Paper feeding device

Abstract: A paper feeding device for sending out paper sheets (P) contained in an intermediate tray (6) from the intermediate tray (6) by a preliminary feed roller (112a) and a pressure plate (121) opposed to this preliminary feed roller (112a) and conveying the paper sheets (P) sent out to an image forming section (3) by a feed roller (112b) and a pressure roller (125) opposed to this feed roller (112b) after an image was formed once by the image forming section (3) comprises a roller supporting the above pressure roller (125), a supporting member (122) integrally rotatably attached to the above roller supporting shaft (125a) and a motor (132) for rotating the above roller supporting shaft (125a).

Description: The present invention relates to paper feeding devices contained in image forming apparatuses such as an electrophotographic copying apparatus and a printer having a duplex image forming function and/or a composite image forming function. Image forming apparatus are known having the function of containing paper sheets on which an image was formed once in an intermediate tray provided inside thereof and then, sending out the paper sheets from the intermediate tray to form an image again on the paper sheets. Such an image forming apparatus contains a paper feeding device for sending out from the intermediate tray the paper sheets contained in the intermediate tray and feeding the same in the direction of an image forming section comprising a photosensitive drum, a developing device and the like. This paper feeding device is provided with, for example, (1) a preliminary feed roller provided in a lower part of the intermediate tray for sending out the paper sheets contained in the intermediate tray, (2) a pressure plate for pressing the paper sheets contained in the intermediate tray against the preliminary feed roller to assist in sending out the paper sheets from the intermediate tray by the preliminary feed roller, (3) a feed roller for conveying the paper sheets sent out from the preliminary feed roller in the direction of the image forming section, (4) a pressure roller for pressing the paper sheets sent out from the preliminary feed roller against the feed roller to assist in conveying the paper sheets by the feed roller. The above described pressure plate can be withdrawn from the feed roller so as not to prevent the paper sheets from being introduced into the intermediate tray. Fig. 4 is a schematic plan view showing a conventional mechanism for withdrawing a pressure plate from a feed roller. A pressure plate 102 is rotatably supported on a supporting shaft 101 fixed to a frame of an image forming apparatus. An end 102a of this pressure plate 102 is rotatably connected to one end 103a of a crank shaft 103 with a pin. The other end 103b of the crank shaft 103 is attached to a disk 109 rotated integrally with a secondary reduction gear 108. The secondary reduction gear 108 is rotated by a driving system 107 of the image forming apparatus through a primary reduction gear 106. The primary reduction gear 106 is connected to the driving system 107 through a spring clutch 105. This spring clutch 105 is intermittently operated by a lever 110 alternately turned to a position represented by a solid line and a position represented by a dot and dash line in Fig.4. The lever 110 is connected to a rod 104a of a solenoid 104. The pressure plate 102 is rotated around the supporting shaft 101 to be removed from the feed roller or to be brought near the feed roller by exciting the solenoid 104 to bring the spring clutch 105 into a connected state. However, in the above described paper feeding device, the driving force for removing the pressure plate 102 from the feed roller is received from the driving system 107 of the image forming apparatus. Accordingly, it is difficult to construct the above pressure plate 102 and a mechanism for rotating the same as an exchangeable unit. Therefore, the paper feeding device has the disadvantage that maintenance thereof takes a lot of time and labor. In addition, the mechanism for rotating the pressure plate 102 is complicated. Accordingly, the paper feeding device also has the disadvantage that the manufacture thereof takes a lot of time and labor and the manufacturing cost thereof is high. An object of the present invention is to provide a paper feeding device in which a pressure plate, a mechanism for driving the pressure plate and a pressure roller can be constructed as a unit and whose maintenance is simply carried out. Another object of the present invention is to provide a paper feeding device having a simple structure and capable of being manufactured by simple processes and at low cost. The above described objects are achieved by a paper feeding device provided by the present invention as defined in claim 1. In the present paper feeding device, the roller supporting shaft is driven through a gear fit to the roller supporting shaft, whereby the roller supporting shaft and the gear are relatively rotatable over a predetermined angle such that the pressure plate can be turned according to the number of paper sheets contained in the intermediate tray. Furthermore, in the above described paper feeding device, it is preferred that the pressure plate be rotatable around an axis parallel to the roller supporting shaft. In the paper feeding device constructed as described above, the pressure plate can be turned in such a direction as to withdraw it from the preliminary feed roller by driving the driving motor in one direction to rotate the supporting member along with the roller supporting shaft. In addition, the pressure plate can be brought near the preliminary feed roller by driving the driving motor in the opposite direction to the above direction to reverse the supporting member rotation along with the roller supporting shaft. The roller supporting shaft and the gear are relatively rotatable over a predetermined angle and the roller supporting shaft can be freely rotated at a predetermined angle with driving of the above gear being stopped. Consequently, the paper sheets contained in the intermediate tray can be pressed against the preliminary feed roller by bringing the pressure plate into contact with the paper sheets irrespective of the number of the paper sheets with the pressure plate being turned toward the preliminary feed roller. When the pressure plate is rotatable around an axis parallel to the roller supporting shaft, the pressure plate can be inclined while following the paper sheets contained in the intermediate tray. Consequently, the pressure plate can be always uniformly brought into contact with the paper sheets. The foregoing and other advantages of the present invention will become more apparent from the following description of embodiments when taken in conjunction with the accompanying drawings. Fig. 1 is a front view showing an embodiment of a paper feeding device according to the present invention; Fig. 2 is a plan view; Fig. 3 is a schematic diagram illustrating an electrophotographic copying apparatus equipped with a paper feeding device according to an embodiment the present invention; and Fig. 4 is a plan view showing a conventional paper feeding device. Fig. 3 is a schematic diagram illustrating an electrophotographic copying apparatus equipped with a paper feeding device A. This electrophotographic copying apparatus comprises a transparent platen 11 and an original cover 12 in an upper part of the main body 1 of the electrophotographic copying apparatus and comprises an optical system 2, an image forming section 3, a first paper conveying section 4, a second paper conveying section 5 and an intermediate tray 6 inside of the main body 1 of the electrophotographic copying apparatus. The optical system 2 is used for exposing a document (not shown) set on the above transparent platen 11 by a light source 21 and leading reflected light from the document to the image forming section 3 with mirrors 22, 23 and 24, a lens 25 and a mirror 26 as represented by a dot and dash line in Fig. 3. The above described image forming section 3 is a section for forming a reproduced image on paper sheets P. This image forming section 3 comprises a corona discharger 32, a developing device 33, a transferring corona discharger 34, a separating corona discharger 35, and a cleaner 36 arranged in this order around a photosensitive drum 31. This image forming section 3 forms an electrostatic latent image corresponding to a document image on the surface of this photosensitive drum 31 by leading the reflected light from the document to the surface of the photosensitive drum 31 uniformly charged by the corona discharger 32. This electrostatic latent image is developed into a toner image by the developing device 33, the toner image is transferred onto the surfaces of the paper sheets P by the transferring corona discharger 34, the paper sheets P are stripped from the surface of the photosensitive drum 31 by the separating corona discharger 35 and then, a toner remaining on the surface of the photosensitive drum 31 is recovered by the cleaner 36. The first paper conveying section 4 comprises paper feeding cassettes 13a and 13b mounted on a side portion of the main body 1 of the electrophotographic copying apparatus such that they can be pulled out, feed rollers 41a, 41b and 41c for sending out the paper sheets P from a stacking bypath 14 one at a time, paper feeding paths 42a ,42b and 42c for guiding the paper sheets P sent out, a registration roller 43 and a delivery roller 44 for feeding to the image forming section 3 the paper sheets P conveyed through the paper feeding paths each predetermined timing, a delivery belt 45 for conveying the paper sheets P on which a reproduced image was formed by the image forming section 3, a heating and fixing device 46 for fixing the reproduced image to the paper sheets P, a delivery roller 47 for conveying the paper sheets P passed through the heating and fixing device 46, and a discharge roller 48 for discharging the paper sheets P from the main body 1 of the electrophotographic copying apparatus. In addition, the second paper conveying section 5 is branched from a portion of a switching craw 49 provided between the delivery roller 47 and the discharge roller 48. An intermediate tray 6 is interposed in a halfway portion of the second paper conveying section 5. In addition, an end on the downstream side of the second paper conveying section 5 is connected to the registration roller 43. When a document is copied on the paper sheets P only once, the paper sheets on which an image was formed are discharged onto a tray 15 as represented by an arrow M in Fig. 3 by causing the first paper conveying section 4 to only convey the paper sheets. In addition, when a document is copied on one side or on both sides of the paper sheets P two or more times, the paper sheets on which the image was formed once are sent to the second paper conveying section 5 as represented by an arrow N in Fig. 3 by switching the switching claw 49 and are contained in the intermediate tray 6 once and then, are fed to the image forming section 3, causing the image forming section 3 to form an image again. The second paper conveying section 5 comprises a guide path 50, a delivery roller 51 and a branching guide plate 7 for feeding the intermediate tray 6 the paper sheets P on which the image was formed once, and comprises delivery rollers 53a, 53b and 53c and the paper feeding paths 54a, 54b and 54c for feeding to the registration roller 43 the paper sheets P sent out from the paper feeding device A provided in the vicinity of an end on the downstream side of the intermediate tray 6. The branching guide plate 7 is turnably supported by a supporting shaft 7a and is turned to positions represented by a solid line and a chain line in Fig. 3 by driving means (not shown). When the branching guide plate 7 is turned to the position represented by the chain line, the paper sheets P are directly fed to the intermediate tray 6 as represented by an arrow X in Fig. 3. The surfaces, on which an image was formed, of the paper sheets P fed to the intermediate tray 6 are lower surfaces. Accordingly, if the the paper sheets P are sent out from the intermediate tray 6 and fed to the image forming section 3, the second copy is made on the same side as the surfaces on which the image was reproduced once (composite copy). In addition, when the branching guide plate 7 is turned to the position represented by the solid line, the paper sheets P are fed to the intermediate tray 6 by way of a reverse section 9 comprising a delivery roller 91, guide paths 92 and 94 and a reverse roller 93. The surfaces, on which the image was formed, of the paper sheets P fed to the intermediate tray 6 are upper surfaces. Accordingly, if the paper sheets P are sent out from the intermediate tray 6 and fed to the image forming section 3, the second copy is made on the reverse side of the surfaces on which the image was reproduced once (duplex copy). The above described paper feeding device A comprises a plurality of feed rollers 112 provided in a lower part of the intermediate tray 6 and pressing means 120 provided in an upper part of the intermediate tray 6. A part of the periphery of the feed roller 112 is projected on the side of the upper surface of the intermediate tray 6 through an opening (not shown) formed in the intermediate tray 6. The above paper feeding device A presses one or a plurality of sheets P of paper contained in the intermediate tray 6 against the feed roller 112 by the pressing means 120 and sends out the same to the downstream side one at a time. The intermediate tray 6 is provided with a stopper 114 for aligning ends of the paper sheets P by applying the ends of the paper sheets P introduced into the intermediate tray 6. This stopper 114 is turned around a fulcrum 114a in sending out the paper sheets P from the intermediate tray 6 to be withdrawn downward from the intermediate tray 6. In addition, a guide plate 111 for aligning the ends of the paper sheets P located above a predetermined position on the side of an upper end of the stopper 114 is provided in an upper part of the intermediate tray 6 with it intersecting the above stopper 114. The above described feed roller 112 comprises a preliminary feed roller 112a and a feed roller 112b respectively rotating around an axis perpendicularly intersecting the direction of sending out the paper sheets P. The above feed roller 112b is provided on the downstream side of the preliminary feed roller 112a. The rollers 112a and 112b are driven to be rotated at predetermined timing by a driving system of the electrophotographic copying apparatus. The above described pressing means 120 comprises a pressure plate 121 for pressing the paper sheets P contained in the intermediate tray 6 against the preliminary feed roller 112a to assist in sending the paper sheets P by the preliminary feed roller 112a and a pressure roller 125 for pressing the paper sheet P sent out by the preliminary feed roller 112a against the feed roller 112b to assist in conveying the paper sheet P by the feed roller 112b. The above described pressure plate 121 is supported on a roller supporting shaft 125a for relatively rotatably supporting the pressure roller 125 through a pair of arms 122 serving as a supporting member, as shown in Fig. 2. The arms 122 has their base ends respectively fixed to both ends of the above roller supporting shaft 125a. The pressure plate 121 is turned by the rotation of the roller supporting shaft 125a. The pressure plate 121 is attached to a shaft 122a constructed in parallel with the roller supporting shaft 125a between top ends of the arms 122. The pressure plate 121 can be rotated around the shaft 122a. Consequently, the pressure plate 121 satisfactorily follows the paper sheet P when it abuts on the paper sheet P. Accordingly, the pressure plate 121 is always brought into surface contact with the paper sheet P. The above described roller supporting shaft 125a is rotatably held by a blanket 127 through bearings 128 provided on both ends of the pressure roller 125. The blanket 127 is supported on a fixing plate 124 attached to a predetermined portion inside of the electrophotographic copying apparatus so as to be rotatable around a supporting shaft 126. Consequently, the pressure plate 121 and the pressure roller 125 can respectively abut on the preliminary feed roller 112a and the feed roller 112b so as to be detachable therefrom centered around the supporting shaft 126. A spring pin 130 is penetrated through the above roller supporting shaft 125a on the side of its one end. Both ends of this spring pin 130 are projected from the peripheral surface of the roller supporting shaft 125a. In addition, a helical gear 129 for transmitting the turning force to the roller supporting shaft 125a is relatively rotatably fit to a portion, through which the above spring pin 130 is penetrated, of the roller supporting shaft 125a. A worm gear 131 is engaged with this helical gear 129. This worm gear 131 is driven to be rotated by a driving moter 132 supported on the fixing plate 124. The above described helical gear 129 is provided with a fan-shaped engaging groove 129a for engaging the spring pin 130 with play. This engaging groove 129a is formed such that the roller supporting shaft 125a and the helical gear 129 can be relatively idled by approximately one-sixth rotation. The roller supporting shaft 125a and the helical gear 129 can be thus relatively rotated in a constant range so as to allow the pressure plate 121 to be freely moved to a position corresponding to the number of paper sheets P contained in the intermediate tray 6 with the arms 122 being turned downward by driving of the driving motor 132 and to prevent overload from being applied to the driving moter 132, the arms 122 and the like by the shift in position where the rotation of the helical gear 129 is stopped to cause the pressure plate 121 not to come into contact with the preliminary feed roller 112a and to cause the pressure plate 121 to be turned more than necessary. The above described fixing plate 124 is provided with an optical sensor 138 for sensing that the arms 122 rose to a predetermined position. When the above optical sensor 138 senses the rise of the arms 122 while the pressure plate 121 is turned upward, driving of the driving motor 132 is stopped in response to a signal from this optical sensor 138. In addition, when the pressure plate 121 is turned downward, the driving motor 132 is driven by a timer in only a constant time period. In the paper feeding device A constructed as described above, the helical gear 129 can be rotated around the roller supporting shaft 125a by driving the driving motor 132 to be rotated in one direction to transmit the driving force of the driving moter 132 to the helical gear 129 from the worm gear 131. On this occasion, the helical gear 129 is engaged with the spring pin 130 after slight idling. The roller supporting shaft 125a is rotated as they are engaged with each other, so that the pressure plate 121 is turned upward through the arms 122. Accordingly, the paper sheets P can be introduced into the intermediate tray 6. Furthermore, the paper sheets P can be pressed against the preliminary feed roller 112a by reversing the driving motor 132 at the time point when the paper sheets P are contained in the intermediate tray 6 to lower the pressure plate 121 onto the above paper sheets P. Meanwhile, as a mechanism for transmitting the driving force of the above driving motor 132 to the roller supporting shaft 125a, the helical gear 129 and the worm gear 131 are replaced with bevel gears. In addition, if the driving motor 132 is arranged such that the axis 132a of rotation thereof is parallel to an axis of the roller supporting shaft 125a, a spur gear can be employed. Besides, the driving force of the driving motor 132 may be transmitted by a timing belt and a chain. Furthermore, a geared motor may be directly connected to the roller supporting shaft 125a through a coupling. As described in the foregoing, the paper feeding device according to the present invention has a dedicated motor for turning the pressure plate. Furthermore, in the paper feeding device, the pressure plate, together with the pressure roller, is supported on the roller supporting shaft through the supporting member, so that they can be integrally constructed as a unit. Consequently, maintenance of the paper feeding device can be substantially simply carried out. In addition, the structure thereof is simple. Consequently, the paper feeding device is manufactured by simple processes and the manufacturing cost thereof can be lowered.

Claims: A paper feeding device comprising: an intermediate tray (6) provided inside of an image forming apparatus for temporarily containing paper sheets (P) after a first image has been formed thereon by an image forming section (3) of the image forming apparatus; a preliminary feed roller (112a) for sending out from said intermediate tray (6) the paper sheets contained in said intermediate tray (6); a pressure plate (121) for pressing the paper sheets contained in said intermediate tray (6) against said preliminary feed roller (112a) to assist said preliminary feed roller (112a) in sending out the paper sheets from said intermediate tray (6); a feed roller (112b) for conveying the paper sheets sent out by said preliminary feed roller (112a) in the direction of the image forming section (3); a pressure roller (125) for pressing the paper sheets sent out by said preliminary feed roller (112a) against said feed roller (112b) to assist said feed roller (112b) in conveying the paper sheets; a roller supporting shaft (125a) for rotatably supporting said pressure roller (125); characterized by a supporting member (122) fixed to said roller supporting shaft (125a) and supporting said pressure plate (121) for pivoting of the pressure plate (121) by rotation of said roller supporting shaft (125a); a gear (129) connected to said roller supporting shaft (125a) to drive said roller supporting shaft (125a), said roller supporting shaft (125a) and said gear (129) being relatively rotatable over a predetermined angle such that said pressure plate (121) can be pivoted to a position according to the number of paper sheets contained in said intermediate tray (6); and a motor (132) for rotating said gear (129) to rotate said roller supporting shaft (125a). The paper feeding device according to claim 1, wherein said roller supporting shaft (125a) has an engaging section (130) projecting in the direction of the shaft diameter, and said gear (129) has an engaging groove (129a) adapted to be engaged with said engaging section (130) at a time point when said gear (129) has rotated over a constant angle. The paper feeding device according to claim 2, wherein said engaging section (130) of said roller supporting shaft (125a) comprises a pin engaging said roller supporting shaft (125a). The paper feeding device according to claim 1, wherein said pressure plate (121) is rotatable around about a second axis (122a) parallel to said roller supporting shaft (125a).

Inventors: HATANO MASARU, SUGIYAMA TSUKASA, HATANO, MASARU, SUGIYAMA, TSUKASA
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO., LTD.
Application year: 1989
Main classification: B65H5
IPC codes: B65H5, B65H1, G03G15, B65H3, B65H83