PAPER FEEDING DEVICE

Abstract: A paper cassette (12) mounted onto a specific position in the image processing apparatus in a manner that can be pulled out, and a preliminary feed roller (103) to carry the paper set on the document tray toward a feed roller (51) which is normally energized in paper pressing direction. When a sheet of paper is inserted, the preliminary feed roller (103) is moved in the opposite direction against the energizing force under a balanced condition in transversal direction by a guide member (104) which is turned upward. When the paper cassette (12) is mounted in the image processing apparatus, the document setting board (13) disposed in the paper cassette (12) is upwardly turned by a pressing mechanism (14). When the paper cassette (12) is pulled out, the feed roller (51) to feed out paper from the paper cassette (12) is turned in reversed direction. A feed channel to guide the paper cassette (12) is formed in a curved manner, and a normally turned delivery roller (52) is provided inside the curved channel (56, 57).

Description: BACKGROUND OF THE INVENTION The present invention relates to a paper feeding device to feed each sheet of image forming paper or document to an image processing apparatus such as copy­ ing machines and facsimile units. Image processing apparatus such as copying machines and facsimile units are hitherto provided with a paper feeding device having a paper cassette and/or a stack bypass enabling to set a number of sheets of image forming paper, and/or a paper feeding device having an automatic document feeder enabling to set a number of sheets of documents. The paper feeding device having the aforementioned paper feed cassette is advantageous in that the cassette can be changed easily when it is necessary to use a paper of different size. For copying machines, as an example, the document size to be copied recently tends to become larger, and a larger size of paper cassette has been used to accept a larger image forming paper corresponding to larger documents which are to be copied. When a paper feed cassette is mounted onto a copying machine proper, therefore, larger area for installing the copying machine is required than for the copying machine itself, which is causing a problem of lowered efficiency in use of the limited office space. To solve the problem, a reverse paper feeding device has been proposed in which a direction of paper feeding from the paper cassette by the feed roller is set in op­ posite to a direction of paper feeding by a resist roller which operates synchronously with the optical system. In this case, the whole copying machine can be made compact even with the paper cassette being mounted by thereon so that the paper cassette may not be projected from the area of a vertical projection, for example, of the optical system which requires the largest plane size. Such a reversing paper feeding device is composed of a feed roller to send out each sheet of paper from the paper cassette, a delivery roller to carry the paper fed from the feed roller toward a resist roller, and a guide member to reverse a direction of the paper carried by the delivery roller. The driving of feed roller and the resist roller are controlled in timing with a specific paper feed­ ing, and driving of the delivery roller is also controlled in timing with the specific paper feeding by using a clutch or the like. Accordingly, the feed roller and the delivery roller are driven to rotate enabling the preliminary paper feed­ ing to the point where the front end of paper comes in contact with the resist roller, thereafter the delivery roller and the resist roller are driven to rotate enabl­ ing a paper feeding for accomplishing a copying operation. With a reversing paper feeding device of the above composition, installation area of the copying machine can be made smaller and exact paper feeding can be ensured. It is necessary, however, to control driving of the delivery roller corresponding to driving condition of the feed roller and the resist roller, which makes the electrical control system and mechanical revolution transfer mechanism more intricated as a disadvantage. And further the device is also disadvantageous in that the position of the delivery roller attached is rather limited making it difficult to design the whole paper feeding device, and additional members are necessary to attach the delivery roller. Besides, in the conventional composition of the paper feeding device to feed each sheet of paper from a paper cassette which has no click to prevent double feeding by means of a feed roller and a friction pad pressed in contact with each other, a pressing mechanism to upwardly turn a document setting board mounted in the paper feed cassette so as to be turned freely is provided in the copying machine, and a pressure releasing lever mechanism to stop upward­ turning of the document setting board by a means of pres­ sure mechanism is also attached. Under the condition where the document setting board is upwardly turned by the pressing mechanism when the paper feed cassette is mounted, therefore, the upper-most paper is pressed to the feed roller to enable paper feeding sheet by sheet. When the upward-turning of the document setting board is stopped by the pressure releasing lever mechanism, on the other hand, the pressing mechanism retreats from the paper cassette and the cassette can be pulled out. By the paper feeding device of aforementioned mecha­ nism, the document setting board can be upwardly turned simply by mounting a paper feed cassette, but the paper feeding device is disadvantageous in that the operation of pulling out the paper cassette is troublesome because the pressure release lever mechanism must be operated before pulling out the cassette. The need of a pressure release lever mechanism in addition to the pressure mechanism makes the composition of the whole paper feeding device more intricated and the manufacturing cost higher. When the paper feeding device of the above composition is adopted, the front end of the next paper is positioned between the feed roller and the friction pad by the friction force between adjacent sheets of papers when feeding of one sheet of paper completes. If copying operation is continued as it is, there will be no problem, however, if it is necessary to change the paper size or the like, a new paper cassette must be mounted after pulling out the currently used paper cassette. While the cassette is changed, the paper of which top end is held between the feed roller and the friction pad remains in the copy­ ing machine, and a new paper feed cassette is set under this condition. Accordingly, the remaining paper is greatly crumpled or folded, and a jamming is finally re­ sulted if the copying operation is kept going on. To solve the above problem, a paper feeding device (Refer to the Japanese Patent Laid-Open Publication No. 203629/1982) has been proposed, in which the contact condition of the feed roller with the friction pad is released when the paper cassette is pulled out to prevent the paper from remaining in the copying machine. By the paper feeding device of the above composition, only the contact condition of the feed roller with the friction pad is released when the paper cassette is pulled out and residual paper is prevented from remaining in the position between the feed roller and the friction pad by being pulled by the friction force between the residual paper and the papers stored in the paper cassette. In such a condition, remaining paper can be prevented from the remaining state rather accurately if the paper size is large, however, if the size is small, the paper carried to the specified position by the feed roller remains in the copying machine even when the paper cassette is pulled out, and jamming is resulted when a new paper feed cassette is set. The problem is outstanding particularly for the type of copying machine in which almost part of the paper cassette is housed into the copying machine because the remaining paper can't be watched or checked easily from outside. The aforementioned paper feeding oevice containing a stack bypass or an automatic document feeder has a preliminary feed roller and a feed roller and the preliminary feed roller is moved in opposite direction to paper pressing direction by a solenoid, a lever, a cam and the like under the con­ dition where transmission of the driving force of the both rollers is cut off so that a number of sheets of paper can be set easily and exactly at the specified position. At paper feeding operation, the preliminary feed roller is moved in paper pressing direction by the solenoid, the lever, the cam and the like and the both rollers are driven under this condition so that the paper is carried sheet by sheet. By the composition to move the preliminary feed roller in paper pressing direction simply by applying force and without using any solenoid, lever, cam, or the like, the papers could be set rather easily at the specified position provided that the number of sheets of paper is comparatively small because the tangential direction of the preliminary feed roller at the point where the upper sheet of paper comes in contact is close to horizontal direction and the preliminary feed roller can be upwardly moved against the applied force. When the number of sheets of paper is increased, however, the tangential direction of the preliminary feed roller at the point where the upper top of paper comes in contact rises sharply and the vertical component of a force to upwardly move the preliminary feed roller against the applied force is quickly reduced, making it difficult to set the papers at the specified position. If the number of sheets of paper is further increased and the upper surface of the papers goes up to the level approximately equal to the center axis of the preliminary feed roller, it becomes almost impossible to move the preliminary feed roller against the applied force and paper can hardly be set at the specified position. However, by employing the above-mentioned mechanism to move the preliminary feed roller with a solenoid, a lever, a cam, and the like paper setting can be made easily. Though the paper setting can be exactly made, the paper feeding device of the aforementioned composition requires a mechanism to move the preliminary feed roller and also a means to control the mechanism, which is disadvantageous in that the whole paper feeding mechanism is intricated and the manufacturing cost is raised. An object of the present invention is to ensure exact preliminary paper feeding and main paper feeding by revers­ ing a paper-feed direction to the opposite without the need of controlling driving a feed roller. Another object of the present invention is to enable automatically turning the document setting board by a pres­ sing mechanism, and automatically retreating of the pres­ sing mechanism from inside the paper cassette following an operation of mounting and pulling out the paper cassette, respectively. A further object of the invention is to prevent a paper from remaining when the paper feed cassette is pulled out. A still further object of the invention is to make the whole paper feeding device simple by eliminating the com­ plicated mechanism to move the preliminary feed roller and the means to control that mechanism so as to make the manu­ facturing cost lower. It is also another object of the invention to prevent inclined paper feeding by raising the preiminary feed roller equally at the right and left sides in longitudinal direction thereof when paper is inserted. In accordance with the present invention, in a paper feeding device in which a direction of delivering a document fed from the inside of a paper cassette by a feed roller is reversed so as to be conducted to a resist roller which operates synchronously with a movement of an optical system, there is provided a guide section which is composed of an outer guide plate and an inner guide plate to form a space for permitting the document to pass therethrough, and a delivery roller which is in use driven to rotate is mounted on the guide section near the feed-roller side. And preferably, the above paper cassette includes therein a document setting board to support a document, and the paper feeding device includes a pressing mechanism for lifting up the document setting board in a state that the paper cassette is set in the image processing apparatus, and a locking mechanism to prevent the pressing mechanism from lifting up the document setting board after removing the paper cassette. More preferably, the paper feeding device includes a drive-force transmitting mechanism to transmit a rotary force in the opposite direction to the paper-feeding direc­ tion to a feed roller in a predetermined timing of removing the paper cassette from the image processing apparatus. Further, in accordance with the present invention, a paper feeding device wherein a feed roller further feeds a document which is fed by a preliminary roller is chara­ cterized in that the preliminary feed roller is in use pushed in a direction to press the document, and there is provided a guide member which turns following an operation of setting the document on a predetermined position so as to move the preliminary feed roller in the opposite direction to the pressing direction on the document. Preferably, the above guide member has on an end thereof a pushing section hanging at least over an end portion on the driving side of the shaft of the preliminary roller, and on the other end of the guide member a receiving section lying at least below the opposite end portion of the shaft of the preliminary roller. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows the outline of the internal mechanism of a copying machine provided with a paper feeding device of the present invention; Fig. 2 is an enlarged longitudinal section of the paper feeding device of Fig. 1; Fig. 3 is an exploded perspective side view of the paper feeding device in Fig. 1; Fig. 4 is a longitudinal section of the principal part showing the condition with no paper feed cassette; Fig. 5 is a longitudinal section of the principal part showing the condition with a paper feed cassette mounted; Fig. 6 is a plan view showing the attached condition of an auxiliary roller; Fig. 7 is a longitudinal section showing the relation­ ship between the feed roller and the friction pad; Fig. 8 is a plan view showing a mechanism to rotate in opposite direction to paper feeding; Fig. 9 is a side view showing paper feed condition; Fig. 10 is a side view showing the condition of pull­ ing out a paper feed cassette; Fig. 11 is a side view showing another embodiment of the mechanism to rotate the feed roller in opposite direc­ tion to paper feeding; Fig. 12 is a side view showing still other embodiment; Fig. 13 is a perspective view of the paper feeding device of Fig. 2; Fig. 14 is a schematic longitudinal section showing the condition of setting a small number of sheets of paper; Fig. 15 is a schematic longitudinal section showing the condition of setting a large number of sheets of paper; Fig. 16 is an enlarged and schematic longitudinal section showing a document tray, feed roller, and preliminary feed roller; Fig. 17 is an enlarged and schematic longitudinal section showing the document tray and feed roller; Fig. 18 is a schematic view showing another embodi­ ment of the mechanism to transmit revolution to the pre­ liminary feed roller; Fig. 19 is a plan view to show another embodiment of the paper feeding device of Fig. 1; Fig. 20 is an exploded perspective view showing the principal part; Fig. 21 is a side view showing the principal part; Fig. 22 is a schematic longitudinal section to show the condition of paper feeding from the paper cassette; and Fig. 23 is a side view showing the condition of pulling out paper feed cassette. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows the outline of the internal mechanism of a copying machine incorporated with a paper feeding device of the present invention. Of the whole housing (1) of the copying machine, the part incorporating the optical system (2) comprising a lamp, reflecting mirrors, and a lens is made wider and the other part incorporating the copying section (3) and the paper conveying section (4) is made narrower. To be more specific, a contact glass (11) to set documents to be copied is provided at the specified position on the housing (1) of the copying machine. The optical system (2) is composed of a lamp (21) to scan and expose documents while moving at a specified speed, reflecting mirrors (22) (23) (24) to lead the reflected light from the documents to a lens (25) while moving after the lamp (21), and a reflecting mirror (26) to lead the light coming through the lens (25) to the copying section (3). The copying section (3) comprises a photoreceptor drum (31) which turns in one direction at every copying operation, corona dischargers (32), a developing device (33), a trans­ ferring corona discharger (34), a separating belt (35) and a cleaner (36) provided around the photoreceptor drum (31). The paper conveying section (4) has the first paper feeding device (5) to feed out paper (P) sheet by sheet from the paper feed cassette (12) set on lower position of the copying section (3), a resist roller (41) driven sinchro­ nously with transferring of the lamp (21), a delivery roller (42) to carry the paper (P) separated from the photoreceptor drum (31) by the separating belt (35), a heating and fusing device (43), and a discharge roller (44) to discharge the paper (P) onto a discharge tray (15). A preliminary feed roller (103) to carry the paper (P) to the resist roller (41) and the 2nd paper feeding device (10) primarily made of a feed roller (102) are also attached to a specific position of a document tray (101) at a specific position of the copying machine housing (1) to enable selection of paper feed from the paper feed cassette (12) and from the document tray (101). Fig. 2 to Fig. 5 show detailed composition of the 1st paper feeding device (5), which is primarily composed of a feed roller (51), delivery roller (52), driven roller (53) as a driven member, and a guide (55). The feed roller (51) rotates while being pressed against the surface of the paper (P) held by a document setting board (13) which is turned upward by the lift-up lever (14) attach­ ed to a specific position in the copying machine housing (1) so as to feed out of paper (P) sheet by sheet and the paper is lead between the feed roller (51) and the friction pad (58) so that double paper feeding is prevented exactly. As shown in Fig. 6, an auxiliary roller (51c) to press the paper (P) on the end thereof is attached, in a manner to slide freely, to a sheet (51a) to which the feed roller (51) is also attached. When the feed roller (51) is mount­ ed together with the shaft (51a), sliding range of the auxiliary roller (51c) is limited by a rib (57a) projected from outer surface of the inner guide member (57) as des­ cribed later. Accordingly, amnufacturing and assembling become easy. The auxiliary roller (51c) may be fixed to the shaft (51a) in advance, but attaching accuracy of the auxiliary roller (51c) must be higher in this case. As shown in Fig. 7, the friction pad (58) is fixed to a contact member (12a) which regulates setting posi­ tion of the paper cassette (12) and is formed narrower than the feed roller (51). An edge parallel to the paper feed direction is formed on the tapered face (58a) and the paper (P) caught between the feed roller (51) and the friction pad (58) is bent along the tapered face (58a) to prevent folding or cutting of the paper, and thus jamming is prevented if the paper (P) is carried as it is. The paper (P) is allowed to be bent further along the feed roller (51) and the friction pad (58) to provide a space (59) where front end of the paper (P) can be corrected. After the space (59), the delivery roller (52) normal­ ly turned and the driven roller (53) pressed against the delivery roller (52) by a plate spring (54) are attached, and the guide member (55) composed of an outer guide plate (56) and an inner guide member (57) is attached between the normally rotated delivery roller (52) or the driven roller (53) and aforementioned resist roller (41). To be more specific, the paper cassette (12) has a document setting board (13) which can be turned in up-and-­ down direction when mounted onto the copying machine housing (1) and by taking a specific position at outer side as the fulcrum point, and also a rectangular opening (63) form­ ed along the front end of the bottom plate of the paper feed cassette (12) to the bottom of the front plate. A support (65) is fixed to the inner end of the bottom plate (64) of the copying machine housing (1) and a lift­ up lever (14) is turnably attached between a set of brackets (66a) and (66b) provided on the support (65). One bracket (66a) is fixed onto the support (65) with a set screw (67) and the other bracket (66b) is made in one piece with the support (65) by bending a part of the support (65), and the push lever (14) is held so as to turn upward and downward by projections (14a)(14b) provided at both sides of the bent part in the middle of the lift-up lever (14) and inserted into through holes (66c)(66d) made on the brackets (66a)(66b). A stopper dent (14c) is also provided on the base of the lift-up lever (14) and another stopper dent (68a) is also provided on a bent part (68) at an inner side of the support (65), and a coil spring (69) to turn the lift-up lever (14) upward (clockwise direction in Fig. 4 and Fig. 5) is provided between the stopper dents (14c) and (68a). A locking means (70) is provided in addition, which is composed of a locking mechanism (71) to lock the lift-up lever (14) in downward turning condition and of an lock-­ releasing mechanism (72) to release locking into upward turning condition. Having an interlocking projection (14d) at a side of the base of the lift-up lever (14) and an interlocked pro­ jection (75c) to be locked with the interlocking projection (14d), the locking means (70) is turned to a locked con­ dition (See Fig. 4) when the interlocking projection (14d) and the interlocked projection (75c) are interlocked with each other. The lock-releasing mechanism (72) has a release lever (75) of an arc shape and supports the release lever (75) between a pair of brackets (76a)(76b) provided on the support (65) in a manner that the lever can be turned freely. That is, one bracket (76a) is made in one piece with the support (65) by bending a part of the support, and the other bracket (76b) is fixed onto the support by a set screw (77) and the release lever (75) is supported so as to turn freely by the projections (75a)(76b) at both sides of the base of the unlocking lever (75) inserted into the through holes (76c)(76d) provided on the brackets (76a)(76b). In addition, the bottom end of a plate spring (78) bent to approximately U-shape is fixed onto the support (65) with a screw (79) and the top end is put in contact with the outer face of the release lever (75) to turn the release lever (75) to the direction of the paper cassette (12) (counter-clock­ wise direction in Fig. 4 and Fig. 5). The interlocked projection (75c) is provided on the release lever (75) corresponding to the interlocking pro­ jection (14d) provided on the lift-up lever (14). When the interlocking projection (14d) interlocks with the interlocked projection (75c), upward turning of the lift­ up lever (14) by the coil spring (69) is prevented as shown in Fig. 4. i.e. locking condition is selected. When the locking projection (14d) is disengaged from the interlocked projection (75c), the lift-up lever (14) is turn­ ed upward by the coil spring (69), i.e. unlocking condition is selected. The unlocking lever (75) has a top end which comes in contact with the front plate of the paper cassette (12) mounted onto the copying machine, and operating pieces (80) extend­ ing downward diagonally are provided at the front side of the front plate of the paper feed cassette (12). There are two operating pieces (80) provided with certain spacing in a transversal direction of the paper feed cassete (12). Corresponding to the operating pieces (80), contained pieces (81) are provided at the top side of the lift-up lever (14). The contacted pieces (81) are made of a contacted member (82) of triangular shape provided at a side of the lift-up lever (14), and a contacted roller (84) supported at the side with a short shaft (83) so as to turn freely, and the surface of the contacted member (82) is inclined upward to the side of the contracted roller (84). It is preferable to provide a guide member (85) of approxi­ mately the same shape as the contacted member (82) symetrical­ ly to the contacted member (82) around the contacted roller (84). The contact member (12a) has a ccntact part (12b) extend­ ing substantially vertically upward and an inclined part (12c) extending upward slantwise from the top end of the contact part (12b) in paper carrying direction, and covers the top of the support (65). The top side of the lift-up lever (14) and the top end of the release lever (75) are projected through an opening (12d) formed at approximately the center in transversal direction of the contact member (12b) (width-direction of the paper P). On the bottom plate (64) of the copying machine housing (1), a housing space (64a) is provided to accept the top end of the lift-up lever (14) when the lever (14) turns downward. As shown in Fig. 8 to Fig. 10, a rack (86) is made at the upper front of one side plate of the paper cassette, and a storage space (87) is provided immediately after the back side of the rack (86). Driving force of the driving power source (not illustrated) is transmitted at a specified timing to one end of the shaft (51a) to which the feed roller (51) is attached through a driving force transmission mechanism ccmprising a gear (88a) and a clutch (88b). To the other end of the shaft (51a), a gear (89), a gear attaching plate (90) and a lever (91) are attached. At a specified position of the gear attaching plate (90), a gear (92) to be interlocked with the gear (89) and another gear (93) to be interlocked with the gear (92) are attached. The lever (91) and the gar attaching plate (90) are turned downward around the shaft (51a) by a tension spring (94) provided between the top end of the lever (91) and a fixed point in the copying machine housing (1). The storage space (57) is provided at a position where the gear (93) can be housed when the paper feed cassette (12) is mounted completely so that the gear (93) following revolution of the feed roller (51) for paper feeding can be turned freely. The feed roller (51) can also be turned in reverse direction to paper feeding by the gear (93) inter­ locked with the rack (86) following pull-out motion of the paper cassette (12). As shown in Fig. 6, the inner guide member (57) is totally made of synthetic resin and a plurality of ribs with convex curvature on the side are provided on the outer surface of the guide member. An outer guide plate (56) made of steel or the like is attached with about 1mm spacing to the top of the ribs and the space between the ribs and the outer guide plate is used for paper transfer. The feed roller (52) is supported, in a manner to turn freely, at a position a little off the above mentioned space of the inner guide member (57), and a switch (60) to detect the paper (P) is held immediately before the resist roller (41). The driven roller (53) is attached to an opening and closing member (61) which is held onto the copying machine housing (1) by a plate spring (54) so as to be opened and closed. When the opening and closing member (61) is opened, the driven roller (53) is kept off the feed roller (52), and under closed condition of the opening and closing member (61), the driven roller (53) is pressed in contact with the feed roller (52). The pressure of the plate spring (54), however, is set smaller than the firmness of the paper (P). The magnet (62) is to keep the opening and closing (61) at closed condition. Operation of the 1st paper feeding device (5) is as shown below. When the paper feed cassette (12) is not set, the lift-up lever (14) turns downward, as shown in Fig. 4, and the interlocking projection (14d) interlocks with the interlocked projection (75c) of the release lever (75) to keep the downward turning operation. When the paper feed cassette (12) is inserted through the opening of the copying machine housing (1) under this condition, lower end of the pair of operating pieces (80) at the front side plate of the paper cassette (2) first comes in contact with the upper face of the corresponding guide member (85). As the cassette is inserted further, it goes over the guide member (85), the contacted roller (84) and the contacted member (82) in the order as mentioned. While going over, the front side of the paper feed cassette (12) is moved up and down to some extent due to the inclined face of the guide member (85) and the contacted member (82). As the paper cassette (12) is kept inserted further, the front side plate comes in contact with the top end of the release lever (75) just before the end of setting of the paper feed cassette (12) i.e. immediately before the front plate of the paper cassette (12) comes in contact with the contact part (12b) of the contact member (12a), then the release lever (75) turns clockwise against the pressure of the plate spring (78) as the paper feed cassette (12) moves. At the end of setting of the paper feed cassette (12), the interlocking projection (14d) of the push lever (14) is released from the interlocked projection (75c) of the release lever (75), then the lift-up lever (14) is turned upward by the coil spring (69) to turn the document setting board (13) upward (counter-clockwise direction in Fig. 5) and to put the feed roller (51) in pressed contact with the paper (P) at the top thereof. (See Fig. 5.) Accordingly, rotary force is transmitted to the shaft (51a) through the driving force transmission mechanism com­ prising the gear (88a) and the clutch (88b) and the feed roller (51) is rotated in the direction indicated by an arrow (51b) to feed the paper (P) out of the paper feed cassette (12). If two or more sheets of papers (P) are sent out at a time, the friction resistance between the friction pad (58) and the paper (P) functions to feed out the upper-most paper (P). During the paper feed operation, the gear (93) is also rotated but the rotation is idle as it is housed in the storage spaces (87) and causes no problem. The sheet of paper (P) sent out between the feed roller (51) and the friction pad (58) is led through the space (59) to the position between the delivery roller (52) and the driven roller (53). Since revolution of the delivery roller (52) is applied as the carrying force of the paper (P), the carrying force is sufficient to carry the paper (P) to put in contact with the resist roller (41) going through the guide (55). Even after the front end of the paper (P) touches the resist roller (41), the paper (P) is carried further for certain time by the feed roller (51), and the paper (P) fits along the whole surface of the outer guide plate (56) as shown by the continuous line in Fig. 2. Because of the firmness of the paper (P), the driven roller (53) is moved against the pressure of the spring (54), which serves to keep the paper (P) under the condition of no carrying force applied although the delivery roller (52) is kept turning. This arrangement exactly prevents the trouble that the paper (P) is carried to the resist roller (41) more than necessary resulting in jamming. If the paper (P) is not very firm, the driven roller (53) is little moved but the contact pressure to the delivery roller (52) is lessened and the delivery roller slips on the paper (P) thus carrying of the paper (P) is stopped. The preliminary paper feeding stops under the condition where the paper (P) is slackened from the regular carrying face by about 5 to 10mm in the space (59) and front end of the paper (P) can be corrected. For the following paper feeding, the feed roller (51) is kept suspended, and the friction between the friction pad (58) and the paper (P) functions as resisting force. When carrying of the paper (P) by the resist roller (41) starts, the paper (P) is immediately pulled and fitted along the outer surface of the inner guide member (57), as shown by the broken line in Fig. 2, as firmness of the paper (P) is no longer enough to separate the driven roller (53) from the delivery roller (52). The driven roller (53) is strongly pressed, therefore, to the delivery roller (52) and revolution of the delivery roller (52) functions for carrying the paper (P) without any slipping. The carrying force applied to the paper (P) by the resist roller (41) and the delivery roller (52) overcomes the resistance to complete the paper feeding to the copying section (3). Should jamming happen between the feed roller (51) and the delivery roller (52), the blocked paper (P) can be removed easily by opening the opening and closing member (61). If the paper cassette (12) must be pulled out to re­ plenish paper (P) or to change the size of the paper in use (P), the release lever (75) first turns downward following transfer of the paper feed cassette (12) to the outside (left side in Fig. 2). The paper feed cassette (12) moves outward further to go off the top of the release lever (75), then each one of the operating piece (80) comes in contact with the contacted part (81) to turn the lift-up lever (14) downward. At the end of downward turning of the lift-up lever (14), the interlocking projection (14d) interlocks with arc-shaped inner surface of the unlocking lever (75) to turn the un­ locking lever (75) upward, then the interlocking projection (14d) goes over the interlocking projection (75c). Accordingly, downward turning the lift-up lever (14) can be maintained by the interlocking projection (14d) interlocked with the interlocked projection (75c) even if the paper cassette (12) move outward further and downward turning power of the lift-up lever (14) by the operating piece (80) is no longer effective. In the initial stage of pulling out of the paper feed cassette (12), the gear (93) goes off the storage space (87) and is interlocked with the rack (86) (See Fig.10.). Accordingly, the gear (93) rotates following outward movement of the paper feed cassette (12) and rotary force in reverse direction to paper feeding is transmitted to the shaft (51a) through the gears (92),(89). In this case, transmission of the driving force is normally shut off by the clutch (88b), and the feed roller (51) is rotated in reverse direction to paper feeding, and the paper (P) of which the top end is caught between the feed roller (51) and the friction pad (58) is carried in reverse direction, i.e. to the paper feed cassette (12) so as to be free. If the paper feed cassette (12) is pulled out while the clutch (88b) is still kept in the condition of driving power transmission, the gar (93) turns upward around the shaft (51a) to be released from the rack (86), and collision of the gear (93) against the rack (86) is prevented. As is made clear in the above description, upward or downward turning of the lift-up lever (14) is selected automatically following setting and pulling-out of the paper cassette (12) resulting in easy setting and pulling-out of the cassette (12). At pulling out of the paper feed cassette (12), the feed roller (51) turns in reverse direction to paper feeding in the initial stage of pulling, and top end of the paper (P) is not caught between the feed roller (51) and the friction pad (58) and the contact area of the paper with the friction pad (58) is kept less. This serves to pull out the paper (P) completely together with the paper feed cas­ sette (12) and prevents the paper (P) from the remain­ ing in the copying machine housing (1). Although the delivery roller (52) is kept turned throughout paper feeding operation, carrying force is applied to the paper (P) only while the driven roller (53) is pressed onto the delivery roller (52). This means that paper carrying force is applied only when the paper (P) is carried by rotating the feed roller (51) while keeping the resist roller (41) suspended to come in contact with the resist roller (41) yet to the point where the paper (P) fits along the inner surface of the outer guide plate (56), and only when the paper (P) is fitted along the outer surface of the inner guide member (57) by turning the resist roller (41) while keeping the feed roller (51) suspended. Under any other condition than above, no or almost no carrying force is applied to the paper (P) and paper feeding is free from any trouble. It is most preferable to position the feed roller (52) at a point where carrying direction of the paper (P) changes sharply, as illustrated, so that selection and control of the condition where carrying force can be transmitted exactly by firmress of the paper (P) and of the condition where carrying force is little transmitted due to slipping can be practiced exactly with no regard to friction resistance of the delivery roller (52). As known from the above description, the driven roller (53) is not necessarily required and can be omitted because carrying force transmission condition and slip condition can be selected only if the contact pressure to the delivery roller (52) can be changed according to transfer condition of the paper (P). If the lift-up lever (14) can be turned by the operat­ ing piece (80), the contacted member (82) can also be omitted and it is possible to provide the operating piece (80) and the contacted part (81) at one side only. When rollers (89') (92') (93') for driving power trans­ mission are used in place of the gears (89) (92) (93) as the mechanism to turn the feed roller (51) in reverse direction to paper feeding, as shown in Fig. 11, and a friction pad (86') is used instead of the rack (86), it is possible to turn the roller (93') following transfer of the paper cassette (12) by the friction force between the friction pad (86') and the roller (93') and to turn the feed roller (51) in reverse direction to paper feeding. When a rachet gear (93") is attached coaxially to the roller (93'), as shown in Fig. 12, and a rachet claw (86") is used in place of the friction pad (86'), the feed roller (51) can be rotated in reverse direction to paper feeding by turning the rachet gear (93") only at the pulling-out operation of the paper feed cassette (12). Fig. 13 to Fig. 17 shows details of the composition of the 2nd paper feeding device (10), which is primarily made of a document tray (101), feed roller (102), preliminary feed roller (103) and a guide member (104). The preliminary feed roller (103) comprises a plurality of friction rollers attached with certain spacing each other to a specified positions of a shaft (107) to which rotary force is transmited through an idle gear (115) and a driving gear (116). Both ends of the shaft (107) are interlocked with a long hole (108a) made at a specified position of a side plate (108) to press the preliminary feed roller in paper pressing direction by its own weight. Rotary force to the shaft (107) is transmitted only when the paper (P) is sensed by a limit switch (100). The guide member (104) is held at a specified potiion at paper insertion inside of the side plate (108) so as to turn freely. Top edges at both ends of the guide member (104) are pro­ jected respectively toward the shaft (107) to form a push­ ing section (104a) stretching out to the upper part of the driving side of the shaft (107) and also a receiving section (104b) stretching out to the bottom at the opposite side to the driving side of the shaft (107) so that the preliminary feed roller (103) can be moved upward without being in­ clined. The guide member (104) is reinforced by a rib (104c) provided on the upper face of the guide member (104). The feed roller (102) is attached to the down-stream side of the preliminary feed roller (103) comprising a center roller (102a) to prevent double feeding of the paper (P) exact­ ly being pressed by a friction pad (112) attached to a speci­ fic position to the top end side of the document tray (101) and an auxiliary rollers (102b) at both sides of the center roller (102a) and attached to a shaft (102c). Like the above-mentioned friction pad (58) (See Fig.7.), the friction pad (112) is narrower than the center roller (102a) and the edge is made to a tapered face (112a) parallel to feeding direction of the paper (P). For ordinary paper (P), only the center roller (102a) is used for paper feeding. When papers of high friction factor such as thick paper, second original, or OHP paper, the carrying force of the auxiliary rollers (102b) is ap­ plied to obtain higher carrying force than the friction with the friction pad (112) so as to ensure exact paper feeding. To be more in detail, the friction pad (112) is pressed upward by the spring (112b) to maintain contact with the center roller (102a). Corresponding to the auxiliary rollers (102b), a dent (102d) is made on the document tray (101), into which the auxiliary rollers (102b) sit to the extent that do not come in contact with the dent (102d). Between the center roller (102a) and the auxiliary roller (102b), and the doucment tray (101), the paper (P) is carried being caught by the rollers (102a) (102b) and the document tray (101), as shown by the alternate one-dot chain line in Fig. 17 so as to transmit the carrying force exactly. Since the auxiliary roller (102b) is not in contact with the dent (102d), the carrying force is somewhat lower than in the case where the roller is in direct contact with the dent, and double feeding of the paper is prevented. The mechanism to transit the rotary force from the driving power source not shown to the shaft (102c) is composed of a clutch (113) connected to one end of the shaft (102c) and a drive gear (114) to transmit the rotary force from the driving power source (not shown) to the clutch (113), and the shaft (102c) is driven only when the rotary force is tramsmitted to the clutch (113). A bend control plate (105) having dents (105a) (105b) at both ends is supported in a manner that the dents (105a) (105b) are interlocked respectively with the shafts (107) (102c), and the lower face (105c) of the bend control plate (105) under the supported condition in this manner comes close to the upper-most paper (P) set on the document tray (101). Accordingly, the spacing between the upper-most paper (P) and the lower face (105c) of the bend control plate (105) is kept approximately constant with nc regard to the quan­ tity of the paper (P). This prevents the paper (P) from being bent upward too much between the feed roller (102) and the preliminary feed roller (103) when carrying force is applied by the preliminary feed roller (103) only. Only one sheet of the bend control plate (105) may be held at a position close to the center roller (102a). It is also possible to support a plurality of sheets of the bend control plate (105) with certain spacing or to bend the bend control plate (105) in the middle so that the inter­ locking positions with the shafts (102c)(107) are offset each other. The mechanism to tranmit the rotary force from the driving power source (not illustrated) to the shaft (107) is composed of an idle gear (115) attached to the shaft (102c) through a bearing (115a) so as to turn freely, and a driv­ ing gear (116) fixed to one end of the shaft (107) and interlocked with the idle gear (115), and is turned to the same direction as that of the shaft (102c). The document tray (101) has a notch (117) approximate­ ly at the center and in perpendicular direction to paper feeding, and a projection (119) on a side control plate (118) is interlocked with the notch (117) and is fastened with a stop ring (120). Accordingly, the side control plate (118) can slide freely along the notch (117). By fitting a cut mark (118a) suitably to paper size in­ dication, one end of the paper (P) can be controlled by a vertical part (118b) rising vertically from the side control plate (118). Paper of a desired size can be fed by fitting the side control plate (118) to the desired size indication. To feed paper of A6 size, for example, fit the cut mark (118a) to A6 position. For feeding A4 size paper, move the side control plate (118) to the position shown by the two­ dot chain line to fit the cut mark (118a) to A4 position. The other end of the paper is controlled by a control part (121) rising vertically from the document tray (101). Since the reference for the 2nd paper feeding device (10) is at the side of the control part (121),i.e. one end reference, the paper (P) is first put in contact with the control part (121) then the side control plate (118) is slided to control the side of the paper (P). A foldable projection (101a) is provided on the document tray (101) and the projection (101a) can be rotated freely around the shaft (122) (122). For large size paper, therefore, the projection (101a) is opened to support the paper (P) on the rear end. For small size paper, the projection (101a) is folded and the side control plate (118) slides on the projection (101a). The document tray (101) is attached to the side plates (108)(108) so as to turn freely around the fulcrum point (123). The top end of the document tray (101) is inclined downward to the down-stream side of paper feed so that the paper (P) can be inserted easily. After passing nearly the bottom of the preliminary feed roller (103), however, the document tray (101) turns upward and the inclination is increased gradually toward the downstream side with the 1st crest (124), the root (125), and 2nd crest (126) that are following for better transfer of paper and reaching to the part where the feed roller (102) comes in contact with the friction pad (112). As Fig. 16 indicates, the inclination from A1 right under the preliminary feed roller (103) to the 1st crest (124) is an easy slope and the height isn't very high. While the inclination from the root (125) to the 2nd crest (126) is a sharp slope and it is so arranged that the top of the 2nd crest (126) comes onto the extension from Al right under the preliminary feed roller (103) to A2 point of the 1st crest (124). If the number of sheets of paper (P) from the 2nd paper feeding device (10) is small, the paper (P) is sent as the preliminary feed roller (103) rotates, as shown in Fig. 14. Even after passing through A2 point, the paper does not fall down into the root (125) because of the firmness and goes to the top of the 2nd crest (126) as shown by one-dot chain line then is support­ ed by the 1st and the 2nd crests (124) (126) to come in contact with a specified position of the feed roller (102), and the transfer stops. If the 1st crest (124) is not provided, in this case, it may possible that the paper (P) falls into the root (125) and does not come in contact with the feed roller (102). While a large number of sheets of paper (P) is fed, the paper (P) follows transfer of the preliminary feed roller (103), as shown in Fig. 15, and falls into the root (125) because of its own weight, where the lower-most paper stops. Upper layers of the paper are inclined toward the feed roller (102). When the upper-most layer comes in contact with the feed roller (102) at a position not so far upward from the position where the feed roller (102) touches the friction pad (112), the paper carrying stops. Smooth paper feeding is ensured because the paper turns to stand-by condition while coming in contact with approximaely the same position of the feed roller (102) with no regard to the stacked number of sheets of the paper (P). According to a test by the in­ ventors of the present invention, for reference, feeding of the paper (P) was most smcoth when the angle ϑ1 from the upstream side of paper feeding of the document tray (101) to A1 point almost right under the preliminary feed roller (103) in Fig. 16 was set at about 10°, the angle ϑ2 from A1 point to A2 point of the 1st crest (124) at about 10°, the angle ϑ3 from A2 point to the lower-most end of the root (125) at about 7°, and the angle ϑ4 from the lower-most end of the root (125) to the upper-most end of the 2nd crest (126) at 25°. The 2nd paper feeding device (10) operates as described below. First the side control plate (118) is slided along the notch (117) so that the cut mark (118a) fits a desired paper size indication marked on the document tray (101), then paper is set. To set paper of especially large size, the projection (101a) is opened by turning around the shafts (122)(122) to support the paper on the rear end. The paper touches the limit switch (100) before reaching the guide member (104), the main motor starts turning and the revolution is transmitted to the idle gear (115) and further to the driving gear (116) to turn the preliminary feed roller (103). Accordingly, the paper is put in contact with the preliminary feed roller (103) going through the paper feed channel formed between the paper guide (104d) of the guide member (104) and the document tray (101) and is carried smoothly to the specified position. At this time, the driving gear (116) is rotated to R2 arrow direction by the rotary force transmitted to the driving gear (116) and lifting force is applied, by which the end at the driving side of the shaft (107) of the preliminary feed roller (103) is pushed upward. However, the upward motion is constrained to some extent by the pressure (104a) of the guide member (104). While the guide member (104) is rotated around the shaft (104e) by the force acting upon the pressing section (104a). Accordingly, the receiving section (104b) at the other end of the shaft (104e) is lited. After all, the preliminary delivery roller (103) is moved upward approximately in horizontal condition, and the paper (F) can be set at the specified position easily. When the number of sheets is small, the paper can be placed at a position easily carried by the feed roller (102) while being put in contact with the 1st and the 2nd creasts (124) (126) of the document tray (101). If the numter of sheets of paper to be set is larger, the lower layer of the paper comes in contact with the root (125) and is prevented from advanc­ ing further, and only the upper layer of the paper is carried. Toward the upper layer, the paper is inclined and the main motor stops when the upper-most layer is put in contact with the specified position for easy carrying by the feed roller (102). Accordingly, the preliminary feed roller (103) is also stopped. When the copying start button (not illustrated) is then pushed, the main motor starts turning, the driving gear (114) of the feed roller (102) turns in R3 arrow direction following the main motor, and the clutch (113) is engaged. Then the rotary force is transmitted to the center roller (102a) and the auxiliary roller (102b). Following the idle gear (115) turning in R1 direction, the driving gear (116) of the preliminary feed roller (103) turns in R2 direction to assists paper feeding from the document tray (101) into the copying machine. At this time, the center roller (102a) is in contact with the friction pad (112) which is pressed from the bottom by a spring to prevent double paper feeding. For carrying papers of high friction coefficient, carry­ ing is assisted by the auxiliary roller (102b). When the paper (P) is fed further through the paper feed channel (45) composed of the upper and lower guide plates, and at a specified time after front end of the paper touches the limit switch (60), the clutch (113) is disengaged to cut off transmission of the rotary force of the driving gear (114) to the feed roller (102), and the feed roller (102) comes to a stop. During the operation, front end of the paper (P) meets the resistance by the resist roller (41), by which diagonal paper feeding is prevented and the timing with exposure is controlled. As soon as the feed roller (102) comes to a stop, the resist roller (41) starts turning to carry the paper (P) toward the transfer section T of the photoreceptor drum (31). Although the guide member (104) is composed of the presser (104a) at one end of the shaft (104e) and of the receiver (104b) at the other end, it is also possible to compose the guide member (104) with a presser and a receiver provided respectively at both ends of the shaft (104e). The upper-stream side of the 1st crest (124) can be of any shape provided that the top end of the document tray (101) is formed as described above, i.e. the shape with the 1st and 2nd crests (124) (126), and a root (125) in-between. A sharp slope from the top of the 1st crest (124) to the root (125) is also acceptable. In the above embodiment, the auxiliary roller (102b) to assist paper feeding is provided at both sides of the center roller (102a) which is in contact with the friction pad (112). The invention, however, is not limit thereto and the rollers to assist paper feeding may be located at any position if it is on the center roller (102a). It may also possible to provide a pair of side control plates (118) so as to be interlocked in reverse direction each other and so that papers of different sizes are set approximately along the center line of the document tray (101) and to provide the center roller (102a) and the friction pad (112) corresponding to the center line. In this case, the guide member (104) can be of the composition having a plurality of receiving sections (104b) and no pres­ sing section (104a). Fig. 18 shows an embodiment to transmit rotary force to the shaft (107) of the preliminary feed roller (103) through a ladder chain (105) and a sprocket (106). The sprocket (106) is provided with an interlocking pro­ jection (109) and the shaft (107) is provided with a pin (110) which can be interlocked with the interlocking pro­ jection (109). Accordingly, the shaft (107) can be rotated only when the sprocket (106) rotates and the pin (110) is interlocked with the interlocking projection (109). When the sprocket (106) is in stop, the preliminary feed roller (103) can be turned freely by almost 360° to the same direction as the turning direction of the sprocket (106). In other words, the paper (P) can be set smoothly onto the document tray (101) because the preliminary feed roller (103) turns following insertion of the paper (P) even when the roller is not driven. Accordingly, the limit switch (100) to detect the paper (P) can be positioned between the preliminary feed roller (103) and the feed roller (102), then the paper (P) can be sent out toward the resist roller (41) by rotating the feed roller (102) after detecting the paper (P) by the limit switch (100). It is also possible to insert a one-way bearing instead of the interlocking projection (109) and the pin (110). In the above embodiment, the 2nd paper feeding device (10) is applied to the stack by-pass mechanism. Even by applying the 2nd paper feeding device (10) to the automatic document feeder, smooth setting and exact feeding of documents can be practiced in the same manner as in the above embodi­ ment. Fig. 19 to Fig. 23 are to show another embodiment of the 1st paper feeding device (5). Major differences from the above embodiment are that the feed roller (51) is attached to the shaft (51a) with a one-way bearing (51d) in-between, a star wheel (51e) is attached to the shaft (51a) at a position far off the feed roller (51), and that a friction pad driving unit (58a) is attached for putting in contact or separating apart the friction pad (58) with the feed roller (51) to follow mounting and dismounting operation of the paper feed cassette (12). All the rest are composed in the same manner as for the above embodiment. According­ ly, the same reference numbers are attached to the same com­ ponents as those of the above embodiment. The details are as described below. As shown in Fig. 19 and Fig. 20, the shaft (51a) is held so as to rotate freely through a pair of frames (51f) and, a clutch (88b) is attached to the projected end of the shaft (51a). To the clutch (88b), a gear (88a) is attached to transmit rotary force from the driving power source not illustrated. The shaft (51a) and a gear (89) are interlocked each other so as to rotate together by inserting the other pro­ jected end of the shaft (51a) into a cylindrical shaft (89a) of the gear (89) and by interlockinga pin (89c) fixed and passed through the shaft (51a) with a pair of dents (89b) on the end of the cylindrical shaft (89a). The lever (91) and a gear attaching plate (90) are to support the shafts of gears (89) (92) (93) so as to turn freely. The top end of the lever (90) is bent toward the gear attaching plate (90) and the lower part of the bent end is bent further to the top side to form an interlock ing plate (91a) onto which a hole (91b) is provided. A shaft (94b) rising from the upper surface plate (94a) at the upper part of the mounted paper feed cassette (12) is loosely inserted into the hole (91b). A washer (94d) is fixed to the top end of the shaft (94b) with a screw (94e), and the shaft (94b)is inserted loosely into a push spring (94f) which is restrained at both ends by the washer (94d) and the interlocking plate (91a). Accordingly, the rack (86) and the gear (93) can be inter­ locked without any shock when the lever (91) and the gear attaching plate (90) are turned downward around the shaft (51a) by the push spring (94f) to mount and dismount the paper feed cassette (12). The feed roller (51) is attached to approximately the middle of the shaft (51a) through a one-way bearing (51d), and rotary force is transmitted to the feed roller (51) only when the shaft (51a) is rotated in paper feeding direction from the paper feed cassette (12). The feed roller (51) turns freely to the shaft (51a) when the shaft (51a) is rotated in reverse direction at pulling out of the paper feed cassette (12) as the gear (93) interlocks with the rack (86) and when rotation of the shaft (51a) is stop­ ped by the clutch (88b). The star wheel (51e) is rotated together with the shaft (51a) and is attached to the shaft (51a) at a position not far off the feed roller (51) so as to be put in contact with the paper (P) accurately when the size of the paper (P) stored in the paper feed cassette (12) is changed. The star wheel (51e) is made of rubber, at least the edge of the peripery, to reduce the area in contact with the paper (P) and to ensure transmission of sufficient friction force. The friction pad driving unit (58a) is composed as described below. As shown in Fig. 21, the upper erd side of the lever (58c) connected to a friction pad support (58b) is supported by a shft (58d) so as to rotate freely. The horizontal plate (12e) at the center of a contact member (12a) has the 1st receiver (12f) extending practical­ ly upright and also the 2nd receiver (12g) extending downward diagonally from the top end of the receiver (12f) to the paper feed cassette (12). In addition, a push spring (58e) is attached between the 2nd receiver (12g) and the friction pad support (58b), and another push spring (58g) of higher repulsion than the push spring (58e) is also attached between the 1st receiver (12f) and an interlock­ ing member (58f) hold on the horizontal plate (12e) so as to interlock the collar (58h) made at the base side of the interlocking member (58f) with the lower end of the lever (58c) at all times. When the paper cassette (12) is not mounted, the inter­ locking member (58f) is projected from the contact part (12b) to the paper feed cassette setting side by the repulsion of the push spring (58g), and the lever (58c) is turned forcefully clockwise around the shaft (58d) by the collar (58h) of the interlocking member (58f). Accordingly, the friction pad (58) is separated from the feed roller (51). When the paper cassette (12) is mounted, on the other hand, the interlocking member (58f)is pushed in by the front plate of the paper cassette (12) against the repulsion of the push spring (58g), and the friction pad support (58b) and also the lever (58c) are turned counter-clockwise around the shaft (58d) by the repulsion of the push spring (58e). Accordingly, the friction pad support (58) is pressed against the feed roller (51) and the feed roller (51) rotates to feed out the paper (P) sheet by sheet. The lift-up lever (14) has a contacted part (81) com­ posed of a projection of isosceles triangular shape, and the upper edge of the opening (63) made on the paper cassette (12) is an inclined face (63a) being forwardly slanted down. In this embodiment, the paper feeding operation proceeds in the following manner. When the paper cassette (12) is set in the copying machine housing (1), the inclined face (63a) goes over the contacted part (81) of isosceles triangular shape of the lift-up lever (14) and the release lever (75) is turned to unlock the lift-up lever (14) like in the case of the above embodiment, then the lift-up lever (14) is turned upward by the coil spring (69). Accordingly, the document setting board (13) is turned upward to press the upper-most paper (P) against the feed roller (51). By setting the paper cassette (12), the interlocking member (58f) is pushed inside against the push spring (58g). By repulsion of the push spring (58c), therefore, the friction pad support (58b) is turned counter-clockwise around the shaft (58d) and the friction pad (58) is pressed against the surface of the feed roller (51). When the shaft (51a) is then rotated through the gear (88a) and the clutch (88b) for paper feeding, the rotary force is transmitted to the feed roller (51) through the one-way bearing (51d) making it possible to feed the paper (P) from the paper cassette (12). In the initial stage of paper feeding from the paper cassette (12), front end of the paper (P) is led between the feed roller (51) and the friction pad (58). Even when two or more sheets of paper (P) are sent out, the paper is sent out sheet by sheet exactly to the down-stream side of the feed roller (51) and the friction pad (58). The paper (P) sent out sheet by sheet, as shown in Fig. 22, is led through the space (59) to the position between the delivery roller (52) and the driven roller (53), then is lead further to the guide (55) while the carrying force is transmitted by the delivery roller (52). Finally, the front end of the paper (P) comes in contact with the resist roller (41) then the preliminary paper feeding completes as the carrying force is kept transmitted for a little while thereafter. As the clutch (88b) is so controlled to shut transmission of the rotary force when the pre­ liminary paper feeding completes, the shaft (51a), the star wheel (51e) and the feed roller (51) stop to rotate. After completion of the preliminary paper feeding in this manner, the resist roller (41) is turned in timing with document exposure operation i.e. the transfer timing of the lamp (21) and the reflecting mirrors (22) (23) (24) to start the main paper feeding. Since the main paper feeding is made by rotating the resist roller (41) while transmission of the rotary force to the feed roller (51) and the star wheel (51e) is being shut off, slackening of the paper (P) at the guide (55) is removed in the initial stage of the main paper feeding. When slackening is removed almost completely, carrying force is transmitted to the paper (P) also by the delivery roller (52). It is possible, therefore, to feed the paper (P) exactly at the same speed as revolution speed of the photo­ receptor drum (31) against the friction resistance caused by contact of the paper (P) with each part. Length of the paper (P), however, is not necessarily constant. Some paper (P) are short to the extent that the rear end is separated from the feed roller (51) when the preliminary paper feeding completes, but other paper (P) may be longer to the extent that the rear end is caught between the feed roller (51) and the friction pad (58) when the preliminary paper feeding completes. If the paper (P) is short, and the resist roller (41) is turned, the feed roller (51) does not resist paper feed at all. Throughout the whole period of paper feeding by the resist roller (41), friction resistance is subjected to almost no change and paper feeding is carried out under even transfer condition, which enables to transfer the toner image formed on the surface of the photoreceptor drum (31) onto the paper surface by the transferring corona discharger (34) without any positional deviation. If the paper (P) is long, rear end of the paper (P) is caught between the feed roller (51) and the friction pad (58) in the initial stage of rotation of the resist roller (41), and outer end of the star wheel (51e) is kept in contact with surface of the paper (P). As the resist roller (41) rotates, therefore, slackening of the paper (P) is removed, then the feed roller (51) and the friction pad (58) function to resist the paper feeding. Being attached to the shaft (51a) through the one-way bearing (51d), the feed roller (51) rotates freely as the paper (P) is transfered and the resistance is smaller than that of the condition where the feed roller (51) is suspended. Accordingly, the resistance hardly changes even when the rear end of the paper (P) goes through the feed roller (51) and the friction pad (58) and transfer deviation of toner image due to changes in the resistance can be avoided almost completely. The shaft (51a) and the feed roller (51) are attached with the one-way bearing (51d) in-between as shown in Fig.23. When the paper feed cassette (12) is pulled out and the shaft (51a) is rotated in reverse direction, therefore, the rotary force in reverse direction is not transmitted to the feed roller (51). Consequently, the paper (P) of which front end is between the feed roller (51) and the friction pad (58) can't be transfered to the paper feed cassette (12) by the feed roller (51). When the paper feed cassette (12) is pulled out, however, the interlocking member (58f) is moved by the push spring (58g), the collar (58h) is interlocked with the lever (58c) and turns the friction pad support (58b) in clockwise direction against the push spring (58e), and the friction pad (58) is separated from the feed roller (51). Thus the front end of the paper is released. The rack (86) and the gear (93) are interlocked each other in the middle of the pull-out motion of the paper feed cassette (12), turning force in reverse direction is trans­ mitted to the shaft (51a) through the gear (92) (89), and the one-way bearing (51d) prevents the feed roller (51) from turning, but the star wheel (51e) is turned in reverse direction of paper feeding. The star wheel (51e) is made of rubber, at least on the edge of the periphery, and keeps certain extent of friction resistance to the paper (P), which makes it possible to feed the paper (P) released as described above to the side of the paper feed cassette (12) and to keep the friction resistance between the friction pad (58) and the paper (P) at a very low level. This serves to prevent exactly the paper (P) from remaining in the copy­ ing machine housing (1) when the paper feed cassette (12) is pulled out. If the paper (P) remains in the copying machine housing (1) when the paper cassette (12) is pulled out with the front end being caught between the feed roller (51) and the friction pad (58), the remaining paper (P) is crumpled when the paper feed cassette (12) is mounted next time, and jamming is very probable. By the above embodiment, however, jamming can be prevented as the paper (P) is not left in the housing (1). For the type of copying machines whre a larger portion of the paper feed cassette (12) is inserted into the housing (1) of the copying machine, the embodiment to prevent residual paper (P) completely is practically very effective as it isn't easy to check for any remaining paper (P) from the outside.

Claims: 1. A paper feeding device provided on an image processing apparatus, for feeding a document from a paper cassette (12) which is set on the image processing apparatus in a state that the most part of the paper cassette (12) is holded within a housing (1) of the image processing apparatus, reversing a direction of conveying the fed document, and delivering the document to a resist roller (41) being driven so as to rotate synchronously with an operation of an image processing section of the image processing apparatus, which comprises: a feed roller (51) for providing a force of pulling out a document stored in the paper cassette (12) sheet by sheet, a guide section composed of an outer guide plate (56) and an inner guide plate (57) to form a curved space for permitting the document to reversely pass therethrough, and a delivery roller (52) disposed at the upstream side in document-delivering direction from the inner guide plate, (57) being normally driven so as to rotate for providing a carrying-force to the document. 2. A paper feeding device according to Claim 1, wherein said feed roller (51) and delivery roller (52) are provided therebetween with a space section (59) capable of forming the document with a bend at a time point of finishing the delivery of document until the top of the document touches the resist roller (41). 3. A paper feeding device according to Claim 1, wherein said guide section is arranged to form a convexly curved surface as a whole, and said outer guide plate (56) and inner guide plate (57) are provided with an interval therebetween, which is so formed that the document comes in contact with an inner surface of the outer guide plate (56) when the document is delivered toward the resist roller (41) and the document comes in contact with an outer surface of the inner guide plate (57) when the document is delivered by the resist roller (41). 4. A paper feeding device according to Claim 1, wherein said feed roller (51) is supplied with a rotatory force only when the document is fed from the paper cassette (12). 5. A paper feeding device according to Claim 1, wherein said delivery roller (52) is provided with a driven member (53) which elastically presses the delivery roller (52) so that the document is delivered in a state that the document is pressingly sandwiched between the delivery roller (52) and the driven member (53). 6. A paper feeding device according to Claim 5, wherein said driven member (53) is a driven-roller which is pressed on the delivery roller (52) by means of a spring (54). 7. A paper feeding device according to Claim 5, wherein said driven member (53) is a leaf spring which is pressed on the delivery roller (52). 8. A paper feeding device according to Claim 1, wherein said feed roller (51) is pressed by a friction pad (58) for avoiding a double feeding of documents. 9. A paper feeding device according to Claim 1, further being characterized in that said paper cassette (12) comprises a document setting board (13) capable of being lifted up around a rearend portion of the paper cassette (12) as a fulcrum and an hole communicating with an outside of the paper cassette (12), and there are provide in the housing of the image processing apparatus a pressing mechanism (14) for lifting up the document setting board (13) when the paper cassette (12) is set on the image processing apparatus, a locking mechanism (71) for automatically locking the pressing mechanism when the paper cassette is removed therefrom so that the pressing mechanism does not lift up the document setting board (13), and a lock-releasing mechanism (72) for automatically releasing the locking mechanism (71) when the paper cassette (12) is set on the document setting board (13) so that the pressing mechanism 14 lifts up the document setting board (13). 10. A paper feeding device according to Claim 9, wherein said pressing mechanism includes a lift-up lever (14) capable of turning up and down and a pushing member for turning the lift-up lever (14) in a direction of lifting up the document setting board (13). 11. A paper feeding device according to Claim 9, wherein said locking mechanism (71) includes a first engaging section disposed at the pressing mechanism and a second engaging section disposed at the locking mechanism (71) to engage with the first engaging section, thereby holding the pressing mechanism so that the pressing mechanism does not lift up the document setting board. 12. A paper feeding device according to Claim 9, wherein said locking mechanism (71) includes an operation piece (80) for turning the pressing member following the operation of removing the paper cassette (12) so that the pressing member does not lift up the document setting board (13). 13. A paper feeding device according to Claim 12, wherein said operation piece (80) is dispose at a front-end plate of the paper cassette (12) and said pressing mechanism has a contact section with which the operation piece (80) is capable of making contact. 14. A paper feeding device according to Claim 9, wherein said lock releasing (72) mechanism includes a release lever (75) capable of turning up and down in relation to an operation of setting the paper cassette (12), said release lever (75) having an engaging section for holding the pressing mechanism when the paper cassette is removed so that the pressing mechanism does not lift up the document setting board (13), and turns the release lever (75) when the paper cassette (12) is set so as to release the holding state of the pressing mechanism. 15. A paper feeding device according to Claim 14, wherein said release lever (75) is capable of coming in contact with the front end plate of the paper cassette (12), and turning up and down following the operation of setting the paper cassette (12). 16. A paper feeding device for feeding a document by a feed roller (51) from a paper casssette (12) which is not mounted with a click to avoid a double feeding of documents, and pressing a friction pad (58) on the feed roller (51) to avoid a double feeding of documents, which comprises a driving force transmitting mechanism for transmitting a rotary force in the opposite direction to the paper-feeding direction to a shaft on which the feed roller is installed in an initial stage of an operation of removing the paper cassette (12). 17. A paper feeding device according to Claim 16, wherein said driving force transmitting mechanism includes a gear (88a) mounted on the shaft and a rack (86) mounted on the paper cassette (12). 18. A paper feeding device according to Claim 16, wherein said driving force transmitting mechanism includes a ratchet gear (93'') mounted on the shaft and a ratchet pawl (86'') mounted on the paper cassette. 19. A paper feeding device according to Claim 16, wherein said driving force transmitting mechanism includes a roller (93') installed on the shaft and a friction member (86') installed on the paper cassette (12). 20. A paper feeding device for feeding a document by a feed roller (51) from a paper cassette (12) which is not mounted with a click to avoid a double feeding of documents, and pressing the friction pad (58) on the feed roller (51) to avoid a double feeding of documents wherein, said feed roller (51) is supplied with a rotary force from a shaft (51a) of the feed roller in a single direction of feeding a document, and said shaft is mounted with a star wheel close to the feed roller, and further there is provided a driving force transmitting mechanism for transmitting a rotary force to the shaft in the opposite direction to the document-feeding direction. 21. A paper feeding device according to Claim 20, wherein said driving force transmitting mechanism includes a gear (93) mounted on the shaft (51a) and a rack (86) mounted on the paper cassette. 22. A paper feeding device according to Claim 20, wherein said driving force transmitting mechanism includes a ratched gear (93'') mounted on the shaft and a ratchet pawl (86'') mounted on the paper cassette (12). 23. A paper feeding device to Claim 20, wherein said driving force transmitting mechanism includes a roller (89';92';93') installed on the shaft and a friction member (86') installed on the paper cassette (12). 24. A paper feeding device (10) for feeding a document on the document tray first by a preliminary feed roller (103) and next by a feed roller (102) wherein, said preliminary feed roller (103) is normally pushed in a direction so as to press down the document and there is provided a guide member (104) for turning the preliminary feed roller (103) so as to move the preliminary feed roller (103) in the opposite direction to the direction of pressing down the document following an operation of putting a document on the document tray. 25. A paper feeding device according to Claim 24, wherein said preliminary feed roller (103) is driven so as to rotate prior to putting the document on the document tray. 26. A paper feeding device according to Claim 24, wherein said preliminary feed roller (103) is rotated following an operation of putting the document on the document tray and the rotary force is transmitted to the preliminary feed roller (103) only in a direction of feeding the document. 27. A paper feeding device according to Claim 24, wherein said guide member (104) comprises a pushing section (104a) at an end thereof stretching out to the upper part of at least the end-portion on the driving force transmitting side of the preliminary feed roller-shaft (107) and a receiving section (104b) at the other end thereof stretching out to the lower part of at least the other end-portion of the preliminary roller-shaft (107).

Inventors: ABE, YUJI, KAJIWARA, MANABU, KANO, ATSUSHI, MIZUNO, MASAYUKI, NAKAMURA, KAZUO, SAKAUE, KENJI
Applicants: MITA INDUSTRIAL CO. LTD.
Application year: 1986
Main classification: G03G15
IPC codes: B65H3, G03G15, B65H1