Abstract:
A drop-prevention mechanism for keeping original document sheets from falling off a document loading table openable on the upper surface of a multifunctional printer having, for example, faxing and photocopying capabilities. A loading section on the loading table loads documents for feeding to an automatic document feeder (ADF) that positions documents onto a rear image-reading part of the upper surface of the multifunctional printer. A discharge section of the loading table beneath the loading section receives documents discharged from the rear image-reading part by the ADF. The loading table is openable to expose a front image-reading part of the upper surface of the printer, where odd-sized documents, books and the like may be manually positioned for photocopying. When the loading table is swung up to expose the front image-reading section, the drop-prevention mechanism pivots catches (drop-prevention members) into position where the near edges of documents left stacked on the loading section abut on the catches, which prevents the documents on the loading table from falling off. When the loading table is swung down and closed onto the printer upper surface, (into the ADF operational position), the drop-prevention mechanism is stowed out of the way, so as not to interfere with the sheet-discharging operation of the ADF.

Description:
BACKGROUND OF THE INVENTION 
     TECHNICAL FIELD 
     The present invention relates to sheet conveyance devices, and in particular, to a sheet conveyance device in an automated document handler mounted on the upper part of an image reproducing apparatus. More specifically, in an image reproducing apparatus equipped with an openable document loading table, the invention concerns a drop-prevention mechanism for preventing documents or copy material sheets from dropping off the apparatus when the loading table is opened. 
     DESCRIPTION OF RELATED ART 
     Conventional facsimile machines, photocopier machines and other image reproducing apparatuses have an automated document conveyance device (sheet conveyance device) on top of the main unit of the image reproducing apparatus. FIG. 7 shows an example of this type of image reproducing apparatus. An automated document conveyance device (hereinafter automatic document feeder, or “ADF device”) is disposed on top of a main unit  600  in the apparatus of FIG.  7 . The ADF device has a document loading table  610  and a conveyance mechanism  620  disposed on the right side of the loading table  610  in the figure. The main unit  600  has a scanner  630  disposed below the loading table  610 ; an optical unit  640  disposed below the scanner  630 ; and an imaging unit  650  disposed below the optical unit  640 . The imaging unit  650  has a photosensitive drum  651 , and on the photosensitive drum  651  a toner image is formed from the image of the document exposed by laser light output from the optical unit  640 , and is transferred to a transfer sheet. The main unit  600  has a transfer sheet supply unit  660  having a sheet supply cassette  661  disposed below the imaging unit  650 ; a fixing unit  670  disposed on the downstream end of the transfer sheet supply unit  660 ; and a transfer-sheet discharge section  680  disposed on the downstream end of the fixing unit  670 . 
     The conveyance mechanism  620  of the ADF device conveys documents loaded onto the loading table  610 , one sheet at a time, toward the imaging unit  650  of the image reproducing apparatus main unit  600  using a sheet-feed roller or other sheet-feed means, and after the document image is read, returns the document onto the loading table  610 . 
     In recent years, with the spread of personal computers, offices have become increasingly networked, and in most offices there is a main printer. Demand has been increasing for equipment that will allow more efficient use of office space and for reduction of the costs associated with office equipment. This has resulted in multifunctional printers (image reproducing devices) that have multiple functions, including facsimile and photocopier capabilities. 
     The ADF devices mounted on such multifunctional image reproducing devices usually include a document loading table, as well as a discharge table for reloading of a document discharged from its image reading unit. This loading table and discharge table are normally mounted through a hinge mechanism along one edge, allowing them to open/shut in the upward direction against the image reproducing device. Thus when photocopying a thick document such as a book or other bound document, or in cases where a conveyed document causes a paper jam, operations can be performed with the ADF device in the open position. 
     As image reproducing apparatuses such as the above have become multifunctional, there has been demand for devices with good operability and which require still less space. Hence devices are offered wherein the discharge table for transfer sheets following image reproduction is disposed parallel to the loading table of the ADF device toward the front side of the main unit; and in order to lessen the effort needed to open and close the ADF device, that are built segregated into a section comprising the loading table and discharge table, and a section comprising a conveyance mechanism, with only the section comprising the loading table and discharge table being openable. 
     However, in a such conventional devices, when the ADF device is opened with a document loaded on the loading table or the discharge table, there is the problem of documents dropping from the loading table or the discharge table to the back of the image reproducing apparatus, that is, falling to the far side when seen from the operational direction. 
     To prevent documents thus from dropping, it is necessary to confirm in advance whether a document is loaded on the loading table or discharge table before opening the ADF device; if the document is loaded, it must first be removed before opening the ADF device. Consequently operability is poor. Furthermore, if several documents end up falling, trouble must be taken to arrange the documents after picking them up. 
     In order to resolve the aforementioned problems, technology such as that described in Japanese laid-open patent application 5-116804 has been proposed. Therein, when the movement of opening the upper part of the image reproducing apparatus main unit is detected, the document holding means, which is also the document feeding means, presses against the upper part of the document, preventing the document from falling. 
     However, in the aforementioned configuration a separate mechanism for pressing against and removal from the document is necessary—i.e., a document holding means—and a detection means for detection of the main unit opening is also necessary, thus increasing the number of parts, rendering the mechanism more complex, and increasing costs. 
     Furthermore, in an apparatus wherein the document loading table and discharge table are provided integrally as described above, the weight of the entire ADF device is increased, and so there is the problem that the burden on the operator is increased in opening and closing the device. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is reliably to keep original documents loaded on the open/closable loading table of a document conveyance device for an image reproducing apparatus from dropping off the conveyance device/image reproducing apparatus when the loading table is opened, meanwhile simplifying construction of such a document conveyance device over, and making it less expensive than, devices discussed in the foregoing. 
     Another object is wherein the loading table is closed in the document conveyance device to avoid interference with document conveyance, and to improve operating performance in opening and closing the loading table, and in preventing documents from dropping from the sheet conveyance device. 
     A further object of the invention is to configure an image reproducing apparatus with a sheet conveyance device meeting the above-noted objects. 
     The sheet conveyance device of this invention is disposed on the top part of an image reproducing apparatus main unit. Thus as a device for conveying sheets, it comprises a loading table, a conveyance mechanism, and a drop prevention mechanism. The loading table is hinge-fitted so that it can open away from the image reproducing apparatus main unit, and sheets are loaded thereon. The conveyance mechanism conveys the sheets loaded onto the loading table. The drop prevention mechanism is retracted so as not to impede the conveyance of sheets when the loading table is closed. When the loading table is opened, the drop prevention mechanism prevents sheets from falling from the loading table with the action of opening the loading table. 
     This device prevents the falling of sheets from on top of the loading table when the loading table is opened, so that there is no need for the user to remove sheets at the time of opening the loading table. 
     In this sheet conveyance device, it is preferable that the loading table be openable independently of the conveyance mechanism. 
     In this sheet conveyance device, it is preferable that the drop prevention mechanism have a rotary shaft, a drop-prevention mechanism, an urging member, and a regulating member. The rotary shaft is rotatably supported on the downstream conveyance direction end of the loading table. The drop-prevention mechanism is rotatable with the rotary shaft, and assumes both a first position, wherein the edges of sheets loaded on the loading table abut on it, and a second position, wherein it is out of contact with the sheet edges. The urging member urges the drop-prevention mechanism toward the first position. The regulating member positions the drop-prevention mechanism in the second position when the loading table is closed. 
     In this sheet conveyance device, the drop prevention mechanism may also comprise a pivot member capable of pivoting with the rotary shaft and the drop-prevention mechanism. Herein, it is preferable: that the urging member urge the drop-prevention mechanism toward the first position by urging the pivot member; that the regulating member be disposed on the top surface of the main unit of the image reproducing apparatus; and that the regulating member be an abutment piece that comes in contact with the aforementioned pivot member when the loading table is closed, to position the aforementioned drop-prevention mechanism in the aforementioned second position. 
     In this sheet conveyance device, it is preferable that wherein an image reading means is disposed in the upper part of the image reproducing apparatus, the abutment piece be disposed in a position away from the image reading means, and that it have a abutment portion that makes contact with the pivot member when the loading table is closed, and an sloped portion that makes contact with the pivot member and facilitates the pivoting of the pivot member that accompanies the opening and closing of the loading table. 
     In this sheet conveyance device, it is preferable that a stowing section be formed at the downstream conveyance direction end of the loading table, for stowing the drop-prevention mechanism in the second position. 
     In this sheet conveyance device, it is preferable that the conveyance mechanism have a supply mechanism and a discharge mechanism. The supply mechanism supplies sheets loaded onto the loading table to the position for reading by the image reading means of the image reproducing apparatus main unit. The discharge mechanism discharges onto the loading table the sheets whose images have been read by the image reading means. 
     The image reproducing apparatus of this invention comprises an image reproducing apparatus main unit and a document conveyance device. The image reproducing apparatus has the following internal parts: an image reading means for reading images from documents; a transfer sheet conveyance mechanism for conveying transfer sheets; and an image reproduction unit for reproducing images read by the image reading means onto conveyed transfer sheets. The document conveyance device is disposed on the top part of the image reproducing apparatus main unit, and comprises a loading table, a conveyance mechanism, and a drop prevention mechanism. The loading table is configured to open away from the main unit of the image reproducing apparatus; documents are loaded thereon. The conveyance mechanism conveys documents loaded onto the loading table. The drop prevention mechanism retracts so as not to impede the conveyance of documents when the loading table is closed; when the loading table is opened, the drop prevention mechanism prevents documents from falling from the loading table when the loading table is opened. 
     In this image reproducing apparatus, it is preferable that the loading table be openable independently of the conveyance mechanism. 
     Moreover, in this image reproducing apparatus, it is preferable that the drop prevention mechanism have a rotary shaft, a drop-prevention mechanism, an urging member, and a regulating member. The rotary shaft is rotatably supported at the downstream conveyance direction end of the loading table. The drop-prevention mechanism can rotate with the rotary shaft; and can assume both a first position, wherein the edges of documents loaded on the loading table abut upon it, and a second position, wherein it brought out of contact with the document edges. The urging member urges the drop-prevention mechanism toward the first position. The regulating member positions the drop-prevention mechanism in the second position when the loading table is closed. 
     From the following detailed description in conjunction with the accompanying drawings, the foregoing and other objects, features, aspects and advantages of the present invention will become readily apparent to those skilled in the art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overall oblique view of an image reproducing apparatus having a drop-prevention mechanism of one embodiment of this application, and a sheet conveyance device wherein the drop-prevention mechanism is adopted; 
     FIG. 2 is a schematic sectional view of internal components of an image reproducing apparatus having the sheet conveyance device shown in FIG. 1; 
     FIG. 3 is an oblique view of chief components of the drop prevention mechanism construction according to the invention; 
     FIG. 4 shows sequential views a-e of an isolated portion of the drop-prevention mechanism illustrating operation thereof; 
     FIG. 5 is a side view showing action of opening/closing the sheet loading table in the sheet conveyance device indicated in FIG. 1; 
     FIG. 6 is a side view showing pivoting of the drop prevention mechanism of this invention; and 
     FIG. 7 is an image reproducing apparatus equipped with a sheet conveyance device of conventional art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of this invention will be explained, with reference to the attached drawings. 
     FIG. 1 is an overall oblique view of an image reproducing apparatus having as an ADF device, a sheet conveyance device embodying one aspect of this invention. The image reproducing apparatus shown here is a hybrid machine combining photocopier functions and facsimile functions. FIG. 2 is a cross-sectional structural diagram of the image reproducing apparatus shown in FIG.  1 . 
     In these figures, an image reproducing apparatus  1  has a main unit  1   a  and an ADF device  1   b  disposed on the top of the main unit  1   a.    
     The main unit  1   a  comprises an image reading means  2 , an optical unit  3 , an image reproduction unit  4  including photosensitive drum  41 , and a transfer sheet conveyance mechanism  5 . An operation panel  6  is provided on the front side of the upper outside surface of the main unit  1   a  (the right side in FIG.  2 ). On the top part of the main unit  1   a  a transfer-sheet discharge section  7  is formed extending from the front to an intermediate point depth-ward into the main unit  1   a . A telephone set  8  is disposed on one side of the main unit  1   a  for the transmission and reception of images of documents to and from outside facsimile machines. Because this image reproducing apparatus  1  will usually perform tasks such as photocopying and sending and receiving facsimile transmissions on the side of the main unit  1   a  where the operation panel  6  is disposed, the side where the operation panel  6  is disposed is called the front side, and the side opposite the side on which the operation panel  6  is disposed is called the back side. 
     A first contact glass plate  11  is disposed on the uppermost part of the main unit  1   a . Also on the uppermost part of the main unit  1   a , further toward the back than the first contact glass plate  11 , a second contact glass plate  12  is disposed. The first contact glass plate  11  is disposed in the stationary document reading area, the stationary document reading area being an area for reading the image of a document by scanning using a scanner  22 , described below, and comprising a means  2  for reading images from stationary documents. When a document is loaded onto the first contact glass plate  11 , the document is detected by a document detection sensor S 1 , and a detection signal is output. The second contact glass plate  12  is disposed in the moving document reading area. The moving document reading area is an area in which a document image is read by moving the document across the stationary scanner  22 . 
     The ADF device  1   b  has a document loading table  13  and a conveyance mechanism  14  for conveying documents. The loading table  13  is disposed above the first contact glass plate  11 , and covers the first contact glass surface in an openable manner. The drop prevention mechanism of this invention is used on this loading table  13 . The conveyance mechanism  14  is provided above the second contact glass plate  12 . A concavity is formed in the upper surface of the loading table  13 ; this concavity serves as a discharge section  17  to receive a document discharged from the conveyance mechanism  14 . 
     The conveyance mechanism  14  comprises a document insertion port  141 , which opens on the front side; a document discharge port  142 ; and a document conveyance unit  143 . The document discharge port  142 , like the document insertion port  141 , opens on the front side of the apparatus; in addition, it is disposed below the document insertion port  141 , and above the discharge section  17 . The document conveyance unit  143  takes in a document inserted into the document insertion port  141 , directing it rearward, and then reverses the conveyance direction at an intermediate position, conveying the document to the document discharge port  142  on the front side. In front of the document insertion port  141  is a document-loading section  144 . 
     The document-loading section  144  is arranged over the loading table  13 , and upward projecting supports  131  are mounted unitarily to, as a pair in opposing positions on the rear end of, the loading table  13  (in the depth direction of the sheet surface of FIG.  2 ). Arranged in the document conveyance unit  143  are, in order going upstream to downstream in the conveyance direction: a forward-feed roller  143   a ; a sheet feed roller  143   b ; a first conveyance roller pair  143   c  (roller  143   c ′, roller  143   c ″); a second conveyance roller pair  143   d  (roller  143   d ′, roller  143   d ″); and a discharge roller pair (a third conveyance roller pair)  143   e  (roller  143   e ′, roller  143   e ″). Also provided is a plying roller  143   f  that is urged toward the sheet feed roller  143   b.    
     The first conveyance roller pair  143   c , second conveyance roller pair  143   d , and discharge roller pair  143   e  each comprise a driving roller and a driven roller. The driving rollers of the forward-feed roller  143   a , sheet feed roller  143   b , and the first conveyance roller pair  143   c , the driving roller of the second conveyance roller pair  143   d , and the driving roller of the discharge roller pair  143   e  all rotate in a direction so as to convey documents in the downstream direction by means of the driving force of a motor M 1 . The plying roller  143   f  comprises a torque limiter; when a single document sheet passes between the sheet feed roller  143   b  and the plying roller  143   f , the torque applied to the plying roller  143   f  is large, causing it to move in accordance with the sheet feed roller  143   b ; when multiple document sheets pass between the sheet feed roller  143   b  and the plying roller  143   f , the torque applied to the plying roller  143   f  is small, causing the torque limiter to be activated, preventing rotation. As a result, because the friction force between document sheets is smaller than the friction force between document sheets and the plying roller  143   f , only the uppermost document sheet is conveyed downstream by the sheet feed roller  143   b.    
     The document conveyance unit  143  is provided with document detection sensors S 2 , disposed upstream of and in the vicinity of sheet feed roller  143   b , and S 3 , disposed downstream of and in the vicinity of the second conveyance roller pair  143   d . When a document, its pages stacked with the image reproduction side up, is loaded into the document-loading section  144  and inserted up to the upstream vicinity of the sheet feed roller  143   b , the document detection sensor S 2  detects the presence of the document, and in response to a subsequently issued instruction signal the driving motor M 1  is driven and the document is conveyed downstream, one sheet at a time. When the leading edge of the conveyed document reaches a position in the downstream vicinity of the second conveyance roller pair  143   d , this is detected by the document detection sensor S 3 , and as a result of the detection signal, control is exercised such that when the leading edge of the document reaches the second contact glass plate  12 , reading of the image is begun by the scanner  22 , described below. Thereafter, control is exercised such that when the trailing edge of the document finishes passing the second contact glass plate  12 , reading of the image by the scanner  22  is ended. A document that has been read is conveyed to the document discharge port  142  by the discharge roller pair  143   e . While the document detection sensor S 2  is turned on, document sheets loaded into the document-loading section  144  are conveyed downstream in succession. 
     When a document sheet passes through the second conveyance roller pair  143   d , the front and back sides are reversed, and when the position of the second contact glass plate  12  is reached, the image reproduction side is facing the second contact glass plate  12 , enabling image reading therefrom. Document sheets which have been conveyed to the document discharge port  142  are discharged into the discharge section  17 , and are stacked up in succession, with the image reproduction side down. As a result, when the document is recovered from the discharge section  17 , the document sheets are stacked in the same order as before copying. 
     The loading table  13  has a pair of arms  132  at opposing positions towards the back (the depth direction in the figure) and extending toward the back, as shown in FIG.  3 . An upstream-side guide  145  having a shaft  145   a  protruding horizontally is formed in a position toward the main unit  1   a , as shown in FIGS. 1 and 2, and the pair of arms  132  is supported by the shaft  145   a  of the upstream guide  145  in a manner such that the tips of the arms are pivotable. Thus, as the hidden lines in FIG. 5 show, when the front side of the loading table  13  is lifted up, the loading table  13  rises together with the document-loading section  144  using the shaft  145   a  as support, so that the document loading face of the first contact glass plate  11  is opened. When the force lifting the loading table  13  is removed, the loading table  13  falls under its own weight, supported by the shaft  145   a , and the document loading surface of the first contact glass plate  11  is covered. 
     As shown in FIGS. 1 and 2, the image reading means  2  comprises a guide rail  21  provided along the sides of the first and second contact glass plates  11 ,  12 , and a scanner  22  disposed in a manner allowing reciprocal motion between the front and back along the guide rail  21 . The scanner  22  comprises a light source  221  employing an LED or the like for irradiating the image side of the document, a CCD or other reading unit  222 , and a mirror  223  to guide the document image to the reading unit  222 . Usually the scanner stands by at the home position, midway between the first contact glass plate  11  and the second contact glass plate  12 . 
     When a document is loaded onto the first contact glass plate  11 , its presence is detected by the document detection sensor S 1 , and the driving motor M 2  is driven in response to a subsequently supplied instruction signal. By this means the scanner  22  moves from the home position to the leading edge of the document toward the operation panel  6 . Next, the light source  221  is illuminated, and the scanner  22  moves from the front side, which is the position of the leading edge of the document, toward the back, to scan the document image, reading an image for each line. After subjecting the read image data to predetermined data. processing, the results are converted into digital signals and stored in memory (not shown in the figures). When reading of document images is finished, the light source  221  is extinguished and the scanner returns to the home position. 
     When a document is loaded into the document-loading section  144 , the document is detected by the document detection sensor S 2 , and subsequently the driving motor M 2  is driven in response to an instruction signal it is given, causing the scanner  22  to move from the home position to the position of the second contact glass plate  12 . When the document is conveyed by the conveyance mechanism  14  and passes over the second contact glass plate  12 , the scanner  22  reads the document image one line at a time. This read image data is, as in the process described above, stored in memory (not shown in the figures). The light source  221  is illuminated prior to reading of the document image, and is extinguished after reading. When conveyance of all document sheets loaded into the document-loading section  144  has ended, the scanner  22  returns to the home position. In this way, at the second contact glass plate  12  position, the scanner  22  reads the document images in a stationary state, and so the time required for moving the scanner such as when in operation at the first contact glass plate  11  can be eliminated, and the amount of an image read per unit time can be increased. 
     The optical unit  3  is provided below the transfer-sheet discharge section  7 ; it exposes, on the surface of the photosensitive drum  41 , document images retrieved from memory which have been read by the scanner  22 , as well as images retrieved from memory which have been transmitted from another facsimile machine. The optical unit  3  comprises an emission unit  31  which converts into laser light for output a modulation signal generated on the basis of the image data, and a reflecting mirror  32  to reflect the laser light from the emission unit  31 , directing it toward the photosensitive drum  41 . The constituent members of the optical unit  3  are unitarily mounted within a housing  33 ; this housing  33  is provided within the main unit  1   a  fixed into place on the frame of the main unit  1   a  by screws or other means. 
     The image reproduction unit  4  comprises, along the perimeter of the photosensitive drum  41 , a charging device  42  in the upper part, a developer unit  43  in front of the charging device, and a cleaning unit  44  in back of the charging device  42 . The photosensitive drum  41  is rotated in the direction of the arrow by the driving force of the driving motor M 3 ; a static charge region is formed on its peripheral surface when opposite the charging device. In this static charge region a latent electrostatic image is formed by the laser light output from the optical unit  3 , and when opposite the developer unit  43 , this latent electrostatic image is developed into a toner image. Below the photosensitive drum  41  is provided a transfer roller  45 ; the toner image on the photosensitive drum  41  is transferred to a transfer sheet when opposite the transfer roller  45 . The toner remaining on the peripheral surface of the photosensitive drum  41  is removed when opposite the cleaning unit  44  downstream in the rotation direction. 
     The constituent members of the image reproduction unit  4  are mounted within a housing  46 , in a unitary structure therewith; this housing  46  is detachably fitted within the main unit  1   a  on the main unit frame (not shown). A cover  48  is provided on the front of the image reproduction unit  4  of the main unit  1   a ; the cover  48  can be opened frontward, supported by a shaft  481  on the lower end of the main unit  1   a . By this means, the cover  48  can be opened, and the image reproduction unit  4  can be withdrawn to the exterior of the main unit  1   a.    
     The transfer sheet conveyance mechanism  5  is formed in the bottom part of the main unit  1   a . It comprises a sheet supply cassette loading unit  52 , a paper supply unit  53 , and a transfer-sheet conveyance path  54 . This transfer sheet conveyance mechanism  5  also comprises a registration roller pair  55  provided along the transfer-sheet conveyance path  54 ; a fixing unit  56 ; a conveyance roller pair  57 ; and a discharge roller pair  58 . The sheet supply cassette loading unit  52  is loaded with a sheet supply cassette  51 , holding stacked transfer paper P. The paper supply unit  53  has a sheet supply roller  531 ; this sheet supply roller  531  feeds from the front the transfer paper P in the sheet supply cassette  51  loaded into the sheet supply cassette loading unit  52 . The transfer-sheet conveyance path  54  guides transfer sheet drawn out from the sheet supply cassette  51  to the transfer-sheet discharge section  7  via the photosensitive drum  41 . 
     The sheet supply cassette  51  has an internal transfer sheet loading table  512  wherein the lower back end provides support for pivoting and the front end is urged upward by a spring  511 . The sheet supply cassette  51  also has an internal guide  513  which guides transfer sheet drawn out by the sheet supply roller  531  to the transfer-sheet conveyance path  54 . This sheet supply cassette  51  is slid from the front of the main unit  1  to fit in the sheet supply cassette loading unit  52 . The sheet supply cassette  51  can be drawn outside the main unit  1   a  by pulling forward when replenishing transfer paper or when a jam has occurred near the sheet supply roller  531 . The guide  513  guides transfer sheets upward to the transfer-sheet conveyance path  54 , and so is formed in a bowed shape, concave upward, near the transfer sheet loading table  512 . On the side of the guide  513  that makes contact with transfer sheets, a plurality of ribs  513   a  are provided at a predetermined interval along the conveyance direction; by this means the transfer sheets can be conveyed smoothly. 
     In addition to the sheet supply roller  531 , the paper supply unit  53  has a plying claw, plying roller, or other plying means (not shown) to prevent feeding of multiple pages of transfer sheets. The sheet supply roller  531  is disposed on the top part of the sheet supply cassette  52  in a position toward the front, and is rotated in the direction of the arrow by the driving force of the driving motor M 3  via a clutch (not shown) to convey transfer sheets to the registration roller pair  55 . 
     The transfer-sheet conveyance path  54  comprises a first pre-transfer guide  541  and a second pre-transfer guide  542  which turn toward the back the transfer sheets drawn out from the front of the sheet supply cassette  51  and feed them between the photosensitive drum  41  and transfer roller  45 ; a post-transfer guide  543  which feeds a transfer sheet onto which an image has been transferred by the photosensitive drum  41  to the fixing unit  56  toward the rear; and a first reversing guide  544  and second reversing guide  545  which reverse the conveyance direction of a transfer sheet after it passes through the fixing unit  56 , and discharge it to the transfer-sheet discharge section  7  toward the front. Each of the guides  541 ,  542 ,  543 ,  544 ,  545  is formed from (synthetic polymer) resin or the like, and is provided with a plurality of ribs  513   a  spaced at predetermined intervals along the conveyance direction on the side ming contact with the transfer sheet; by this means transfer sheet can be efficiently conveyed. 
     The registration roller pair  55  is provided between the first pre-transfer guide  541  and the second pre-transfer guide  542 , and is driven by the driving force of the driving motor M 3  via a clutch (not shown). Transfer sheets are fed between the photosensitive drum  41  and the transfer roller  45  in synchronization with the formation of a latent electrostatic image on the photosensitive drum  41  by the optical unit  3 . When feeding of one sheet of transfer sheet is completed, the clutch is released and driving is stopped. Immediately before this registration roller pair  55  a transfer sheet sensor S 4  is provided; a predetermined time after the leading edge of the transfer sheet is detected, the driving of the sheet supply roller  531  is stopped. 
     The fixing unit  56  comprises a heating roller  561 , disposed above, and a pressure roller  562 , disposed below; it is provided between the post-transfer guide  543  and the first reversing guide  544 . The heating roller  561  has an internal heater, and the pressure roller  562  presses against the heating roller  561  with a predetermined spring force. The toner image on a transfer sheet conveyed between these rollers is fixed, and the transfer sheet, with fixed toner image, is conveyed toward the first reversing guide  544 . The conveyance roller pair  57  is disposed between the first reversing guide  544  and the second reversing guide  545 , and the discharge roller pair  58  is disposed at the very end of the second reversing guide  545 . A transfer sheet sensor S 5  is disposed at an approximately midway position in the conveyance direction of the second reversing guide  545 , for detecting irregularities in the conveyance of transfer sheet. 
     The operation panel  6  is provided with a start switch  61 , a mode selection key  62  to select between a photocopier mode and a facsimile transmission mode, an enlargement/reduction key  63 , a numeric keypad  64 , and other function keys  65  provided to enable the user to set various other functions, in addition to a display unit  66  enabling the user to visually confirm function settings. 
     The operation of an image reproducing apparatus configured as described above will be explained. The mode selection key  62  of the operation panel  6  is used to select photocopier mode or facsimile transmission mode. Then a document is loaded into the document-loading section  144 , this is detected by a document detection sensor. When the start switch  61  of the operation panel  6  is turned on, the document is conveyed by the conveyance mechanism  14  onto the second contact glass plate  12 . The document image is read by the scanner  22 , which has moved from the home position to the second contact glass plate  12  position, and the document image that has been read is stored in memory. A document that has been read is discharged to the discharge section  17 . When the document for photocopying or for facsimile transmission is a book or other bound document, the document is loaded directly onto the first contact glass plate  11 . This is then detected by the document detection sensor S 1 . When the start switch  61  is turned on, the image side of the document is scanned by the scanner  22  and the image is read. The read image is stored in memory. When an image is transmitted via a telephone line from an outside facsimile machine, the signal is detected, reception mode is set automatically, and the received image data is stored in memory. 
     When in facsimile transmission mode, the image data stored in memory is read and is transmitted to the other facsimile machine via telephone lines. When in photocopier mode or in facsimile reception mode, the image stored in memory is transferred to transfer sheet(s), which are discharged to the transfer-sheet discharge section  7 . 
     In other words, when in photocopier mode or facsimile reception mode, the photosensitive drum  41  is charged by the charging device  42 , and laser light corresponding to the image data stored in memory is emitted to expose the photosensitive drum  41 , thereby forming a latent electrostatic image. Then, toner supplied to the photosensitive drum  41  from the developer unit  43  adheres to the latent electrostatic image to form a toner image. 
     Meanwhile, a transfer sheet stored in the sheet supply cassette  51  is fed toward the registration roller pair  55  by the sheet supply roller  531  via the first pre-transfer guide  541 . In synchronization with the formation of the latent electrostatic image, this transfer sheet is conveyed to the gap between the photosensitive drum  41  and the transfer roller  45  by the registration roller pair  55  via the second pre-transfer guide  542 . Next the toner image of the photosensitive drum  41  is transferred to the transfer sheet by the transfer roller  45 , to which has been applied a voltage of polarity opposite the polarity of the latent electrostatic image. Following this, the transfer sheet is separated from the photosensitive drum  41 , and is conveyed to the fixing unit  56  via the post-transfer guide  543 . This fixing unit  56  fixes the toner image on the transfer sheet. The transfer sheet with fixed toner image is then discharged to the transfer-sheet discharge section  7  by the conveyance roller pair  57  and discharge roller pair  58 , via the first reversing guide  544  and the second reversing guide  545 . 
     Next one example of a specific configuration of the drop prevention mechanism will be explained. FIGS. 3,  4  and  5  show a specific example of a drop prevention mechanism; FIGS. 4 a  through  4   e  show the actions of the drop prevention mechanism over time, accompanying the opening of the ADF device. 
     The drop prevention mechanism comprises a rotary shaft  133 , a pair of abutting members (pivot members)  135  fixed at both ends of the rotary shaft  135 , springs  134  (urging means) which urge each of the abutting members  135  in the direction of the arrow B (referring to FIG.  5 ), and drop prevention members  137 . 
     The rotary shaft  133  passes through the loading table  133 , wherein it is rotatably supported. The abutting members  135  are provided on a frame unit, shown in FIG.  3  and FIG. 5, on the upper surface of the image reproducing apparatus main unit, and abut on at least one abutment  136 . As shown in FIG. 4, the abutting members  135  are formed such that the lowermost part, which makes contact with the abutment  136 , describes a gentle arc shape. They pivot from the state in FIG. 4 e  to the state in FIG. 4 a  when the ADF device  1   b  is swung from the horizontal position to the upward opened position. 
     Specifically, the abutment  136  comprises a flat part, the upper face of which is parallel to the upper face of the image reproducing apparatus main unit, and a sloped part which inclines gently downward. When the ADF device  1   b  is closed on the upper surface of the apparatus main unit  1   a , the abutment  136 , the abutting members  135  and the drop prevention members  137  of the drop prevention mechanism are in the positional relation shown in FIG. 4 e . It is preferable that the drop prevention member  137  be configured such that it is inside a recessed stowage  201  provided in the loading table  13  so as not to impede document conveyance, and that it is stowed within the conveyance mechanism  14  (FIGS. 3,  5 ) provided on the end toward the connection with the loading table  13 . Hence the drop prevention member  137  is hidden by the lower roller  14 X when in this document-transfer horizontal position, and the document is discharged by the rollers  14 Z,  14 X. When the loading table  13  begins to pivot upward, the abutting members  135  gradually and smoothly are made to pivot in the direction of the arrow B in FIG. 5 by the urging force of the spring  134 , while maintaining a state of contact with the inclined part of the upper face of the abutment  136 . By means of the pivoting of the abutting members  135 , the rotary shaft  133  rotates in the direction of the arrow B; by means of the rotation of the rotary shaft  133 , the drop prevention member  137 , which is fixed to the same shaft, also pivots in the direction of the arrow B. 
     The drop prevention member  137  pivots from the state of being stowed in the stowage  201  into its active position to act on the document, where it protrudes. The drop prevention members  137  are provided with a bend which makes contact with and supports the bottom end (that is, the downstream end in the conveyance direction) of documents when the loading table  13  is disposed in the opened position. Hence when the document table  13  is opened, the bend prevents documents from dropping from the end of the loading table  13 . 
     Next, when the loading table is closed from its opened state so that it is disposed horizontally, in the opposite manner from when it was opened, the abutting members  135  and drop prevention members  137  pivot in sequence from the state shown in FIG. 4 a  to the state of FIG. 4 e . That is, the lower part of the abutting members  135  make contact with the upper face of the abutment  136  on the main unit side of the apparatus, pivoting in opposition to the urging force of the. spring  134 . As described above, the abutment  136  is provided with a gently inclined part in its upper face, so that the arc-shaped part provided at the bottom of the abutting members  135  smoothly pivots along the inclined face. This pivot of the abutting members  135  is accompanied by rotation of the rotary shaft  133  to which the abutting members  135  are fixed. By this means the drop prevention member  137  pivots to be stowed in the stowage  201 , so that the drop prevention member  137  does not obstruct document discharge. 
     The shape of the abutment  136  in this embodiment consists of a flat portion and an inclined portion; however, the shape of the abutment  136  is not limited to this. The shape may be a gentle circular arc shape or a semicircular shape, as long as the pivoting of the abutting members  135  is smooth and appropriate. The abutment may also be used as a position-regulating member to maintain a gap enabling appropriate conveyance of documents between the upper face of the apparatus main unit  1   a  and the ADF device  1   b . In addition, a rotary shaft provided with a drop-prevention mechanism may also be disposed on the side of the document-loading section  144  so as to be linked with the pivoting of the drop prevention mechanism of the loading table  13 , to prevent pivoting of the loading table  13  from causing documents to drop prior to image reading. 
     One embodiment of this invention, an image reproducing apparatus provided with a transfer-sheet discharge section  7  to discharge transfer sheets, has been described. However, in cases where a separate transfer-sheet conveyance path is provided to enable conveyance toward the top of the apparatus, the apparatus may be configured such that detection sensors detect that the ADF device is not currently being used and that no document is stacked in the loading table  13  or in the document-loading section  144 , and transfer sheets can be discharged according to user selection of the loading table  13  or the document-loading section  144 . It would thus be easy to remove transfer sheets and make visual confirmation, for greater convenience. 
     While only selected embodiments have been chosen to illustrate the present invention, to those skilled in the art it will be apparent from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention is provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.