This application claims priority from Japanese Patent Application No. 2019-017576 filed on Feb. 4, 2019, the content of which is incorporated herein by reference in its entirety.
Aspects of the disclosure relate to an image forming apparatus.
A known image forming apparatus includes an image forming unit configured to form an image on one side of a sheet and to form an image on the other side of the sheet transported, along a retransport path, back to the image forming unit.
A skew roller pair and a reference guide are disposed on a side of the retransport path in a width direction orthogonal to a transport direction. A first transport roller pair is disposed upstream of the skew roller pair in the transport direction, and a second transport roller pair is disposed downstream of the skew roller pair in the transport direction. The skew roller pair alone transports in a skewed manner, along the retransport path, the sheet positioned between the first transport roller pair and the second transport roller pair. The sheet is pressed against the reference guide which thus restricts the position of the sheet in the width direction.
In such a known image forming apparatus, a plurality of sheets may be simultaneously processed to improve throughput in duplex mode for forming images on both sides of a sheet. In an example, a sheet may be caused to wait in the middle of the retransport path to allow a next sheet to be transported to the image forming unit. In this case, if the sheet to be caused to wait is stopped while being nipped only by the skew roller pair, the sheet may rotate about the skew roller pair due to a frictional resistance acting on the sheet being stopped. Thus, the sheet may rotate in such a direction that an edge of the sheet is away from the reference guide.
As a result, in the known image forming apparatus, the sheet to be caused to wait in the retransport path may not follow the reference guide, and the reference guide may fail to restrict the position of the sheet in the width direction.
Aspects of the disclosure provide an image forming apparatus configured to restrict the position of a sheet in a width direction when the sheet is caused to wait at a retransport assembly.
According to one or more aspects of the disclosure, an image forming apparatus includes an image forming unit configured to form an image on a sheet, a retransport assembly configured to transport, back to the image forming unit, the sheet having the image formed on one side thereof by the image forming unit, and a controller configured to control the retransport assembly and to execute a waiting operation to cause the sheet to wait at the retransport assembly. The retransport assembly includes a first transport roller pair, a second transport roller pair disposed downstream of the first transport roller pair in a transport direction, a skew roller pair, and a reference wall. The skew roller pair is disposed downstream of the first transport roller pair and upstream of the second transport roller pair in the transport direction and is configured to alone transport, in a skewed manner toward an end of the retransport assembly in a width direction orthogonal to the transport direction, the sheet spaced from the first transport roller pair and the second transport roller pair. The reference wall is positioned at the end of the retransport assembly in the width direction and extends along the transport direction. The controller is configured to execute the waiting operation by stopping the skew roller pair and one of the first transport roller pair and the second transport roller pair in a state in which the sheet is nipped by the skew roller pair and the one of the first transport roller pair and the second transport roller pair.
Aspects of the disclosure are illustrated by way of example and not by limitation in the accompanying figures in which like reference characters indicate similar elements.
Illustrative embodiments of the disclosure will be described with reference to the drawings.
A front-rear direction and an up-down direction are shown in
As shown in
The main body 2 includes a housing and an inner frame disposed inside the housing (not shown). The inner frame includes a pair of side frames 90L and 90R schematically shown in
As shown in
A sheet tray 2C is attached to the sheet tray receptacle 2A. The sheet tray 2C has a substantially box shape extending substantially horizontally and is open upward. The sheet tray 2C stores therein a stack of sheets SH which undergo image forming. Sheets SH include plain paper sheets, transparent sheets, and cardboard sheets.
A discharge tray 2T is disposed at the top of the main body 2. A sheet SH having an image formed thereon is discharged onto the discharge tray 2T.
The feeder 20, the image forming unit 3, and the discharge unit 29 are disposed inside the main body 2 at a position above the sheet tray receptacle 2A and the sheet tray 2C. The feeder 20, the image forming unit 3, and the discharge unit 29 are assembled to the inner frame (not shown).
As schematically shown in
As shown in
In the feeder 20, a feed roller 21 feeds from the sheet tray 2C one sheet SH at a time, separated by a separation roller 22 and a separation pad 22A, to the transport path P1. Then, a transport roller pair 23A and 23B, and a registration roller pair 24A and 24B disposed at the U-shaped portion of the transport path P1 transport the sheet SH toward the image forming unit 3.
A sensor 3S is disposed between the registration roller pair 24A and 24B, and the image forming unit 3. A known optical sensor, such as a photo-interrupter, is used as the sensor 3S to detect an actuator pivoting upon being contacted by a sheet.
When the sensor 3S detects a sheet SH transported by the registration roller pair 24A and 24B, the detection result is transmitted to the controller C1. The controller C1 determines, on the basis of the detection result, a timing when the sheet SH reaches the image forming unit 3 and controls timings for starting and stopping the above-described various elements.
The image forming unit 3 is of the direct tandem type capable of color printing. The image forming unit 3 has a known structure including a process cartridge 7, a transfer belt 6, a scanner 8, and a fixer 9.
The process cartridge 7 is a group of four cartridges corresponding to black, yellow, magenta, and cyan toners and arranged in series or tandem along a substantially horizontal portion of the transport path P1. The four cartridges of the process cartridge 7 each includes, for a corresponding toner color, a photosensitive drum 5, a developing roller (not shown), a charger, and a toner storage.
A transfer belt 6 is disposed below the photosensitive drums 5 to define therebetween the substantially horizontal portion of the transport path P1. The transfer belt 6 circulates while cooperating with the photosensitive drums 5 to nip a sheet being transported.
A scanner 8 includes laser sources, a polygon mirror, f-theta lenses, and reflecting mirrors. The scanner 8 emits laser beams downward to irradiate respective photosensitive drums 5 in the process cartridge 7.
A fixer 9 is disposed further to the rear than the process cartridge 7. The fixer 9 includes a heat roller 9A positioned on an upper side of the transport path P1, and a pressure roller 9B pressed upward toward the heat roller 9A to define the transport path P1 therebetween. The heat roller 9A and the pressure roller 9B of the fixer 9 heat and press a sheet SH having passed below the process cartridge 7.
A sensor 9S is disposed further to the rear than the heat roller 9A and the pressure roller 9B in the transport path P1. The sensor 9S has the same structure as the sensor 3S.
When the sensor 9S detects a sheet SH transported past the fixer 9, the detection result is transmitted to the controller C1. The controller C1 determines, on the basis of the detection result, a timing when the sheet SH leaves the image forming unit 3 and controls timings for starting and stopping the above-described various elements.
The discharge unit 29 includes a discharge roller 29A, a discharge pinch roller 29B, and a flap 29F. The discharge roller 29A and the discharge pinch roller 29B are positioned most downstream in the transport path P1.
The flap 29F is disposed in the main body 2 at a position further to the rear than and partially lower than the discharge roller 29A and the discharge pinch roller 29B. A lower end of the flap 29F is supported by a frame member (not shown) pivotably between a position shown by a solid line in
The flap 29F is retained by a spring (not shown) at the position shown by the two-dot dashed line in
The image forming unit 3 forms an image on a sheet SH transported along the transport path P1, as described below. As a photosensitive drum 5 in each of the four cartridges rotates, the surface of the photosensitive drum 5 is uniformly and positively charged by an associated charger, and then the surface of the photosensitive drum 5 is irradiated with a laser beam scanned at high speed by the scanner 8. An electrostatic latent image, which corresponds to an image to be formed on the sheet SH, is formed on the surface of the photosensitive drum 5. Subsequently, toner is supplied from an associated corresponding toner storage onto the surface of the photosensitive drum 5, in accordance with an electrostatic latent image on the photosensitive drum 5. In a state in which a sheet SH is stored in the sheet tray 2C, one side SH1 of the sheet SH faces down. When the sheet SH is transported along the transport path P1 and passes through the image forming unit 3, the one side SH1 of the sheet SH faces up to the photosensitive drums 5. Thus, the toner carried on the surface of the photosensitive drum 5 is transferred onto the one side SH1 of the sheet SH, and the transferred toner is heated and pressed by the fixer 9. Consequently, the transferred toner is fixed onto the sheet SH.
The sheet SH transported past the fixer 9 is pinched by the discharge roller 29A and the discharge pinch roller 29B, and is discharged onto the discharge tray 2T by the discharge roller 29A rotating forward.
A retransport path P2 is defined in the main body 2 to allow image forming also on the other side of a sheet SH opposite to the one side SH1. The retransport path P2 extends downward from the discharge unit 29 along a rear surface of the main body 2 and is redirected to extend, below the sheet tray 2C, frontward substantially horizontally. Then, the retransport path P2 is redirected at a position near the front of the main body 2 to extend upward and merge into a position between the separation roller 22 and the transport roller pair 23A and 23B.
A sheet SH is transported along the retransport path P2 in a transport direction D1. The transport direction D1 is changed from downward to frontward to be substantially horizontal, and is further changed to upward. A width direction of a sheet SH transported along the retransport path P2 corresponds to the left-right direction.
The discharge unit 29 also serves as a switch-back mechanism configured to switch back a sheet SH transported along the transport path P1 and to transport the sheet SH into the retransport path P2. Specifically, the controller C1 switches the discharge roller 29A rotating in a forward direction to rotate in a reverse direction at a predetermined timing after the sensor 9S ceases to detect a trailing edge of a sheet SH in the middle of discharging the sheet SH toward the discharge tray 2T by the discharge roller 29A and the discharge pinch roller 29B which pinch the sheet SH therebetween. The predetermined timing is set such that the sheet SH is switched back after the flap 29F pivots to the position shown by the two-dot dashed line in
The image forming apparatus 1 includes a retransport assembly 10. The retransport assembly 10 includes a switch-back guide 61 shown in
In the retransport assembly 10, the switch-back guide 61, the retransport unit 100, the connecting unit 200, and the return guide 69 transport a sheet SH, switched back by the discharge unit 29, back to the image forming unit 3 along the retransport path P2. After the image forming unit 3 forms an image on the other side of the sheet SH opposite to the one side SH1, the sheet SH is discharged onto the discharge tray 2T. A specific structure of the retransport assembly 10 will now be described in detail.
The switch-back guide 61 defines a portion of the retransport path P2 such that the portion extends downward from the discharge unit 29 along the rear surface of the main body 2. A first transport roller 11 and a pinch roller 11P are disposed at a middle of the switch-back guide 61 in the transport direction D1.
The first transport roller 11 is rotatable about a first axis X11 parallel to a width direction orthogonal to the transport direction D1. The pinch roller 11P is pressed against the first transport roller 11. As shown in
The left side frame 90L includes a third transmitter G3. The third transmitter G3, which is only schematically shown, includes a plurality of gears and transmission shafts to transmit a drive force from the drive source M1 to the first transport roller 11. The third transmitter G3 may include a clutch configured to switch between transmission and block of the drive force from the drive source M1.
As shown in
The return guide 69 is disposed inside a front end portion of the sheet tray 2C. The return guide 69 is an example of a second curved portion. Specifically, the front end portion of the sheet tray 2C includes an extending portion 2C1. The extending portion 2C1 extends downward beyond a bottom surface 2C2 of the sheet tray 2C to a position near a bottom wall 2D.
An entrance of the return guide 69 is open to a rearward facing surface of the extending portion 2C1. An exit of the return guide 69 is open to an upward facing surface of the front end portion of the sheet tray 2C. The return guide 69 defines, in the retransport path P2, a portion redirected from frontward to upward and extending upward to merge into the transport path P1.
The portion defined by the return guide 69 is a third retransport path portion P23 through which a sheet SH passes inside the return guide 69 frontward and then toward a junction with the transport path P1. An upstream end of the third retransport path portion P23 in the transport direction D1 is located at the extending portion 2C1.
The retransport unit 100 is disposed below the sheet tray 2C to extend horizontally. The retransport unit 100 defines, in the retransport path P2, a curved portion changing the transport direction from downward to frontward, and a portion of a substantially horizontal portion extending frontward. The portion of the substantially horizontal portion defined by the retransport unit 100 is referred to as a first retransport path portion P21.
The retransport unit 100 is movable between a stored position (shown in
Pulling out the retransport unit 100 from the stored position to the pulled-out position allows a user to remove any sheet SH jammed in the retransport path P2.
As shown in
As shown in
When the guide ribs 119L and 119R are guided by guide rails (not shown) formed in the side frames 90L and 90R, the retransport unit 100 moves between the stored position (shown in
As shown in
The curved transport surface 116G is positioned at a rear end of the first guide member 110 and defines the curved portion of the retransport path P2 which changes the transport direction from downward to frontward. The curved transport surface 116G is a curved surface substantially formed by distal ends of a plurality of ribs.
As shown in
The first transport surface 110G is connected to a downstream end of the curved transport surface 116G in the transport direction D1 and extends substantially horizontally to a front end of the first guide member 110. The first transport surface 110G defines from below the first retransport path portion P21. The first transport surface 110G is a flat surface substantially formed by distal ends of a plurality of ribs.
As shown in
A distance in the width direction between the left reference line LL1 and the right reference ling LR1 is set to be equal to a length in the width direction of a sheet SH, which is transported on the first transport surface 110G. In the width direction, a distance between the centerline LC1 and the left reference line LL1 is set to be equal to a distance between the centerline LC1 and the right reference ling LR1.
By aligning a left edge of a sheet SH transported on the first transport surface 110G with the left reference line LL1, a center of the sheet SH in the width direction aligns with the centerline LC1. The centerline LC1 also aligns with a center of the image forming unit 3 in the width direction.
As shown in
As shown in
As shown in
In
As shown in
As shown in
As shown in
The first transmitter G1 includes a spur gear (not shown) which rearwardly meshes with the spur gear 13G. The spur gear 13G leaves the spur gear of the first transmitter G1 when the retransport unit 100 moves from the stored position (shown in
The skew roller 13P and the drive roller 13, which hereinafter may be collectively referred to as skew roller pair 13, nip, on the first transport surface 110G, a sheet SH transported by the first transport roller 11 and the pinch roller 11P, and transport the sheet SH toward the connecting unit 200. In this case, the skew roller 13P, which rotates about the inclined axis X13P as the drive roller 13 rotates, transports the sheet SH in a skewed manner toward the reference wall 32.
As shown in
The first guide member 110 also includes, at the center in the width direction of the front end face, an actuator pusher 110J protruding frontward.
As shown in
The connecting unit 200 defines, in the retransport path P2, a substantially horizontal portion extending frontward. The substantially horizontal portion extending frontward is referred to as a second retransport path portion P22.
The second retransport path portion P22 is connected to a downstream end of the first retransport path portion P21 and to an upstream end of the third retransport path portion P23 in the transport direction D1. In short, the retransport path P2 has the first retransport path portion P21, the second retransport path portion P22, and the third retransport path portion P23 in the transport direction D1.
A substantially horizontal portion of the retransport path P2 is divided into the first retransport path portion P21 and the second retransport path portion P22. Thus, as shown in
As shown in
The lower beam 230 is disposed at the bottom of the connecting unit 200. The lower beam 230, which may be a sheet metal member, extends in the left-right direction. As shown in
As shown in
The second transport surface 210G and the first transport surface 110G are an example of a horizontal portion. As shown in
As shown in
In a state in which the retransport unit 100 is located at the stored position, the positioning protrusions 210K are fitted in the corresponding positioning recesses 110K. In this way, as shown in
As shown in
As shown in
As shown in
Each second transport roller 12 is rotatable about a second axis X12 parallel to the width direction, with its upper end exposed from the second transport surface 210G. As shown in
As shown in
As shown in
As shown in
The second transport rollers 12 and the pinch rollers 12P, which hereinafter may be collectively referred to as second transport roller pair(s) 12 and 12P, nip, on the second transport surface 210G, a sheet SH transported in a skewed manner by the skew roller 13P and the drive roller 13, and transport the sheet SH toward the return guide 69 which defines the third retransport path portion P23.
As shown in
As shown in
As shown in
As shown in
The actuator 70 (70A) shown in
The actuator 70 (70B) shown in
The actuator 70 (70A) shown in
As shown in
In contrast, as shown in
As shown in
As schematically shown in
In a state in which the drive source M1 is inactive, the controller C1 determines that the retransport unit 100 is at the stored position upon receipt of an ON signal from the photo-interrupter 70U and determines that the retransport unit 100 is not at the stored position upon receipt of an OFF signal from the photo-interrupter 70U.
In a state in which the drive source M1 is active, the controller C1 determines, upon receipt of an ON signal from the photo-interrupter 70U, that the actuator 70 is at the first standby position and that no sheet SH is present on the second transport surface 210G, and determines, upon receipt of an OFF signal from the photo-interrupter 70U, that the actuator is at the passage allowing position and that a sheet SH is present on the second transport surface 210G.
In short, the actuator 70 is used for detection of the presence and absence of a sheet SH on the second transport surface 210G, as well as the position of the retransport unit 100.
The skew roller pair 13 and 13P transports the sheet SH (SHa) in such a state toward the reference wall 32 of the reference guide 30. This causes a left edge of the sheet SH (SH a) to contact the front end of the side wall 118A of the side chute 118, while being skewed relative to the left reference line LL1.
The skew roller pair 13 and 13P turns, the sheet SH (SHa) on the first transport surface 110G, clockwise in
In this way, the retransport assembly 10 properly restricts the position of the sheet SH in the width direction such that the left edge of the sheet SH (SHb) is aligned with the left reference line LL1 and a center of the sheet SH (SHb) in the width direction is aligned with the centerline LC1.
In addition, when the skew roller pair 13 and 13P alone transports the sheet SH (SHb) in the transport direction D1, the actuator 70 (70A) at the first standby position is pushed by the sheet SH (SHb) to pivot to the passage allowing position. Consequently, the controller C1 determines that the sheet SH is present on the second transport surface 210G and uses this determination for various timing controls.
As shown in
The image forming apparatus 1 may simultaneously process a plurality of sheets SH to improve throughput in duplex mode for forming images on both sides of a sheet SH. In an example, a sheet SH may be caused to wait in the middle of the retransport path P2 to allow a next sheet SH to be transported to the image forming unit 3.
In this case, the controller C1 controls the retransport assembly 10 on the basis of the position of the actuator 70 for detecting whether a sheet SH is present on the second transport surface 210G. The controller C1 executes a waiting operation for a sheet SH to wait at the retransport assembly 10 when a predetermined time elapses since a timing at which the actuator 70 pivots to the passage allowing position.
In this illustrative embodiment, in order to execute the waiting operation, the controller C1 controls the first transmitter G1 and the second transmitter G2 to stop the skew roller pair 13 and 13P and the second transport roller pairs 12 and 12P in a state in which, as shown in
When a predetermined time elapses, the controller C1 controls the first transmitter G1 and the second transmitter G2 to rotate the skew roller pair 13 and 13P and the two second transport roller pairs 12 and 12P, thereby transporting the waiting sheet SH (SHc) toward the third retransport path portion P23.
By executing the waiting operation as described above, the image forming apparatus 1 may properly perform simultaneous processes of a plurality of sheets SH.
In the image forming apparatus 1 according to the above-described embodiment, as shown in
As shown in
When a sheet SH is caused to wait, as shown in
In this respect, movement of the sheet SH (SHc) may be stabilized by nipping the sheet SH (SHc) to be caused to wait at two positions in the transport direction D1 by the skew roller pair 13 and 13P and the second transport roller pairs 12 and 12P. Consequently, the sheet SH may be prevented from rotating about the skew roller 13P in a counterclockwise direction in
Thus, in the above-described image forming apparatus 1, the position of the sheet SH in the width direction may be properly restricted when the sheet SH is caused to wait at the retransport assembly 10.
When a waiting sheet SH is transported again in the image forming apparatus 1, a frictional resistance and an inertial force may act on the sheet SH. In this case, particularly, a force F2 obtained by summing the inertial force and the frictional resistance is likely to act on the sheet SH. The force F2 is also likely to act on the sheet SH upstream in the transport direction D1 at a position opposite from the reference guide 30 in the width direction. In this case also, movement of the sheet SH (SHc), which is nipped at two positions in the transport direction D1, may be stabilized when being transported toward the third retransport path portion P23.
In the above-described image forming apparatus 1, as shown in
In the above-described image forming apparatus 1, as shown in
In the above-described image forming apparatus 1, as shown in
In the above-described image forming apparatus 1, as shown in
In the above-described image forming apparatus 1, as shown in
In the above-described image forming apparatus 1, when the retransport unit 100 is moved to the pulled-out position, the actuator 70 remains in the main body 2 and thus is less likely to be broken. Regardless of the retransport unit 100 moving between the stored position and the pulled-out position, as shown in
According to a modified illustrative embodiment shown in
While the disclosure has been described with reference to particular embodiments, various changes, arrangements and modifications may be applied therein without departing from the spirit and scope of the disclosure.
Number | Date | Country | Kind |
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JP2019-017576 | Feb 2019 | JP | national |
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Number | Date | Country | |
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20200249612 A1 | Aug 2020 | US |