Device for preventing double paper feed in image-forming apparatuses

Abstract: An overlapped-transfer preventing paper supply device in an im­ age-forming apparatus, in which an overlapped-transfer pre­ venting portion (23) of a sheet comprises an overlapped-trans­ fer preventing member and a rotary paper supply member. A sheet-­ returning member (43) for returning a sheet located in the vi­ cinity of said overlapped-transfer preventing portion to a sheet-housing portion (22) is movably provided from a down­ stream side to an upstream side of said overlapped-transfer preventing portion and driving means (31) for putting an ap­ pointed sheet-returning signal therein to move said sheet-re­ turning member in a sheet-returning direction is provided. The sheet, which has been subjected to the overlapped-transfer preventing operation, located in the vicinity of the over­ lapped-transfer preventing portion can be returned to the sheet-housing portion (22) and the sheet located in the vicini­ ty of said overlapped-transfer preventing portion (23) can be surely prevented from being smashed. Also the jamming due to said sheet can be surely prevented from being produced.

Description: The present invention relates to an overlapped-transfer preventing paper supply device in an image forming apparatus such as electrophotographic copying machine and printer, according to the preamble of claim 1. The DE-A 32 21 261 discloses an overlapped-transfer preventing paper supply device having a stripping member being in contact with a paper transfer belt. An overlapping sheet is stopped by the stripping member. The stripping member is rotatably supported and biased by a spring whereby the stripping member is rotated opposite to the feeding direction if a paper cassette is removed from the apparatus, to release the sheet of paper stopped by the stripping member. For example, an electrophotographic copying machine comprises a device for supplying a transfer portion with a non-copied sheet one by one at every time of putting in a paper supply signal, an intermediate paper supply device for copying on both sides for supplying a transfer portion with a sheet, on which one side has been copied, at every time of putting in a paper resupply signal or a paper supply device of a sheet manuscript for supplying the appointed position of a manuscript-table with the sheet manuscript at every time of putting in a paper supply signal. Such the paper supply devices include one of the overlapper-transfer preventing mode, in which an overlapped-transfer preventing member, such as a friction pad and a pad roller, is arranged so as to be engaged with a rotary paper supply member to prevent the double transfer of sheets by a so-called frictional separation, and one of the overlapped-transfer preventing mode, in which a pad roller and a rotary paper supply member are arranged so as to be partially overlapped and a sheet goes zigzag between said both members to prevent the double transfer of sheets by the firmness of the sheet. However, in the above described overlapper-transfer preventing devices, the sheet, which has been subjected to the overlapped-transfer preventing operation, is run away from a sheet-housing portion, such as a paper supply cassette and a paper supply deck, and its pointed end is positioned in the vicinity of an overlapped-transfer preventing portion comprising said overlapped-transfer preventing member and said rotary paper supply member, sometimes put into the overlapped-transfer preventing portion. Under such the condition, in the case where said paper supply cassette is pulled out or a paper-placing plate of the paper supply deck is descended to supply said paper supply cassette, paper supply deck and the like with the sheets, the sheet, which has been subjected to said overlapped-transfer preventing operation, is left in the paper supply portion and a problem has occurred in that when subsequently the paper supply cassette, paper supply deck and the like are set, not only the sheet left in said paper supply portion is smashed to be useless but also the jamming is brought about due to said smashed sheet. The invention aims at the elimination of the above described inconvenience due to the location of the sheet at said overlapped-transfer preventing portion and the elimination of an inconvenient situation brought about contrary to the expectation by the control carried out in the achievement of the above described object. This object is achieved by the features of claim 1. According to the invention, when the sheet-returning signal is put in, said sheet-returning member is moved in the sheet-returning direction and the sheet located in the vicinity of said overlapped-transfer preventing portion is returned to the sheet-housing portion. The above described sheet-returning signal is transmitted on the basis of a detected signal of the completion of the image forming operation, a supply signal of the sheet into the sheet-housing portion, a detected signal of the descending operation of said sheet-housing portion when said sheet-housing portion is moved down to supply the sheets, and the like. If the above described sheet-returning control is achieved in spite of the generation of jamming, said jammed sheet is broken by said sheet-returning member to be useless. However, according to the invention, when jamming is brought about in the vicinity of the overlapped-transfer preventing portion, the control of returning the above described sheet to the sheet-housing portion is restrained to prevent said jammed sheet from being broken. Fig. 1 is a side view showing an overlapped-transfer preventing paper supply device; Fig. 2 is a rough longitudinally sectional view showing an electrophotographic copying machine as one example of an image forming apparatus; Fig. 3 is a front view showing an overlapped-transfer preventing paper supply device; Fig. 4 is a plan view showing an overlapped-transfer preventing paper supply device in which a rotary paper supply member is developedly shown; Fig. 5 is a side view showing an overlapped-transfer preventing paper supply device in which a section of a pad roller is shown; Fig. 6 is a diagram describing the operation; Fig. 7 is a diagram showing the condition that a sheet is jammed in the vicinity of an overlapped-transfer preventing portion; Fig. 8 is a side view showing principal parts of a sheet-returning member in another preferred embodiment; and Fig. 9 is a side view showing an overlapped-transfer preventing paper supply device according to another preferred embodiment. The preferred embodiments of the present invention will be below described with reference to the drawings. Referring now to Fig. 2 roughly showing a both sides copying machine as one example of an image forming apparatus, a manuscript-weight 2 provided with an automatic manuscript supply device 1 is provided in an upper portion of a body 3 of the copying machine, said body 3 of a copying machine being provided with a photoreceptor 4 built thereover, a charging device 5, a developing device 6, a transfer device 7, a sheet-separating device 8 and a cleaning device 9 being arranged around said photoreceptor 4, an optical system movable type exposure device 10 being arranged in an upper space of said body 3 of a copying machine, and a supplied-paper conveying device 13 for conveying a sheet within a hand inserting portion 11 or a paper supply cassette 12 to said transfer device 7, a discharged-paper conveying device 15 for conveying the transferred and separated sheet to a fixing device 14 and a pair of paper-discharging rolls 17 for discharging the fixed sheet into a tray 16 being provided. And, an intermediate tray 18 for stocking up the sheet, on which one side has been copied, is disposed in a space below said body 3 of a copying machine, an overlapped-transfer preventing paper supply device 19 being disposed in a paper resupply portion of said intermediate tray 18, a switchback mechanism 20 for selectively discharging said fixed sheet into said intermediate tray 18 being provided, and a conveying device 21 for use in a paper resupply being disposed ranging from said overlapped-transfer preventing paper supply device 19 to said transfer device 7. In addition, an elevator type paper supply deck 22 capable of housing a large volume of sheet therein is disposed below said paper supply cassette 12 and an overlapped-transfer preventing paper supply device 23 for joinedly supply said conveying device 21 for use in the paper resupply with the sheet housed in said elevator type paper supply deck 22 is provided. And, the one side copy mode, in which an image is copied on one side of the sheet supplied from said hand inserting portion 11 or said cassette case 12 or said paper supply deck 22 and said sheet, on which one side has been copied, is discharged into the tray 16, and the both sides copy mode, in which an image is copied on a back side of the sheet, of which one side has been subjected to the copying operation, supplied from said intermediate tray 18 in an appointed timing and said sheet, of which both sides have been subjected to the copying operation, is discharged into said tray 16, can be selected. Next, a concrete construction of the overlapped-transfer preventing paper supply device 23 in said paper supply deck 22 is described. This overlapped-transfer preventing paper supply device 23, as shown in Fig. 1 and Figs. 3 to 5, comprises a pair of paper supply guide plate, that is an upper paper supply guide plate 24 and a lower paper supply guide plate 25, provided with an opening (a), (b), respectively, disposed in a paper supply portion of said paper supply deck 22, a paper supply roller (one example of the rotary paper supply member) 26 formed of rubber provided with a plurality of roller portions (c), of which a part is downward projected from the opening (a) of the upper paper supply guide plate 24 and a pad roller (one example of the overlapped-transfer preventing member) 27 formed of rubber similarly provided with a plurality of roller portions (d), of which a part is upward projected from the opening (b) of said lower paper supply guide palte 25 under the condition that said part is overlapped on the roller portion (c) of said paper supply roller 26 as seen from an axial shaft line direction of the roller so that when the sheets, which have been drawn out by means of a forwardly feeding roller 28, are sent into a zigzag course of both rollers 26, 27 under the overlapped condition, a pointed end of the sheet on the side of said pad roller 27 may be engaged with said pad roller 27 to supply merely the sheet on the side of said paper supply roller 26. That is to say, an overlapped transfer preventing portion for overlapping a part of said both rollers 26, 27 zigzag to prevent the double supply of sheets is constructed. And, a mechanism 29 for adjusting an overlapping size of said pad roller 27 relative to said paper supply roller 26 (as above described, an overlapping size of both roller portions (c), (d) when the roller portions (c), (d) of both rollers 26, 27 are arranged so as to be partially overlapped) and a mechanism 30 for adjusting a size of a gap [a size of a gap between end faces of said both roller portions (c), (d) when the above described both roller portions (c), (d) are arranged so as to be partially overlapped] are provided and driving means 31 for rotating said pad roller 27 in a direction opposite to the paper supply direction an appointed angle by an appointed angle is provided to restrain an unbalanced abrasion of the overlapped transfer preventing roller 27 in said overlapped-transfer preventing portion. Sheet-returning means 32 for returning the sheet located in the vicinity of said overlapped-transfer preventing portion to said paper supply deck 22 when the detected signal of the descending operation for descending said paper supply deck 22 to supply the sheets is constructed by the use of the driving system of said driving means 31. Speaking in detail, an axis of rotation 47 provided with said paper supply roller 26 is pivoted on brackets 33, 33 connceted with the body 3 of a copying machine so as to be rotated in the paper supply direction in an appointed timing by means of driving means (not shown). On the other hand, said pad roller 27, said mechanism 29 for adjusting the overlapping size and said mechanism 30 for adjusting the size of the gap and said driving means 31 are united to form the following construction. That is to say, a rising plate member 34a of a base 34 fixedly placed on said body 3 of a copying machine is provided with a pair of brackets 35, 35 cut up and connected therewith, said brackets 35, 35 being provided with a holding member 37 through a holding axis 36 parallel to said pad roller 27 so that said holding member 37 may be connected therewith swingably and movably in the direction of axis shaft line, said holding member 37 being provided with an axis 38 pivoted thereon so as to be reciprocally rotatable, and said reciprocally rotatable axis 38 being provided with said pad roller 27 through one-way transmission means 39, which allows merely the rotation in the direction opposite to the paper supply direction, on one side thereof. And, a screw axis (e) is provided so as to pass through from the rising plate member 37a of said holding member 37 to the rising plate member 34a of said base 34, a screw member (f) being screwed in said screw axis (e), and energizing means 41 formed of a compression coil spring being disposed between said both rising plate members 37a, 34a so that the overlapping size of the pad roller 27 relative to said paper supply roller 26 may be adjusted by the swing of said holding member 37 around the holding axis 36 due to the rotary operation of said screw member (f). In addition, said holding axis 36 is provided with a screw portion (g) formed on one side thereof and a screw member (h) is screwed in said screw portion (g) so that said holding axis 36 may be moved in merely the direction of axis shaft line and energizing means 42 for giving said holding member 37 an energizing force in the direction opposite to the moving direction of the holding axis 36 is disposed between said bracket 35 and said holding member 37 so that the size of the gap between said paper supply roller 26 and said pad roller 27 may be adjusted by the movement of the holding member 37 in the direction of axis shaft line of said holding axis 36 due to the rotary operation of said screw member (h). Besides, an axis of rotation 38, which is reciprocally rotated on both sides of said pad roller 27, is provided with a sheet-returning member 43 formed of relatively hard materials, for example synthetic resins (polyacetal as one example), fixedly mounted thereon, a worm-wheel gear G₁ being fixedly mounted on the other end side of said reciprocal axis of rotation 38, and a motor M provided with a worm-gear G₂ engaged with said gear G₁ being mounted on said holding member 37 so that said sheet-returning member 43 may be reciprocally rotated by the regular and opposite rotations of said motor M. In addition, a size from a center of rotation to an idle end portion of said reciprocal axis of rotation 38 of the above described sheet-returning member 43 is larger than a radius of said pad roller 27, the idle end portion of the reciprocal axis of rotation being formed in the shape of curved surface, and a length of said idle end portion being set so that the idle end portion may not be brought into contact with said axis of rotation 47. Here, a reciprocally rotatable control member 46 is electrically connected with said motor M so that when a sheet-returning signal, which is transmitted on the basis of a detected signal of the descending motion of said paper supply deck 22 by a level switch s₁ (refer to Fig. 2) detecting a level of said paper supply deck 22, is put in said control member 46, said motor M may be reciprocally rotated by an appointed number of times, whereby controlling so as to at first rotate said reciprocal axis of rotation 38 in the direction opposite to the paper supply direction about one rotation and subsequently rotate said reciprocal axis of rotation 38 in the opposite direction. The driving means 31 for reciprocally rotating said reciprocal axis of rotation 38 about one rotation comprises said worm-wheel gear G₁, said worm-gear G₂ and said motor M. And, said reciprocal axis of rotation 38 is reciprocally rotated at every time of descending said paper supply deck 22 and said pad roller 27 is rotated less than one rotation merely in the direction opposite to the paper supply direction with the reciprocal rotation of said reciprocal axis of rotation 38, whereby the unbalanced abrasion of said pad roller 27 can be prevented. In addition, as shown in Fig. 6, the sheet, of which overlapped-transfer has been prevented, located in the vicinity of said overlapped-transfer preventing portion can be returned to said paper supply deck 22 by first rotating said sheet-returning member 43 integrally with said reciprocal axis of rotation 38 in the direction opposite to the paper supply direction and then upward projecting said sheet-returning member 43 from said opening (b) on the downstream side of said overlapped-transfer preventing portion to move said member 43 over the upstream side of said overlapped-transfer preventing portion, and as a result, the sheet, which has been located in the vicinity of said overlapped-transfer preventing portion, can be prevented from being smashed and the jamming due to said sheet can be prevented from being produced when said paper supply deck 22 is descended to feed the sheet and then said paper supply deck 22 is ascended to the appointed position. Subsequently, said sheet-returning member 43 is rotated to the initial position integrally with the reciprocal axis of rotation 38 for the next returning of the sheet. Furthermore, a sensor S for detecting the generation of the jamming between said overlapped-transfer preventing portion and said pair of conveying rollers 44 is provided on an immediate downstream side of said overlapped-transfer preventing portion. And, as shown in Fig. 7, if the sheet-returning signal is emitted under the condition that the sheet is jammed on the downstream side in the vicinity of said overlapped-transfer preventing portion and said sheet-returning member 43 is moved from the downstream side to the upstream side of the overlapped-transfer portion so as to return the sheet, which is located in the vicinity of said overlapped-transfer preventing portion to the paper supply deck 22, said jammed sheet is broken by the movement of said sheet-returning member 43 to be useless. In order to eliminate such the inconvenience, when the jam-detecting signal in the vicinity of said overlapped-transfer preventing portion was detected, said motor M is adapted not to be driven even though said sheet-returning signal was emitted. That is to say, the above described jam-detecting signal is put in said control portion 46 and restraining means 45, which does not drive said motor M in preference to said sheet-returning signal when said jam-detecting signal was put in, is provided in said control portion 46 so that the returning control to the paper supply deck 22 of the sheet by means of said sheet-returning member 43 may not be carried out and the sheet jammed in the vicinity of said overlapped-transfer preventing portion may not be useless. In addition, although the idle end portion of said sheet-returning member 43 is adapted not to be brought into contact with the axis of rotation 47 in the preferred embodiment, said sheet-returning member 43 may be formed of thin elastically deformable materials so that the idle end portion thereof can be brought into contact with the axis of rotation 47 when it is moved from the downstream side to the upstream side of the overlapped-transfer preventing portion, as shown in Fig. 8. Next, another preferred embodiment of the overlapped-transfer preventing paper supply device 23 is shown in Fig. 9. In this preferred embodiment, a shaft 49 is provided with a reciprocally rotatable semicircular friction pad 48 as the overlapped-transfer preventing member, a part of a circumferential surface of said friction pad 48 being brought into contact with the paper supply roller 26, and the sheet-returning member 43 for returning the sheet located in the vicinity of the overlapped-transfer preventing portion to the paper supply deck 22 being connected with a portion on the downstream side in the paper supply direction of said friction pad 48. Driving means 31 comprising a solenoid 50 and a returning spring 51 is provided. The above described solenoid 50 is excited by putting a primary paper supply signal therein to rotate the sheet-returning member 43 in the paper supply direction against an energizing force of said returning spring 51. If said solenoid 50 is deexcited on the basis of a detected signal of the completion of the image-forming operation, both said friction pad 48 and the sheet-returning member 43 are rotated in the direction opposite to the paper supply direction by the energizing force of said returning spring 51 to return the sheet located in the vicinity of said overlapped-transfer preventing portion to the paper supply deck 22. In addition, although the sheet-returning member 43 is adapted to be moved in the sheet-returning direction in coupled with the rotation of said pad roller 27 or friction pad 48 in the direction opposite to the paper supply direction in the above described respective preferred embodiments, said sheet-returning member 43 may be adapted to singly move in the sheet-returning direction. Besides, although said paper supply deck 22 is used as the sheet-housing portion and the overlapped-transfer preventing paper supply device 23 for said sheet-housing portion is described in the respective preferred embodiments, the hand-inserting portion 11, the paper supply device of the paper supply cassette 12 or the intermediate tray 18 for use in the paper resupply for copying both sides can be used as the sheet-housing portion. In addition, the present invention can be applied to the paper supply device in various kinds of image-forming apparatus such as printer and facsimile without limiting to a copying machine. Furthermore, although the sheet-returning signal for moving said sheet-returning member 43 in the sheet-returning direction is emitted on the basis of the detected signal of the descending operation of the sheet-housing portion and the detected signal of the completion of the image-forming operation in the respective preferred embodiments, also other modifications are possible, for example the sheet-returning signal may be emitted on the basis of the sheet-feeding signal for the sheet-housing portion. As above described, according to the first invention, said sheet-returning member is adapted to move from the downstream side to the upstream side of said overlapped-transfer preventing portion on the basis of the sheet-returning signal emitted on the basis of the detected signal of the descending operation of said sheet-housing portion when said sheet-housing portion is descended to feed the sheet, the detected signal of the completion of the image-forming operation, the sheet-feeding signal for the sheet-housing portion or the like, whereby the sheet, which has been subjected to the overlapped-transfer preventing operation, located in the vicinity of said overlapped-transfer preventing portion can be returned to the sheet-housing portion and the sheet located in the vicinity of said overlapped-transfer preventing portion can be prevented from being smashed. In addition, the jamming due to said sheet can be surely prevented from being formed. And, according to the invention, additionally the control for returning the above described sheet to the sheet-housing portion is not executed while the jamming is generated in the vicinity of said overlapped-transfer preventing portion, whereby the sheet jammed in the vicinity of said overlapped-transfer preventing portion can be prevented from being broken by said sheet-returning member to be useless and the conventional disadvantages can be rationally eliminated by the simple improvement on the whole.

Claims: An overlapped-transfer preventing paper supply device in an image-forming apparatus, in which an overlapped-transfer preventing portion (23) for a sheet is composed of an overlapped-transfer preventing member (27,48) and a rotary paper supply member (26), characterized by a sheet-returning member (43) for returning a sheet located in the vicinity of said overlapped-transfer preventing portion (23) to a sheet-housing portion (22), the sheet returning member (43) being movable from a downstream side to an upstream side of said overlapped-transfer preventing portion (23), the overlapped-transfer preventing member (27, 48) being mounted on a reciprocally rotatable shaft (38,49) together with the sheet-returning member (43), the shaft (38,49) being rotated in sheet-returning direction in response to a sheet-returning signal. An overlapped-transfer preventing paper supply device as claimed in claim 1, characterized in that the overlapped-transfer preventing member comprises a pad roller (27) mounted on said reciprocally rotatable shaft (38) through a one-way transmission means (39), the pad roller (27) being rotatable merely in a direction opposite to the paper supply direction. An overlapped-transfer preventing paper supply device as claimed in claim 1, characterized in that the overlapped-transfer preventing member comprises a reciprocally rotatable semicircular friction pad (48). An overlapped-transfer preventing paper supply device, characterized by a sensor (S) for detecting jamming in the vicinity of the overlapped-transfer preventing portion (23) and restraining means for restraining the movement of the sheet-returning member (43) in the sheet-returning direction on the basis of a jamming-detecting signal from said sensor. An overlapped-transfer preventing paper supply device as claimed in one of claims 1 to 4, characterized in that said sheet-returning signal is emitted on the basis of a detected signal of a descending operation of the sheet-housing portion (22). An overlapped-transfer preventing paper supply device as claimed in one of claims 1 to 4, characterized in that said sheet-returning signal is emitted on the basis of a detected signal of a completion of an image-forming operation. An overlapped-transfer preventing paper supply device as claimed in one of claims 1 to 4, characterized in that said sheet-returning signal is emitted on the basis of a sheet-feeding signal to the sheet-housing portion (22).

Inventors: FUKUOKA NOBORU, TANJO TORU, FUKUOKA, NOBORU, TANJO, TORU
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO., LTD.
Application year: 1989
Main classification: B65H3
IPC codes: B65H3, G03G15