Sheet supplying apparatus, image forming apparatus

It is an object of the present invention to provide sheet supplying apparatus. The sheet supplying apparatus has a tray; a guide mechanism; a movement conversion mechanism; a rotary member; a cam and slider mechanism and a compression spring. The movement conversion mechanism converts an up and down motion of the tray to a rotational motion. The rotary member comprises a transmitted portion configured to receive a rotational motion converted from the up and down motion of the tray in cooperation with the movement conversion mechanism and a driven portion configured to receive a rotational driving force to lift the tray. The cam and slider mechanism converts the rotational motion of the rotary member to a linear motion of a linearly movable member. The compression spring elastically presses the linearly movable member of the cam and slider mechanism in the rotational axis direction to lift the tray.

TECHNICAL FIELD

This specification relates generally to the structure of a sheet supplying apparatus.

BACKGROUND

There is proposed a sheet supplying apparatus externally attached to an image forming apparatus such as an MFP (Multi Function Peripheral). This sheet supplying apparatus is attached to the exterior of one side of the image forming apparatus. Several thousand sheets for printing are stacked on a tray provided for stacking the sheets. Therefore, the sheet supplying apparatus is also called LCF (LARGE-CAPACITY-FEEDER). The tray moves up as the number of stacked sheets decreases by a lift mechanism in the sheet supplying apparatus to keep the top position of the sheets stacked on the tray at certain height. The sheets stacked on the tray are picked up by a pickup roller one by one in order from the sheet at the top position, delivered to a separating and conveying roller pair configured to, for example, prevent double feeding of sheets, and fed to a sheet conveying system in the MFP.

In the sheet supplying apparatus, a sheet stacking section in which a tray capable of moving up and down is provided in a housing-like exterior member which is configured to be drawn out therefrom in a drawer like fashion. When the sheet stacking section is drawn out the tray appears.

When a user refills the sheet stacking section with sheets, in order to supply sheets, a user draws out the sheet stacking section and sequentially stacks up the sheet bundles on the tray.

In the sheet supplying apparatus, a driven portion of the lift up mechanism is engaged with a driving source of the sheet supplying apparatus when the sheet stacking section is fully attached in the housing-like exterior member, i.e., not drawn out. On the other hand, the engagement between the driven portion and the driving source is released when the sheet stacking section is drawn out from the housing-like exterior member.

However, when the sheet stacking section is drawn out from the housing-like exterior member while a large number of sheets are stacked on the tray, the tray with the large number of sheets suddenly falls or drops because of the disengagement between the driven portion and the driving source.

It is possible to use, for example, a centrifugal brake or a helical torsion spring having high torsional torque to prevent a tray with a large number of sheets from a collision against an end of the tray guide member (shock absorption).

However, the centrifugal brake and the helical torsion spring having high torsional torque are generally expensive.

SUMMARY

According to an aspect of the present invention, there is provided a sheet supplying apparatus including: a tray; a guide mechanism; a movement conversion mechanism; a rotary member; a cam and slider mechanism and a compression spring. Plural sheets are stacked on the tray. The guide mechanism freely guides the tray in an up and down direction. The movement conversion mechanism converts an up and down motion of the tray to a rotational motion. The rotary member is rotatably supported around a predetermined rotational axis and comprises a transmitted portion configured to receive a rotational motion converted from the up and down motion of the tray in cooperation with the movement conversion mechanism and a driven portion configured to receive a rotational driving force from a driving source to lift the tray. The cam and slider mechanism converts the rotational motion of the rotary member around the rotational axis to a linear motion of a linearly movable member parallel to the rotational axis. The compression spring elastically presses the linearly movable member of the cam and slider mechanism in the rotational axis direction to lift the tray.

According to another aspect of the present invention, there is provided an image forming apparatus including: a tray; a guide mechanism; a movement conversion mechanism; a rotary member; a cam and slider mechanism; a compression spring; a sheet conveyer and an image forming unit. Plural sheets are stacked on the tray. The guide mechanism freely guides the tray in an up and down direction. The movement conversion mechanism converts an up and down motion of the tray to a rotational motion. The rotary member is rotatably supported around a predetermined rotational axis and comprises a transmitted portion configured to receive a rotational motion converted from the up and down motion of the tray in cooperation with the movement conversion mechanism and a driven portion configured to receive a rotational driving force from a driving source to lift the tray. The cam and slider mechanism converts the rotational motion of the rotary member around the rotational axis to a linear motion of a linearly movable member parallel to the rotational axis. The compression spring elastically presses the linearly movable member of the cam and slider mechanism in the rotational axis direction to lift the tray. The sheet conveyer conveys a sheet stacked on the tray along a predetermined conveying path. The image forming unit forms an image onto a surface of the sheet conveyed by the sheet conveyer.

DETAILED DESCRIPTION

An embodiment of the present invention is explained below with reference to the accompanying drawings.

In the embodiments herein, the tray is coupled to a drive in the sheet feeding apparatus, and when the drawer on which the tray is supported is withdrawn to replace the sheets on the tray, the coupling between the tray and the sheet feeding apparatus is decoupled, and the tray falls under its own weight and the weight of any sheets still remaining thereon. To reduce the shock otherwise caused by rapid falling of the tray106, the drawer includes a shock absorbing mechanism. The shock absorbing mechanism includes a rod shaped rotary member109having at least one protrusion109eextending radially therefrom, and a sleeve like cylindrical member108with an internal spiral pitch groove. The cylindrical member108is fixed against rotation, and the rotary member is supported at the ends thereof so that it can rotate around its rotational axis. The rotary member109extends through the cylindrical member108, and rotation of the protrusion109eby rotation of the rotary member109causes the cylindrical member108to move in the direction of the rotational axis of the rotary member. A coil spring110surrounds a portion of the rotary member109, and is compressed by the axial motion of the cylindrical member108. One end of a wire rope111wis windable around one end of the rotary member, extends over a pulley, and is attached at the other end thereof to the tray106. As the tray106falls, the rope unwinds from around the rotary member109and causes the cylindrical member108to slide axially and compress the spring110, dampening the falling of the tray106.

First Embodiment

An image forming apparatus according to a first embodiment of the present invention is explained below. First, an image processing system including a sheet supplying apparatus according to this embodiment is explained with reference toFIGS. 1 to 3.

FIGS. 1 to 3are schematic configuration views depicting an image processing system (MFP: multi-function peripheral) according to this embodiment of the invention.

As shown inFIG. 1, the image processing system according to this embodiment includes an image forming apparatus2and a sheet supplying apparatus1.

The image forming apparatus2forms an image on a sheet on the basis of image data acquired by scanning an original or image data received via a network.

The sheet supplying apparatus1can supply a large number of sheets (for example, several thousand sheets) as recording media to the image forming apparatus2.

InFIG. 1, an X axis, a Y axis, and a Z axis are axes orthogonal to one another. The Z axis is an axis corresponding to an up-to-down direction of the sheet supplying apparatus1and the image forming apparatus2. A relation among the three axes X, Y, and Z is the same in the other figures.

InFIG. 1, in an image forming apparatus2, which is an example of an image forming apparatus including a printer function and a copy function, paper feeding cassettes201configured to store sheets for printing are arranged in plural stages in a lower part. A printer section202is arranged on the paper feeding cassette section201s. The sheets stored in the paper feeding cassettes201are fed to the printer section202(image forming unit) by a sheet conveyer220(FIGS. 2 and 3) in which a sheet conveying path extends in the up-down direction. The sheets having images printed thereon by the printer section202are discharged to a paper discharge tray at the upper end of the image forming apparatus2. The sheet conveyer220is arranged on one side of the image forming apparatus2.

As shown inFIG. 2, the sheet supplying apparatus1is slidably supported by slide guide102extending in a Y axis direction from the lower end of the image forming apparatus2. The sheet supplying apparatus1performs paper feeding to the sheet conveyer220of the image forming apparatus2in a state in which the sheet supplying apparatus1is attached to the one side of the image forming apparatus2(FIG. 1). The sheet conveyer220is also configured to convey a sheet supplied from the sheet supplying apparatus1along a predetermined conveying path to the printer section202.

When a user refills the sheet supplying apparatus1with sheets, at first, the user pulls the sheet supplying apparatus1away from the image forming apparatus2in the Y axis direction as shown inFIG. 2. Then, the user draws out a sheet stacking section ST from a casing101, which is supported by a slide guide104, in the X axis direction (FIG. 3).

FIG. 4is a partial schematic perspective view of the sheet supplying apparatus1of the first embodiment.

The sheet stacking section ST has, for example, a base plate101b, a front cover103(shown inFIGS. 1 to 3), a side guide105, a tray106, a guide mechanism101g, a movement conversion mechanism111, a rotary member109, a supporting portion130, a cam and slider mechanism H and a compression spring110.

The guide mechanism101gguides the tray106so that the tray106can slide freely in an up and down direction (Z axis direction). The guide mechanism101gis, for example, a linear motion guide. The user can stack plural sheets on the tray106guided by the guide mechanism101g. InFIG. 4, the tray106is at a highest position (first height position).

The movement conversion mechanism111converts an up and down motion of the tray106in the Z axis direction to a rotational motion around the X axis direction. The movement conversion mechanism111includes a pulley111pand a wire rope111w. One end of the wire rope111wis connected to an end portion of the tray106and the other end of the wire rope111is connected across the pulley111pto a rotational cylindrical body109d.

The rotary member109is a longitudinal member supported rotatably around a predetermined rotational axis which is parallel with X axis. The rotary member109is supported rotatably at one end thereof by a side wall101cextending from one end of the base plate101b, and at the other end by a side wall (not shown) extending from an opposite end of the base plate101b.

The rotary member109includes the rotational cylindrical body (transmitted portion)109dat one end thereof in the rotational axis direction. The transmitted portion109dconverts the up and down motion of the tray106into rotation of the rotary member, by winding and unwinding the wire rope111wthereabout in cooperation with the movement conversion mechanism111. With this structure, the tray106will move upwardly as the rotational cylindrical body109drotates and thereby winds up the wire rope111wthereon.

The rotary member109also includes a driven portion109bconfigured to receive a rotational driving force to lift up the tray106from a driving source (not shown) of the sheet supplying apparatus1through a coupler107band gears107c,107dand107ein a gear train, when the sheet stacking section ST is fully inserted into the casing101. Each of the coupler107band the gears107c,107dand107eis rotatably supported by a shaft107f,107gand107hfixed to a casing107awhich is fixed on the base plate101b. In this embodiment, the driven portion109bis, for example, a gear. The rotational driving force is transmitted from the gear107eto the driven portion109bas the gear. Here, a coupler of the driving source of the sheet supplying apparatus1engages with the coupler107bwhen the sheet stacking section ST is fully inserted into the casing101. However, it is possible to apply other force transmission mechanisms such as a belt drive transmission system and a chain drive transmission system to transmit the driving force from the driving source to the driven portion109b.

The cam and slider mechanism H converts rotational motion M1of the rotary member109around the rotational axis into linear motion M2of a cylindrical member (linearly movable member)108parallel to the rotational axis.

FIGS. 5 and 6are partial sectional views in an X-Z plane including the rotational axis of the rotary member109seen from a direction parallel to the Y axis showing a basic structure of the cam and slider mechanism H in the first embodiment.

The cam and slider mechanism H has a protrusion109eof the rotary member109and a cylindrical member108(FIG. 6). The protrusion109eintegrally rotates with the main body of the rotary member109. The rotary member109is inserted through the cylindrical member108.

FIGS. 7 and 8are sectional views in an X-Z plane including the rotational axis of the rotary member109seen from a direction parallel to the Y axis showing an inner structure of the cylindrical member108in the first embodiment. In the embodiment, the cylindrical member108has two spiral grooves108cof the same pitch located 180 degrees apart and extending inwardly of the inner surface thereof, into which two different protrusions109edisposed 180 degrees apart on the rotary member109protrude.

The compression spring110elastically presses on an end portion108eof the cylindrical member108of the cam and slider mechanism H in the rotational axis direction to apply a force to lift the tray106, and compressed is by sliding movement of the cylindrical member108caused by engagement of the protrusions109ewith the grooves108cas the rotary member109is rotated as the wire rope111wis pulled by the falling tray106.

Specifically, the compression spring110is a coil spring. Here, a volute spring also can be applied as the compression spring110to receive a large load which is larger than the load normal coil spring can accommodate with good space efficiency.

The rotary member109is inserted through the compression spring110along a spiral center axis of the compression spring110(FIG. 6). The rotary member109also has a stopper109cto engage against one end of the compression spring110.

The rotary member109has a plurality of the protrusions109eprovided at different angular positions in a rotational direction of the rotary member109(FIG. 6) along the same spiral pitch of the grooves108cof the cylindrical member108. With this structure the cam and slider mechanism H stably transmits the rotational force of the rotary member109to the cylindrical member108. The protrusions109eare arranged at an equal angle around the rotational axis of the rotary member109. In this embodiment, the rotary member109has two protrusions109eat opposed angular positions, i.e., 180 degrees apart around the rotary member axis (FIGS. 6 and 8), and each fits into a different groove108c. Also, it is possible to forma continuous protrusion such as a worm gear on an outer surface of the rotary member109along a rotational direction of the rotary member.

The cylindrical member108includes an anti-rotation bracket108bsecured thereto having a plurality of legs108bwhich contact the inner surface of the base plate101b. The anti-rotation bracket can slide on the inner surface of the base plate101b, but the portion of the legs thereof which contact the inner surface of the base plate101extend in the Y direction whereas the cylindrical member108extends in the X direction, and thus the legs108bprevent the rotation of the cylindrical member108around the rotational axis but allow movement thereof in the X direction.FIG. 9is a partial schematic perspective view of the sheet supplying apparatus1when the tray106is at its lowest position (second height position).FIG. 10is a partial sectional view in an X-Z plane including the rotational axis of the rotary member109seen from a direction parallel to the Y axis showing the cam and slider mechanism H when the tray106is at its lowest position.

When the sheet supplying apparatus1is in use with the image forming apparatus, the tray106is moved up by the driving force from the driving source of the sheet supplying apparatus1as the number of stacked sheets in the tray106decreases to keep the top position of the sheets stacked on the tray106at certain height.

The engagement between the coupler107b(driven portion) and the driving source (not shown) is released when the sheet stacking section ST is drawn out from the casing101. If the sheet stacking section ST is drawn out from the casing101while a large number of sheets are stacked on the tray106, the tray with the large number of sheets will rapidly fall because the tray106is no longer supported in the Z direction as a result of the disengagement between the coupler107band the driving source as shown inFIGS. 9 and 10.

Even when the tray106with the large number of sheets falls as a result of the disengagement between the coupler107band the driving source, the compression spring110and the cam and slider mechanism H efficiently absorb the shock because of the weight of the tray106and the sheets stacked thereon by both of the elastic pressing force by the compression spring110as the compression spring is compressed and a frictional resistance of the cam and slider mechanism H, i.e., they dampen the speed at which the falling tray comes to rest at its lowest position. As shown inFIG. 4, with the tray106in the raised position, the spring110is in a free state, i.e., it is not compressed by the cylindrical member108. As the tray106falls from the position thereof inFIG. 4to that inFIGS. 9 and 10, the end of the wire rope111wconnected to the tray106moves in the downward direction. As the wire rope111wis connected to the receiving member109cacross pulley111p, this causes the wire rope111wat the rotational cylindrical body109dpull upwardly, causing the rotational cylindrical body109dand the rotary member109connected thereto to rotate in a direction causing the cylindrical member to move the end of the spring110it contacts in the direction of the stopper109c, thereby compressing the spring110and dampening the falling of the tray106.

When the drawer is closed and coupler107bis engaged with the driving source, the rotational force form the driving source can be transmitted to the driven portion109bto rotate the rotary member109through the gears107c,107dand107ein the gear train, and thereby lift the tray106with the wire rope111wand rewind the wire rope111won the rotation cylindrical body109d. With this structure, the tray106moves upwardly as the rotational cylindrical body109drotates and thereby winds up the wire rope111wthereon and pull the tray106upwardly to keep the top position of the sheets stacked on the tray106at certain height. The sheets stacked on the tray are picked up by a pickup roller one by one in order from the sheet at the top position, and delivered to the sheet conveyer220in the image forming apparatus2.

In this embodiment, the end of the compression spring110does not always need to touch the end portion108eof the cylindrical member108and the end portion of the stopper109c. Even when there is a clearance between the end portion of the compression spring110and either one of the end portions of the cylindrical member108or the stopper109cin the state that the tray106is at the highest position, both end portions of the compression spring110will be engaged with both of the end portions of the cylindrical member108and the stopper109cin the state that the tray106is at a certain height which is lower than the highest position.

FIG. 11is a graph showing the relation between the height of the tray106and time just after the sheet stacking section ST is drawn out from the casing101. InFIG. 11, its vertical axis is for the height of the tray106, and the horizontal for the time. As shown inFIG. 11, the tray106suddenly falls down from the timing of the disengagement between the coupler107band the driving source till start timing of the compression of the compression spring110since the weight of the tray106and the sheets stacked thereon are received only by the frictional resistance by the cam and slider mechanism H. On the other hand, after the compression of the compression spring110starts, a falling speed of the tray106gradually decreases by both of the elastic pressing force by the compression spring110and a frictional resistance of the cam and slider mechanism H. Here, the highest position and the lowest position inFIG. 11are determined based on the amount of the sheets on the tray106and the weight of the tray106and the sheets stacked thereon.

Second Embodiment

An image forming apparatus according to a second embodiment of the present invention is explained below.

The second embodiment is a modification of the first embodiment. In the following explanation, in this embodiment, components having functions same as those explained in the first embodiment are denoted by the same reference numerals and signs and explanation of the components is omitted. Only point of the second embodiment different from the first embodiment is a structure of the cylindrical member.

FIG. 12is a partial sectional view in an X-Z plane seen from a direction parallel to the Y axis showing a basic structure of a cylindrical member108′ in the second embodiment.

In this embodiment, an inclination angle θ1to the Y-Z plane (the plane orthogonally crossing a spiral center axis) of an inclined guide surface108c1on which the protrusion109econtacts when the tray106is at around a first height position is smaller than an inclination angle θ2of an inclined guide surface108c2on which the protrusion109econtacts when the tray106is at around a second height position lower than the first height position.

By this structure, the moving distance of the cylindrical member108′ in the rotational axis direction (amount of compression) per a unit rotation angle increases as the tray106moves downward. That is, a receiving force to elastically receive a weight of the tray106and sheets thereon when the tray106is at the second height position is larger than the receiving force when the tray106is at the first height position higher than the second height position.

According to the above embodiments, it is possible to efficiently absorb a shock because of the weight of the tray106and the sheets stacked thereon by both of the elastic pressing force by the compression spring110and a frictional resistance of the cam and slider mechanism H.

In the above embodiments, the sheet supplying apparatus of the present invention is externally attached to an image forming apparatus. However, it is also possible to apply the present invention to a paper feeding cassette which is insertable into a main body of the image forming apparatus.

In the above embodiments, the movement conversion mechanism111converts an up and down motion of the tray106in the Z axis direction to a rotational motion around the X axis direction with the pulley111pand a wire rope111. However, it is also possible to include a gear train into the movement conversion mechanism111to convert the up and down motion of the tray106to the rotational motion around the X axis direction.

In the above embodiments, the cylindrical member108has a spiral groove108cformed on the inner surface108q. However, the linearly movable member needs not necessarily be the cylindrical shape. That is, it is possible to form the spiral groove on an inner surface of a linearly movable member having other shape, as long as the groove can be stably guided by the protrusion109e.

The present invention can be carried out in various forms without departing from main characteristics thereof. The embodiments are merely exemplars in every aspect and should not be limitedly interpreted. The scope of the present invention is indicated by the scope of claims. The text of the specification does not restrict the scope of the invention. All variations and various improvements, alterations, and modifications belonging to the scope of equivalents of the scope of claims are within the scope of the present invention.