This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Applications Nos. 2013-269286 and 2014-92414 filed on Dec. 26, 2013 and Apr. 28, 2014 respectively, the entire contents of both of which are incorporated herein by reference.
The present disclosure relates to a unit retraction device for retracting into an apparatus body a unit that is extractably and insertably loaded in the apparatus body, and to an image forming apparatus, such as a copier, printer, or facsimile machine, provided with such a unit retraction device.
Conventionally, an image forming apparatus such as a copier, printer, or facsimile machine is, in a bottom part of its apparatus body, provided with a paper feed cassette for accommodating a plurality of sheets of paper (recording medium) in such a way that the paper feed cassette is extractable out of the apparatus body. By a feeding means, comprising a pickup roller or the like, arranged over the paper feed cassette and by a separating/transporting means, comprising a paper feed roller pair or the like, the paper accommodated in the paper feed cassette is fed out one sheet after another so as to be transported to an image formation section and on to a fusing device, so that an image is formed on the paper.
In an image forming apparatus as mentioned above, the paper feed cassette is loaded into and unloaded out of the apparatus body manually by a user on occasions of paper replenishment and paper size change. On such occasions, the paper feed cassette may not be completely inserted into a predetermined position (loaded position) inside the apparatus body. In that case, the paper feed cassette is positioned improperly, leading to an image being formed off the center of the paper in its width direction, or to transport failure.
Moreover, the paper feed cassette along with the paper accommodated in it may turn out to be so heavy that the user finds difficulty inserting the paper feed cassette into the loaded position. For easier handling of the paper feed cassette, there have been proposed various retraction devices for retracting the paper feed cassette into the loaded position inside the apparatus body.
For example, in one known retraction device, when the paper feed cassette has been loaded up to a predetermined position, engagement by an engaging portion of the retraction device is released so that a retraction force is discontinued. In another known retraction device, a force storing means is provided which, after engaging with a sheet accommodating means, gradually stores a retraction force as the sheet accommodating means moves in the loading direction, wherein retraction into the loaded position is achieved by releasing the retraction force in the force storing means before or after the retraction force by a retracting means becomes maximal.
A known image forming apparatus is provided with a retraction force generating means comprising a plurality of biasing members which generate biasing forces in different biasing directions and a plurality of rotary members for generating a retraction force from the biasing forces of those biasing members. Yet another retraction device is provided with a restricting member which suppresses increase in retraction speed by generating a load commensurate with the retraction speed with which a paper feed tray is retracted. This retraction device can suppress increase in the retraction speed of the paper feed tray, and can thereby suppress impact during loading of the paper feed tray.
According to one aspect of the present disclosure, a unit retraction device is provided with a hook member and a retraction force generating mechanism, and retracts into a retraction completion position inside an apparatus body a unit that is insertably or extractably loaded in the apparatus body. The hook member engages with an engaged portion provided on the unit. The retraction force generating mechanism exerts a retraction force on the unit when the hook member engages with the engaged portion in a retraction start position of the unit. The retraction force generating mechanism includes a first rotary member which is rotatably disposed on a first rotation pivot and to a rotating end part of which the hook member is coupled, a biasing member of which one end is hooked to the first rotary member and which biases the first rotary member in such a direction that the hook member retracts the unit into the apparatus body, and a second rotary member to which the other end of the biasing member is hooked and which is rotatably disposed on a second rotation pivot. The second rotary member rotates in the same direction as the first rotary member as the first rotary member rotates under the biasing force of the biasing member.
Further features and advantages of the present disclosure will become apparent from the description of embodiments given below.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Hereinafter, with reference to the accompanying drawings, embodiments of the present disclosure will be described.
In the image formation section P, there are arranged, along the rotation direction of a photosensitive drum 1 (in the counter-clockwise direction in
The photosensitive drum 1 has, for example, a photosensitive layer laid on the surface of an aluminum drum, and its surface is electrically charged by the charging device 2. The surface is then irradiated with a laser beam from the exposure unit 3, which will be described later, to form an electrostatic latent image through attenuation of electrical charge. While there is no particular restriction on the material of the above-mentioned photosensitive layer, it is particularly preferable to use, among others, amorphous silicon (a-Si), which excels in durability, or an organic photoconductor (OPC) layer, which generates little ozone and yields a high-resolution image.
The charging device 2 electrically charges the surface of the photosensitive drum 1 uniformly. Used as the charging device 2 is, for example, a corona discharger which achieves electrical discharge by applying a high voltage to an electrode comprising a thin piece of wire or the like. Instead of a corona discharger, a contact-type discharger can be used which applies a voltage to the photosensitive surface with a charging member, as exemplified by a charging roller, kept in contact with it. The exposure unit 3 shines, based on original image data read by an image reading section 21, a light beam (for example, laser beam) on the photosensitive drum 1 to form an electrostatic latent image on its surface.
The developing device 4 makes toner attach to the electrostatic latent image on the photosensitive drum 1 to form a toner image. The developing device 4 is supplied with toner from a toner container 5 via an intermediary hopper 6. Here, one-component developer (hereinafter also referred to simply as toner) composed of a magnetic toner component alone is contained in the developing device 4.
The transfer roller 7 transfers, without disturbing, the toner image formed on the surface of the photosensitive drum 1 to paper that comes transported through a paper transport passage 11. The cleaning device 8 includes a cleaning roller or cleaning blade that makes line contact with the photosensitive drum 1 in its longitudinal direction, and removes residual toner, that is, the toner that remains on the surface of the photosensitive drum 1 after transfer of the toner image to the paper.
The image reading section 21 is composed of a scanning optical system, which includes a scanner lamp for illuminating a document during copying and a mirror for deflecting the light from the document; a condenser lens for condensing and focusing the light reflected from the document; and a CCD sensor for converting the focused image light into an electrical signal (none is illustrated) or the like. The image reading section 21 reads a document image and converts it into image data.
During copying, the image reading section 21 reads the image data of a document and converts it into an image signal. On the other hand, in the image formation section P, while the photosensitive drum 1 is rotated in the counter-clockwise direction in
Toward the image formation section P where the toner image has thus been formed, paper 18 is fed out of a paper feed cassette 10 by a paper feed unit 12, so that the paper is transported to the image formation section P with predetermined timing through the paper transport passage 11 and via a registration roller pair 13. Then, in the image formation section P, the toner image on the surface of the photosensitive drum 1 is transferred to the paper 18 by the transfer roller 7. The paper 18 having the toner image transferred to it is separated from the photosensitive drum 1, and is transported to a fusing device 9, where the toner image is fused to the paper 18 under heat and pressure.
The paper 18 having passed through the fusing device 9 has its transport direction switched by a bifurcating portion 16 between two directions. When an image is formed on only one side of the paper 18, the paper 18 is discharged onto a discharge tray 15 by a discharge roller pair 14.
On the other hand, when images are formed on both sides of the paper 18 respectively, the paper 18 having passed through the fusing device 9 is first transported toward the discharge roller pair 14, and then, after the tail end of the paper 18 has passed by the bifurcating portion 16, the discharge roller pair 14 is rotated in the reverse direction and the bifurcating portion 16 so switches the transport direction as to feed the paper 18, from its tail end, into a reversing transport passage 17, so that the paper 18, with the image side reversed, is transported once again to the registration roller pair 13. The next image formed on the photosensitive drum 1 is then transferred by the transfer roller 7 to the side of the paper 18 where no image has been formed yet. The paper 18 is then transported to the fusing device 9, where the toner image is fused, and is then discharged onto the discharge tray 15.
As shown in
At the front face of a housing 100a, a front cover 24 is provided in an openable/closable fashion. Opening the front cover 24 allows maintenance and replacement of members inside the housing 100a.
As shown in
A paper stack plate 28, on which paper 18 (see
Since paper is fed out in the direction indicated by arrow B toward the paper transport passage 11 (see
The walls 25a and 25b parallel to the insertion and extraction direction of the paper feed cassette 10 (the direction indicated by arrows A and A′) are, on their respective outer faces, fitted with guide rails 40a and 40b. In the body (housing 100a) of the image forming apparatus 100, support portions (unillustrated) are provided which slidably support the guide rails 40a and 40b. Sliding the guide rails 40a and 40b along the support portions permits the paper feed cassette 10 to be inserted into and extracted out of the housing 100a.
Next, a description will be given of a unit retraction device 50 for assisting insertion of the paper feed cassette 10.
As shown in
On the bottom face of the housing 51, a guide groove 51a is formed along the insertion and extraction direction of the paper feed cassette 10 (the direction indicated by arrows A and A′ in
The first and second gears 53 and 55 are each a fan-shaped gear rotatably supported on the bottom face of the housing 51 at a first or a second rotation pivot 53a or 55a respectively. The idle gear 57 meshes with both the second gear 55 and the first gear 53, and thereby permits the second gear 55 and the first gear 53 to rotate in the same direction.
The first gear 53 is meshed with a small-diameter portion of the double gear 59, and the rotary damper 60 is meshed with a large-diameter portion of the double gear 59. The rotary damper 60 generates a large load (attenuating force) when rotated at high speed, and generates a small load when rotated at low speed. The load is transmitted, as a braking force, to the double gear 59.
The double gear 59 is a one-way gear which can transmit a rotation driving force in one direction only. The small- and large-diameter portions of the double gear 59 are coupled together via a one-way mechanism, and the one-way mechanism achieves meshing in one direction only. Thus, only rotation in one direction is transmitted between the first gear 53 and the double gear 59 to permit the first gear 53 and the double gear 59 to rotate in synchronism. The one-way mechanism comprises, for example, a one-way clutch, a latch, or a ratchet.
Specifically, when the paper feed cassette 10 is retracted into the image forming apparatus 100, the first gear 53 rotates in the counter-clockwise direction in
To the first gear 53, an arm member 61 is fixed. The arm member 61 is rotatable along with the first gear 53 about its rotation pivot, that is, the first rotation pivot 53a. To the rotating end of the arm member 61, a hook member 63 is coupled which is rotatable about a rotation pivot 61b relative to the arm member 61.
On the hook member 63, there are formed a first engagement groove 63a which is used in ordinary retraction operation; a second engagement groove 63b which is used in recovery operation from a state where the unit retraction device 50 is in a completely retracted state without achieving engagement with the engagement projection 80 of the paper feed cassette 10; and a locking portion 63c which engages with a claw portion 65a of the damper holder 65 to restrict movement of the hook member 63 thereby to restrict rotation of the arm member 61.
The arm member 61 has an engagement hole 61a, with which one end of a tension spring 70 is engaged, and the other end of the tension spring 70 is engaged with a boss portion 55b on the second gear 55. Thus, the arm member 61 is biased in the counter-clockwise direction about the first rotation pivot 53a by the tension spring 70.
Next, with reference to
When the paper feed cassette 10 is inserted into the body of the image forming apparatus 100 over a predetermined distance, as shown in
The biasing force F acting from the tension spring 70 to the engagement hole 61a of the arm member 61 can be split into a component force F1 that acts in the direction tangential to the rotation orbit O (indicated by a broken-line arc in the figure) of the engagement hole 61a and a component force F2 that acts from the engagement hole 61a to the rotation pivot (first rotation pivot 53a) of the arm member 61. The component force F1 is a rotation moment that makes the arm member 61 rotate, and acts as a force for retracting the paper feed cassette 10. In the state shown in
As the paper feed cassette 10 is retracted further from the state shown in
Meanwhile, the second gear 55, which is meshed with the first gear 53 via the idle gear 57, also rotates in the counter-clockwise direction about the second rotation pivot 55a. That is, the boss portion 55b, to which the other end of the tension spring 70 is hooked, rotates in the same direction as the engagement hole 61a, to which the one end of the tension spring 70 is hooked.
Specifically, as the arm member 61 rotates, one end of the tension spring 70 (the engagement hole 61a) rotates in the direction in which it approaches the other end of the tension spring 70 (the boss portion 55b), and the tension spring 70 contracts. Thus, the biasing force F becomes smaller. Meanwhile, however, also the boss portion 55b rotates in the direction away from the engagement hole 61a, and thereby reduces attenuation of the biasing force F resulting from contraction of the tension spring 70. Thus, the biasing force F only becomes slightly smaller than in
As the paper feed cassette 10 is retracted further from the state shown in
When the engagement projection 80 moves up to the end point of the guide groove 51 a as shown in
During the retraction operation of the paper feed cassette 10, the load (torque) from the rotary damper 60 acts on the first gear 53 via the double gear 59. For example, when the amount of paper accommodated in the paper feed cassette 10 is small, and thus the load of retracting the paper feed cassette 10 is small and the speed of retraction by the component force F1 is high, the rotary damper 60 exerts a large torque, reducing the retraction speed of the paper feed cassette 10. By contrast, when the amount of paper accommodated in the paper feed cassette 10 is large, and thus the load of retracting the paper feed cassette 10 is large, the rotary damper 60 exerts a small torque to prevent failure of retraction of the paper feed cassette 10 by the component force F1.
On the other hand, when the paper feed cassette 10 is extracted from the state shown in
When the paper feed cassette 10 is extracted out of the image forming apparatus 100, the double gear 59, which is a one-way gear, interrupts transmission of a rotation driving force between the first gear 53 and the double gear 59, and thus the load of the rotary damper 60 is not transmitted to the first gear 53 and the arm member 61. Thus, the paper feed cassette 10 can be extracted smoothly without being affected by the load from the rotary damper 60.
If, before insertion of the paper feed cassette 10, some external force causes the locking portion 63c to disengage from the claw portion 65a, then, as shown in
Specifically, when, in the state shown in
In the unit retraction device 50 according to this embodiment, the arm member 61 (and the first gear 53) to which one end of the tension spring 70 is hooked and the second gear 55 to which the other end of the tension spring 70 is hooked rotate in the same direction, and this reduces attenuation of the biasing force F of the tension spring 70 resulting from rotation of the arm member 61. Thus, it is possible to secure a predetermined or larger retracting force throughout the period from the start to the completion of retraction of the paper feed cassette 10, and thus to perform retraction operation smoothly.
Moreover, even after completion of retraction, a predetermined biasing force remains acting on the hook member 63. Thus, the engagement projection 80 can be reliably kept at the end point of the guide groove 51 a. As a result, the paper feed cassette 10 can be stably kept loaded in the ready-to-feed-paper position inside the image forming apparatus 100.
Moreover, throughout the period from the start to the completion of retraction of the paper feed cassette 10, the rotation moment (component force F1), which makes the arm member 61 rotate, continues increasing. This, combined with the effect of reducing attenuation of the biasing force F achieved by rotation of the first and second gears 53 and 55 in the same direction, amplifies the force for retracting the paper feed cassette 10.
Moreover, coupling the first gear 53, to which the arm member 61 is fixed, with the rotary damper 60 permits the paper feed cassette 10 to be retracted into the image forming apparatus 100 at constant speed irrespective of the amount of paper accommodated inside the paper feed cassette 10.
The structure of other parts of the unit retraction device 50 and the retraction operation of the paper feed cassette 10 by the unit retraction device 50 are similar to those in the first embodiment, that is, as shown in
In this embodiment, as shown in
Moreover, as shown in
On the top face of the first gear 53 (the face opposite the large-diameter portion 59b), a projection portion 54 is provided which is tapered in a large-diameter portion 59b side part. The projection portion 54 intervenes between the first gear 53 and the large-diameter portion 59b as shown in
In the structure according to this embodiment, as described above, there is provided a rotary damper 60 which, when a retraction force generating mechanism (the first gear 53, second gear 55, arm member 61, tension spring 70, etc.) retracts the paper feed cassette 10 inward into the body of the image forming apparatus 100, generates a load commensurate with the retraction speed thereby to suppress increase in the retraction speed. Thus, it is possible to suppress increase in the retraction speed of the paper feed cassette 10, and thus to reduce impact during loading of the paper feed cassette 10.
Providing the retraction force generating mechanism which applies a retraction force to the hook member 63 helps suppress the load on the user during loading of the paper feed cassette 10.
The first gear 53 is provided with the projection portion 54, and immediately before the paper feed cassette 10 reaches the retraction completion position, the projection portion 54 intervenes between the first gear 53 and the large-diameter portion 59b and makes the large-diameter portion 59b retract from the first position to the second position, where it does not mesh with the small-diameter portion 59a. Thus, immediately before the paper feed cassette 10 reaches the retraction completion position during loading of the paper feed cassette 10, the load on the paper feed cassette 10 from the rotary damper 60 discontinues. Thus, it is possible to prevent the retraction force from becoming, before the paper feed cassette 10 reaches the retraction completion position, so low that retraction is halted, and thus to reliably retract the paper feed cassette 10 into the retraction completion position.
The double gear 59 has a ratchet mechanism so that, only when the paper feed cassette 10 is retracted into the body of the image forming apparatus 100, as the small-diameter portion 59a rotates, the large-diameter portion 59b rotates together. Thus, when the paper feed cassette 10 is extracted out of the image forming apparatus 100, the ratchet mechanism interrupts transmission of the rotation driving force between the first gear 53 and the double gear 59, and thus the load from the rotary damper 60 is not transmitted from the double gear 59 to the first gear 53. It is thus possible to smoothly extract the paper feed cassette 10 without being affected by the load from the rotary damper 60.
Although in this embodiment the projection portion 54 is provided on the first gear 53, the projection portion 54 can instead be provided on the large-diameter portion 59b of the double gear 59.
The embodiments described above are in no way meant to limit the present disclosure, and many modifications and variations are possible within the spirit of the present disclosure. For example, although the embodiments described above deal with structures where the first gear 53 to which the arm member 61 is fixed to which one end of the tension spring 70 is hooked is coupled via the idle gear 57 with the second gear 55 on which the boss portion 55b is provided to which the other end of the tension spring 70 is hooked, and the first and second gears 53 and 55 rotate in the same direction, the idle gear 57 can be replaced with a linking mechanism that makes the first and second gears 53 and 55 rotate simultaneously in the same direction.
Although the embodiments described above deal with a unit retraction device 50 for retracting a paper feed cassette 10 into the body of an image forming apparatus 100, application is possible not only to a paper feed cassette 10 but equally, in cases where a developing device 4 or a fusing device 9 is insertably or extractably loaded in the body of an image forming apparatus 100, as a retraction device for such a unit.
The present disclosure is applicable not only to monochrome multifunction peripherals like the one shown in
The present disclosure is applicable to a retraction device for retracting into an apparatus body a unit that is retractably and insertably loaded in the apparatus body. Based on the present disclosure, it is possible to provide, with a simple structure, a unit retraction device that can reliably retract a unit into a predetermined position inside an apparatus body without an undue load on the user.
Number | Date | Country | Kind |
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2013-269286 | Dec 2013 | JP | national |
2014-092414 | Apr 2014 | JP | national |