Paper feeding device

Abstract: A paper feeding device for feeding a document by a feed roller (51) from a paper cassette (12) is presented. The device is not provided with a click to avoid a double feeding of documents. A friction pad (58) is pressed on the feed roller (51) to avoid a double feeding of docu­ ments. It 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 opera­ tion of removing the paper cassette (12).

Description: 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 copying 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 opposite 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 feeding, 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 feeding 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 enabling 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 paper 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 paper setting board by a means of pressure mechanism is also attached. Under the condition where the paper 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 paper 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 mechanism, the paper 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 copying 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 resulted 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 but 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. It is therefore the object of the invention to ensure that on extraction of a paper cassette, no sheet of paper, regardless of its size, remains in the paper feeding device and that, instead, a partially fed sheet is moved back towards the cassette and is extracted along with it. To this end, the paper feeding device according to claim 1 includes a drive-force transmitting mechanism to transmit a rotary force in the opposite direction to the paper-feeding direction to a feed roller in a predetermined timing of removing the paper cassette from the image processing apparatus. 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 a plan view to show an embodiment of the paper feeding device of Fig. 1; Fig. 3 is an exploded perspective view showing the principal part; Fig. 4 is a side view showing the principal part; Fig. 5 is a schematic longitudinal section to show the condition of paper feeding from the paper cassette; and Fig. 6 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 transferring 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 sinchronously 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. 6 are to show an embodiment of the 1st paper feeding device (5). 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 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). The details are as described below. As shown in Fig. 2 and Fig. 3, 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 projected end of the shaft (51a) into a cylindrical shaft (89a) of the gear (89) and by interlocking a 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 interlocking 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 interlocked 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 stopped 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 periphery, 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. 4 , the upper end 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 practically 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 interlocking 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 interlocking 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) composed 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) , 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 preliminary 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 photoreceptor 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.6 . 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 transmitted 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 copying 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: A paper feeding device for an image forming machine, to feed a sheet of paper into the image forming machine from a removably mounted paper cassette (12), said device comprising: a paper feeding roller (51,) mounted on a shaft (51a) and positioned to be adjacent to one end of the paper cassette when the paper cassette is mounted in the image forming machine; moving means for moving said paper feeding roller in a paper feeding direction to feed a sheet of paper from the cassette into the image forming machine, characterized by a driving force transmitting mechanism (86, 89, 90, 91, 92, 93) responsive to movement of the paper cassette over a first distance during removal of the paper cassette from the image forming machine for rotary movement of said paper feeding roller in the direction opposite to the paper feeding direction to withdraw a sheet of paper partially fed into the image forming machine away from the image forming machine by a second distance greater than the first distance, operative to withdraw the sheet of paper from the machine and return it into the paper cassette when the paper cassette is removed from the image forming machine. A paper feeding device according to claim 1, wherein said driving force transmitting mechanism includes a gear (93) coupled in a force locking manner to the shaft (51a) of said paper feeding roller and a rack (86) mounted on the paper cassette (12). A paper feeding device according to claim 1, wherein said driving force transmitting mechanism includes a ratchet gear (93) coupled in a force locking manner to said shaft (51a) and a ratchet pawl (86) mounted on the paper cassette. A paper feeding device according to claim 1, wherein said driving force transmitting mechanism includes a roller (93) coupled in a force locking manner to said shaft (51a) and a friction member (86) installed on the paper cassette. A paper feeding device according to claim 1, further comprising a one-way bearing (51d) mounting said feed roller (51) on said shaft (51a) and allowing said feed roller to rotate only in the paper feeding direction as said shaft is rotated; and a star wheel (51e) mounted on said shaft for rotation therewith. A paper feeding device according to claim 5, wherein said driving force transmitting mechanism includes a gear (93) coupled in a force locking manner to the shaft (51a) of said paper feeding roller and a rack (86) mounted on the paper cassette (12). A paper feeding device according to claim 5, wherein said driving force transmitting mechanism includes a ratchet gear (93) coupled in a force locking manner to said shaft (51a) and a ratchet pawl (85) mounted on the paper cassette. A paper feeding device according to claim 5, wherein said driving force transmitting mechanism includes a roller (93) coupled in a force locking manner to the shaft (51a) and a friction member (86) installed on the paper cassette.

Inventors: SHIBATA KYOTAKA, SHIBATA, KYOTAKA
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO., LTD.
Application year: 1989
Main classification: G03G15
IPC codes: B65H3, B65H1, G03G15