Sheet feeding or delivering – Delivering – To receiver for pack of sheets
Reexamination Certificate
2000-07-20
2001-11-20
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Delivering
To receiver for pack of sheets
C271S214000, C271S217000
Reexamination Certificate
active
06318718
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet stacking device capable of staking a great many sheets.
2. Related Background Art
Conventionally, a sheet stacking device connected to, or accompanying an image forming apparatus such as a copying machine or the like has needed a spacing for stacking sheets between a sheet ejecting port to the sheet stacking device and a stacking tray, which is set equal to or larger than a thickness of a bundle of sheets to be stacked.
In the case of the sheet stacking device capable of stacking a great many sheets, a large spacing needs to be formed from the sheet ejecting port to the stacking tray in order to secure a stacking capacity.
However, if there is a long distance from the sheet ejecting port to an actual sheet stacking position, the sheets fall by a long distance to the tray after ejection, resulting in the difficulty of maintaining high stacking alignment.
Thus, the stacking tray of such a sheet stacking device includes a mechanism moved up and down according to a stacking quantity.
Specifically, the stacking tray is located in an upper position when a stacking quantity is small, and a distance from the sheet ejecting port is set short. Then, by lowering the stacking tray as a sheet staking quantity is increased, control is performed such that a distance from the sheet ejecting port to a position for stacking sheets on the stacking tray can be substantially constant.
However, since the weight of the stacking tray is heavy while a great many sheets are stacked thereon, a great force needs to be provided for lifting/lowering the tray.
Accordingly, it is necessary to increase an output by using a large motor or torque by reducing an elevating speed.
If the large motor is used, the stacking tray can be lifted/lowered at a relatively high speed even when the number of sheets to be stacked is large. Compared with the case of using a small motor, however, motor costs, installation space, power consumption, and so on, are larger. Thus, it is difficult to provide an inexpensive and compact device.
If an elevating speed is reduced by using the small motor, moving time becomes very long, for example when the stacking tray in a lowest position is moved to a highest position, and the sheets cannot be fed to the stacking device during such a period. Consequently, work efficiency falls.
SUMMARY OF THE INVENTION
The present invention was made to solve the foregoing problems, and it is an object of the invention to provide a sheet stacking device capable of preventing a reduction in the work efficiency of a sheet stacking operation even if a small output motor is employed.
In order to achieve the above-described object, in accordance with an aspect of the invention, there is provided a sheet stacking device, comprising: stacking means for sacking and containing sheets; and lifting and lowering means for moving the stacking means up and down.
In this case, the lifting and lowering means includes driving force converting means for changing the distance of moving the stacking means as an input and output ratio with respect to a predetermined driving force entered from a driving source, and changing the elevating speed of the stacking means according to the input and output ratio.
Preferably, the driving force converting means may include a suspension member for suspending the sacking means, and a winding member having a conical winding portion for winding the suspension member, and lift/lower the stacking means by rotating the winding member. Then, the elevating speed of the stacking means is changed according to the winding length of the suspension member, which is changed depending on the diameter difference of the winding portion.
Preferably, the winding member may wind the suspension member by the small diameter side of the winding portion when the stacking means is located in a lower side, and wind the same by the large diameter side of the winding portion when the stacking means is located in an upper side.
Preferably, the driving force converting means may include a supporting member for supporting the stacking means by a spiral and pitch-changed cam face, and lift/lower the stacking means by rotating the supporting member. Then, the elevating speed of the stacking means may be changed according to the pitch length of the cam face of the supporting member.
Preferably, for the cam face of the supporting member, the pitch length of an abutting portion may be set small when the stacking means is located in a lower side, and large when the stacking means is located in an upper side.
Preferably, the driving force converting means may include a speed changing mechanism for changing and converting the rotation ratio of a rotary-driving force from the driving source, position detecting means for detecting the elevating position of the stacking means, and control means for controlling the speed changing mechanism according to the detected elevating position of the stacking means.
Preferably, the driving force converting means may include a speed changing mechanism for changing and converting the rotation ratio of a rotary-driving force from the driving source, sheet stacking amount detecting means for detecting the amount of sheets stacked on the stacking means, and control means for controlling the speed changing mechanism according to the detected sheet stacking amount.
Preferably, the driving force converting means may reduce a torque necessary for a rotary-driving force from the driving source by lifting/lowering the stacking means at a speed lower when a staking amount is large than a speed when a stacking amount is small, according to the amount of sheets stacked on the sheet stacking means.
In accordance with another aspect of the invention, there is provided an image forming apparatus, comprising: image forming means for forming an image on a sheet; and the sheet stacking device described above, wherein an image is formed by the image forming means, and an ejected sheet is stacked.
According to the above-described invention, a driving force necessary for the lifting/lowering operation of the sheet stacking means can be reduced without any reductions in the work efficiency of a sheet stacking operation. Thus, it is possible to employ a small output driving source, and to reduce the size of the driving source and the consumption of power.
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Araki Tomoyuki
Fukatsu Masayoshi
Hayakawa Yasuyoshi
Ogata Atsushi
Waragai Tsuyoshi
Bollinger David H.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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