Patent Grant
11643290
This application claims priority from Japanese Patent Application No. 2019-158615 filed on Aug. 30, 2019, the content of which is incorporated herein by reference in its entirety.
Aspects disclosed herein relate to a sheet feeder and an image forming apparatus including the sheet feeder.
Some sheet feeders are known that feed a sheet from outside an apparatus to inside the apparatus. Such a sheet feeder includes a sheet tray for supporting sheets to be fed, a photosensor including a light emitter and a light receiver facing each other, and an actuator including a contact element and a shielding plate. The contact element is pivotable by contact with a sheet supported on the sheet tray. The shielding plate is configured to pass through between the light emitter and the light receiver in association with the rotation of the contact element. The sheet feeder is configured to detect the presence or absence of a sheet on the sheet tray depending on whether the shielding plate is between the light emitter and the light receiver.
The photosensor of the sheet feeder is configured to detect the presence or absence of a sheet on the sheet tray. The light receiver may, however, receive light from outside, and thereby false detection may occur.
Thus, it is known that, to reduce such false light detection, the actuator further includes a light shield to cover the photosensor.
Aspects of the disclosure provide a sheet feeder to further help reducing effects of outside light on a photosensor.
According to one or more aspects of the disclosure, a sheet feeder includes a sheet tray, a feed roller, a sheet feed frame, a contact element, a guide frame, a photosensor, a shield, and a linkage. The feed roller is configured to feed a sheet on the sheet tray. The sheet feed frame holds the feed roller. The contact element is pivotable relative to the sheet feed frame. The guide frame is disposed below the sheet feed frame. The photosensor includes a light emitter for emitting a light and a light receiver for receiving the emitted light. The shield is movable between a light transmission position and a light shield position. The linkage connects the contact element and the shield such that the shield is movable in association with pivoting of the contact element. The light receiver receives the light emitted from the light emitter when the shield is at the light transmission position. The shield at the light shield position shields the light receiver from the light emitted from the light emitter.
This configuration may reduce effects of light from outside on the photosensor, and thus may prevent false light detection.
Illustrative embodiments of the disclosure will be described with reference to the accompanying drawings.
Image Forming Apparatus
An image forming apparatus 1 illustrated in
In the following description, right and left sides of the page of
The casing 2 is box-shaped, and accommodates the sheet feed unit 3, the image forming unit 5, the discharge unit 7, and the sheet feeder 4. The casing 2 has an opening 2A at its front and a multi-purpose tray (hereinafter referred to as a MP tray) 21 configured to open and close the opening 2A. The MP tray 21 is an example of a sheet tray configured to support a sheet. The casing 2 has an upper surface covered by an upper cover 23.
The MP tray 21 is rotatable about a rotation axis 21A located at its lower end and extending horizontally in a left-right direction. The MP tray 21 is movable between a closed position to close the opening 2A and an open position to open the opening 2A. The MP tray 21 at the open position is configured to support one or more sheets S. FIG. 1 illustrates the MP tray 21 at the open position. The upper cover 23 includes a sheet discharge tray 23A inclined downward to the rear.
The sheet feed unit 3 includes a sheet cassette 31, a feed roller 32, a separation roller 33, a separation pad 33A, and a registration roller pair 35, and is configured to feed a sheet S from the sheet cassette 31 to the image forming unit 5. The casing 2 defines therein a conveyance path P1 extending from the sheet cassette 31 via the image forming unit 5 to the sheet discharge tray 23A.
The sheet cassette 31 is configured to accommodate a stack of sheets S. The feed roller 32 is configured to feed a sheet S from the sheet cassette 31, and the separation roller 33 and the separation pad 33A separate the sheet S from subsequent sheets S, so that the sheet S is singly conveyed toward the conveyance path P1.
The sheet S is then conveyed along the conveyance path P1 by the registration roller pair 35, which is located downstream from the separation roller 33, toward the image forming unit 5. The registration roller pair 35 temporarily stops feeding the sheet, aligns the leading end of the sheet S, and then starts rotating at a predetermined timing to convey the sheet S toward a transfer position in the image forming unit 5.
The image forming unit 5 is disposed above the sheet cassette 31 and configured to form an image on the sheet S. The image forming unit 5 includes a process cartridge 50 configured to transfer an image on a sheet S conveyed from the sheet feed unit 3, an exposure unit 56 configured to expose a surface of a photosensitive drum 54 in the process cartridge 50, and a fixing unit 60 configured to fix the image transferred on the sheet S by the process cartridge 50.
The process cartridge 50 includes a developing roller 53, the photosensitive drum 54, and a transfer roller 55. The exposure unit 56 includes a laser diode, a polygon mirror, a lens, and a reflecting mirror, and is configured to expose a surface of the photosensitive drum 54 by irradiating the surface with a laser beam based on image data inputted in the image forming apparatus 1 to expose the surface.
The photosensitive drum 54 is disposed adjacent to the developing roller 53. The surface of the photosensitive drum 54 is positively and uniformly charged by a charger, and then exposed by the exposure unit 56. Exposed areas on the surface of the photosensitive drum 54 are lower in electric potential than the other areas thereon, so that an electrostatic latent image is formed on the surface of the photosensitive drum 54 based on the image data. The electrostatic latent image on the surface of the photosensitive drum 54 is developed into a visible developer image with positively charged toner supplied from the developing roller 53.
The transfer roller 55 is disposed facing the photosensitive drum 54, and receives a negative transfer bias from a power source. While a sheet S is nipped at a transfer position between the transfer roller 55 and the photosensitive drum 54, the developer image on the photosensitive drum 54 is transferred to the sheet S due to the transfer bias.
The fixing unit 60 includes a heat roller 61 and a pressure roller 62. The heat roller 61 is configured to rotate by a drive force from the image forming apparatus 1, and is configured to be heated by a heater. The pressure roller 62 is disposed facing the heat roller 61 and is rotatable. The sheet S having the transferred developer image is conveyed to the fixing unit 60, in which the sheet S is nipped and conveyed by the heat roller 61 and the pressure roller 62, and thus the developer image is fixed onto the sheet S due to the heat.
The discharge unit 7 includes a discharge roller pair 71 configured to discharge the sheet S conveyed from the fixing unit 60 to the outside of the casing 2, specifically, to the sheet discharge tray 23A.
The sheet feeder 4 is disposed adjacent to the opening 2A of the casing 2 and configured to feed one or more sheets S on the MP tray 21 at the open position through the opening 2A of the casing 2 toward the image forming unit 5. The sheet feeder 4 includes a feed roller 41 to feed a sheet S, a separation roller 42 disposed downstream from the feed roller 41 in a conveyance direction in which a sheet S is conveyed, and a separation pad 43 disposed facing the separation roller 42. The feed roller 41, the separation roller 42, and the separation pad 43 are disposed substantially in the center of the casing 2 in the left-right direction corresponding to a width direction of a sheet S orthogonal to a sheet feed direction.
The sheet feeder 4 includes a sheet detector 9 to detect presence or absence of a sheet S on the MP tray 21. The sheet detector 9 includes a contact element 91 contactable with the sheet S on the MP tray 21. The sheet detector 9 is configured to detect the presence of the sheet S on the MP tray 21 when the contact element 91 contacts the sheet S. The casing 2 defines inside a sheet feed path P2, which is a part of the conveyance path P1, extending from the separation roller 42 to the registration roller pair 35.
The feed roller 41 is configured to feed a sheet S from the MP tray 21. The separation roller 42 and the separation pad 43 separate the sheet S from subsequent sheets S, so that the sheet S is singly conveyed toward the sheet feed path P2. The registration roller 35 is configured to further convey the sheet S conveyed along the sheet feed path P2 toward the image forming unit 5.
The sheet feeder 4 includes a sheet feed frame 25 located above the sheet feed path P2 and a guide frame 27 located below the sheet feed path P2. That is, the guide frame 27 is disposed below the sheet feed frame 25. The guide frame 27 includes an internal space. The feed roller 41, the separation roller 42, and the contact element 91 are held by the sheet feed frame 25. Leading ends of sheets S on the MP tray 21 contact the guide frame 27. A sheet S fed by the feed roller 41 is guided by the guide frame 27 and conveyed into the sheet feed path P2.
As illustrated in
Sheet Detector
As illustrated in
The contact element 91 is a tongue-shaped part extending downward from the sheet feed frame 25, and pivotably supported by the sheet feed frame 25. The contact element 91 is located upstream from the feed roller 41 in a sheet feed direction in which a sheet S is fed. As illustrated in
The photosensor 92 is located in the internal space of the guide frame 27 and includes a light emitter 921 for emitting light and a light receiver 922 for receiving light emitted from the light emitter 921. The light emitter 921 and the light receiver 922 are spaced from each other in the left-right direction.
The shield 93 is a plate-like member located in the internal space of the guide frame 27 and is movable, e.g., pivotable, between a light transmission position to allow transmission of light emitted from the light emitter 921 to the light receiver 922 and a light shield position to shield the light receiver 922 from light emitted from the light emitter 921.
The shield 93 at the light shield position is located between the light emitter 921 and the light receiver 922 to shield the light receiver 922 from light emitted from the light emitter 921. The photosensor 92 is configured to, when the light receiver 922 is shielded from the light emitted from the light emitter 921, detect that no sheets S are on the MP tray 21.
The shield 93 at the light transmission position is located away from a position between the light emitter 921 and the light receiver 922, thereby allowing the light receiver 922 to receive light emitted from the light emitter 921. The photosensor 92 is configured to, in response to that the light receiver 922 receives the light emitted from the light emitter 921, detect that a sheet S is on the MP tray 21.
The linkage 94 connects the contact element 91 and the shield 93 such that the shield 93 is movable, e.g., pivotable, in association with pivoting of the contact element 91. The linkage 94 includes a first extension 95, a second extension 96, and a connection 97.
The first extension 95 is a shaft extending from the contact element 91 toward one side in the left-right direction beyond the sheet feed range W. In this embodiment, the first extension 95 extends from the contact element 91 to the right. The first extension 95 is rotatably supported by the sheet feed frame 25. The contact element 91 is pivotable about the first extension 95.
The second extension 96 is a shaft extending from the shield 93 toward one side in the left-right direction beyond the sheet feed range W. In this embodiment, the second extension 96 extends from the shield 93 to the right. The second extension 96 is rotatably supported by the guide frame 27. The shield 93 is pivotable about the second extension 96. The first extension 95 is located upstream from the second extension 96 in the sheet feed direction and above the second extension 96 in an up-down direction.
The connection 97 connects the first extension 95 and the second extension 96 outside the sheet feed range W in the left-right direction. The connection 97 is located outside the sheet feed range W in the left-right direction, and thus may be prevented from interfering with a sheet S to be fed in the sheet feed range W. The connection 97 includes a first connection 971, a second connection 972, a boss 973, and a slide groove 974, which are all located outside of the sheet feed range W in the left-right direction.
The first connection 971 extends from the first extension 95 toward the second extension 96. The first connection 971 is pivotable about the first extension 95 as the contact element 91 pivots. The second connection 972 extends from the second extension 96 toward the first extension 95. The second connection 972 and the shield 93 are integrally pivotable about the second extension 96 integrally with the shield 93.
The boss 973 is located at the first connection 971 and protrudes from the first connection 971 to the right. The slide groove 974 is defined in the second connection 972 and receives the boss 973 slidably. The boss 973 located at the first connection 971 is engaged in the slide groove 974 defined in the second connection 972, thereby the first extension 95 communicating with the second extension 96.
The shield 93 is located downstream from the contact element 91 in the sheet feed direction. The boss 973 is located downstream from the contact element 91 in the sheet feed direction, more specifically, closer to the shield 93 than the contact element 91. The slide groove 974 is located upstream from the shield 93 in the sheet feed direction, more specifically, closer to the contact element 91 than the shield 93.
The contact element 91 pivots integrally with the first connection 971 as contacting with a sheet S on the MP tray 21, and the boss 973 pivots as the first connection 971 pivots. The boss 973 slides in the slide groove 974 while pivoting, thereby pivoting the second connection 972 which in turn pivots the shield 93.
In this embodiment, the boss 973 is located at the first connection 971 and the slide groove 974 is defined in the second connection 972. In some embodiments, the boss 973 may be located at the second connection 972 and the slide groove 974 may be defined in the first connection 971.
In the sheet detector 9 structured as above, when no sheets S are on the MP tray 21, that is, when the contact element 91 is in an initial state out of contact with any sheet S, as illustrated in
As illustrated in
As illustrated in
In the sheet detector 9, the photosensor 92 is located inside the guide frame 27, i.e., located in the internal space of the guide frame 27, which is disposed below the sheet feed frame 25. The guide frame 27 shields and prevents stray light from outside from entering the light receiver 922. This structure sufficiently reduces effects of light from outside the photosensor 92, and thus reduces false detection of a sheet S on the MP tray 21.
As the number of sheets S on the MP tray 21 changes from zero to one or more, the contact element 91 protruding downward pivots downstream in the sheet feed direction. The greater the number of sheets S on the MP tray 21, the greater the angle of the contact element 91 pivoting downward in the sheet feed direction. The shield 93 is configured to pivot to move from the light shield position to the light transmission position, as the linkage 94 communicates the pivoting movement of the contact element 91 to the shield 93.
In this embodiment, an angle of the contact element 91 relative to the vertical direction is represented by θ1, and an angle of the shield 93 relative to the vertical direction is represented by θ2 as shown in
The linkage 94 is configured to communicate movement of the contact element 91 to the shield 93 such that a pivoting amount of the shield 93 according to a pivoting amount of the contact element 91 is less when the number of sheets S on the MP tray 21 changes from one to two or more than when the number of sheets S on the MP tray 21 changes from zero to one.
As the number of sheets S on the MP tray 21 changes from zero to one, to enable the photosensor 92 to detect that a sheet S is on the MP tray 21, the shield 93 is preferably structured to have a relatively great amount of movement such that the shield 93 moves from the light shield position to the light transmission position.
In contrast, while the number of sheets on the MP tray 21 changes from one and reaches the maximum, the shield 93 moves slightly and is maintained at the light transmission position such that the movement of the shields 93 produces no significant effect on sheet detection. Because the moving amount of the shield 93 according to the pivoting amount of the contact element 91 is small, a small space is enough to allow the shield 93 moving inside the guide frame 27, thereby facilitating accommodation of the shield 93 inside the guide frame 27.
Thus, the moving amount of the shield 93 according to the pivoting amount of the contact element 91 is set to be great enough when the number of sheets S on the MP tray 21 changes from zero to one, and is set to be less while the number of sheets Son the MP tray 21 reaches the maximum from one than when the number of sheets S on the MP tray 21 changes from zero to one.
The connection 97 of the linkage 94 is structured so that the moving amount of the shield 93 according to the pivoting amount of the contact element 91 when the number of sheets S changes from one to two or more is less than when the number of sheets S on the MP tray 21 changes from zero to one.
Movement of Shield Corresponding to Pivoting of Contact Element
The first groove portion 974A extends in the sheet feed direction from a position of the boss 973 located when the contact element 91 is in the initial state out of contact with any sheet S, toward the shield 93. In other words, when the contact element 91 is in the initial state, the first groove portion 974A is elongated in the front-rear direction along the sheet feed direction.
The second groove portion 974B extends continuously from the first groove portion 974A diagonally downward relative to the sheet feed direction. When the contact element 91 is in the initial state, the second groove portion 974B is inclined relative to the horizontal direction and elongated diagonally downward to the rear.
The boss 973 is slidably engageable in the slide groove 974 having the first groove portion 974A and the second groove portion 974B, thereby moving the shield 93 in association with the pivoting of the contact element 91.
As illustrated in
When the contact element 91 is in the initial state, an inner peripheral surface of the first groove portion 974A and a moving direction of the boss 973 form an angle represented by θ3a. When the contact element 91 in the initial state starts pivoting, the second connection 972 having the slide groove 974 pivots upward about the second connection 96 and the shield 93 moves to the front.
As illustrated in
As the contact element 91 further pivots from the state illustrated in
In this state, the angle formed between the inner peripheral surface of the first groove portion 974a and the moving direction of the boss 973 is θ3C. In this case, the second connection 972 pivots upward about the second extension 96 by the pivoting of the contact element 91, and thus the shield 93 moves to the front. This allows the shield 93 to move, i.e., pivot, from the light shield position to the light transmission position.
The angles θ3A, θ3B, and θ3C 3 correspond to the angles θ1A, θ1B, and θ1C, respectively, and each of the angles θ3A, θ3B, and θ3C has a relatively great value.
As the contact element 91 further pivots from the state illustrated in
In this case, the second connection 972 pivots upward about the second extension 96 as the contact element 91 pivots, and thus the shield 93 moves to the front. The angle θ3D is less than any of the angles θ3A, θ3B, and θ3C, and the moving amount of the shield 93 according to the pivoting amount of the contact element 91 is less than when the angle θ1 is in the range of θ1A to θ1C.
As the contact element 91 further pivots from the state illustrated in
In this case, the second connection 972 pivots upward about the second extension 96 as the contact element 91 pivots, and thus the shield 93 moves to the front. When the angle θ1 is θ1E, the angle θ3E is less than any of the angles θ3A, θ3B, and θ3C, and the moving amount of the shield 93 according to the pivoting amount of the contact element 91 is less than when the angle θ1 is in the range of θ1A to θ1C.
As the contact element 91 further pivots from the state illustrated in
In this state, the angle formed between the inner peripheral surface of the first groove portion 974A and the moving direction of the boss 973 is θ3F. In this case, the second connection 972 pivots upward about the second extension 96 as the contact element 91 pivots, and thus the shield 93 moves to the front. When the angle θ1 is θ1F, the angle θ3F is less than any of the angles θ3A, θ3B, and θ3C, and the moving amount of the shield 93 according to the pivoting amount of the contact element 91 is less than when the angle θ1 is in the range of θ1A to θ1C.
Thus, in the sheet detector 9, each of the angles θ3D, θ3E, and θ3F between the inner peripheral surface of the first groove portion 974A and the moving direction of the boss 973 when the angle θ1 of the contact element 91 relative to the vertical direction is in a range of θ1D to θ1F, is less than any of the angles θ3A, θ3B, and θ3C when the angle θ1 is in a range of θ1A to θ1C.
Thus, the moving amount of the shield 93 according to the pivoting amount of the contact element 91 can be set smaller when the angle θ1 is in a range of θ1D to θ1F than when the angle θ1 is in a range of θ1A to θ1C.
In other words, the moving amount of the shield 93 corresponding to the pivoting amount of the contact element 91 can be determined by altering the shapes of the first groove portion 974A and the second groove portion 974B of the slide groove 974. This embodiment illustrates that the first groove portion 974A extends in the sheet feed direction from the position of the boss 973 located when the contact element 91 is in the initial state out of contact with any sheet S, toward the shield 93, and the second groove portion 974B extends continuously from the first groove portion 974A diagonally downward relative to the sheet feed direction.
This configuration enables adjustment of the moving amount of the shield 93 according to the pivoting amount of the contact element 91 such that the moving amount of the shield 93 of when the number of sheets S on the MP tray 21 changes from one to two or more is less than the moving amount of the shield 93 of when the number of sheets S on the MP tray 21 changes from zero to one. This facilitates accommodation of the shield 93 inside the guide frame 27.
The boss 973 is pivotable together with the contact element 91. The slide groove 974 is defined in the connection 97 integrally movable with the shield 93. Slidable engagement of the boss 973 in the slide groove 974 enables easy adjustment of the moving amount of the shield 93 according to the pivoting amount of the contact element 91.
The above embodiment illustrates that the shield 93 and the second connection 972 of the connection 97 are connected by the second extension 96 and are thus integrally movable, e.g., pivotable, about the second extension 96. In some embodiments, however, the shield 93 and the second connection 972 may be connected as follows.
Referring to
The insertion shaft portion 981a is located at a left end portion of the first shaft 981. The second connection 972 is fixed at a right end portion of the first shaft 981. The shield 93 is fixed at a left end portion of the second shaft 982. The first shaft 981 has a first engagement piece 981B protruding from its outer surface, and the second shaft 982 has a second engagement piece 982A protruding from its outer surface.
A coil spring 99 is wound around the first shaft 981 and located between the first engagement piece 981B and the second engagement piece 982A. The coil spring 99 has a first engagement portion 991 engaging with the first engagement piece 981b and a second engagement portion 992 engaging with the second engagement piece 982A.
The coil spring 99 urges the first shaft 981 and the second shaft 982 in their circumferential directions to increase an acute angle D formed between the first engagement piece 981b and the second engagement piece 982A as shown in
The coil spring 99 urges the second engagement piece 982A and the restriction piece 981C so as to contact with each other. When no external force acts on the shield 93, the first shaft 981 and the second shaft 982 are rotatable integrally.
As illustrated in
As the contact element 91 pivots from the initial state because some sheets are placed on the MP tray 21, the second connection 972 pivots about the first shaft 981 integrally with the first shaft 981, as illustrated in
As the contact element 91 further pivots while the shield 93 is at the light transmission position, the shield 93 also pivots and contacts an inner surface 27A of the guide frame 27, as illustrated in
In contrast, the contact element 91 and the first shaft 981 rotate against the urging force of the coil spring 99. The rotation of the contact element 91 and the first shaft 981 after the shield 93 and the second shaft 982 stop rotating causes the first engagement piece 981B to reach near the second engagement piece 982A in the circumferential direction, and reduces the angle D formed between the first engagement piece 981b and the second engagement piece 982A to be less than that illustrated in
The shield 93 stops moving during the pivoting of the contact element 91, thereby reducing the moving amount of the shield 93 according to the pivoting amount of the contact element 91. This also reduces the moving amount of the shield 93 in the guide frame 27, facilitating accommodation of the shield 93 inside the guide frame 27.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-158615 | Aug 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20080048138 | Miwa | Feb 2008 | A1 |
| 20180088513 | Wada | Mar 2018 | A1 |
| Number | Date | Country |
|---|---|---|
| S62-181543 | Nov 1987 | JP |
| S62-194645 | Dec 1987 | JP |
| H02-233434 | Sep 1990 | JP |
| H07-237778 | Sep 1995 | JP |
| 09124183 | May 1997 | JP |
| H10-109781 | Apr 1998 | JP |
| 2008-050109 | Mar 2008 | JP |
| 2018-052686 | Apr 2018 | JP |
| Entry |
|---|
| Japanese Office Action (with English translation) dated Mar. 7, 2023 (Application No. 2019-158615). |
| Number | Date | Country | |
|---|---|---|---|
| 20210061598 A1 | Mar 2021 | US |
