Abstract:
The present invention related to a sheet conveying apparatus comprising a first unit, a second unit and a guide member. The first unit includes a first sheet conveyance route, a second sheet conveyance route, a first delivery opening for delivering, from the first unit, a sheet or sheets from the first sheet conveyance route, and a second delivery opening for delivering, from the second unit, a sheet or sheets from the second sheet conveyance route. The second unit is positioned with a space to the first unit, the second unit having a third sheet conveyance route, and a single introduction opening for introducing, to the third sheet conveyance route, a sheet or sheets delivered from the first delivery opening and the second delivery opening. At least a part of the guide member is disposed at a space between the first unit and the second unit, having a first guide surface for guiding the sheet or sheets from the first delivery opening to the introduction opening, and a second guide surface for guiding the sheet or sheets from the second delivery opening to the introduction opening.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a sheet conveying apparatus, a sheet feeding apparatus, and a sheet delivering apparatus for feeding or delivering original documents and recording sheets to an image forming apparatus such as a printer, facsimile machine, or photocopier. 
     2. Description of Prior Art 
     Image forming apparatuses such as printers, facsimile machines, and photocopiers are recently produced with high performance in accordance with increased processing speed, and have a trend to increase the capacity of the sheet stacking apparatus and the sheet delivering apparatus. 
     Such an image forming apparatus capable of processing sheets in a large volume can be used in coupling with, in meeting usage of the users, large capacity sheet feeding apparatus or sheet stacking apparatus (sheet processing apparatus) as their optional choices. 
     A type of the large capacity sheet conveying apparatuses has sheet containing means and feeding means provided on left and right sides. In this sheet feeding apparatus, the conveyance route from one sheet containing means is disposed over the other sheet containing means and the feeding means. 
     FIG. 8 shows such a conventional apparatus. The conventional image forming apparatus X is constituted of a lower sheet feeding apparatus  300  and an upper laser beam printer  400 . In this sheet feeding apparatus  300 , a sheet S fed from a left side sheet containing means  303  by a feeding means  305  passes through a conveyance route  306  placed above a right side sheet containing means  304  and is sent to the image forming apparatus after merging with a conveyance route  307  from the right side sheet containing means  304 . Position sensor units  301 ,  302  are formed on the right and left sides slightly before the merging point to detect the sheet position. The sensor unit is constituted of a flag, a rotary shaft of a flag, and a photo sensor. In the laser beam printer  400 , a sheet conveyance route  402  extends from a tray stacking sheets S and reaches a delivery tray  405  by way of a process cartridge  407  and a fixing means  404 , as the image forming means. An option conveyance route  406  in connection with the conveyance route  310  integrating the two conveyance routes  302 ,  307  at the sheet feeding apparatus  300  as described above merges to the sheet conveyance route  402 . 
     In the sheet feeding apparatus, however, a merging space is required in a vertical direction because the conveyance route from the left side sheet containing means and the right side sheet containing means are merged in the sheet feeding apparatus, so that the stacking height of the right and left side sheet containing means is limited, and so that the sheet feeding apparatus cannot store many sheets. 
     The position sensor units  301 ,  302  for the left side sheet containing means and the right side sheet containing means are placed independently at positions separating from one another, and therefore, wiring for the photo sensor becomes complicated, and the apparatus becomes expensive since a pair of the flag rotary shafts and sensor holders has to be provided. 
     SUMMARY OF THE INVENTION 
     An invented structure to accomplish the above objects has a sheet conveying apparatus characterized in including a first unit and a second unit formed with a space between the first and second units, the first unit including a first sheet conveyance route, a second sheet conveyance route, a first delivery opening for delivering, from the first unit, a sheet or sheets from the first sheet conveyance route, and a second delivery opening for delivering, from the second unit, a sheet or sheets from the second sheet conveyance route, the second unit having a third sheet conveyance route, and a single introduction opening for introducing, to the third sheet conveyance route, a sheet or sheets delivered from the first delivery opening and the second delivery opening, and a guide member, disposed at a space between the first unit and the second unit, having a first guide surface for guiding the sheet or sheets from the first delivery opening to the introduction opening, and a second guide surface for guiding the sheet or sheets from the second delivery opening to the introduction opening. 
     According to the invention, because the guide member, at least partly, is disposed between the first unit and the second unit, the merging point of the plural conveyance routes can be placed in the space between the units, and therefore, the first unit can be made compact. Particularly, where the first unit is a sheet feeding apparatus for feeding the sheet to the second unit having the image forming means, the conveyance route can be placed at a further upper position, and the sheet stacking amount can be made relatively larger. 
     In another aspect, an invented sheet feeding apparatus includes a detecting means for detecting whether any sheet exists in two sheet conveyance routes located adjacently. The detecting means includes in a region between the two conveyance routes two sensors, a rotary shaft, and two sensor flags rotatably with respect to the rotary shaft, placed at a position for shielding each conveyance route. Each of the sensor flags has a region that a contacting portion of the flag in contact with the sheet coincides with each other in a sheet width direction as the perpendicular direction to the sheet conveyance direction. With the guide member having the sensor thus structured, the plural conveyance routes can be detected with such a simple structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross section showing the whole structure of a printer to which a deck is mounted; 
     FIG. 2 is a cross section showing a conveyance portion according to a first embodiment of the invention; 
     FIG. 3 is a perspective view showing a sensor unit according to the first embodiment of the invention; 
     FIG. 4 is a top view showing a sensor unit according to the first embodiment of the invention; 
     FIG. 5 is a perspective view showing a sensor unit according to a second embodiment of the invention; 
     FIGS.  6 ( a ) and  6 ( b ) are cross sections, each showing a state of a merging guide according to a third embodiment of the invention; 
     FIGS.  7 ( a ) and  7 ( b ) are cross sections, each showing a state of a merging guide according to a fourth embodiment of the invention; and 
     FIG. 8 is an illustration showing a conventional apparatus. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1 to FIG. 4, a sheet feeding apparatus as a first embodiment of the invention is described. It is to be noted that in this embodiment, a sheet feeding apparatus  14  coupled to a laser beam printer  1  (hereinafter, referred to as “LBP  1 ”), as an example, is described for the invention. 
     Numeral A is an image forming apparatus and is constituted of a sheet feeding portion (image forming apparatus  13 ) as a first unit and an image forming portion (LBP  1 ) as a second unit. 
     First of all, in the LBP  1 , numeral  2  is a cassette containing sheets S in a stacking manner and is attached to a lower portion of the LBP  1  detachably in a near side direction. Numeral  3  is a pickup roller and sends the sheets S stacked on the cassette  2  from the topmost side. Numeral  4  is a retard roller pair for separately conveying the sent sheets sheet by sheet. 
     Numeral  7  is a process cartridge incorporating known processing mean for forming images on the conveyed sheet and is detachably attached to the apparatus body. 
     In the process cartridge  7 , incorporated are a photosensitive drum  7   a  as an image carrier, a charger  7   b  for charging the surface of the drum  7   a , a developing apparatus for developing latent images formed on the drum  7   a  to produce developed images (toner images), a cleaner  7   d  for removing waste toner remaining on the surface of the drum  7   a , and the like. 
     Latent images are recorded on the photosensitive drum  7   a  by radiating laser beam from a laser exposing apparatus  8  according to image information. A transfer roller  9  is pushed to the photosensitive drum  7   a , and when the sheet S passes between the photosensitive drum  7   a  and the transfer roller  9 , the toner image on the photosensitive drum  7   a  is transferred to the sheet S in application of a voltage having a reverse polarity to the toner image. 
     Numeral  10  is a fixing apparatus for fixing the transferred image by application of heats and pressure to the sheet S after image transfer. 
     The image forming means is made of the process cartridge  7 , the transfer roller  9 , the fixing apparatus  10 , and the like. 
     The sheet S after image transfer is conveyed through a reverse path  18  and delivered by a delivery roller pair  11  on a delivery tray  12  formed on the top of the apparatus in a face down manner in which the image side faces down. 
     Next, the sheet feeding apparatus as the first unit is described. A deck as a sheet feeding apparatus is also used as the mounting base of the LBP  1  and placed below the LBP  1 . The sheet feeding apparatus  13  contains in a stacking manner the sheets S having a relatively large size which cannot be contained in the cassette  2 . The sheet feeding apparatus  13  can supply the sheets S in a large volume to the LBP  1 . 
     Storages  15 ,  115  are structured to be pulled in a near side direction by rollers  16 ,  116  formed on left and right sides and a guide  85  formed at a frame  17 . Numerals  14 ,  114  are trays movable up and down in stacking the sheets S (respectively, first sheet feeding means, and second sheet feeding means) disposed in the left and right storages  15 ,  115  and are installed to be pulled with the storages to stack the sheets S on the trays  14 ,  114 . 
     At the frame of the sheet feeding apparatus  13 , provided are pickup rollers  19 ,  119  for feeding out the sheets S on the trays  14 ,  114  from the topmost sheet of the sheets S, and retard roller pair  20 ,  120  for separately conveying sheets S sheet by sheet. 
     The trays  14 ,  114  are suspended inside the storages  15 ,  115  where wire ropes  22   a ,  22   b ,  22   c ,  22   d  and  122   a ,  122   b ,  122   c ,  122   d  are secured around four corners. The other ends of wire ropes are coupled to respective winches  24 ,  124  arranged on front and rear sides of the lower portion of the storages  15 ,  15  by way of pulleys  23   a ,  23   b ,  23   c ,  23   d  and  123   a ,  123   b ,  123   c ,  123   d  formed rotatably at a top of the storages  15 ,  115 . 
     The winches  24 ,  124  are secured to winding shafts  25 ,  125 , respectively, to which gears not shown are attached and are coupled to a gear of a motor M formed at the frame where the storages  15 ,  115  are attached to the frame. The winches  24 ,  124  are rotated by drive of the motor M, thereby lifting up the trays  14 ,  114  upon winding the respective wire ropes on the bodies of the winches  24 ,  124 . 
     Where the storages  15 ,  115  are pulled out of the frame, the gears of the winches  24 ,  124  are disengaged from the gear of the motor M 1  secured to the frame  17 , and the respective wound wire ropes are wound back by self-weights of the sheets S and the trays  14 ,  114  to move down the trays  14 ,  114 . 
     Brake dumpers, not shown, are formed at the winding shafts  25 ,  125  to soften impacts given when the trays  14 ,  114  move down and are coupled to gears attached to the winding shafts  25 ,  125 . 
     Paper surface sensors, not shown, are formed at the frame for detecting the paper surface (top surface) of the trays  14 ,  114  moving up, and when the sensors detect the paper surface (top surface) of the trays  14 ,  114  moving up, the motor M rotating the winches  24 ,  124  stops driving. 
     The sheets S stacked on the trays  14 ,  114  are fed out by the pickup rollers  19 ,  119  and the retard rollers  20 ,  120  formed at the frame  17 , and where the paper surface is lowered, the motor M is driven to move the trays  14 ,  114  up until the detecting means detects the paper surface. The topmost surface of the sheets S stacked on the trays  14 ,  114 , thus, can be always maintained at substantially a constant level. 
     Now, a sheet conveyance route and operation in which the sheets S from the tray  14  on the right side are sent to the LBP  1  as an image forming apparatus. A first sheet conveyance route  126  extending from the left side tray  14  and a second sheet conveyance route  26  extending from the right side tray  114  have a first delivery opening  126   a  and a second delivery opening  26   a , which are independent of each other and are formed on a top of the sheet feeding apparatus  13 , and a merging guide  50  is arranged between the routes. 
     The sheets S are fed out by the pickup roller  19 , and the sheets S separated by the retard roller pair  20  are delivered out of the sheet feeding apparatus  13  through the second conveyance route  26  after moving rotationally a flag  31  of a position sensor unit  30 . A second guide surface  50   c  is formed by the merging guide at a part of the sheet conveyance route  26 . The sheets S pass by the merging guide  50  being formed of ribs provided in a plural number extending in the sheet width direction and having a tip  50   a  located at a higher position than the mounting surface  80  for the sheet feeding apparatus  13  and rubber pads  80  of the LBP  1 . That is, a merging point G 1  of the conveyance route  26  from the right side feeding means and the conveyance route  126 , as described above, from the left side feeding means is formed above the merging guide  50 , and a sheet from either route is conveyed to the LBP  1 . At that time, because the opening width d of a second delivery opening  26   a  and a second delivery opening  126   a  formed at a top of the sheet feeding apparatus  13  is narrower than a width D of an introduction opening of the LBP  1 , the sheet S can enter smoothly into the LBP  1 . 
     Next, operation for feeding sheets from the left side tray  114  to the image forming apparatus is described. 
     The sheet S fed out of the pickup roller  119  and separated by the retard roller pair  120  is delivered from the sheet feeding apparatus  13  after rotating the flag  31  of the position sensor unit  30  upon passing a conveyance portion  51  formed at a top of the storage  15 . The sheet S is conveyed to the LBP  1  upon passing the merging point G 1  for the first sheet conveyance route  126  from the left side feeding means defined by the merging guide  50  having the tip at a higher position than the mounting surface for the sheet feeding apparatus  13  and the rubber pads  80  of the LBP  1 . 
     The sheet S is at that time conveyed as sliding on a first guide surface  50   b  along the first guide surface  50   b , having a radius of curvature, of the merging guide  50 . As for the sheet conveyance from this side, the sheet S can be entered smoothly into the LBP  1  because the width d of the outlet of the sheet feeding apparatus  13  is set narrower than the width D of the introduction opening of the LBP  1 . 
     The sheet S fed from the respective feeding means is successively sent to a conveyance roller pair  41 , and then passes a merging point G 2  also for a conveyance route  45  provided for sheets fed by the pickup roller  3  from the cassette  2  of the LBP  1  to be sent to the image forming portion by a roller pair  42 ,  43 . 
     Since a part of the merging guide  50  and the merging point G 1  are provided between the sheet feeding apparatus  13  and the LBP  1 , no merging point is required to be formed inside the sheet feeding apparatus  13 . Therefore, the conveyance portion  51  located over the storage  15  can be placed upwardly, so that the sheet stacking amount can be relatively increased in the storages  15 ,  115  serving as a sheet stacking means. 
     Now, a structure of the conveyance portion around the merging point G 1  is described. FIG. 2 is a cross section around the merging point G 1 ; FIG. 3 is a perspective view of the position sensor unit  30 ; FIG. 4 is a top view of the position sensor unit  30 . 
     The position sensor unit  30  is located at a region between the sheet conveyance route  126  from the left side feeding means  19  and the sheet conveyance route  26  from the right side feeding means  19 . In the structure of the unit  30 , two photo sensors  34 ,  35  and a rotary shaft  36  are secured to a stay  33 , and the flag  32  and the flag  31  are independently rotatable around the rotary shaft  36  where the flag  32  is urged in the counterclockwise direction by a pulling spring  38  and where the flag  31  is urged in the clockwise direction by a pulling spring  37 . 
     Shapes of the flags  31 ,  32  are described. Actuators  31   a ,  32   a  serving as contact portions that the flags  31 ,  32  are in contact with the sheet, both have a predetermined width located at a position including a center position in the width direction of the sheet to be fed. 
     Even where the actuators  31   a ,  32   a  are disposed to occupy the common position in the width direction of the respective sheet conveyance routes, the actuators  31   a ,  32   a  are formed with cutouts  31   d ,  32   d , respectively, as to avoid interference with each other where the flags  31 ,  32  are independently operable where the sheets S are conveyed to the respective conveyance routes. 
     The flag  31  and the flag  32  have walls  31   b ,  32   b , respectively, and the flags urged by the pulling springs  37 ,  38  are stopped at positions at which the walls  31   b ,  32   b  of the respective flags are in contact with the photo sensors  34 ,  35  to set the positions. 
     Photo-shielding portions of the photo sensors  34 ,  35  have photo shielding plates  31   c ,  32   c  of the flags, respectively. Where no sheet exists, the photo shielding plates  31   c ,  32   c  of the flags cut off light from the light emitting devices of the photo sensors so that the light does not reach the light receiving device, and the photo sensors enter into the off state. When the sheet S exists, the flags  31 ,  32  moves rotatively to render the photo shielding plates  31   c ,  32   c  of the flags move back from the light emitting devices to pass the light. 
     Next, operation of the flags is described. Where no sheet exists in the conveyance routes or it is at the initial stage, the flags  31 ,  32  are urged by the pulling springs  37 , 38  to positions to shield the light at the photo sensors  34 ,  35 , respectively. Where the flag  32  is rotated in the clockwise direction and the flag  31  is rotated in the counterclockwise direction where the front end of the sheet S is conveyed through the conveyance routes, the photo shielding plates  31   c ,  32   c  shielding the photo sensors  34 ,  35  also rotate to render the photo sensors  34 ,  35  at a light passing state. When the rear end of the sheet S passes, the flags  31 ,  32  are returned to the initial state by the pulling springs  37 ,  38 . 
     With this structure, the position sensor unit, which was independently formed for each conveyance route in conventional apparatuses, can be made in a united body, so that the apparatus can be made compact and less complicated. Moreover, inexpensive sheet feeding apparatuses can be provided because the position sensor can be made less complicated. 
     Referring to FIG. 5, a second embodiment is described. 
     Although the two photo sensors are provided in the position sensor unit  30  in the first embodiment, the second embodiment has a feature that a single photo sensor is formed. 
     FIG. 5 is a perspective view of a position sensor unit  130 . A stay  133  is secured to a rotary shaft  136  in the same way as those in the first embodiment, and the flag  131  and the flag  132  are rotatable around the rotary shaft  136  where the flag  132  is urged in the counterclockwise direction by a pulling spring  138  and where the flag  131  is urged in the clockwise direction by a pulling spring  137 . 
     Differences in the structure from the first embodiment are only that a sole photo sensor  134  is provided at a center of the stay  133  and that the photo-shielding plates of the flags  131 ,  132  have different shapes. A wall serving as a stopper for rotation of the flags is not shown. 
     Next, operation of flags is described. Where no sheet exists in the conveyance routes or it is at the initial stage, the flags  131 ,  132  are urged by the pulling springs  137 ,  138  to positions to pass the light at the photo sensor  134 , though in the first embodiment at the shielding state. 
     Where the flag  132  is rotated in the clockwise direction where the front end of the sheet S is conveyed through the conveyance route  126  to contact with the actuator  132   a  in the case that the sheet S is fed from the left side feeding means  119 , the photo shielding plates  132   c  at a position escaping from the photo sensor  134  also rotates to render the photo sensor  134  at a light shielding state. When the rear end of the sheet S passes, the flag  132  is returned to the initial state by the pulling spring  138 . 
     Where the flag  131  is rotated in the counterclockwise direction where the front end of the sheet S is conveyed through the conveyance route  26  to contact with the actuator  131   a  in the case that the sheet S is fed from the right side feeding means  19 , the photo shielding plates  131   c  at a position escaping from the photo sensor  134  also rotates to render the photo sensor  134  at a light shielding state. When the rear end of the sheet S passes, the flag  131  is returned to the initial state by the pulling spring  137 . 
     With this position sensor  130 , judgment as to whether the sheet is conveyed from either the right side feeding means or the left side feeding means cannot be made since only one photo sensor is provided in this embodiment, but the controller for the image forming apparatus (A) body for controlling the sheet feeding apparatus  13  knows which feeding means makes feeding, so that this information can be utilized. 
     Referring to FIGS.  6 ( a ) and  6 ( b ), the third embodiment is described next. 
     In the first and second embodiments, the merging guide  50  is provided having the merging point G 1  between the sheet feeding apparatus and the LBP  1 , but the third embodiment has a feature that the merging guide  150  is made of two parts and that the front end member  151  moves up and down by external force. Other structures and operations are the same as those in the first embodiment, so the duplicated description is omitted. 
     In general, when the LBP  1  is mounted to the sheet feeding apparatus  13 , several operators hold the LBP  1  and work to set the LBP  1  on the sheet feeding apparatus  13 . The LBP  1  and the sheet feeding apparatus  13  are set to the right place by engaging positioning pins, not shown, formed at the sheet feeding apparatus  13  with positioning holes, not shown, formed at the LBP  1 . However, in some cases, the apparatus cannot be mounted properly. In such a case, if the rubber pads  80  of the LBP  1  contact with the tip  50   a  of the merging guide, the merging guide may be disadvantageously damaged due to the weight of the LBP  1 . 
     In this embodiment, the tip member  151  has a structure capable of escaping up to a position that the rubber pad  80  can be installed at a place capable of supporting the LBP  1 . 
     The merging guide  150  is described herein. The tip member  151  is structure not of ribs but of a united part extending in the sheet width direction. Among parts constituting the merging guide  150 , the tip member  151  is slidably provided in the up and down direction with respect to a base member  152 , and the tip member  151  is urged upward at both ends by the compression spring  153 . The position of the tip member is determined by contact between a stopper portion  151  a formed at the tip member  151  and a stopper portion  152   a  of the base member. In FIG. 6, the compression spring  153  located on the rear side is shown. 
     FIG.  6 ( b ) shows a state that the rubber pad  80  is mistakenly placed on the tip portion of the merging guide  150 . In this case, the tip member  151  moves down upon contraction of the compression spring  153  due to the weight of the LBP  1 . This structure can prevent the merging guide  150  from being damaged. 
     Referring to FIGS.  7 ( a ) and  7 ( b ), the fourth embodiment is described next. 
     In the third embodiment, the tip member  151  of the merging guide escapes downward when the rubber pad  80  of the LBP  1  is placed on the merging guide  150 , but in the fourth embodiment, the merging guide is in an escaping state while the LBP  1  is not set on the sheet feeding apparatus  13 , and the fourth embodiment has a feature that the merging guide moves upward in association with the mounting operation of the LBP  1 . Other structures and operations are the same as those in the third embodiment, so the duplicated description is omitted. 
     Referring to FIGS.  7 ( a ) and ( b ), a merging guide  250  is described herein. A tip member  251  is structure not to ribs in the same way as those in the third embodiment but of a united part extending in the sheet width direction. Among parts constituting the merging guide  250 , the tip member  251  is slidably provided in the up and down direction with respect to a base member  252 , and the tip member  251  is set downward where the image forming apparatus is not mounted as shown in FIG.  7 ( b ). 
     As shown in FIG.  7 ( a ), where the image forming apparatus is mounted, the rubber pads  80  urge a lever  253  upwardly at two points on a front side and a rear side at the opposite ends, thereby positioning a stopper portion  251   a  in contact with a stopper portion  252   a  of the base member. With this state, the lever  253  is projecting from the mounting surface of the rubber pads, or namely the top surface of the sheet feeding apparatus  13 . A contact portion  253   b  of the lever is disposed at a position where the rubber pad is mounted. 
     When the image forming apparatus  1  is set at the sheet feeding apparatus  13 , the rubber pad  80  rotates the lever  253  in the counterclockwise direction around a shaft  253   a , and thereby the lever  253  pushes up the bottom of the tip member  251  of the merging guide. 
     According to this structure, the tip member  251  of the merging guide does not move upward until the LBP 1  is mounted to a right position of the sheet feeding apparatus  13 , so that the rubber pads  80  can be set without contacting with the merging guide  250  during installation.