max . Distances T 1  and T 2  are respectively the distance between the front edge and the first hole A and that between the third hole and the back edge of the paper sheet P min . Distances T 3  and T 4  are respectively the distance between the front edge and the first hole and that between the third hole C and the back edge of the paper sheet P max . Normally, it is set such that T 1 =T 2  and T 3 =T 4 .  
         [0053]    The punch unit  31  is also set such that x 1 &lt;T 2  and hence that the paper sheet P min  remains nipped by the transportation rollers  44  until the last (third) of the holes is punched in and that the fluttering of the paper sheet P min  can be prevented. Similarly, it is so set that x 2 &lt;T 1  such that the paper sheet P min  remains nipped by the transportation rollers  44  and  45  in front and at the back of the first punched hole A when it is punched and that the fluttering of the paper sheet P min  can be prevented. Since the larger paper sheet P max  is also punched at the same pitches P 1  and P 2  and since T 2 &lt;T 4  and T 1 &lt;T 3 , the following inequalities also hold: x 1 &lt;T 2 &lt;T 4  and x 2 &lt;T 1 &lt;T 3 . Thus, the same effects as described above can be obtained with the larger paper sheet P max .  
         [0054]    As indicated also in FIG. 9, the peripheral speed of the transportation rollers  44  is defined as v 1  and that of the transportation rollers  45  is defined as v 2 . Load PRI indicates the load force with which the follower roller  44   b  presses the driver roller  44   a , and load PR 2  indicates the load force with which the follower roller  45   b  presses the driver roller  45   a . The gripping forces on the paper sheet P due to the loads PR 1  and PR 2  are respectively defined as G 1  and G 2  (not shown).  
         [0055]    If v 1 &lt;v 2  and G 1 &gt;G 2 , the paper sheet P is subjected to a tensile force by the transportation rollers  45  while it is nipped by the transportation rollers  44  and  45 . Since G 2  is smaller than G 1 , furthermore, the paper sheet P slips against the transportation rollers  45 . This prevents the transportation rollers  45  from pulling the paper sheet P too strongly. In other words, the paper sheet P remains pulled without getting loose between the transportation rollers  44  and  45 , and this condition serves to prevent the paper sheet P from fluttering and to allow holes to be punched in a stable manner.  
         [0056]    The processing by the paper processing apparatus  2  is explained next with reference to the flowchart shown in FIG. 11. When the CPU  141  receives a command from the image forming apparatus  1  that a punching process should be started, together with data such as the size of the paper sheet P and the number of holes to be punched, the roller controller  142  is controlled so as to cause all driver rollers (the oblique driver rollers  41   a ,  42   a  and  43   a , the transportation driver rollers  44   a ,  45   a ,  47   a ,  48   a  and  49   a , reversion driver roller  46   a  and the discharge driver roller  50   a ) to start rotating (Step S 1 ). Next, the punch  103  is moved to a specified angular wait position (or home position H.P as shown in FIG. 12) (Step S 2 ) such that the position of the punch  103  can always be controlled reliably independent of where the punch  103  was previously.  
         [0057]    [0057]FIG. 12 will be referenced to explain the action of the punch  103  and the die  106  when a hole is punched in the paper sheet P. As explained above, the punch  103  and the die  106  are moving in synchronism and in mutually opposite directions. FIG. 12A shows the moment when the punching is about to start, FIG. 12B shows the moment at the time of punching and FIG. 13C shows the moment at the end of the punching operation. As explained above, the paper sheet P is transported in the direction of arrow Y, and the punch  103  is waiting at its wait orientation H.P when it is not engaging in a punching operation. Orientations Q 1 , Q 2  and Q 3  indicate respectively the orientation of the punch  103  at the beginning of, during and at the end of a punching operation. Explained more in detail, Q 1  is the orientation when the paper sheet P begins to be nipped between the holder member  104  and the die  106  and Q 3  is the orientation when the paper sheet P becomes freed from the nipping by the holder member  104  and the die  106 . In other words, the paper sheet P remains nipped between the holder member  104  and the die  106  from the beginning to the end of a hole punching operation. Thus, the paper sheet P is prevented from fluttering during the entire course of the punching operation such that a hole can be created in a stable manner.  
         [0058]    The width of the die  106  in the direction parallel to the direction of transportation of the paper sheet P is indicated by W 1  and that of the holder member  104  in the same direction is indicated by W 2  (as shown also in FIG. 6). They are designed such that W 1 &gt;W 2  in order to prevent the paper sheet P from being folded as it is pressed by the holder member  104  against the die  104  at the beginning or at the end of the punching operation. The depths D 1  and D 2  respectively of the die  106  and the holder member  104  as shown in FIGS. 6 and 7 are also designed such that D 1 &gt;D 2  for the same reason. These conditions, however, need to be satisfied only on the surfaces contacting the paper sheet P.  
         [0059]    With reference again to the flowchart of FIG. 11, the CPU  141  undertakes to carry out the punching operation in Step S 3 , a detail of which is explained with reference to another flowchart shown in FIG. 13.  
         [0060]    The CPU  141  is initially waiting until a signal is received from the paper sensor  105 . When a detection signal is received from the paper sensor, indicating that the paper sheet P has been detected (YES in Step S 31 ), the punch  103  is caused to wait at the wait orientation H.P for a specified length of time (Step S 32 ). This specified length of time is calculated by the CPU  141  from the size of the paper sheet P, the distance between the front edge of the paper sheet P and the first hole A (with reference to FIG. 10), the angle between the wait orientation H.P and the orientation Q 2 , peripheral speed of the punch  103 , and the speed of transportation of the paper sheet P. In other words, the distance between the front edge of the paper sheet P and the first hole A can be varied by adjusting the wait time of the punch  103  at its wait orientation H.P.  
         [0061]    When an internal clock (not shown) indicates that the specified wait time has elapsed (YES in Step S 32 ), the CPU  141  rotates the punch  103  from the wait orientation H.P to the start orientation Q 1  at a rotational speed of Vf (Step S 33 ). During this time, the paper sheet P begins to be nipped between the holder member  104  and the die  106 .  
         [0062]    Next, the CPU  141  carries out the punching operation by rotating the punch  103  at another rotational speed of Vp from the start orientation Q 1  to the end orientation Q 3  (Step S 34 ). At the end of this period, the paper sheet P is freed from the nipping between the holder member  104  and the die  106 . Thereafter, the punch  103  is rotated from the end orientation Q 3  to the wait orientation H.P at a rotational speed indicated as Ve (Step S 35 ) and waits for the next punching command (Step S 36 ).  
         [0063]    [0063]FIG. 14 shows graphically the rotational speeds of the punch  103  described above. When the paper processing apparatus  2  is operated so as to carry out the punching process while the paper sheet P is being transported, the peripheral speed of the punch  103  during the punching operation must match the speed of transportation of the paper sheet P within an allowable range. During the period over which the holder member  104  and the die  106  are nipping the paper sheet P, the peripheral speed of the punch  103  must match the speed of transportation of the paper sheet P within an allowable range in order that the former will not affect the latter. Thus, the CPU  141  functions so as to synchronize the peripheral speed Vp of the punch  103  and the speed of transportation of the paper sheet P within a specified allowable range between the start orientation Q 1  and the end orientation Q 3 .  
         [0064]    At orientations not within the range between the start orientation Q 1  and the end orientation Q 3 , there is no need to synchronize the peripheral speed Vp of the punch  103  and the speed of transportation of the paper sheet P. If the distance between the holes to be punched is not equal to the circumferential length of the punch  103  and if the peripheral speed of the punch  103  and the speed of transportation of the paper sheet P are matched within all ranges of the rotation of the punch  103 , it may happen that the punch  103  does not rotate in time for the next punching process. This is why the CPU  141  rotates the punch  103  at a faster speed than the speed of transportation of the paper sheet P at orientations not within the range between the start orientation Q 1  and the end orientation Q 3 . Thus, the speed of the punch  103  is varied as explained above and illustrated in FIG. 14, where Vp&lt;Vf, Ve such that a constant pitch can be kept between the holes.  
         [0065]    With reference back to FIG. 13, the CPU  141  counts a specified length of time by means of its internal clock to keep the punch  103  waiting at the wait orientation H.P (Step  36 ). This specified length of time is calculated by the CPU  141  from the pitch of the punched holes, the peripheral speed of the punch  103  and the speed of transportation of the paper sheet P. Thereafter, if the specified number of holes have not yet been punched (NO in Step S 37 ), the program returns to Step S 33  and the subsequent steps are repeated. If it is determined that the specified number of holes have been punched (YES in Step S 37 ), the program returns to Step S 4  in the flowchart of FIG. 11 and waits until the reversion sensor  21  outputs a signal to indicate that the back edge of the paper sheet P has been detected (YES in Step S 4 ). After a specified length of time has elapsed thereafter, the solenoid  143  for the motion reversing unit  14  is activated (Step S 5 ) to rotate the reversion driver roller  46   a  such that the arcuate portion of its periphery will face the transportation path. This specified length of time after the reversion sensor  21  detects the back edge of the paper sheet P is determined to be sufficiently long for the paper sheet P to have safely passed the position of the transportation rollers  45 .  
         [0066]    The paper sheet P is thereafter further transported in the downstream direction by means of the transportation driver and follower rollers  45   a  and  45   c . The CPU  141  waits until the discharge sensor  22  detects the back edge of the paper sheet P (YES in Step S 6 ) and, if it is determined that not all of the originally specified number of paper sheets have been processed (NO in Step S 7 ), the CPU  141  returns to Step S 2  and the subsequent steps are repeated. If all of the originally specified number of paper sheets have been processed (YES in Step S 7 ), the CPU  141  controls the roller controller  142  to stop all of the driver rollers (the oblique driver rollers  41   a ,  42   a  and  43   a , the transportation driver rollers  44   a ,  45   a ,  47   a ,  48   a  and  49   a , reversion driver roller  46   a  and the discharge driver roller  50   a ) (Step S 8 ) to complete the processing. The paper sheet P which has passed the discharge sensor  22  is discharged into the tray  15  by means of the discharge rollers  50 .