Patent Publication Number: US-2002000149-A1

Title: Paper punching device

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a paper punching device for punching the papers after the images have been formed thereon, in an image-forming machine such as a copier or a printer, on which the paper punching device is mounted.  
       DESCRIPTION OF THE PRIOR ART  
       [0002] In recent years, there are widely put into practical use image-forming machines such as copiers and printers have been provided with a paper punching device for punching the papers after the images have been formed thereon, so that the papers can be filed. As the paper punching devices, there have been known those of the type in which the papers on which the image has been formed are once conveyed onto a paper-receiving plate for every manuscript and are punched at one time on the paper-receiving plate, and those of the so-called piece-by-piece punching type in which punches are arranged in the punching portion along the conveyer passage for conveying a paper on which the image has been formed, the paper is once stopped when it passes through the punching portion and then, is punched while it is at rest. Of the above two punching systems, the so-called piece-by-piece punching system is capable of effecting the punching in synchronism with the image-forming operation and hence, offers an advantage of effecting the punching at nearly the same time as that of operation for forming the image. Image-forming machines equipped with the punching device of the so-called piece-by-piece punching type have been disclosed in Japanese Utility Model Publication (Kokoku) No. 25919/1991 and Japanese Laid-open Patent Publication (Kokai) No. 190696/1991.  
       [0003] The paper punching device disclosed in the above Japanese Examined Utility Model Publication (Kokoku) No. 25919/1991 is constituted by a stopper which is arranged in the conveyer passage for conveying the paper on which the image has been formed to once stop the paper with its leading edge uniformly positioned, two punches disposed, on the upstream of the stopper, at right angles with a direction in which the paper is conveyed, and a cam operation mechanism for reciprocatingly moving the punches up and down. The punching device disclosed in the above Japanese Laid-open Patent Publication (Kokai) No. 190696/1991 is constituted by two punches disposed in a punching portion of the conveyer passage for conveying the paper on which the image has been formed, at right angles with the direction in which the paper is conveyed, a cam operation mechanism for reciprocatingly moving the punches up and down, and a paper-stop means for once stopping the paper in a state where the to-be-punched portion on the side of the trailing edge of the paper being conveyed is made correspondence to the above punching portion.  
       [0004] The paper punching devices disclosed in the above two publications are of the constitution which is capable of punching the holes in a number of only one kind. When it is desired to punch the holes of different kinds, it becomes necessary to replace the punches and the cam operation mechanism.  
       [0005] In order to solve the above-mentioned problem, Japanese Laid-open Patent Publication (Kokai) No. 26328/1999 discloses a paper punching device in which two kinds of holes have been set for effecting the punching, and the holes of either kind are selected to effect the punching. The paper punching device disclosed in the above publication comprises plural punches disposed in the paper conveyer passage at right angles with the direction of conveying the papers, plural pushing mechanisms for operating the plural punches, pushing mechanism-positioning means for operating said plural pushing mechanisms in a direction in which they are arranged to bring them to a first position and a second position, a cam shaft disposed along the direction in which the plural pushing mechanisms are arranged, and plural cams formed on the cam shaft to actuate the pushing mechanisms. The pushing mechanism-positioning means includes a changeover shaft mounting the plural pushing mechanisms, and a change-over shaft-operating mechanism for operating the change-over shaft in the axial direction to bring the plural pushing mechanisms to the first position and to the second position. When the change-over shaft is actuated by the pushing mechanism-positioning means to bring the plural pushing mechanisms to the first position, some pushing mechanisms correspond to some cams out of the plural cams. When the plural pushing mechanisms are brought to the second position, the other pushing mechanisms correspond to the other cams.  
       [0006] However, the paper punching device disclosed in the above Japanese Laid-open Patent Publication (Kokai) No. 26328/1999 contains very many constituent parts and the device as a whole becomes bulky since it is provided with the pushing mechanism-positioning means having a change-over shaft that is disposed in parallel with the cam shaft and mounts the plural pushing mechanisms. Besides, in the paper punching device disclosed in the above publication, the pushing mechanism tends to become bulky since the plural pushing mechanisms mounted on the change-over shaft are moved in the axial direction so as to selectively correspond to the plural punches. In the paper punching device disclosed in the above publication as descried above, the mechanisms themselves become of a large-size since they are constituted by many parts, resulting in an increase in the number of parts and in the size of the mechanisms and producing large noise due to the operation of the individual parts, which are problems.  
       SUMMARY OF THE INVENTION  
       [0007] It is an object of the present invention to provide a paper punching device in which a change-over mechanism for selectively operating the necessary punches out of plural punches can be constituted in a compact size by using a decreased number of parts.  
       [0008] In order to accomplish the above-mentioned object according to the present invention, there is provided a paper punching device disposed on a paper conveyer passage for punching plural holes in a paper that passes on said paper conveyer passage, comprising:  
       [0009] plural punches disposed on the upper side of said paper conveyer passage at right angles with the direction in which the paper is conveyed;  
       [0010] plural pushing members mounted on the upper ends of said plural punches; and  
       [0011] a punch-operating mechanism for operating said plural pushing mechanisms;  
       [0012] wherein said punch-operating mechanism includes a cam shaft disposed along a direction in which said plural pushing mechanisms are arranged, plural cams mounted on said cam shaft, a cam drive mechanism for rotatively driving said cam shaft, and a cam position change-over mechanism which operates said cam shaft in the axial direction so as to be selectively brought to a first position where some cams out of the plural cams correspond to some pushing members out of said plural pushing members and to a second position where the other cams out of said plural cams correspond to the other pushing members out of said plural pushing members.  
       [0013] It is desired that each pushing member is provided with a return member having a pair of support portions mounted on both ends thereof and extending upward and a return operation portion coupling the upper ends of said pair of support portions together, and that the cam acts on the lower surface of said return member.  
       [0014] It is further desired that the return operation portion of said return member is provided with sub-return operation portions corresponding to said cam in a state where said cam has not been brought to the position corresponding to the pushing member. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 is a view schematically illustrating an embodiment of an image-forming machine equipped with an after-treatment device having a paper punching device constituted according to the present invention;  
     [0016]FIG. 2 is a plan view illustrating, partly in a cutaway manner, a three-hole-punching state of the paper punching device constituted according to the present invention;  
     [0017]FIG. 3 is a plan view illustrating, partly in a cutaway manner, a two-hole-punching state of the paper punching device constituted according to the present invention;  
     [0018]FIG. 4 is a sectional view along the line A-A in FIG. 2;  
     [0019]FIG. 5 is a front view of a pushing mechanism constituting the paper punching device according to the present invention;  
     [0020]FIG. 6 is a perspective view of a rotation control member constituting a spring clutch used for the paper punching device constituted according to the present invention;  
     [0021]FIG. 7 is a side view of a flapper-type solenoid used for the paper punching device constituted according to the present invention;  
     [0022]FIG. 8 is a plan view illustrating a relationship between the flapper-type solenoid and the rotation control member constituting the spring clutch, that are used for the paper punching device according to the present invention;  
     [0023]FIG. 9 is a view illustrating operations of the flapper-type solenoid and of the rotation control member constituting the spring clutch, that are used for the paper punching device according to the present invention;  
     [0024]FIG. 10 is a view illustrating operations of a punching unit and of an operation cam of the punching unit, that are used for the paper punching device according to the present invention;  
     [0025]FIG. 11 is a block diagram illustrating the constitution of a control means for controlling the paper punching device according to the present invention; and  
     [0026]FIG. 12 is a flow chart illustrating the processing procedure of the control means shown in FIG. 11. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0027] The invention will be described in further detail with reference to the accompanying drawings which illustrate preferred embodiments of the paper punching device constituted according to the present invention.  
     [0028]FIG. 1 illustrates an electrostatic copier  2  which is an image-forming machine, and an after-treatment device  4  equipped with a paper punching device disposed being coupled to the electrostatic copier  2  and constituted according to the present invention.  
     [0029] The electrostatic copier  2  that is shown is provided with a machine housing  5  of a rectangular parallelepiped shape. On the upper surface of the machine housing  5  is disposed a stationary transparent plate  6  on which will be placed a manuscript that is to be copied. An automatic manuscript conveyer device  7  is disposed on the upper side of the stationary transparent plate  6 . The automatic manuscript conveyer device  7  includes a manuscript-placing portion on which the manuscript to be copied is placed and a manuscript conveyer portion having a manuscript conveyer belt mechanism for conveying the manuscript placed on the manuscript-placing portion to a predetermined position of the stationary transparent plate  6 .  
     [0030] As shown in FIG. 1, a photosensitive material drum  8  is rotatably disposed nearly in the central portion in the machine housing  5 . The photosensitive material drum  8  is rotatively driven in a direction indicated by an arrow by a drive means that is not shown. The photosensitive material drum  8  is surrounded, as viewed in the direction of rotation indicated by the arrow, by a corona discharger  9  for electric charging, a developer  10 , a corona discharger  11  for transfer, a corona discharger  12  for peeling-off, a cleaning unit  13  and a charge-removing lamp  14  in this order. The illustrated electrostatic copier includes an optical system constituted by an irradiation lamp  15  disposed above the photosensitive material drum  8 , a first mirror  16 , a second mirror  17 , a third mirror  18 , a lens  19  and a fourth mirror  20 . This optical system is so constituted that the manuscript placed on the stationary transparent plate  6  is irradiated with light from the irradiation lamp  15 , and the reflected optical image is focused on the outer peripheral surface of the photosensitive material drum  8  through the first mirror  16 , second mirror  17 , third mirror  18 , lens  19  and fourth mirror  20 .  
     [0031] The illustrated electrostatic copier  2  includes a paper feeder  22  for feeding the paper onto the transfer zone between the corona discharger  11  for transfer and the photosensitive material drum  8 .  
     [0032] The paper feeder  22  includes paper cassettes  23  and  24  for holding the papers on which images are to be transferred, paper delivery rollers  25  and  26 , pairs of handling rollers  27  and  28 , a guide passage  29 , pairs of conveyer rollers  30  and  31 , and a pair of resist rollers  32 . The pairs of rollers of the thus constituted transfer paper feeder  22  are rotatively driven in the directions indicated by arrows by a drive means that are not shown.  
     [0033] On the transfer paper delivery side of the transfer zone, there are disposed a transfer paper conveyer belt mechanism  33 , a fixing device  34  having a pair of fixing rollers  340 , and a pair of discharge rollers  35 . The conveyer belt mechanism and the rollers are driven in the directions indicated by arrows by a drive means that are not shown.  
     [0034] While the photosensitive material drum  8  is rotatively driven in the direction indicated by the arrow in the thus constituted electrostatic copier  2 , the corona discharger  9  electrically charges the photosensitive material on the photosensitive material drum  8  substantially uniformly into a particular polarity, the manuscript placed on the stationary transparent plate  6  is irradiated with light from the irradiation lamp  15 , and the reflected optical image is projected onto the photosensitive material drum  8  via the first mirror  16 , second mirror  17 , third mirror  18 , lens  19  and fourth mirror  20 , so that an electrostatic latent image is formed on the photosensitive material drum  6 . Thereafter, the electrostatic latent image on the photosensitive material drum  8  is developed into a toner image by the developer  10 . On the other hand, the paper held in the paper cassette  23  or  24  of the paper feeder  22  is delivered onto the guide passage  29  by the delivery roller  25  or  26  through the pair of handling rollers  27  or  28 , is once stopped by the pair of resist rollers  32 , and is conveyed onto the transfer zone in synchronism with the toner image formed on the photosensitive material drum  8 . The toner image is transferred onto the paper conveyed onto the transfer zone as the paper passes through between the photosensitive material drum  8  on which the toner image is formed and the corona discharger  11  for transfer. The paper onto which the toner image is transferred is peeled off the photosensitive material drum  8  by the action of the corona discharger  12  for peeling-off, is conveyed by the transfer paper conveyer belt mechanism  33  to the fixing device  34  where the image is fixed by heating, and is discharged by the pair of discharge rollers  35  through a discharge port  36 . After the transfer step has been completed as described above, the toner adhered to the outer peripheral surface of the photosensitive material drum  8  is removed by the cleaning unit  13 . Further, the surface of the photosensitive material is irradiated with charge-removing light from the charge-removing lamp  14 , so that the electric charge is removed therefrom.  
     [0035] The after-treatment device  4  will be described next.  
     [0036] The after-treatment device  4  in the illustrated embodiment has a device housing  40 . The device housing  40  has a paper introduction port  401  at a position opposed to the discharge port  36  at an end of the copier body  2 , and has, arranged therein, a first paper conveyer passage  41  extending from the paper introduction port  401 . An introduction portion on the side of the paper introduction port  401  in the first paper conveyer passage  41  is constituted by a pair of guide plates  411  and  412  that are opened up and down on the side of the discharge port  36 . A pair of discharge rollers  43  constituted by a drive roller  431  and a driven roller  432  are disposed at an end on the discharge side of the first paper conveyer passage  41 . The drive roller  431  constituting the pair of discharge rollers  43  is transmission-coupled to an electric motor  44  (M 1 ) as a drive source via a drive mechanism that is not shown, and is rotatively driven in a direction indicated by an arrow. A second paper conveyer passage  45  is branched from an intermediate portion of the first paper conveyer passage  41 , and extends to, for example, a staple-treatment portion (not shown) which is an after-treatment device.  
     [0037] A branching pawl  46  is disposed at a branching portion between the first paper conveyer passage  41  and the second paper conveyer passage  45 . The branching pawl  46  is operated to a first position indicated by a solid line in FIG. 1 and to a second position indicated by a broken line in FIG. 1 by an electromagnetic solenoid  47  (SOLL). When the electromagnetic solenoid  47  (SOLL) is de-energized, the branching pawl  46  is brought to the first position indicated by the solid line in FIG. 1, whereby the paper introduced through the paper introduction port  401  is conveyed toward the pair of discharge rollers  43  passing through the first paper conveyer passage  41 . When the electromagnetic solenoid  47  (SOLL) is energized, on the other hand, the branching pawl  46  is brought to the second position indicated by the broken line in FIG. 1, whereby the paper introduced through the paper introduction port  401  is conveyed toward the second paper conveyer passage  45  from the branching portion of the first paper conveyer passage  41 .  
     [0038] A paper punching device  50  is disposed between the pair of guide plates  411 ,  412  and the branching portion of the first paper conveyer passage  41  from where the second paper conveyer passage  45  is branched. The paper punching device  50  will be described later in detail. On the discharge side of the housing  40  (left side in FIG. 1), there are disposed a tray  48  for non-sorting at an upper portion and a tray  49  for sorting under the tray  48  for non-sorting so as to be allowed to be shifted up and down.  
     [0039] Next, the paper punching device  50  will be described in detail with reference also to FIGS.  2  to  7 .  
     [0040] The paper punching device  50  includes a paper guide means  60  and a punching unit  70 .  
     [0041] The paper guide means  60  is constituted by an upper guide plate  61  and a lower guide plate  62  as chiefly shown in FIG. 4. The end on the upstream side of the upper guide plate  61  (right end in FIG. 4) is tilted upward and is connected to the guide plate  411 . Further, the end on the upstream side of the lower guide plate  62  (right end in FIG. 4) is tilted downward. In the upper guide plate  61  are formed plural through holes  611  (five holes in the illustrated embodiment) corresponding to the number of punches that will be described later at right angles with the direction in which the paper is conveyed (at right angles with the surface of the paper in FIG. 1) in a predetermined punching portion. In the lower guide plate  62  are formed plural punching holes  621  (five holes in the illustrated embodiment) at positions corresponding to the plural through holes  611  formed in the upper guide plate  61  in the predetermined punching portion. Therefore, the lower guide plate  62  having punching holes  621  works as a punching die.  
     [0042] A pair of resist rollers  65  constituted by a drive roller  651  and a driven roller  652  are disposed at the end on the downstream side of the paper guide means  60  constituted as described above. The drive roller  651  is disposed protruding upward through an opening  622  formed in the lower guide plate  62 , and the driven roller  652  is disposed protruding downward through an opening  612  formed in the upper guide plate  61 . The drive roller  651  constituting the pair of resist rollers  65  is transmission-coupled to the electric motor  44  (M 1 ) through an electromagnetic clutch  66  (CLT 1 ) and is rotatively driven in a direction indicated by an arrow. When the electromagnetic clutch  66  (CLT 1 ) is de-energized, the drive roller  651  and the electric motor  44  (M 1 ) are not transmission-coupled. When the electromagnetic clutch  66  (CLT 1 ) is energized, the drive roller  651  and the electric motor  44  (M 1 ) are transmission-coupled. In the illustrated embodiment, a paper detector  67  (SW 1 ) is disposed between the paper guide means  60  and the pair of guide plates  411 ,  412 . The paper detector  67  (SW 1 ) detects the paper introduced into the after-treatment device  4  from the copier body  2  through the paper introduction port  401 , and sends a detection signal to a control means that will be described later.  
     [0043] The punching unit  70  includes plural punch guides  71  (five punch guides in the illustrated embodiment), plural punches (five punches in the illustrated embodiment)  72  ( 72 - 1 ,  72 - 2 ,  72 - 3 ,  72 - 4 ,  72 - 5 ) disposed in the plural punch guides  71  so as to slide up and down, pushing mechanisms  73  ( 73 - 1 ,  73 - 2 ,  73 - 3 ,  73 - 4 ,  73 - 5 ) fitted to the upper ends of the plural punches  72 , and a punch-operating mechanism  74  for selectively operating each of the plural pushing mechanisms  73 .  
     [0044] The plural punch guides  71  are constituted by cylindrical members having through holes  711  corresponding to the outer diameter of the punches  72  and having outer peripheral surfaces formed in a square shape in cross section, disposed on the upper guide plate  61  at positions corresponding to the plural through holes  611 , and have mounting flanges  712  attached to the lower ends thereof and secured to the upper guide plate  61  by plural screws  715 . The thus constituted plural punch guides  71  are disposed in a direction at right angles with the direction in which the paper is conveyed along the first paper conveyer passage  41  (in a direction perpendicular to the surface of the paper in FIGS. 1 and 4).  
     [0045] Each punch  72  has a punching blade  721  at the lower end thereof and an annular engaging groove  722  in the outer peripheral surface at the upper end thereof. The thus constituted punches  72  are fitted in the through holes  711  formed in the plural punch guides  71  so as to slide up and down. Among the punches  72 - 1 ,  72 - 2 ,  72 - 3 ,  72 - 4  and  72 - 5  as shown in FIGS. 2 and 3, the punches  72 - 1 ,  72 - 3  and  72 - 5  are disposed in the three-hole-punching portion, and the punches  72 - 2  and  72 - 4  are disposed in the two-hole-punching portion.  
     [0046] Next, the pushing mechanisms  73  will be described with reference chiefly to FIGS. 4 and 5.  
     [0047] The pushing mechanism  73  in the illustrated embodiment includes a pushing member  730  having a horizontal pushing portion  731  and a cylindrical support portion  732  hanging down from the central portion of the pushing portion  731 , and a return member  733  mounted on both ends of the pushing portion  731  and is formed like an arch facing upward. The pushing portion  731  constituting the pushing member  730  is formed in a rectangular shape, and a cam  77  that will be described later acts on the upper surface thereof.  
     [0048] The cylindrical support portion  732  constituting the pushing member  730  has side portions  732   a ,  732   b  corresponding to both side surfaces of the punch guide  71  of a rectangular shape in cross section, and a back side portion (not shown) corresponding to the back side surface of the punch guide  71 , and is opened on the side corresponding to the front side surface of the punch guide  71 . Guide portions  732   c  and  732   d  are provided at the lower front ends of the side portions  732   a  and  732   b  and protrude inward. The gap between the guide portions  732   c  and  732   d  is slightly larger than the diameter of the punch  72 , so that the punch  72  is inserted into between the guide portions  732   c  and  732   d  in a manner as will be described later. The support member  732  having the side portions  732   a ,  732   b , the back side portion (not shown) and the guide portions  732   c ,  732   d , permit the punch guide  71  to be fitted therein to slide up and down, thereby to support the pushing member  73 .  
     [0049] On the upper inner surfaces of the side portions  732   a  and  732   b  constituting the support portion  732 , there are provided engaging portions  732   e  and  732   f  protruding inward. The gap between the engaging portions  732   e  and  732   f  is set to correspond to the annular engaging groove  722  formed in the upper outer peripheral surface of the punch  72 . By inserting the punch  72  in the support member  732  from the front side of the support member  732  passing between the guide portions  732   c  and  732   d  and by bringing the annular engaging groove  722  formed in the upper outer peripheral surface of the punch  72  into engagement with the engaging portions  732   e  and  732   f , therefore, the pushing member  730  is mounted on the punch  72 . The thus constituted pushing member  730  is molded as a unitary structure by using a suitable synthetic resin.  
     [0050] A compression coil spring  79  is disposed between the upper end of the punch guide  71  and the engaging portions  732   e ,  732   f  of the support portion  732  of the pushing member  730 . Due to the resilient force of the compression coil spring  79 , the pushing member  730  is urged upward at all times.  
     [0051] The return member  733  constituting the pushing mechanism  73  has support portions  733   a ,  733   b  extending up and down, and a return operation portion  733   c  coupling the upper ends of the support members  733   a  and  733   b  together, which are formed as a unitary structure using a suitable synthetic resin. Engaging portions  733   d  and  733   e  having an engaging groove are provided at the lower ends of the support portions  733   a  and  733   b . By bringing the engaging grooves of the engaging portions  733   d  and  733   e  into engagement with both ends of the pushing portion  731 , the return member  733  is mounted on the pushing member  730 . The return operation portion  733   c  has a lower surface on which the cam  77  that will be described later acts. That is, after the punching operation, the punch  72  moves upward to a predetermined retracted position with the turning of the cam  77  due to the resilient force of the compression coil spring  79 . Here, when the resisting force between the punch  72  and the punched paper is larger than the resilient force of the compression coil spring  79 , it becomes difficult to operate the punch toward the retracted position. In the illustrated embodiment, however, when the resisting force makes it difficult to operate the punch  72  toward the retracted position, the cam  77  that turns acts on the lower surface of the return operation portion  733   c  of the return member  733  to push the return member  733  up, making it possible to bring the punch  72  coupled to the pushing member  730  mounting the return member  733  to the predetermined retracted position.  
     [0052] In the illustrated embodiment, sub-return operation portions  733   f  and  733   g  are provided on both sides of the central portion of the return operation portion  733   c  constituting the return member  733 , the sub-return operation portions  733   f  and  733   g  protruding in the axial direction of the cam shaft  81  mounting the cam  77  that will be described later (see FIGS. 2 and 3). The sub-return operation portions  733   f  and  733   g  have their lower flat surfaces in flush with the lower surface of the return operation portion  733   c , and will be opposed to the cam  77  when the cam  77  is brought to the non-acting position being displaced in the axial direction from the acting position where the cam  77  is opposed to the pushing portion  731  and to the return member  733  as will be described later. When the cam  77  is brought to the non-actin position, therefore, the punch  72  does not act. In case the punch  72  has moved down due to some cause, however, the cam  77  acts on the lower surface of either the sub-return operation portion  733   f  or  733   g  to bring the punch  72  to the predetermined return position. Though the illustrated embodiment has dealt with the case where the sub-return operation portions  733   f  and  733   g  were provided on both sides of the central portion of the return operation portion  733   c  constituting the return member  733 , it should be noted that this is to form the return members  733  in common, and the sub-return operation portion may be provided on either side corresponding to the cam  77  in a state where the cam  77  is brought to a position not corresponding to the pushing portion  731 .  
     [0053] Next, the punch-operating mechanism  74  will be described with reference to FIGS.  2  to  8 . The punch-operating mechanism  74  includes a cam mechanism  75 , a cam drive mechanism  80  for selectively rotatively driving the cam mechanism  75 , and a cam position change-over mechanism  90  for changing the cam mechanism  75  over to a first position (three-hole-punching position in the illustrated embodiment) and to a second position (two-hole-punching position in the illustrated embodiment).  
     [0054] The cam mechanism  75  in the illustrated embodiment includes a cam shaft  76  disposed along the direction in which the pushing member  730  is arranged to constitute the plural pushing mechanisms  73 , plural cams (five cams in the illustrated embodiment)  77  ( 77 - 1 ,  77 - 2 ,  77 - 3 ,  77 - 4 ,  77 - 5 ) mounted on the predetermined positions of the cam shaft  76 , and plural guide cylinder sleeves (five guide cylinder sleeves in the illustrated embodiment)  78  ( 78 - 1 ,  78 - 2 ,  78 - 3 ,  78 - 4 ,  78 - 5 ) mounted on the cam shaft  76  neighboring the cams  77  ( 77 - 1 ,  77 - 2 ,  77 - 3 ,  77 - 4 ,  77 - 5 ).  
     [0055] The cam shaft  76  is disposed through space defined by the pushing portions  731  of the pushing members  730  constituting the plural pushing mechanisms  73  and by the return members  733 , and is rotatably supported at its both ends by a front side plate  91  and a back side plate  92  mounted on the upper guide plate  61  with screws  911  and  921  via bearings  93  and  94 .  
     [0056] The cams  77  ( 77 - 1 ,  77 - 2 ,  77 - 3 ,  77 - 4 ,  77 - 5 ) are formed of a suitable synthetic resin and have outer peripheral surfaces that work as cam surfaces. The guide cylinder sleeves  78  ( 78 - 1 ,  78 - 2 ,  78 - 3 ,  78 - 4 ,  78 - 5 ) are formed of a suitable synthetic resin and have a radius of the outer peripheral surfaces thereof corresponding to the shortest radius of the cams  77 . When the cams  77  are not opposed to the pushing portions  731  of the pushing members  730 , therefore, the guide sleeves  78  are brought to a position to correspond to the pushing portions  731 . Due to the thus constituted guide sleeves  78 , the cam shaft  76  can be smoothly operated in the axial direction by the cam position change-over mechanism  90  which will be described later. The cam  77  and the guide sleeve  78  may be molded as a unitary structure.  
     [0057] Next, described below is the cam operation mechanism  80 .  
     [0058] The cam drive mechanism  80  in the illustrated embodiment includes a drive gear  81  disposed at an end on the back side of the cam shaft  77  (upper side in FIGS. 2 and 3), and a spring clutch  83  for transmitting, or disconnecting, the driving force of the drive gear  81  to, or from, the cam shaft  77 . The drive gear  81  is allowed to move relative to the cam shaft  77  in the axial direction, and is rotatably mounted on a drive sleeve  82  that is so fitted as to rotate together with the cam shaft  77 . The drive gear  81  is transmission-coupled to the electric motor  44  (M 1 ) through a drive mechanism that is not shown. In the drive sleeve  82  is formed an elongated hole  82   a  elongating in the axial direction, and a pin  821  secured to the cam shaft  77  is fitted to the elongated hole  82   a . In FIGS. 2 and 3, the left end of the drive sleeve  82  is rotatably supported by the bearing  94 . Therefore, the cam shaft  77  is allowed to slide in the axial direction in a range of the elongated hole  82   a  formed in the drive sleeve  82 . On the back side of the drive sleeve  82  of the cam shaft  77  (upper side in FIGS. 2 and 3), there is slidably mounted a spring shoe  95  to come in contact with an end surface on the back side of the drive sleeve  82 , and there is secured another spring shoe  96  on a further back side. A compression coil spring  97  is disposed between the spring shoe  95  and the spring shoe  96 . Due to the resilient force of the compression coil spring  97 , therefore, the end surface on the front side of the drive sleeve  82  comes in contact with the bearing  94 , and the cam shaft  77  is urged toward the back side (upper side in FIGS. 2 and 3).  
     [0059] Next, the spring clutch  83  will be described.  
     [0060] The spring clutch  83  in the illustrated embodiment includes a first boss member  831  formed integrally with the drive gear  81 , a second boss member  832  that is disposed being opposed to the first boss member  831  and is constituted to rotate together with the drive sleeve  82 , a coil spring  833  fitted upon covering the first boss member  831  and the second boss member  832 , and a rotation control member  834  disposed upon covering the coil spring  833 .  
     [0061] The coil spring  833  is engaged, at its one end, with a groove formed in the second boss member  832  and is engaged, at its other end, with a groove formed in the rotation control member  834 . The rotation control member  834  includes a main body  834   a  which is a hollow sleeve member and an anchoring pawl  834   b  formed on the outer periphery of the main body  834   a , as shown in FIG. 6. The anchoring pawl  834   b  includes an anchoring portion  834   c  disposed at a predetermined gap from the outer peripheral surface and a support portion  834   d  for coupling an end on the back side of the anchoring portion  834   c  to the main body  834   a.    
     [0062] In the thus constituted spring clutch  83 , when the flapper of the flapper-type solenoid  84  (SOL 3 ) that will be described later comes into engagement with the anchoring pawl  834   b  to limit the rotation of the rotation control member  834 , the coil spring  833  expands due to the rotation of the first boss member  831  formed integrally with the drive gear  78 . Accordingly, the drive gear  78  and the first boss member  831  simply rotate on the cam shaft  81  without transmitting the driving force to the cam shaft  81 . On the other hand, so far as the flapper of the flapper-type solenoid  84  (SOL 3 ) that will be described later does not engage with the anchoring pawl  834   b , the rotation control member  834  is allowed to rotate. Therefore, the coil spring  833  contracts and comes into intimate contact with the outer peripheral surfaces of the first boss member  831  and of the second boss member  832 , so that the first boss member  831  and the second boss member  832  are connected together via the coil spring  833 . Therefore, the driving force transmitted to the drive gear  8  is transmitted to the cam shaft  81  through the first boss member  831 , coil spring  833 , second boss member  832 , driving sleeve  82  and pin  821 .  
     [0063] Next, the flapper-type solenoid  84  (SOL 3 ) for controlling the spring clutch  83  will be described with reference also to FIGS. 7 and 8.  
     [0064] The flapper-type solenoid  84  (SOL 3 ) includes a bracket  841  attached to the back side plate  92  by a fastening means such as screws, a solenoid  842  mounted on the bracket  841 , a flapper  843  that is disposed on the upper side of the solenoid  842  and is supported, at its one end (right end portion in FIGS. 7 and 8), by the bracket  841  pivotably on a support portion  841   a  as a fulcrum, and a coil spring  844  stretched between a spring-mounting portion  843   a  formed at an end of the flapper  843  (right end in FIGS. 7 and 8) and the bracket  841 .  
     [0065] The flapper  843  has, at the other end (left end portion in FIGS. 7 and 8) thereof, an engaging portion  843   b  for coming into engagement with the anchoring pawl  834   b  of the rotation control member  834 , as shown in FIG. 8. The engaging portion  843   b  is formed protruding toward the anchoring pawl  834   b  so as to come into engagement with the anchoring portion  834   c  of the anchoring pawl  834   b . In the thus constituted flapper-type solenoid  84  (SOL 3 ), when the solenoid  842  is de-energized, the flapper  843  is urged by a coil spring  844  to swing in the clockwise direction on the support portion  841   a  as a fulcrum, as indicated by a solid line in FIG. 7. In this state, the engaging portion  843   b  of the flapper  843  is brought to a position to come into engagement with the anchoring portion  834   c  of the anchoring pawl  834   b . When the solenoid  842  of the flapper-type solenoid  84  (SOL 3 ) is energized, on the other hand, the flapper  843  is attracted by the attracting force of the solenoid  842  against the resilient force of the coil spring  844  as indicated by a two-dot chain line in FIG. 7.  
     [0066] Next, the cam position change-over mechanism  90  will be described with reference to FIGS. 2 and 3. The cam position change-over mechanism  90  in the illustrated embodiment includes an electromagnetic solenoid  900  (SOL 2 ) disposed on the front side of the cam shaft  77  (on the lower side in FIGS. 2 and 3) and a coupling member  902  for coupling a plunger  901  of the electromagnetic solenoid  900  (SOL 2 ) to the cam shaft  77 .  
     [0067] In the thus constituted cam position change-over mechanism  90 , when the electromagnetic solenoid  900  (SOL 2 ) is de-energized, the plunger  901  protrudes as shown in FIG. 2, the cam shaft  76  is moved backward (upward in FIGS. 2 and 3) due to the resilient force of the compression coil spring  97  and is brought to the first position (three-hole-punching position) in FIG. 2. In a state where the cam shaft  76  is brought to the first position, the cams  77 - 1 ,  77 - 3  and  77 - 5  are brought to the positions so as to correspond to the pushing mechanisms  73 - 1 ,  73 - 3  and  73 - 5 . When the electromagnetic solenoid  900  (SOL 2 ) is energized, on the other hand, the plunger  901  is attracted overcoming the resilient force of the compression coil spring  97 . Accordingly, the cam shaft  76  moves toward the front side (downward in FIGS. 2 and 3) and is brought to the second position (two-hole-punching position) shown in FIG. 3. In a state where the cam shaft  76  is brought to the second position, the cams  77 - 2  and  77 - 4  are brought to the positions so as to be corresponded to the pushing mechanisms  73 - 2  and  73 - 4 .  
     [0068] The after-treatment device  4  equipped with the illustrated paper punching device  50  further has a control means  100  shown in FIG. 11. The control means  100  is constituted by a microcomputer and includes a central processing unit (CPU)  101  for executing the processing according to a control program, a read-only memory (ROM)  102  for storing the control program, a random access memory (RAM)  103  for storing the results of processing, a timer  104  (T), a counter  105 , an input interface  106 , and an output interface  107 . The input interface  106  of the thus constituted control means  100  receives a detection signal from the paper detector  67  (SW 1 ) or the like, and sends, through an output interface  107  thereof, control signals to the electric motor  44  (M 1 ), electromagnetic solenoid  47  (SOL 1 ), electromagnetic solenoid  750  (SOL 2 ), flapper-type solenoid  84  (SOL 3 ) and electromagnetic clutch  66  (CLT 1 ), etc. The control means  100  is connected to a control means  200  of the copier body  2 , and control signals are exchanged between them. The control means  200  of the copier body  2  receives copy data from a copying start key  201  (SW 2 ), a two-hole-punching key  202  (SW 3 ), a three-hole-punching key  203  (SW 4 ), a staple key  204  (SW 5 ) arranged on the operation panel of the copier body  2  or the like.  
     [0069] The after-treatment device equipped with the paper punching device of the illustrated embodiment is constituted as described above. The punching operation will now be described with reference to FIGS. 9 and 10 which illustrate the operation conditions, and FIG. 12 which is a flowchart.  
     [0070] When the control means  100  starts operating, the control means  200  of the copier body  2  first checks whether the two-hole-punching key  202  (SW 3 ) is depressed to specify the two-hole punching (step S 1 ). When the two-hole punching is specified, the routine proceeds to step S 2 . When the two-hole punching has not been specified, the routine proceeds to step S 3 . When the two-hole punching has been specified at step S 1 , the routine of the control means  100  proceeds to step S 2  to energize the electromagnetic solenoid  900  (SOL 2 ) that constitutes the cam position change-over mechanism  90  to operate the cam shaft  76 . As the electromagnetic solenoid  900  (SOL 2 ) is energized, the cam shaft  76  is brought to the second position (two-hole-punching position) shown in FIG. 3 as described above, and the cams  77 - 2  and  77 - 4  are brought to the positions corresponding to the pushing members  730  of the pushing mechanisms  73 - 2  and  73 - 4 . When the two-hole punching has not been specified at step S 1 , on the other hand, the control means  100  proceeds to step S 3  where the control means  200  of the copier body  2  checks whether the three-hole-punching key  203  (SW 4 ) is depressed to specify the three-hole punching. When the three-hole punching has not been specified at step S 3 , the control means  100  judges that the punching has not been specified and returns back to the start. When the three-hole punching has been specified at step S 3 , the control means  100  proceeds to step S 4  to de-energize the electromagnetic solenoid  900  (SOL 2 ). When the electromagnetic solenoid  900  (SOL 2 ) is de-energized, the cam shaft  76  is brought to the first position (three-hole-punching position) shown in FIG. 2 as described above, and the cams  77 - 1 ,  77 - 3  and  77 - 5  are brought to the positions corresponding to the pushing members  730  of the pushing mechanisms  73 - 1 ,  73 - 3  and  73 - 5 .  
     [0071] When the pushing mechanism  73  is set to the two-hole-punching state or to the three-hole-punching state, both the flapper-type solenoid  84  (SOL 3 ) and the rotation control member  834  are under a state as shown in FIG. 9( a ). That is, the flapper-type solenoid  84  (SOL 3 ) has been de-energized, and the flapper  843  is brought to a position where the anchoring portion  843   b  engages with the anchoring portion  834   c  of the anchoring pawl  834   b . Further, the cam  77  mounted on the cam shaft  76  and the pushing mechanism  73  are under a state shown in FIG. 10( a ). That is, the smallest diameter portion of the cam  77  is in contact with the upper surface of the pushing portion  731  of the pushing member  730  constituting the pushing mechanism  73 . Therefore, the punch  72  operated by the pushing mechanism  73  is brought to the retracted position. Here, in this embodiment, it is presumed that the electromagnetic solenoid  47  (SOL 1 ) has been de-energized, and the branching pawl  46  has been brought to the first position indicated by the solid line in FIG. 1.  
     [0072] When the pushing mechanisms  73  are set to the two-hole-punching state or to the three-hole-punching state as described above, the control means  100  proceeds to step S 5  and checks whether the paper detector  67  (SW 1 ) has been turned on. That is, the control means  100  checks whether the leading edge of the paper having image formed thereon in the copier body  2  and introduced into the after-treatment device  4  passing through the paper introduction port  401 , has reached the paper detector  67  (SW 1 ). When the paper detector  67  (SW 1 ) has not been turned on at step S 5 , the control means  100  waits until it is turned on. When the paper detector  67  (SW 1 ) has turned on, the control means  100  so judges that the leading edge of the paper has reached the paper detector  67  (SW 1 ), and proceeds to step S 6  to de-energize the electromagnetic clutch  66  (CLT 1 ) that disconnects or connects the transmission of power to the pair of resist rotors  65 , so that the pair of resist rotors  65  are maintained in a halted state, the electric motor  44  (M 1 ) is driven and the timer  104  (T) is set to a predetermined set time T 1 . The predetermined set time T 1  is a time required until the leading edge of the paper that has passed over the paper detector  67  (SW 1 ) comes into contact with the nipping portion of the pair of resist rollers  65  that are in a halted state, and has been set to be, for example, 150 μsec. Even after the leading edge has come in contact with the nipping portion of the pair of resist rollers  65 , the paper P is still being sent by the pair of discharge rollers  35  of the copier body  2 . Therefore, the paper P is guided by the end on the upstream side of the upper guide plate  61  constituting the paper guide means  60  and by the guide plate  411  provided in the paper introduction port, and becomes curved to form a so-called loop as indicated by a dot-chain line in FIG. 1.  
     [0073] Next, the control means  100  proceeds to step S 7  and checks whether the elapsed time TS has reached the above set time T 1  after the paper detector  67  (SW 1 ) had been turned on. When the elapsed time TS does not still reach the set time T 1 , the control means  100  waits until it reaches the set time T 1 . When the elapsed time TS has reached the set time T 1 , the control means  100  so judges that the leading edge of the paper has come in contact with the nipping portion of the pair of resist rollers  65  and, then, proceeds to step S 8  to energize the flapper-type solenoid  84  (SOL 3 ). When the flapper-type solenoid  84  (SOL 3 ) is energized, the flapper  843  is attracted to be pulled downward from the state of FIG. 9( a ), and the engaging portion  843   b  is brought to a position in a gap between the anchoring portion  834   c  of the anchoring pawl  834   b  and the outer peripheral surface of the main body  834   a . Therefore, the rotary control member  834  is allowed to rotate, and the driving force transmitted to the drive gear  78  is transmitted to the cam shaft  76  via the spring clutch  83 . Therefore, the rotation control member  834 , too, rotates in a direction indicated by an arrow as shown in FIG. 9( b ). Further, as the control means  100  energizes the flapper-type solenoid  84  (SOL 3 ) at step S 8 , simultaneously it sets the timer  104  (T) to a predetermined set time T 2 . The predetermined set time T 2  is a time required until the rotation control member  834  is turned by about 90 degrees from the state of FIG. 9( a ) to the state of FIG. 9( b ) after the flapper-type solenoid  84  (SOL 3 ) had been energized, and has been set to be, for example, 25 μsec. When the rotation control member  834  is allowed to turn, the driving force transmitted to the drive gear  78  is transmitted to the cam shaft  77  through the spring clutch  83  as described above. Accordingly, the cam shaft  76  is rotated in the direction indicated by an arrow from a state of FIG. 10( a ) to a state of FIG. 10( b ).  
     [0074] Next, the control means  100  proceeds to step S 9  to energize the flapper-type solenoid  84  (SOL 3 ) and to check whether the elapsed time TS has reached the above set time T 2  after the rotation control member  834  had started rotating. When the elapsed time TS does not reach the set time T 2 , the control means  100  waits until it reaches the set time T 2 . When the elapsed time TS has reached the set time T″, the control means  100  so judges that the rotation control member  834  has turned by about 90 degrees from a state of FIG. 9( a ) to a state of FIG. 9( b ), and proceeds to step S 10  to de-energize the flapper-type solenoid  84  (SOL 3 ). The control means  100  further sets a timer  104 (T) to a predetermined set time T 3 . The predetermined set time T 3  is a time required until the rotation control member  834  rotates by about 270 degrees from the state of FIG. 9( b ) to reach a position of FIG. 9( c ), and has been set to be, for example, 75 μsec. The cam  77  mounted on the cam shaft  76 , too, rotates in the direction indicated by an arrow from the state shown in FIG. 10( b ). The punch  72  reaches the lowest punching position in a state where the cam  77  has turned by about 180 degrees from the state of FIG. 10( b ) to the state of FIG. 10( c ). In this state, the punch  72  operated by the pushing mechanism  73  has its punching blade  721  at the lower end thereof moved down to a position under the lower guide plate  62  passing through the hole  611  formed in the upper guide plate  61  and through the punching hole  621  formed in the lower guide plate  62 . During this period, two holes or three holes are punched in the paper P that has been conveyed between the upper guide plate  61  and the lower guide plate  62 . As the cam shaft  76  or the cam  77  further rotates in the direction of the arrow from the state of FIG. 10( c ), the punch  72  operated by the pushing mechanism  73  rises to a position above the upper guide plate  61 . Then, as the cam shaft  76  rotates by  270  degrees from the state of FIGS.  9 ( b ) and  10 ( b ) (rotates one turn from the state of FIGS.  9 ( a ) and  10 ( a )), the anchoring portion  834   c  of the anchoring pawl  834   b  of the rotation control member  834  comes in contact with the engaging portion  843   b  of the flapper  843  of the flapper-type solenoid  84  (SOL 3 ) as shown in FIG. 9( a ) to limit the rotation of the rotation control member  834 . Therefore, the transmission of drive power by the spring clutch  83  is interrupted and the cam shaft  76  ceases to rotate. In this state, the cam  77  mounted on the cam shaft  76  and the pushing mechanism  73  return to the state (retracted position) shown in FIG. 10( a ).  
     [0075] At the time of returning back to the retracted position shown in FIG. 10( a ) from the state of being punched by the punch  72  shown in FIG. 10( c ), it becomes difficult to move the punch  72  toward the retracted position when the resisting force between the punch  72  and the paper having been punched is larger than the resilient force of the compression coil spring  79 . In the illustrated embodiment, however, the cam  77  that rotates acts on the lower surface of the return-operation portion  733   c  of the return member  733  to push up the pushing mechanism  73 . Therefore, the punch  72  coupled to the pushing mechanism  73  can be brought to the predetermined retracted position.  
     [0076] In the state shown in FIG. 10( c ), when the cam  77  has not been brought to the positions to correspond to the pushing member  730 , the punch does not operate. If the punch  72  has moved down due to some cause, however, either the sub-return operation portion  733   f  or  733   g  is constituted to correspond to the cam  77 . Therefore, the cam  77  acts on the lower surface of the sub-return operation portion  733   f  ( 733   g ) to push the pushing mechanism  73  up thereby to bring the punch  72  to the predetermined retracted position.  
     [0077] When the flapper-type solenoid  84  (SOL 3 ) is de-energized at step S 10  and the timer  104  (T) is set to the predetermined set time T 3 , the control means  100  proceeds to step S 11  to check whether the elapsed time TS has reached the above set time T 3  after the flapper-type solenoid  84  (SOL 3 ) had been de-energized. When the elapsed time TS does not reach the set time T 3 , the control means  100  waits until it reaches set time. When the elapsed time TS has reached the set time T 3 , the control means  100  so judges that the punching operation has finished and proceeds to step S 12  to energize the electromagnetic clutch  66  (CLT 1 ). When the electromagnetic clutch  66  (CLT 1 ) is energized, the pair of resist rollers  65  are driven to convey the paper subjected to the two-hole punching or to the three-hole punching toward the pair of discharge rollers  42 , and then the paper is discharged by the pair of discharge rollers  42  onto a tray  48  for non-sorting. The control means  100  sets the timer  104  (T) to a predetermined set time T 4 . The predetermined set time T 4  is a time required for judging whether the punching operation has ended for the last paper on which the image has been formed in the copier body  2  and which has been conveyed to the after-treatment device  4 .  
     [0078] Next, the control means proceeds to step S 13  to check whether the elapsed time TS has reached the set time T 4  after the paper punched had been conveyed toward the pair of discharge rollers  43  by driving the pair of resist rollers  65 . When the elapsed time TS does not reach the set time T 4 , the control means  100  proceeds to step S 14  to check whether the paper detector  67  (SW 1 ) has been turned on. When the paper detector  67  (SW 1 ) has been turned on, it is so judged that the leading end of the next paper has reached the paper detector  67  (SW 1 ), and the routine returns to step S 6  to repeat the procedures of step S 6  through step S 14 . When the paper detector  67  (SW 1 ) has not been turned on at step S 14 , the next paper is not conveyed from the copier body  2 . Therefore, the routine returns back to step  13 , and the procedures of step S 13  and step S 14  are repeated. When the elapsed time TS has reached the set time T 4  after the paper punched had been conveyed toward the pair of discharge rollers  42  by driving the pair of resist rollers  65  while repeating the procedures of step S 13  and step  14 , the control means  100  so judges that the punching operation has ended for the last paper on which the image has been formed in the copier body  2  and which has been conveyed to the after-treatment device  4 . The control means  100 , then, proceeds to step S 15  and de-energizes the electromagnetic solenoid  750  (SOL 2 ) that operates the change-over shaft  74 , de-energizes the electromagnetic clutch  66  (CLT 1 ) and brings the electric motor  44  (M 1 ) into a halt to end the punching operation.  
     [0079] In the foregoing has been described the invention by way of a illustrated embodiment. The invention, however, is in no way limited to the illustrated embodiment only. In the illustrated embodiment, the invention is applied to the after-treatment device. According to the present invention, however, the paper punching device may be incorporated in the image-forming apparatus.  
     [0080] Being constituted as described above, the paper punching device according to the invention exhibits actions and effects as described below.  
     [0081] That is, according to the present invention, the punch-operating mechanism includes a cam shaft disposed along a direction in which said plural pushing mechanisms are arranged, plural cams formed on said cam shaft, a cam drive mechanism for rotating said cam shaft, and a cam position change-over mechanism which operates said cam shaft in the axial direction so as to be selectively brought to a first position where some cams out of the plural cams correspond to some pushing members out of said plural pushing members and to a second position where the other cams out of said plural cams correspond to the other pushing members out of said plural pushing members. Upon moving the cam shaft in the axial direction, it is allowed to select two kinds of holes. Therefore, the device can be constituted in a compact size using a decreased number of parts. As a result of decrease in the number of parts that operate, the obtained paper punching device produces small noise.