PAPER FEEDER

Abstract: A paper feeder for successively delivering stacked cut sheets into a record/write section or the like. During the initial reverse direction of paper delivery of paper delivering rollers, a proper sagging of a cutform sheet is formed to adjust the direction of the cut sheet upstream of the paper delivering rollers, and, during the subsequent forward rotation of paper delivery of the paper delivering rollers, a paper feeding roller is temporarily rotated, whereby the paper delivering rollers can perform an accurate pull-in operation without imposing abrupt fluctuations in load on the paper delivering rollers and the cut sheet.

Description: The present invention is directed to a paper feeder for feeding sheets of cutform paper which may be applied to a printer or a copying machine. A paper feeding means for sequentially feeding sheets of cutform paper accommodated in a feed tray to a record/write portion or the like takes the following mechanism. Typically, the stack of cutform paper is pushed against a feed roller from the underneath. The uppermost sheet of cutform paper is fed out towards the paper feeding roller, which is positioned forward of the feed roller in the usual paper feeding direction, by a frictional force applied by the feed roller. Thereafter, the feed roller is brought into a loose rotating state, and a main paper feeding process is carried out by the paper feeding roller. In this type of feeding mechanism, however, if a pressure of contact between the uppermost sheet of cutform paper and the feed roller differs in respective parts along the direction of the roller axes, the cutform paper cannot be fed out in the correct direction. The paper feeding roller which has taken over the feeding operation then pulls in the cutform paper in an as-inclined state. As a result, this causes not only inconvenience where an inclined original image is copied on the paper surface, and recording/writing processes are effected obliquely but also the problem of producing a paper jam and skew. Various prior art proposals have been made in an attempt to overcome such problems. Japanese Patent Publication No. 58-6633 and Japanese Patent Application No. JP-A-57 189 951 propose an apparatus arranged as follows. At the onset of feeding the paper, the paper feeding roller makes reverse rotations, at which point the cutform paper is retrained from being pulled in. The cutform paper is adjusted in the proper direction. At a stage where sagging of the cutform paper is produced, the feed roller is stopped. Simultaneously, the paper feeding roller is changed over to forward rotations. The cutform paper is thus properly pulled in the record/write portion. This type of apparatus, however, presents the following problems. The paper feeding roller changed over to the forward rotations pulls in the cutform paper. During this process, fluctuations in intensive load based on a frictional contact between the feed roller and the cutform paper instantaneously when sagging disappears act on the cutform paper and the feed roller as well. In consequence, a pull-in deviation is caused, or the cutform paper is to be ruptured. Japanese Patent Application No. JP-A-60 067 340 discloses a paper sheet transfer unit where the paper feeding roller rotates in the opposite direction to the feed roller for a given period in order to reduce the likelihood of the paper sheets becoming skewed EP-A 0 294 955 discloses a paper feeding apparatus in which the (auxiliary paper) feed roller rotates so as to feed paper to the platen paper feed roller (or platen) regardless of the direction of rotation of the paper feed roller. According to one aspect of the invention, there is provided a paper feeder comprising: a feed roller for sequentially feeding sheets of cutform paper to form a stack; a paper feeding roller disposed in a paper feeding direction forward of said feed roller; a driving means for rotating said paper feeding roller each paper feeding operation initially in an anti-feeding direction and subsequently in said feeding direction; and a driving force transmitting means operating while interlocked with said driving means to rotate said feed roller in said feeding direction so as to cause sagging of said cutform paper between said paper feeding roller and said feed roller during rotation in said anti-feeding direction of said paper feeding roller; characterised in that when said paper feeding roller rotates in said feeding direction, the driving force transmitting means stops causing said feed roller to rotate for a time period whereafter the feed roller is caused to rotate in said feeding direction again. According to another aspect of the invention, there is provided a method of feeding paper, including: applying a driving force to a paper feeding roller to rotate it initially in an anti-paper feeding direction for each paper feeding operation; applying a driving force to a feed roller to rotate it in the paper feeding direction while said paper feeding roller is rotating in said anti-paper feeding direction so as to cause sagging of the paper between the rollers; characterised in that, when the paper feeding roller rotates in said feeding direction, a driving force is not applied to the feed roller for a time period, whereafter a driving force is applied to cause the feed roller to rotate the said feed direction again. The driving force transmitting means may prevent abrupt fluctuations in load being applied to the cutform paper and the paper feeding roller at the time when the paper feeding roller changes from being rotated in the anti-feeding direction to the feeding direction. The paper feeder may cause the cutform paper to sag between the feed roller and the paper feeding roller during initial rotations of the paper feeding roller in an anti-feeding direction, thereby adjusting the orientation of the paper. Subsequently, when the paper feeding roller is rotated in the paper feeding direction, the feed roller may be temporarily rotated. As a result, the paper feeding roller may accurately take up the paper without exerting abrupt fluctuations in load on the paper feeding roller and the paper. The invention will now be described by way of example with reference to the accompanying drawings, in which:- FIGS. 1(a) through 1(c) are block diagrams of a driving force transmission mechanism in one embodiment of the present invention, each showing an operating state thereof; FIG. 2 is a diagram showing one example of a printer to which the transmission mechanism is applied; FIG. 3 is a sectional view depicting a shaft end of a feed roller; FIGS. 4(a) through 4(e) are diagrams of assistance in explaining a series of paper feeding operations; FIG. 5 is a diagram showing operational timings; FIGS. 6(a) and 6(b) are charts each showing a life-span of the feed roller in a comparison between the apparatus of the invention and the conventional apparatus; FIG. 7 is a perspective view depicting a driving force transmission mechanism in another embodiment of this invention; and FIGS. 8(a) to 8(d) are diagrams of assistance in explaining the respective operating states of the transmission mechanism described above. FIGS. 1 through 4 show one embodiment of this invention which employs a D-shaped feed roller. To start with, an outline of a printer to which the apparatus of this invention may be applied will be explained referring to FIG. 2. In the Figures, the numeral 1 represents a feed roller assuming a D-shape in section and partly formed with a notched portion 1a which does not contact a sheet of cutform paper s. The feed roller 1 includes an arc member 1b an effective paper feed peripheral length of which is set longer than a length corresponding to an appropriate quantity of sagging generated between a platen roller 3 and the roller 1. The roller 1 makes one rotation per feeding operation, thus singly feeding out sheets of cutform paper (s) laminated in a feed tray 2. During a standby, the roller 1 is constructed to be intermittently driven through a driving force transmission mechanism which will be mentioned later so that the roller 1 stops in a non-contact state to direct the notched member 1a towards the cutform paper s. Designated at 3 is a platen roller driven by an unillustrated motor to make forward and reverse rotations. The platen roller 3 is constructed to initially make a reverse rotation for temporarily restraining a passage of the top end of the cutform paper s, thus adjusting a direction of the cutform paper s fed by the feed roller 1. Subsequently, the platen roller is switched to make a forward rotation for feeding out the cutform paper s to a recording head 5. FIG. 1 illustrates the driving force transmission mechanism, conceived as one embodiment of the invention, for rotating the feed roller 1 at a predetermined timing to interlock with the forward/reverse rotations of the platen roller 3. Referring to the Figure, the numeral 11 denotes a driving pinion attached to the shaft of an unillustrated driving motor. The pinion 11 is constructed to transmit the driving force to a platen gear 13 fixed via a reduction gear 12 to a shaft end of the platen roller 3 on one hand and meshes with a gear wheel 15 on the other hand. The pinion 11 transmits the rotations in the feeding direction to the feed roller 1 at a periphery speed slightly higher than that of the platen roller 3 through a sun gear 16 rotating integrally therewith and a planet gear mechanism which will be mentioned later. Indicated at 17 is a deformation T-shaped lever swayably pivotally supported on the shaft of the sun gear 16. Fitted to both ends of the lever 17 are first and second planet gears 18, 19 which constantly engage with the sun gear 16. As illustrated in FIG. 1(a), when the driving pinion 11 causes the platen roller 3 to rotate in an arrowed direction, i.e., in a direction opposite to the feeding direction, the lever 17 rotates anticlockwise in the Figure through the planet gears 18, 19. The second planet gear 18 meshes directly with a feed roller gear 21, whereby the rotary driving force in the arrowed direction in the Figure is transmitted to this gear 21. As illustrated in FIG. 1(c), when the driving pinion 11 makes the platen roller 3 rotate in the feeding direction, the lever 17 rotate clockwise in the Figure through the planet gears 18, 19. The second planet gear 19 meshes with an idler 20, whereby the rotary driving force in the same arrowed direction is transmitted to the feed roller gear 21 through this idler 20. On the other hand, as depicted in FIG. 3, a feed roller gear 21 and a ratchet 22 integral therewith are loosely fitted to a shaft 10 of the feed roller 1. Fixed to this shaft 10 is a clutch plate 23 adjacent to the ratchet 22. An engaging lever 24 including a pawl 24a is pivotally supported on the clutch plate 23 in a biased state so that the engaging lever 24 constantly engages with the ratchet 22 with the aid of a spring 25. A top end 24b of this engaging lever 24 extends in a rotary region of the deformation T-shaped lever 17. As illustrated in FIG. 1(c), the top end 24 impinges on a top end of a pawl stopper arm 1a partially branched off, when the deformation T-shaped lever 17 rotates clockwise in the Figure. The engagement with the ratchet 22 is thereby released. Note that the numeral 6 in FIG. 2 denotes a paper end detecting sensor, disposed on this side of the platen roller 3, for outputting a signal to an unillustrated control circuit to change over the driving motor to the forward rotations when a predetermined amount of sagging of the cutform paper s is reached. Designated at 7 is a delivery roller for ejecting the cutform paper s undergoing a recording process onto a delivery tray 9 in cooperation with a presser lever 8. Next, the feeding operation by the apparatus discussed above will be explained with reference to FIGS. 1, 4 and 5. In a standby status, the driving motor is in a stop status after making the forward or reverse rotations. For this reason, the deformation T-shaped lever 17 rotates, as illustrated in FIG. 1(c), clockwise together with the sun gear 16 which also rotates clockwise. The lever 17 at its rotary terminal causes the stopper arm 17a to protrude into the rotary region of the engaging lever 24, thus holding it. In that position, the lever 17 restrains the rotations of the clutch plate 23, thereby stopping the feed roller 1 in such a posture that the feed roller 1 does not contact the cutform paper s, viz., the notched member 1a is directed to the cutform paper s (FIG. 4(a)). At a timing a, a feed instruction signal is outputted from an unillustrated sequence control circuit of the printer. At this time, the driving motor is switched to make the reverse rotations from the forward rotations or from the stopping status. As a result, the platen roller 3, as illustrated in FIG. 1(a), starts rotating in the arrowed direction in the Figure, i.e., in the anti-feeding direction through the driving pinion 11, the reduction gear 12 and the platen gear 13. On the other hand, the gear wheel 15 meshing with the driving pinion and the sun gear 16 integral therewith start rotating in the direction opposite thereto, i.e., in the anticlockwise direction. The T-shaped lever 17 is rotated anticlockwise in the Figure through the planet gears 18, 19 meshing therewith. The engaging lever 24 is thereby released from being stopped by the pawl stopper arm 17a. A pawl 24a provided on the lever 24 is engaged with one of engaging recesses 22a of the ratchet 22. At the same moment, the first planet gear 18 is meshed directly with the feed roller gear 21 to give the rotations in the feeding direction thereto. Hence, the clutch plate 23 rotates in the same direction as that of the feed roller gear 21, thereby transmitting the rotations to the feed roller 1 stopping in such a way that the notched member 1a faces to the cutform paper s. The upper most cutform paper s among sheets of cutform paper s laminated on the feed tray 2 is fed out to the platen roller 3 (FIG. 4(b)). With subsequent rotations of the feed roller 1, the cutform paper s passing under the paper end detecting sensor 6 is fed between the platen roller 3 rotating in the anti-feeding direction and a pinch roller 4. The passage thereof is hindered herein, and a predetermined amount of sagging is caused on this side. In this state, a front edge of the cutform paper s uniformly contacts peripheral faces of the two rollers 3, 4 by dint of a flexibility of its own, whereby the cutform paper is adjusted in the proper direction (FIG. 4(c)). On the other hand, the sequence control circuit receives a detection signal from the paper end detecting sensor 6 at a timing b. The sequence control circuit then outputs a signal at an interval of time T1 till sagging of the cutform paper s further grows. The sequence control circuit changes over the driving motor from the reverse rotations to the forward rotations at a timing c. In consequence of this, the platen roller 3 is, as depicted in FIG. 1(b), immediately changed over to the rotations in the feeding direction. The cutform paper s blocked between the pinch roller and the platen roller 3 is fed out to a printing head 5. On the other hand, the sun gear 16 is changed over to the clockwise rotations, reversal to the previous rotations, in the Figure through the gear wheel 15. The sun gear 16 makes the deformation T-shaped lever 17 rotate clockwise in the Figure through the planet gears 18, 19 meshing therewith. The first planet gear 18 is separated from the feed roller gear 21 (FIG. 1(b)). The driving force of the feed roller 1 is cut off, and hence the roller 1 enters a loose rotating state for a slight time Δt. In the meantime, the platen roller 3 feeds out the cutform paper s, while sagging formed on this side disappears (FIG. 4(d)). In this manner, after the slight time Δt has elapsed, the deformation T-shaped lever 17 which continues to rotate clockwise comes to the rotary terminal at a timing d. At this time, the second planet gear 19 is caused to mesh with the idler 20. For this reason, the feed roller gear 21 starts rotating via the idler 20. The rotations are transmitted via the ratchet 22, the engaging lever 24 and the clutch plate 23 to the feed roller 1. The cutform paper s is fed out at a peripheral speed higher than that of the platen roller 3. As a result, sagging is again produced between the platen roller and the feed roller 1. Hence, the platen 3 feeds out the cutform paper s to the printing head 5 without continuously undergoing the load (FIG. 4(e)). In this way, the feed roller 1 makes one rotation, and the notched member 1a again comes to such a position as to confront with the cutform paper s at a timing d. At this time, as illustrated in FIG. 1(c), the engaging lever 24 impinges on the top end of the pawl stopper arm 17. The lever 24 turns rightward to release the engagement with the ratchet 22. At this portion, the clutch plate 23 integral with the feed roller 1 is stopped. Therefore, the feed roller 1 reverts to the standby posture depicted in FIG. 4(a) from the position shown in FIG. 4(e). In this state, a first set of cutform paper S is all fed in by the platen roller 3 which goes on rotating. The driving motor is stopped in response to a signal outputted from the sequence control circuit at a timing f. Concomitantly, the platen roller 3 is also stopped, and it follows that one cycle of feeding the paper is finished. Incidentally, the D-shaped feed roller 1 employed in this embodiment includes the arc member the peripheral length of which is set longer than a length corresponding to an appropriate amount of sagging formed between the platen roller and the roller 1 (FIG. 6(a)). With this arrangement, the paper can be fed again after the platen roller 3 has been changed over to the rotations in the feeding direction. That provides an allowance as compared with a case where the peripheral length is simply set to the length corresponding to the appropriate amount of sagging (FIG. 6(b)). Even when a frictional force on the peripheral face drops down due to a long-term use, it is possible to maintain a feeding function to generate the appropriate amount of sagging at the onset of feeding the paper. FIGS. 7 and 8 in combination show a second embodiment of this invention in association with a driving force transmission mechanism of the paper feeder which uses an ordinary round type feed roller. Referring to the Figures, the numeral 33 represents a platen gear driven by an unillustrated driving motor to make forward and reverse rotations. Engaged with this platen gear 33 are two pieces of planet gears 38, 39 which are axially supported on the ends of first and second levers 36, 37 each rotating with the platen shaft serving as a fulcrum. The rotations are transmitted to a feed roller gear 31 by any one of the planet gears 38, 39 in accordance with the rotating direction of the platen gear 33. The platen gear 33 is constructed to rotate an unillustrated feed roller fixed onto the shaft thereof in the feeding direction at a peripheral speed slightly lower than that of the platen. The first lever 36 incorporated into this mechanism is of a crank type and has its one end on which the first planet gear 38 is axially supported. The other end of the lever 36 is formed with an inclined surface 36a for raising the gear. As illustrated in FIG. 8(d), the gear raising inclined surface 36a acts to thrust up the second planet gear 39 in the axial direction at the rotary terminal of the lever 36 in the anticlockwise direction. This gear 39 is thereby separated from a platen gear 33 and an idler 32 and well. The lever 36 rotates clockwise during reverse rotations of the platen gear 33, i.e., during clockwise rotations in the Figure. The lever 36 is configured to cause the planet gear 38 axially supported on the top end thereof to mesh with the feed roller gear 31, whereby the gear 31 is rotated in the feeding direction. On the other hand, the second lever 37 has its one end vertically provided with a shaft on which the second gear 39 is supported rotatably slidably and axially. In the normal state, the gear 39 is biased by a coil spring 37a interposed between the lever 37 and the gear itself, with the result that the gear 39 is thrust out in such a position as to mesh with the platen gear 33 and the idler 32 as well. A rotary range of this lever 37 is restricted by bilaterally provided stoppers 40, 40. As illustrated in FIG. 8(c), during the forward rotations of the platen gear 33, viz., rotations in the anticlockwise direction in the Figure, the lever 37 rotates anticlockwise. The lever is constructed to transmit the rotations in the feeding direction to the feed roller by engaging the retained second planet gear 39 with the idler 32 meshing with the feed roller gear 31. In this embodiment, the platen gear 33 driven by the unillustrated driving motor in response to a feed instruction signal, as depicted in FIG. 7, rotates in the arrowed direction, i.e., the anti-feeding direction in the Figure. Then, the second lever 37 rotates clockwise in the Figure to release the engagement between the second planet gear 39 and the idler 32. The first lever 36 rotates clockwise in the Figure. The first planet gear 38 axially supported on the lever 36 meshes with the feed roller gear 31, thereby rotating an unillustrated feed roller in the feeding direction (FIG. 8(a)). For this reason, as in the same way with the first embodiment, the cutform paper fed out by the feed roller is hindered by the platen roller making the reverse rotations. As a result, sagging is produced on this side thereof (FIG. 4(c)). If sagging exceeds a constant quantity, the sequence control circuit switches the driving motor to the forward rotations in accordance with a detection signal given from a paper detecting sensor. The first lever 36 is thereby rotated anticlockwise in the Figure to cut off the transmission of the driving force to the feed roller by use of the first planet gear 38 (FIG. 8(b)). The second lever 37 rotating anticlockwise causes the retained second planet gear 39 to mesh with the idler 32 at an interval of slight time Δt required for the rotation. The rotary driving force in the same direction is again transmitted to the feed roller (FIG. 8(c), the timing (d) in FIG. 5)). Hence, the feed roller, as in the same way shown in the FIG. 4(d), restrains an excessive load on the platen roller by resuming the paper feed in such a course that the platen roller pulls in the sagged cutform paper. The feed roller also prevents an intensive tensile force from acting on the cutform paper during that period. After a further slight time has elapsed, and when the first lever 36 reaches the rotary terminal in the anticlockwise direction, the gear raising inclined surface 36a provided at the other end of the first lever 36 intrudes into the underside of the second planet gear 39. This gear 39 is thereby thrust up toward the second lever 37, resisting the coil spring 37a. The second planet gear 39 is released from the engagement with the platen gear 33 and the idler 32, thereby cutting off the transmission of the driving force to the feed roller gear 31. Incidentally in this embodiment, as discussed above, the peripheral speed of the platen roller is set slightly higher than that of the feed roller. Hence, the platen roller absorbs sagging of the paper till the driving force of the feed roller is cut off and gradually increases the tensile force on the cutform paper. Even if the driving force of the feed roller is thereafter cut off, the cutform paper is continuously fed in towards the head without undergoing abrupt fluctuations in load. As discussed above, according to the present invention, the feed roller is allowed to rotate with a quantity enough to cause sagging of the cutform paper during the rotations in the anti-feeding direction of the paper feeding roller. Subsequently, with a changeover of the paper feeding roller to the rotations in the feeding direction, the feed roller is allowed to temporarily rotate in the feeding direction once gain. During the rotations of the paper feeding roller in the anti-feeding direction, sagging of the cutform paper is produced on this side thereof. The direction thereof is thereby properly adjusted. At the same moment, the feed roller is again rotated in the feeding direction when changing over the paper feeding roller to the rotations in the feeding direction. The abrupt fluctuations in load on the paper feeding roller are thereby eliminated. Simultaneously, the tensile force acting on the cutform paper is reduced to prevent damages to the cutform paper. This leads to well-formed images. Industrial Applicability The present invention has been described so far by exemplifying the printer in which the platen roller is disposed in front of the feed roller. A pair of paper feeding rollers may be disposed in this portion in place of the platen roller to permit the same rotary operation as the above. When being applied to an electronic photo device, a pair of resist rollers as a substitute for these rollers may be disposed.

Claims: A paper feeder comprising: a feed roller (1) for sequentially feeding sheets of cutform paper (s) from a stack; a paper feeding roller (3) disposed forward of said feed roller in a paper feeding direction; a driving means (11) for rotating said paper feeding roller (3) each paper feeding operation, initially in an anti-feeding direction and subsequently in said feeding direction; and a driving force transmitting means (11 to 24b) operating while interlocked with said driving means (11) to rotate said feed roller (1) in said feeding direction so as to cause sagging of said cutform paper (s) between said paper feeding roller (3) and said feed roller (1) during rotation in said anti-feeding direction of said paper feeding roller (3); characterised in that when said paper feeding roller (3) rotates in said feeding direction, the driving force transmitting means (11-24b) stops causing said feed roller to rotate for a time period (Δt), whereafter the feed roller is caused to rotate in said feeding direction again. The paper feeder as claimed in claim 1, wherein said feed roller (1) has a D-shape in section, and a peripheral length of an arc member of said roller is larger than a length corresponding to an amount of sagging caused between said paper feeding roller and said feed roller. The paper feeder as claimed in claim 1, wherein a peripheral speed of said paper feeding roller (3) is set higher than that of said feed roller (1). A method of feeding paper, including: applying a driving force to a paper feeding roller (3) to rotate it initially in an anti-paper feeding direction and subsequently in a feeding direction for each paper feeding operation; applying a driving force to a feed roller (1) to rotate it in the paper feeding direction while said paper feeding roller (3) is rotating in said anti-paper feeding direction so as to cause sagging of the paper between the rollers (1,3); characterised in that, when the paper feeding roller rotates in said feeding direction, a driving force is not applied to the feed roller (1) for a time period (Δt), whereafter a driving force is applied to cause the feed roller (1) to rotate the said feed direction again.

Inventors: HIRANO SEIICHI, MURAYAMA SUSUMU, HIRANO, SEIICHI, MURAYAMA, SUSUMU
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1991
Main classification: B65H9
IPC codes: B65H5, B65H3