The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2013-106851 filed in Japan on May 21, 2013 and Japanese Patent Application No. 2014-045930 filed in Japan on Mar. 10, 2014.
1. Field of the Invention
The present invention relates to a sheet feed device including a sheet storage member to store multiple sheets and a unit to move the sheet storage member up and down, and relates to an image forming apparatus including the sheet feed device.
2. Description of the Related Art
In recent years, a large-capacity sheet feed tray capable of storing more than a thousand sheets may be provided in a sheet feed device installed in an image forming apparatus. In such a sheet feed device, a sheet feed member including a roller pair or the like feeds the sheets one by one in order from the topmost sheet to the image forming apparatus.
In this type of the sheet feed device, the sheet feed tray is drawn from the sheet feed device to supply or replace sheets. In this case, the sheet feed tray moves down to the lowermost position due to the weights of stacked sheets. Therefore, it becomes possible to easily supply or replace sheets.
In the sheet feed device configured as described above, if the sheet feed tray is drawn while a large number of sheets are left in the sheet feed tray, a bottom plate of the tray moves downward due to the weights of the sheets before the tray is drawn. Therefore, in some cases, the sheet feed tray may move downward rapidly. To prevent such a situation, there is a known sheet feed device including a buffer mechanism (damper) to prevent the bottom plate of the tray from moving downward rapidly when the sheet feed tray is drawn (see, for example, Japanese Laid-open Patent Publication No. 2008-184300 and Japanese Laid-open Patent Publication No. 6-156754). In the conventional sheet feed device as described above, a predetermined load torque is applied to the bottom plate of the sheet feed tray when the bottom plate moves downward.
In the conventional sheet feed device including the damper as the buffer mechanism, a value of a load resisting force of the damper may be set on the assumption that a small number of sheets are stacked. In this case, if a large number of sheets are stacked, the load resisting force of the damper is so weak that the bottom plate of the tray may move downward rapidly, resulting in noise, such as an impact sound, or damage in the apparatus. In contrast, the value of the load resisting force of the damper may be set on the assumption that a large number of sheets are stacked. In this case, the load resisting force of the damper strongly acts when a small number of sheets are stacked. Therefore, the bottom plate may not move down to the predetermined lowermost position, and a user may need to manually move the bottom plate downward to supply or replace sheets.
Incidentally, while a rotary damper is used as the buffer mechanism in the technologies disclosed in Japanese Laid-open Patent Publication No. 2008-184300 and Japanese Laid-open Patent Publication No. 6-156754, there is also a known structure, in which a direct acting damper including a piston rod/cylinder is directly arranged in an upright manner in the sheet feed tray. Even in this case, the bottom plate may move downward by its own weight when a small number of sheets are stacked. In contrast, when a large number of sheets are stacked, it is possible to prevent the bottom plate from moving downward rapidly by applying a load resisting force to the bottom plate by the direct acting damper.
However, to directly arrange the direct acting damper in an upright manner in the sheet feed tray, it is necessary to increase a buffer stroke. Therefore, it becomes necessary to use a long-shaped damper, and a large space is needed inside the sheet feed tray.
In view of the above circumstances, there is a need to provide a sheet feed device capable of preventing a bottom plate of a tray for stacking multiple sheets from moving downward rapidly at low costs, and to provide an image forming apparatus including the sheet feed device.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to the present invention, there is provided a sheet feed device comprising: a sheet feed tray configured to be enabled to be drawn from a main body of an image forming apparatus; a bottom plate arranged in the sheet feed tray and configured to stack thereon a plurality of sheets; a driving unit configured to move the bottom plate upward; a drive transmitting unit configured to transmit a driving force from a drive source arranged on the main body to the driving unit; and a one-way rotation transmitting unit configured to unidirectionally transmit input from the drive transmitting unit to the driving unit and configured to be arranged on one side of the drive transmitting unit opposite to a side connected to the driving unit.
The present invention also provides an image forming apparatus comprising a sheet feed device, wherein the sheet feed device comprises: a sheet feed tray configured to be enabled to be drawn from a main body of an image forming apparatus; a bottom plate arranged in the sheet feed tray and configured to stack thereon a plurality of sheets; a driving unit configured to move the bottom plate upward; a drive transmitting unit configured to transmit a driving force from a drive source arranged on the main body to the driving unit; and a one-way rotation transmitting unit configured to unidirectionally transmit input from the drive transmitting unit to the driving unit and configured to be arranged on one side of the drive transmitting unit opposite to a side connected to the driving unit.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
In an embodiment of the present invention, a one-way clutch is not left on a driving unit that is left on a main body of an image forming apparatus when a sheet feed tray is detached. The clutch is detached from the image forming apparatus together with the sheet feed tray. The clutch is provided on a shaft connecting an output side of a gear train, which is arranged on the sheet feed tray to be detached from the main body of the image forming apparatus, and an elevation pulley. The clutch is arranged on an opposite side of a side connected to a drive source of the image forming apparatus. With this configuration, it becomes possible to prevent reverse winding of the elevation pulleys when the gear train of the sheet feed tray continuously rotates by an inertial force.
An embodiment of the present invention will be explained below with reference to drawings.
The sheet feed device 3 will be explained below with reference to
The drive transmitting unit 9 according to the present embodiment includes, as illustrated in the drawing, multiple gears 9a to 9f, an idler gear 9g, and multiple rotary shafts 91 and 92. The drive transmitting unit may include an input shaft 12a extending from the motor 12 on which the gear 9a is mounted and may include the drive shaft 8. Incidentally, the drive shaft 8 also serves as an output shaft of the one-way clutch 10, and the gear 9f in the last stage among the gears 9a to 9f and the one-way clutch 10 are mounted on the same shaft. Furthermore, a braking unit 14 includes a rotary damper, although details are not illustrated in the drawing. Moreover, each of the gears 9a to 9f is fixed on a side plate or a shaft of the sheet feed tray 4. The gear 9f is fixed on the drive shaft 8.
Furthermore, a remaining amount detection sensor 15 and a filler 16 are provided to detect a remaining amount of sheets on the sheet feed tray 4. The remaining amount detection sensor 15 is fixed to the main body 2 of the image forming apparatus (or the sheet feed tray 4), and the filler 16 is attached to the input shaft 12a extending from the motor 12 in a rotatable manner.
The one-way clutch 10 allows relative rotation of the gear 9f and the drive shaft 8 in the direction of an arrow R1, and restricts relative rotation in the direction of an arrow R2. Therefore, the following operations (1) to (3) are performed when the bottom plate 5 moves up and down. This will be explained below with reference to
(1) When the bottom plate 5 moves upward, the gears 9a to 9f start rotating in the directions of arrows illustrated in
(2) A state illustrated in
(3) After the bottom plate 5 moves down to the lower limit position inside the sheet feed tray 4 as illustrated in
As for the remaining amount of sheets, the remaining amount detection sensor 15 detects the amount of elevation of the bottom plate 5 based on the rotation speed of the filler 16, and indirectly calculates the remaining amount of sheets based on the amount of elevation of the bottom plate 5. A value of the remaining amount of sheets detected by the remaining amount detection sensor 15 as described above is displayed, as a remaining amount display, on a display panel of an operating unit of the image forming apparatus for example. It may be possible to change the output of air for separating the topmost sheet from other sheets or change the elevation amount of the bottom plate 5, depending on the value of the remaining amount of sheets.
The idler gear 9g engages with a gear (not illustrated) mounted on the rotary shaft 91 behind the gear 9b and with the rotary damper of the braking unit 14. A predetermined braking force (torque) is applied to the rotary damper such that the braking force slightly increases with an increase in the acceleration of the bottom plate 5 when the bottom plate 5 moves downward.
Furthermore, numerals 1.0, 2.0, 2.4, 4.0, 4.0, and 5.3 in a field “reduction ratio” indicate reduction ratios of the gears identified by the numbers (1 to 6) in the first row, respectively. As for the reduction ratio of the gear train, the reduction ratios of the first gear 9a to the sixth gear 9f are 1.0, 2.0, 2.4, 4.0, 4.0, and 5.3, respectively, and the reduction ratio of the gear train is obtained such that 5.3/1.0=5.3.
In the state illustrated in
Specifically, the wire 6 includes two wires 6a and 6b. As illustrated in
The operation in the states illustrated in
(1) When the sheet feed tray 4 is drawn from the main body 2, engagement between the not-illustrated driving coupling 13a arranged on the main body 2 of the image forming apparatus and the not-illustrated driven coupling 13b arranged on the sheet feed tray 4 is released.
(2) Accordingly, the bottom plate 5 starts moving downward by its own weight (the state in
(3) The bottom plate 5 moves downward rapidly at a predetermined speed (a predetermined speed by the action of the braking unit 14) by inertia of the downward movement. In this case, the bottom plate may move downward so rapidly that it may hit against the bottom surface of the sheet feed tray 4 (the lower limit position of the bottom plate 5 moving downward) (
(4) The gears 9a to 9d continue to rotate in a downward direction by inertia (the directions of the arrows indicating rotation in
(5) The bottom plate 5 stops at the lower limit position of the sheet feed tray 4, so that the rotation of the drive shaft 8 is stopped.
(6) Even though the drive shaft 8 is stopped, the gears 9a to 9d continue to rotate. Therefore, the drive shaft 8 continues to rotate in the direction of the arrow illustrated in
(7) If the drive shaft 8 rotates, the elevation pulleys 7 rotates in the direction of the arrow illustrated in
(8) Furthermore, if the elevation pulleys 7 further continues to rotate in the direction of arrow in
Specifically, in the conventional sheet feed tray 4, when the sheet feed tray 4 is drawn after the bottom plate 5 has moved up, the bottom plate 5 may move downward rapidly by its own weight or the weights of sheets, and, after the bottom plate 5 reaches the lowermost position, the gears 9a to 9f continue to rotate by the inertial force of the downward movement. Therefore, the drive shaft 8 rotates so as to wind up the wire 6 in a reverse direction, and an extra load is applied to the elevation pulleys 7 and the wire 6, resulting in damage.
To cope with this, in the sheet feed tray 4 according to the present embodiment, the drive shaft 8 is connected to the gear 9f via the one-way clutch 10 as described above. Therefore, after the bottom plate 5 reaches and stops at the lowermost position, the inertial force of the gear train 9 is used to cause the one-way clutch 10 to spin around. Therefore, it becomes possible to prevent the elevation pulleys 7 and the wire 6 from being damaged.
The gear train 9 is configured to transmit, to the drive shaft 8, a force to decelerate the rotation speed of the drive source 11 to move the sheet feed tray 5 up and down as described above. The gear train 9 includes a combination of gears with the reduction ratios of 5 or greater. Specifically, the reduction ratio is set to be equal to or grater than a value such that the output of the drive source 11 becomes five times greater than the output of the drive shaft 8.
When the sheet feed tray 4 is drawn after the bottom plate 5 has moved upward, the bottom plate 5 moves downward rapidly by its own weight or the weights of sheets. The force for downward movement needs an inertial force that causes the gears of the gear train 9 to move. The inertial force prevents the bottom plate 5 from moving downward rapidly. If the reduction ratio is set to 5 or greater, the rotation speed of each of the gears of the gear train 9 is increased by the reduction ratio when the bottom plate 5 rapidly moves downward, so that each of the gears rotates at the increased speed and the inertial force serving as the braking force increases proportionally. Therefore, it becomes possible to prevent an impact sound and damage of the bottom plate due to the rapid downward movement of the bottom plate 5.
In the embodiments as described above, examples have been explained in which the rotary damper is used as the braking unit 14. However, other devices or elements, such as torque limiters, may be used. If the braking unit 14 is provided in the gear train 9 as in the configuration as described above, the braking unit 14 only receives a force of a reduced torque due to the increased speed of the gear train. Therefore, it becomes possible to reduce a torque needed for the braking member. As a result, it becomes possible to employ the braking unit 14 at low costs, enabling to reduce overall costs.
The sheet feed device of the above embodiments can be configured at low costs. Therefore, an image forming apparatus including the sheet feed device can prevent the bottom plate with a large number of stacked sheets from rapidly moving downward. Furthermore, the image forming apparatus can be provided at low costs.
The present invention is not limited to the embodiments as described above, and may be embodied in various forms by person skilled in the art within the scope of technical ideas of the present invention.
According to an embodiment of the present invention, it becomes possible to prevent a bottom plate for stacking multiple sheets from rapidly moving downward and prevent related components for moving the bottom plate up and down from being damaged, at low costs. Therefore, it becomes possible to provide a sheet feed device and an image forming apparatus including the sheet device at low costs.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
Number | Date | Country | Kind |
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2013-106851 | May 2013 | JP | national |
2014-045930 | Mar 2014 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
3730516 | Debray | May 1973 | A |
4033578 | Taylor | Jul 1977 | A |
5794928 | Araseki et al. | Aug 1998 | A |
20100038846 | Baena et al. | Feb 2010 | A1 |
20110148027 | Fuda | Jun 2011 | A1 |
20110187042 | Fuda | Aug 2011 | A1 |
20110193284 | Fuda | Aug 2011 | A1 |
20110221119 | Fuda | Sep 2011 | A1 |
Number | Date | Country |
---|---|---|
4-23742 | Jan 1992 | JP |
06-156754 | Jun 1994 | JP |
8-58989 | Mar 1996 | JP |
2000-247454 | Sep 2000 | JP |
4827753 | Sep 2011 | JP |
Number | Date | Country | |
---|---|---|---|
20140346728 A1 | Nov 2014 | US |