Patent Grant
10280018
This disclosure relates to a sheet feeding apparatus for feeding a sheet, and an image forming apparatus equipped with the sheet feeding apparatus.
Conventionally a sheet feeding apparatus that includes a manual feed tray, on which a sheet is set manually by users, is widely used as a document feeding apparatus or a manual sheet feeding apparatus provided in an image forming apparatus such as a facsimile, a printer, and a copier. In many cases, such a sheet feeding apparatus includes a leading-edge positioning member such as a shutter to regulate a position of the leading edge of the sheet in a sheet feeding direction.
Japanese Patent Laid-Open No. 06-115748 discloses an automatic sheet feeding apparatus in which a stopper is provided between a feed roller and a separation roller to be movable in a vertical direction perpendicular to a sheet surface. The stopper is biased downward by the compression spring, which is inserted to a concaved guide portion of a structural member and arranged to abut against the ceiling of the concaved guide portion with the upper end of the spring, while abutting against the upper end of the stopper with the lower end of the spring. The stopper thus regulates the number of sheets among the sheets on a document tray to be fed to the separation roller disposed downstream of the stopper.
However, in such a configuration, the leading edge of a sheet bundle may strongly abut against the stopper in such a case where a user vigorously sets the sheet bundle onto the document tray. Then, there is a concern that the stopper may be damaged, or the leading edge of the abutting sheet may be buckled.
According to an aspect of this disclosure, a sheet feeding apparatus includes an apparatus body, a supporting portion held by the apparatus body and configured to support a sheet, a feed portion configured to feed the sheet supported on the supporting portion, a conveyance portion disposed downstream of the feed portion in a sheet feeding direction, a separation portion disposed in pressure contact with the conveyance portion and configured to separate sheets fed from the feed portion one by one in a separation nip portion formed between the conveyance portion and the separation portion, a sheet regulation member disposed upstream of the separation nip portion in the sheet feeding direction, the sheet regulation member being configured to take a regulation posture to regulate the sheet on the supporting portion not to enter the separation nip portion and a retracted posture to allow the sheet on the supporting portion to enter the separation nip portion, a lock portion configured to lock the sheet regulation member in the regulation posture, and a damper portion configured to allow the sheet regulation member locked in the regulation posture by the lock portion to be displaced if external force in the sheet feeding direction and equal to or more than a predetermined amount is applied to the sheet regulation member.
According to another aspect of this disclosure, a sheet feeding apparatus includes an apparatus body, a supporting portion held by the apparatus body and configured to support a sheet, a feed roller configured to feed the sheet supported on the supporting portion, a conveyance roller disposed downstream of the sheet feed portion in a sheet feeding direction, a feed holder configured to hold the feed roller and pivotally supported by the apparatus body between an approach position where the feed roller approaches the supporting portion and a separation position where the feed roller is separated from the supporting portion with respect to the approach position, an engagement member configured to engage with the feed holder to move the feed holder, a resilient member disposed between the engagement member and the feed holder, a separation roller disposed in pressure contact with the conveyance roller and configured to separate sheets fed from the feed roller one by one with a separation nip portion formed between the conveyance roller and the separation roller, a sheet regulation member held by the feed holder and disposed upstream of the separation nip portion in the sheet feeding direction, the sheet regulation member being configured to take a regulation posture to regulate the sheet on the supporting portion not to enter the separation nip portion and a retracted posture to allow the sheet on the supporting portion to enter the separation nip portion, and a lock member configured to lock the sheet regulation member in the regulation posture with the feed holder at the separated position and to release locking of the sheet regulation member in the regulation posture if the feed holder is rotated from the separation position to the approach position. In a case where the sheet regulation member is locked in the regulation posture by the lock portion, the resilient member is elastically deformed if external force in the sheet feeding direction and equal to or more than a predetermined amount is applied to the sheet regulation member.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention.
Now, embodiments of the present disclosure will be described with reference to the drawings. It is noted that in the following description, a state in which an image forming apparatus is seen from a front side, i.e., viewpoint of
An image forming apparatus 201 according to the first embodiment is an image forming apparatus such as a full-color laser printer, a general arrangement of which is illustrated in
The manual sheet feeding apparatus 100M includes a rotation base 111b pivotally supported by the apparatus body 201A and a manual feed tray 111 on which the sheet P is manually stacked. The manual sheet feeding apparatus 100M is provided with a separation conveyance portion 110 including a conveyance roller 102, and a retard roller 103, i.e., a separation member, which rollers contact with each other. Still further, the manual sheet feeding apparatus 100M is provided with a pickup roller 101, i.e., a feed roller, coupled with the conveyance roller 102 through a feed holder 107, and a drawing roller pair 104 positioned downstream of the separation conveyance portion 110 in a sheet feeding direction. The conveyance roller 102 is positioned downstream of the pickup roller 101 in the sheet feeding direction (a direction of an arrow H in
The image forming unit 201B is a so-called four-drum full-color image forming unit having a laser scanner 210, four process cartridges 211, and an intermediate transfer unit 201C. The process cartridges form toner images of respective colors, which are yellow (Y), magenta (M), cyan (C) and black (K). Each process cartridge 211 includes a photoconductive drum 212, i.e., image bearing member, a charger 213, i.e., a charging unit, a developer 214, i.e., an image developing unit, and a cleaner, i.e., a cleaning unit (not illustrated). It is noted that a toner cartridge 215 storing toners of respective colors is drawably attached to the apparatus body 201A at an upper portion of the image forming unit 201B.
The intermediate transfer unit 201C includes an intermediate transfer belt 216, i.e., intermediate transfer body, wound around a drive roller 216a and a tension roller 216b, and the unit is arranged above the four process cartridges 211. The intermediate transfer belt 216 is arranged to contact the photoconductive drums 212 of the respective process cartridges 211, and driven to rotate in a counterclockwise direction, i.e., direction of arrow Q, by the drive roller 216a driven by a drive unit (not illustrated). The intermediate transfer unit 201C has primary transfer rollers 219 that contact an inner peripheral surface of the intermediate transfer belt 216 at positions opposing to the respective photoconductive drums 212, and primary transfer portions T1 are formed as nip portions of the intermediate transfer belt 216 and the photoconductive drums 212. Further, the image forming unit 201B includes a secondary transfer roller 217 that contacts an outer peripheral surface of the intermediate transfer belt 216 at a position opposing to the drive roller 216a. A secondary transfer portion T2 where a toner image borne on the intermediate transfer belt 216 is transferred to the sheet P is formed as a nip portion of the secondary transfer roller 217 and the intermediate transfer belt 216.
In the respective process cartridges 211 arranged as described, an electrostatic latent image is formed on the surface of the photoconductive drum 212 by the laser scanner 210, and toner is supplied from the developers 214 to form toner images of respective colors charged with negative polarity. The toner images are sequentially transferred in multi layers, i.e., primarily transferred, to the intermediate transfer belt 216 at the respective primary transfer portions T1 by applying a transfer bias voltage of positive polarity to the primary transfer rollers 219, and a full-color toner image is formed on the intermediate transfer belt 216.
Simultaneously as the above-described toner image forming process, the sheet P fed from the sheet feeding unit 201E is conveyed toward a registration roller pair 240, where skewing of the sheet P is corrected by the registration roller pair 240. The registration roller pair 240 conveys the sheet P to the secondary transfer portion T2 at a timing matching the transfer timing of the full-color toner image formed on the intermediate transfer belt 216. The toner image borne on the intermediate transfer belt 216 is secondarily transferred to the sheet P at the secondary transfer portion T2 by applying a transfer bias voltage of positive polarity to the secondary transfer roller 217.
The sheet P to which the toner image has been transferred is heated and pressed by the fixing portion 220, and a color image is fixed onto the sheet P. The sheet P with the fixed image is discharged by a sheet discharge roller pair 225 to the sheet discharge tray 230 and supported on the tray. It is noted that, when images are to be formed on both sides of the sheet P, the sheet P having passed the fixing portion 220 is switched back by a reverse conveyance roller pair 222 capable of forward/reverse rotation provided in a reverse conveyance portion 201D. Thereafter, the sheet P is conveyed again to the image forming unit 201B via a re-transport path R, so as to form an image on the backside of the sheet P.
Configuration of Manual Sheet Feeding Apparatus
Next, configuration of the manual sheet feeding apparatus 100M, i.e., the sheet feeding apparatus according to this embodiment, will be described in detail with reference to
As illustrated in
The retard roller 103, i.e. a separation portion, is supported rotatably about a retard roller shaft 103a supported by the apparatus body 201A, and is disposed below the conveyance roller 102. The pickup roller 101, the conveyance roller 102, and the retard roller 103 (
As illustrated in
As illustrated in
The drive gear 160 is attached to one end portion of a rotation shaft 161. A gear 162 is attached to the other end portion of the rotation shaft 161. The gear 162 is engaged with the feeding drive input gear 163. The feeding drive input gear 163 is engaged with the gear 166 through a gear 165 supported by a shaft 164. A gear 167 is coaxially fixed to the retard roller shaft 103a on which the gear 166 is supported. The gear 167 is engaged with a cam drive gear 168 attached to the end portion of a rotation shaft 132a, which pivotally supports a cam 132 with respect to the apparatus body 201A. It is noted that the retard roller shaft 103a may be the same member as a rotation shaft 138 to which a cam follower 131 is rotatably supported.
On the back side of the feed holder 107, an engagement member 108 (see
A first one-way clutch 163a is provided between the conveyance roller shaft 102a and the feeding drive input gear 163. In addition, a second one-way clutch 166a is provided between the retard roller shaft 103a and the separation drive input gear 166. A third one-way clutch 168a is provided between the rotation shaft 132a and the cam drive gear 168.
The first one-way clutch 163a transmits the rotation of the feeding drive input gear 163 caused by the forward rotation of the feed motor 117 to the conveyance roller shaft 102a. In addition, the first one-way clutch 163a does not transmit the rotation of the feeding drive input gear 163 caused by the reverse rotation of the feed motor 117 to the conveyance roller shaft 102a.
The second one-way clutch 166a transmits the rotation of the separation drive input gear 167 to the retard roller shaft 103a (the rotation shaft 138) when the feed motor 117 outputs the forward rotation. In addition, the second one-way clutch 166a does not transmit the rotation of the separation drive input gear 167 to the retard roller shaft 103a when the feed motor 117 outputs the reverse rotation.
The third one-way clutch 168a transmits the rotation of the cam drive gear 168 caused by the rotation of the feeding drive input gear 163, the gear 165, and the separation drive input gear 167 caused by the reverse rotation of the feed motor 117 to the rotation shaft 132a. In addition, the third one-way clutch 168a does not transmit the rotation of the cam drive gear 168 caused by the rotation of the separation drive input gear 167 to the rotation shaft 132a when the feed motor 117 outputs the reverse rotation.
The feed holder 107 is pivotally supported to pivot between a feeding position, i.e., an approach position, and a standby position, i.e., a separation position, about the conveyance roller shaft 102a as a pivot, while holding the pickup roller 101 and the leading-edge positioning member 133, i.e., a sheet regulation member. The feeding position is a position illustrated in
Since the one-way clutches 163a, 166a, and 168a are configured as described above, the conveyance roller shaft 102a and the retard roller shaft 103a are rotated through the operation of the first and second one-way clutches 163a and 166a when the feed motor 117 outputs the forward rotation. The pickup roller 101, the conveyance roller 102, and the retard roller 103 are thus rotated. In this case, since the cam drive gear 168 idles by the third one-way clutch 168a, the cam 132 is not rotated.
When the feed motor 117 outputs the reverse rotation, the feeding drive input gear 163, the gear 166, and the separation drive input gear 167 idle by the slipping of the first and second one-way clutches 163a and 166a. The pickup roller 101, the conveyance roller 102, and the retard roller 103 are thus not rotated. On the other hand, since the cam drive gear 168 is rotated through the third one-way clutch 168a, the cam 132 is rotated. The feed holder 107 is then elevated through the cam follower 131. In this way, the sheet feeding operation and the elevating operation of the pickup roller 101 in the present embodiment is separately performed by switching the forward/reverse rotation of the feed motor 117.
As illustrated in
The torsion coil spring 136 constitutes a damper portion, or an external force absorbing portion, which absorbs external force (impact caused by butting of a sheet bundle, typically) applied from the vicinity of the manual feed tray 111 to the leading-edge positioning member 133 that is locked in a regulation posture (see
The torsion coil spring 136 is a torsion spring interposed between the apparatus body 201A supporting the conveyance roller shaft 102a and the feed holder 107 pivoting about the conveyance roller shaft 102a as a pivot. When an impact is applied to the leading-edge positioning member 133 in the regulation posture, the torsion coil spring 136 absorbs the impact through the rotational movement of the feed holder 107 about the conveyance roller shaft 102a as a pivot along with the rotation of the leading-edge positioning member 133 about an engagement position V (see
In addition, as illustrated in
As described above, the feed holder 107 is normally biased in the direction of the arrow R7 illustrated in
The retard roller 103 is supported by a separation unit (not illustrated) biased upward by a spring (not illustrated), and comes into pressure contact with the conveyance roller 102 through the separation unit so as to generate a nip pressure in a separation nip portion N1. A torque limiter 105 (see
Next, the cam follower 131 and the cam 132 illustrated in
As illustrated in
In
The feed holder 107 in a state of
On the other hand, in a lifting operation of the pickup roller 101, the cam 132 is rotated in the direction of the arrow R9 from the state of
Next, a mechanism for positioning the end position using the leading-edge positioning member 133 and the lock member 134 will be described with reference to
The leading-edge positioning member 133 held by the feed holder 107 is configured to pivot in directions of arrows R7a and R7b in the drawing with respect to a supporting portion 153 which is provided below the roller cover 158 in the unit member 156 (
The lock member 134 is disposed to face the leading-edge positioning member 133 that is erected as illustrated in
The leading-edge positioning member 133 is disposed upstream of the separation nip portion N1 in the sheet feeding direction (a direction of an arrow H). The leading-edge positioning member 133 is configured to be displaceable between the regulation posture of
The leading-edge positioning member 133 is supported by the feed holder 107 to be rotated by its own weight so as to take the regulation posture when the feed holder 107 is rotated from the feeding position (approaching position) to the standby position (separated position). Then, the lock member 134 is engaged on the downstream part, in the sheet feeding direction, of the leading-edge positioning member 133 rotated to the regulation posture, and thus locked to the regulation posture.
On the apparatus body 201A, a guide portion 155 is disposed at a position below the leading-edge positioning member 133 and the lock member 134. In the guide portion 155, there are formed an inclined guide surface 155a which is inclined upward toward the downstream side in the sheet feeding direction (the direction of the arrow H), and a flat guide surface 155b which is horizontally extended further toward the downstream side from the inclined guide surface 155a.
In addition, inside the supporting portion 153 in the feed holder 107, there is formed an engagement projecting portion 107d which disposed to face to and engage with an upper projecting portion 133d of the leading-edge positioning member 133 supported by the pivotal shaft 133a. The leading-edge positioning member 133 pivots by its own weight such that a distal end portion 133b is headed downward without engaging the upper projecting portion 133d with the engagement projecting portion 107d, and thus moves to the regulation posture of
Control System
Next, a control system of the manual sheet feeding apparatus 100M as the sheet feeding apparatus according to this embodiment will be described with reference to
As illustrated in
The drawing roller detection sensor 114 is disposed downstream of the drawing roller pair 104 (see
The drawing roller detection sensor 114 and the sheet detection sensor 115 are configured by a photo-interrupter. That is to say, the drawing roller detection sensor 114 detects whether the sheet P is pulled out by the drawing roller pair 104 through positions of light-blocking plates (not illustrated) which are arranged to go in and out between a light-emitting unit and a light-receiving unit (not illustrated). In addition, the sheet detection sensor 115 detects whether there is the sheet P on a stack surface 111a of the manual feed tray 111. That is, when the light-blocking plate goes out with respect to the drawing roller detection sensor 114 or the sheet detection sensor 115, the light-blocking plate blocks a light path between the light-emitting unit and the light-receiving unit of the photo-interrupter. Then, the output signal of the light-receiving unit falls down to a Low level. On the other hand, when the light path is not blocked, the output signal rises to a High level. Therefore, it is possible to detect whether the sheet P is pulled out or whether there is the sheet P on the stack surface 111a with reference to the position where the output signal of the light-receiving unit is changed.
Operation in Sheet Feeding and Control
Next, the operation in a sheet feeding and the control thereof will be described with reference to
First, in
When the feed motor 117 is forwardly rotated at the feeding position by the control of the control portion 113, the pickup roller 101, the conveyance roller 102, and the retard roller 103 are rotated respectively. Then, the sheet on the manual feed tray is fed one by one by the pickup roller 101. It is noted that, a time to forwardly rotate the feed motor 117 is set for each sheet on the basis of the detection of the drawing roller detection sensor 114 which is disposed downstream of the drawing roller pair 104.
Then, when the feed motor 117 is reversely rotated by the control of the control portion 113 after the inputted print job is ended, the cam 132 is rotated in the direction of the arrow R9 illustrated in
In a case where the sheets are continuously fed, an all-sheet conveyance portion calculates and determines a sheet interval (an interval between sheets conveyed continuously) at which the trailing edge of the preceding sheet can be detected. Therefore, the feed motor 117 is repeatedly turned on and off to control the rotations of the pickup roller 101, the conveyance roller 102, and the retard roller 103.
In addition, in this embodiment, the elevating operation of the pickup roller 101 is not performed at the time of continuously passing the sheets (the sheets are continuously fed), and the pickup roller 101 is lifted up after the print job is ended. Therefore, it is possible to improve productivity of the manual sheet feeding apparatus 100M by reducing the sheet interval as narrow as possible.
Operation of Positioning Leading Edge of Sheet
Next, the operation of positioning of the leading edge of the sheet P stacked on the manual feed tray 111 will be described with reference to
At the standby position illustrated in
At the standby position, the leading edge of the sheet P stacked on the manual feed tray 111 abuts against the leading-edge positioning member 133. Upon abutting against the leading-edge positioning member 133, the abutting force of the sheet P generates a force to rotate the leading-edge positioning member 133 in a clockwise direction (a direction of an arrow R10b) in the drawing. However, this force is blocked by the lock member 134 through the leading-edge positioning member 133. Thus, when the sheet P abuts on the leading-edge positioning member 133, the leading-edge positioning member 133 retains the posture illustrated in
Then, the state is changed from the standby position illustrated in
Thereafter, when the sheet is fed to the downstream in the sheet feeding direction (the direction of the arrow H) by the rotation of the pickup roller 101, the leading edge of the sheet P abuts against the leading-edge positioning member 133. The sheet P is fed while the leading-edge positioning member 133 is rotated in the clockwise direction (the direction of the arrow R10b). In this case, such resistance that may be a hindrance in feeding the sheet P is minimized, and it is possible to establish a stable feeding state.
State Transition from Feeding Operation Position to Feeding Standby Position
Next, a state transition from the feeding position to the standby position will be described. When the feeding operation at the feeding position is ended, the pickup roller 101 is lifted up by the feed motor 117 driven by the control of the control portion 113 together with the feed holder 107 which is rotated in a direction of an arrow R7b of
At that time, in a case where there is no sheet on the manual feed tray, or in a case where the leading edge of the sheet is on the upstream side in the sheet feeding direction from the abutment portion of the leading-edge positioning member 133 (a portion denoted by K in
On the other hand, in a case where the leading edge of the sheet left on the manual feed tray is left on the downstream side in the sheet feeding direction from the abutment portion (the portion denoted by “K” in
In this way, the lock member 134 is configured to be swingable, so that the leading-edge positioning member 133 moves to the standby position without giving stress to the leading edge of the sheet P. When the sheet P is removed from the manual feed tray 111 in this state, the leading-edge positioning member 133 and the lock member 134 are swung by their own weight and return to the initial state (
Prevention of Overload Caused by Abutment
Next, configuration for preventing overload caused by the abutment will be described. In this embodiment, it is paid attention to a time when the sheet is set in the manual sheet feeding apparatus 100M provided with the pickup roller 101, the leading-edge positioning member 133, and the control portion 113. As already described above, the torsion coil spring 136 is interposed in the end portion of the feed holder 107 to which the leading-edge positioning member 133 is attached so as to absorb the force loaded on the leading-edge positioning member 133 by the elastic deformation of the torsion coil spring 136.
In general, at the standby position of the feed holder 107, the leading-edge positioning member 133 for setting the sheet on the manual feed tray 111 is locked. This lock is designed to prevent the sheet P from a separation failure even when, in setting operation, the sheets are forced into the separation nip portion N1 as a bundle. At that time, it might happens that an overload caused by the abutment of the sheets when the user sets the sheets, or disturbance beyond expectation are applied to the apparatus. Taking such situations into consideration, there is a concern that the components may be damaged or the sheet is folded at the setting time.
In the present embodiment, the leading-edge positioning member 133 abuts on the lock member 134 to be locked in normal cases. On the contrary, when there occurs an overload state in which an overload (excessive load) equal to or more than a predetermined amount is applied, as illustrated in
In other words, when the overload in a direction of an arrow W of
In this way, even in a case where the overload is applied on the leading-edge positioning member 133 in a state where the leading-edge positioning member 133 is locked by the lock member 134, the feed holder 107 is rotated, while the torsion coil spring 136 absorbing the load. Therefore, the shutter function of the leading-edge positioning member 133 is appropriately released without causing damage on the components. In addition, a force of the torsion coil spring 136 in the sheet passing state is an unloaded state with respect to the leading-edge positioning member 133 (see
In this embodiment, in a case where a load equal to or more than a predetermined amount (for example, a load equal to or more than 15 [N]) is applied to the positioning member 133, the lock is set to be released even at the standby position. This load is determined on an assumption that how much load is applied to the positioning member 133 when a bundle of thick sheets is set in a normal manner. In addition, a spring pressure of the torsion coil spring 136 is set to satisfy the following relation, so that the lock of the lock member 134 is released in a condition in which a load equal to or more than an allowable quantity (for example, 15 [N] or more) is applied.
In this embodiment, the spring pressure of the torsion coil spring 136 is set to be optimized as described below (see
M=F cos θ×La×α (1)
Furthermore, the parameters are set to satisfy a relation of the following equation,
M>Ma (2)
where Ma [N mm] refers to a moment of force of the pickup roller pressing spring 106. This relation means that the moment applied to the feed holder 107 when the torsion coil spring 136 starts to be elastically deformed is larger than the moment which is applied to the feed holder 107 by the pickup roller pressing spring 106.
As described above, with the settings to satisfy the equation (1), it is possible to set an optimized spring pressure (optimized pressure) of the torsion coil spring 136 attached to the conveyance roller shaft 102a, i.e., the rotation base of the feed holder 107. A biasing force of the pickup roller pressing spring 106 is applied to the feed holder 107. Herein, with the settings to satisfy the inequation (2), the feed holder 107 is appropriately retained at the standby position by the torsion coil spring 136 of the rotation base (root) when the feed holder 107 is lifted up to the standby position (
According to the above-described embodiment, the leading edge of the sheet is appropriately regulated in setting of the sheet, and the overload is appropriately absorbed by the torsion coil spring 136 in a case where the overload is applied by a conflict of a sheet bundle. Therefore, it is possible to prevent inconvenience such that the leading-edge positioning member 133 is damaged or the leading edge of the sheet is buckled. In addition, the leading-edge positioning member 133 takes the retracted posture illustrated in
In addition, in this embodiment, the torsion coil spring 136 is used as a damper portion which is interposed between the apparatus body 201A supporting the conveyance roller shaft 102a and the feed holder 107 pivoting about the conveyance roller shaft 102a as a pivot. With this configuration, in a case where an impact is applied to the leading-edge positioning member 133 in the regulation posture, the impact is absorbed through the feed holder 107 which rotates in conjunction with the rotation of the leading-edge positioning member 133. Therefore, the structure of absorbing the overload generated by the impact caused by a conflict of a sheet bundle is realized with a simple and inexpensive configuration.
Next, a second embodiment of this disclosure will be described with reference to
In this embodiment, a compression spring 149 is interposed in the lock member 134. The lock member 134 is configured to be compressed so as to allow the leading-edge positioning member 133 to be displaced when overloaded, so that the overload is absorbed. That is, the lock member 134, i.e., a lock portion of this embodiment, includes an engagement portion 134c which is engaged with the leading-edge positioning member 133 in the regulation posture as illustrated in FIGS. 12A and 12B, and a retaining portion 134d, i.e., a held portion, which contains the pivotal shaft 135 supported by the apparatus body 201A. The engagement portion 134c and the retaining portion 134d are formed to make a space therebetween to provide the compression spring 149, i.e., a resilient member, in a compressed state. The engagement portion 134c is supported by the retaining portion 134d in a sliding manner. The compression spring 149 serves as a damper portion in this embodiment.
Then, the following relation is satisfied in order to set an optimal spring pressure of the compression spring 149 in this embodiment. That is, when the leading-edge positioning member 133 is in the regulation posture and the compression spring 149 is compressed between the engagement portion 134c and the retaining portion 134d, a load caused by an impact is referred to as F [N]. In addition, a distance between an overload point U where the impact is applied to the leading-edge positioning member 133 and the pivotal shaft (regulation pivotal shaft) 133a is referred to as Dc [mm]. A spring pressure of the compression spring 149 is referred to as Fb [N]. Furthermore, a distance between the engagement position V (an engagement position between the lock member 134 and the leading-edge positioning member 133) and the pivotal shaft 133a is referred to as Db [mm]. A safety factor is referred to as a. Then, those parameters are set such that the following relation is satisfied.
Fb<(F×Dc)/Db×α (3)
In this embodiment, it is possible to prevent that the components are damaged due to the overload, and that the leading edge of the sheet is buckled, if the above inequation (3) is satisfied. In addition, the leading edge of the sheet is appropriately regulated in setting of the sheet by the biasing force of the compression spring 149, which is interposed between the engagement portion 134c and the retaining portion 134d. On the other hand, when an excessive impact is applied to the leading-edge positioning member 133 in the regulation posture, the compression spring 149 is compressed. Thus, the engagement portion 134c pressed to the leading-edge positioning member 133 is allowed to be displaced, so that the impact is excellently absorbed. Still further, in this embodiment, the leading-edge positioning member 133 abuts on the lock member 134 in which the compression spring 149 is interposed. Thus, it is possible to effectively prevent the damage of the components as the lock member 134 directly receives the overload.
Next, a third embodiment of this disclosure will be described with reference to
This disclosure is not limited to the configurations (“shutter” configurations) in the above-described first and second embodiments. Other configurations may be used to bias the spring so as to prevent the damage of the components in case of overloaded. In this third embodiment, another shutter configuration different from those used in the first and second embodiments will be described.
In this embodiment, as illustrated in
A stopper 137 is fixed to the feeding frame 109 to determine the lower limit of a pivot range of the lock member 134. The pickup roller 101 is held on the upstream side in the sheet feeding direction in the feed holder 107. The pivotal shaft 133a is provided coaxially to the pickup roller shaft 101a of the pickup roller 101. The leading-edge positioning member 133 is pivotally (swingably) supported by the pivotal shaft 133a. In the leading-edge positioning member 133, the distal end portion 133b is provided on the downstream side in the regulation posture of
In the upper edge of the feed holder 107, one end portion of the lock member 134 (a lock portion) is pivotally (swingably) supported by the pivotal shaft 135. The pivotal shaft 135 is positioned in the middle of the conveyance roller 102 and the pickup roller 101. The lock member 134 includes an engagement claw portion 134a at a position to be engageable with the upper end claw portion 133c of the leading-edge positioning member 133. Further, the lock member 134 includes an engagement projecting portion 134b at a position to be engageable with the stopper 137.
The manual sheet feeding apparatus having the above configurations is held at the standby position illustrated in
In this state, when the sheet bundle (P) is stacked in the manual feed tray 111 and the leading edge of the sheet abuts on the leading-edge positioning member 133, the leading-edge positioning member 133 receives a rotation force to the counterclockwise direction of
Then, when the feed holder 107 moves to the feeding position from the standby position, the feed motor 117 is rotated by the control of the control portion 113, and the feed holder 107 is lifted down about the conveyance roller shaft 102a as a pivot. Therefore, the pickup roller 101 and the leading-edge positioning member 133 held by the feed holder 107 are lifted down while being rotated in the direction of the arrow R7a, and take the feeding position illustrated in
At that time, a returning force toward the opposite direction acts on the leading-edge positioning member 133 by the weight of the member about the pivotal shaft 133a as a pivot. However, since this force is not regulated only by the own weight of the member, the leading-edge positioning member 133 is easily rotated by a small force at the time of feeding the sheet P. In other words, the lock member 134, which is held by abutting on the stopper 137, is released from the stopper 137, so that the leading-edge positioning member 133 swings about the pivotal shaft 133a to the retracted posture as illustrated in
Next, a state transition from the feeding position to the standby position will be described. That is, when the feeding operation is ended, the feed holder 107 is lifted up in the direction of the arrow R7b in
Then, the configuration of absorbing the overload on the leading-edge positioning member 133 may be provided in the above-described configuration described using
With the use of the above lock member 134, when the impact is applied to the leading-edge positioning member 133 in the regulation posture, the tension spring 169 is extended to separate the engagement portion 134c from the retaining portion 134d in order to absorb the impact. In other words, when the overload is applied on the leading-edge positioning member 133, the tension spring 169 is extended, and releases the upper end claw portion 133c locked by the engagement claw portion 134a of the lock member 134 while absorbing the overload. The tension spring 169 (the resilient member) serves as a damper portion which absorbs the impact added from the manual feed tray 111 with respect to the leading-edge positioning member 133 which is locked in the regulation posture by the lock member 134.
With such a configuration, it is possible to prevent that the components are damaged during overloading and the sheet is buckled in the leading-edge positioning mechanism which includes the leading-edge positioning member 133 and the lock member 134, without being limited to the configurations as described in the first and second embodiments.
It is noted that in the first, second, and third embodiments, the spring materials such as the torsion coil spring 136, the compression spring 149, and the tension spring 169 are used as the damper portions, but the materials for the damper portion is not limited thereto. In addition, the descriptions in these embodiments have been made using the electro-photographic system image forming apparatus 201, and instead the present disclosure may be applied to an inkjet image forming apparatus which forms an image in a sheet by ejecting ink from a nozzle for example.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-175816, filed on Sep. 7, 2015, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-175816 | Sep 2015 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6152631 | Park | Nov 2000 | A |
| 7595916 | Morimoto | Sep 2009 | B2 |
| 7686291 | Miyazawa | Mar 2010 | B2 |
| 8052139 | Su | Nov 2011 | B1 |
| 8118299 | Sato | Feb 2012 | B2 |
| 8210520 | Su | Jul 2012 | B2 |
| 20080265487 | Butikofer | Oct 2008 | A1 |
| 20170008712 | Tateishi | Jan 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 06-115748 | Apr 1994 | JP |
| 2002-193469 | Jul 2002 | JP |
| 2012-020821 | Feb 2012 | JP |
| 2014-189342 | Oct 2014 | JP |
| Entry |
|---|
| Japanese Office Action issued in corresponding Japanese Application No. 2015175816 dated Aug. 15, 2017. |
| Number | Date | Country | |
|---|---|---|---|
| 20170066608 A1 | Mar 2017 | US |
