Sheet supplying device and image forming device

A sheet supplying device has: a base; a tray; a feed roller provided rotatably at the base and positioned above the tray. When the feed roller rotates while frictionally engaging with a topmost sheet of the stack of sheets, the feed roller can convey the sheet. The sheet supplying device further includes a driving mechanism able to drive the feed roller to rotate; an urging member urging the tray toward the feed roller; a first eccentric cam rotatably provided at the base, and including a large-radius outer peripheral portion and a small-radius outer peripheral portion, the first eccentric cam rotating interlockingly with rotation of the feed roller; and a second eccentric cam rotatably provided at the tray, and including a large-radius outer peripheral portion and a small-radius outer peripheral portion, the second eccentric cam being able to engage with the first eccentric cam.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese Patent Application No. 2003-432569, the disclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming device which records images on sheets of recording media (papers or the like of predetermined sizes), and to a sheet supplying device which conveys sheets one-by-one from a stack of sheets.

2. Description of the Related Art

Generally, in an image forming device such as a copier or a printer or the like, images are formed on recording media sheets in an image forming section. These sheets are stacked in a sheet supplying device which is provided within the image forming device, and are successively supplied from the sheet supplying device to the image forming section.

As shown inFIG. 16, a sheet supplying device100has a presser plate102on which sheets (recording media) are placed. The presser plate102is urged upward by a coil spring104. Above the presser plate102, a supporting shaft106is supported so as to rotate freely with respect to a main body frame130(not all of the main body frame130is illustrated). A feed roller108, which is half-moon-shaped and conveys the sheets, is fixed to the supporting shaft106. Core rollers110are attached to the both sides of the feed roller108. The core rollers110rotate in a state of contacting a separating pad112provided at the main body frame130.

Cams114are fixed to the both end portions of the supporting shaft106. The cams114abut rollers124provided at flanges122which project from the both side portions of the presser plate102.

A driven gear116is attached to one end portion of the supporting shaft106. A portion of the peripheral surface of the driven gear116is cut out. A driving gear118, which is driven to rotate by a motor (not illustrated), is meshably disposed at the lower side of the driven gear116. The driving gear118meshes with the driven gear116at a predetermined timing so as to transmit the driving force of the driving gear118to the driven gear116, such that the supporting shaft106can rotate one time.

As shown inFIG. 17A, at times other than when sheets are being fed, the portions of the cams114where the eccentric radii are large abut the rollers124of the presser plate102, and press the presser plate102downward in a direction resisting the urging force of the coil spring104. At this time, the sheets stacked on the presser plate102are set apart from the feed roller108.

As shown inFIG. 17B, when the cams114rotate in the direction of the arrow due to the rotation of the supporting shaft106, the rollers124rotate while abutting the cams114, and the presser plate102is pushed upward by the urging force of the coil spring104. The feed roller108and the core rollers110also rotate together with the rotation of the supporting shaft106.

As shown inFIG. 17C, when the cams114rotate further in the direction of the arrow, the rollers124move along the cams114, and the presser plate102is gradually pushed upward. As shown inFIG. 17D, the presser plate102rises to the position at which the rollers124abut bearing portions114aof the cams114. At this time, the topmost portion of the stack of sheets stacked on the presser plate102contacts the feed roller108, and the sheets are fed out as the feed roller108rotates. Conveying, in an overlapping manner, of the sheets which are fed out is prevented by the friction with the separating pad112.

When the cams114rotate further, the presser plate102is pushed downward in the direction of resisting the urging force of the coil spring104, and the cams114rotate one time. In this way, the presser plate102is lowered to the position shown inFIG. 17A. (See, for example, Japanese Patent No. 2619959.)

In the sheet supplying device100shown inFIG. 16, the presser plate102is moved upward and downward by the rotation of the cams114provided at the supporting shaft106of the feed roller108, and feeding of the topmost sheet of the stack of sheets is carried out. However, when an attempt is made to increase the accommodating capacity (the feeding capacity) of the sheets stacked on the presser plate102, a problem arises in that the cams114inevitably become large.

Namely, in the feeding operations shown inFIGS. 17A through 17D, when the presser plate102is raised, the topmost portion of the stack of sheets is pressed by the feed roller108and feeding is carried out. When the presser plate102is lowered, the topmost portion of the stack of sheets is moved away to a position at which it does not contact the feed roller108. Accordingly, when an attempt is made to increase the sheet accommodating capacity, the stroke of the presser plate102must be made to be large, and the cams114become large. Namely, there is the relation that the size of the cams114which move the presser plate102upward and downward determine the sheet accommodating capacity. Accordingly, a way to satisfy the antithetical needs for an increase in the sheet accommodating capacity and a decrease in the overall size of the device is desired.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances and provides a sheet supplying device and an image forming device which enable the device to be made compact overall and which enable an increase in the accommodating capacity of sheets (e.g., recording media).

In accordance with one aspect of the present invention, there is provided a sheet supplying device comprising: a base; a tray on which a stack of sheets can be placed, the tray being able to be raised and lowered with respect to the base; a feed roller provided rotatably at the base and positioned above the tray, and when the feed roller rotates while frictionally engaging with a topmost sheet of the stack of sheets, the feed roller can convey the sheet; a driving mechanism able to drive the feed roller to rotate; an urging member urging the tray toward the feed roller; a first eccentric cam rotatably provided at the base, and including a large-radius outer peripheral portion whose radius is large and a small-radius outer peripheral portion whose radius is small, the first eccentric cam rotating interlockingly with rotation of the feed roller; and a second eccentric cam rotatably provided at the tray, and including a large-radius outer peripheral portion whose radius is large and a small-radius outer peripheral portion whose radius is small, the second eccentric cam being able to engage with the first eccentric cam, wherein, when the respective small-radius outer peripheral portions of the first eccentric cam and the second eccentric cam substantially contact one another, the tray approaches the feed roller so as to be able to convey the sheet, and when the respective large-radius outer peripheral portions of the first eccentric cam and the second eccentric cam substantially contact one another, the tray moves away from the feed roller so as to be unable to convey the sheet.

In accordance with another aspect of the present invention, there is provided a sheet supplying device comprising: a base; a tray on which a stack of sheets can be placed, the tray being able to be raised and lowered with respect to the base; a feed roller provided rotatably at the base and positioned above the tray, and when the feed roller rotates while frictionally engaging with a topmost sheet of the stack of sheets, the feed roller can convey the sheet; a driving mechanism able to drive the feed roller to rotate; an urging member urging the tray toward the feed roller; a first eccentric cam provided rotatably at the base, and having a first rotating supporting shaft, and including a large-radius outer peripheral portion, whose radius is large, and a small-radius outer peripheral portion, whose radius is small, such that the first rotating supporting shaft is disposed between the large-radius outer peripheral portion and the small-radius outer peripheral portion, the first eccentric cam rotating interlockingly with rotation of the feed roller; a second eccentric cam provided rotatably at the tray, and having a second rotating supporting shaft, and including a large-radius outer peripheral portion, whose radius is large, and a small-radius outer peripheral portion, whose radius is small, such that the second rotating supporting shaft is disposed between the large-radius outer peripheral portion and the small-radius outer peripheral portion; and a third eccentric cam having a third rotating supporting shaft, and including a large-radius outer peripheral portion, whose radius is large, and a small-radius outer peripheral portion, whose radius is small, such that the third rotating supporting shaft is disposed between the large-radius outer peripheral portion and the small-radius outer peripheral portion, wherein the first rotating supporting shaft, the third rotating supporting shaft, and the second rotating supporting shaft are lined up in that order in a vertical direction and are separated from one another and parallel to one another, the third rotating supporting shaft can move translationally in the vertical direction, and in a first case in which the large-radius outer peripheral portion of the first eccentric cam substantially contacts one of the large-radius outer peripheral portion and the small-radius outer peripheral portion of the third eccentric cam, and the large-radius outer peripheral portion of the second eccentric cam substantially contacts another of the large-radius outer peripheral portion and the small-radius outer peripheral portion of the third eccentric cam, the tray moves away from the feed roller so as to be unable to convey the sheet, and in a second case in which the small-radius outer peripheral portion of the first eccentric cam substantially contacts the small-radius outer peripheral portion of the third eccentric cam, and the small-radius outer peripheral portion of the third eccentric cam substantially contacts the small-radius outer peripheral portion of the second eccentric cam, the tray approaches the feed roller so as to be able to convey the sheet.

In accordance with yet another aspect of the present invention, there is provided a sheet supplying device comprising: a base; a tray on which a stack of sheets can be placed, the tray being able to be raised and lowered with respect to the base; a feed roller provided rotatably at the base and positioned above the tray, and when the feed roller rotates while frictionally engaging with a topmost sheet of the stack of sheets, the feed roller can convey the sheet; a driving mechanism able to drive the feed roller to rotate; an urging member urging the tray toward the feed roller; a first eccentric cam provided rotatably at the base, and having a first rotating supporting shaft, and including a large-radius outer peripheral portion, whose radius is large, and a small-radius outer peripheral portion, whose radius is small, such that the first rotating supporting shaft is disposed between the large-radius outer peripheral portion and the small-radius outer peripheral portion, the first eccentric cam being able to rotate independently of rotation of the feed roller; a second eccentric cam provided rotatably at the tray, and having a second rotating supporting shaft, and including a large-radius outer peripheral portion, whose radius is large, and a small-radius outer peripheral portion, whose radius is small, such that the second rotating supporting shaft is disposed between the large-radius outer peripheral portion and the small-radius outer peripheral portion; and a third eccentric cam having a third rotating supporting shaft, and including a large-radius outer peripheral portion, whose radius is large, and a small-radius outer peripheral portion, whose radius is small, such that the third rotating supporting shaft is disposed between the large-radius outer peripheral portion and the small-radius outer peripheral portion, wherein the first rotating supporting shaft, the third rotating supporting shaft, and the second rotating supporting shaft are lined up in that order in a vertical direction and are separated from one another and parallel to one another, the third rotating supporting shaft can move translationally in the vertical direction, and in a first case in which the large-radius outer peripheral portion of the first eccentric cam substantially contacts one of the large-radius outer peripheral portion and the small-radius outer peripheral portion of the third eccentric cam, and the large-radius outer peripheral portion of the second eccentric cam substantially contacts another of the large-radius outer peripheral portion and the small-radius outer peripheral portion of the third eccentric cam, the tray moves away from the feed roller so as to be unable to convey the sheet, and in a second case in which the small-radius outer peripheral portion of the first eccentric cam substantially contacts the small-radius outer peripheral portion of the third eccentric cam, and the small-radius outer peripheral portion of the third eccentric cam substantially contacts the small-radius outer peripheral portion of the second eccentric cam, the tray approaches the feed roller so as to be able to convey the sheet.

In accordance with still yet another aspect of the present invention, there is provided an image forming device having a sheet supplying device, the sheet supplying device comprising: a base; a tray on which a stack of sheet-shaped recording media can be placed, the tray being able to be raised and lowered with respect to the base; a feed roller provided rotatably at the base and positioned above the tray, and when the feed roller rotates while frictionally engaging with a topmost recording medium of the stack of recording media, the feed roller can convey the recording medium; a driving mechanism able to drive the feed roller to rotate; an urging member urging the tray toward the feed roller; a first eccentric cam provided rotatably at the base, and including a large-radius outer peripheral portion whose radius is large and a small-radius outer peripheral portion whose radius is small, the first eccentric cam rotating interlockingly with rotation of the feed roller; and a second eccentric cam provided rotatably at the tray, and including a large-radius outer peripheral portion whose radius is large and a small-radius outer peripheral portion whose radius is small, the second eccentric cam able to engage with the first eccentric cam, wherein, when the respective small-radius outer peripheral portions of the first eccentric cam and the second eccentric cam substantially contact one another, the tray approaches the feed roller so as to be able to convey the recording medium, and when the respective large-radius outer peripheral portions of the first eccentric cam and the second eccentric cam substantially contact one another, the tray moves away from the feed roller so as to be unable to convey the recording medium.

Other objects, features and advantages of the present invention will be apparent to those skilled in the art from the explanation of the preferred embodiments of the present invention illustrated in the appended drawings, and from the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

FIRST EMBODIMENT

Hereinafter, a sheet supplying device of a first embodiment of the present invention will be described in detail with reference toFIGS. 1 through 7.

As shown inFIG. 7, a sheet supplying device10is provided at the lower portion of an image forming device200, and successively feeds, one-by-one, recording media (sheets) P to a process cartridge204structuring an image forming section.

As shown inFIGS. 1 and 7, presser plates14, on which the sheets P are stacked, are provided in the sheet supplying device10. Insertion holes58, through which pass poles56which stand upright at a base18, are formed at both end portions of the presser plate14in a direction orthogonal to the sheet feeding direction. The presser plate14can move upward and downward while being guided by the poles56. The presser plate14is urged upward by coil springs20provided at the base18.

A supporting shaft22is disposed above the presser plate14. The supporting shaft22is supported so as to be freely rotatable with respect to a main body frame of the image forming device200. A half-moon-shaped feed roller24, which feeds the sheets P (not shown inFIG. 1) which are stacked on the presser plate14, is fixed to the supporting shaft22. Core rollers26, whose radii are somewhat smaller than the radius of the half-moon-shaped feed roller24, are fixed to the both sides of the feed roller24.

As shown inFIG. 1, a separating roller28is rotatably supported at the portion of a main body frame300opposing the feed roller24and the core rollers26. The separating roller28is formed as a member whose surface has great frictional force. Due to the rotation of the supporting shaft22, the core rollers26rotate in a state of abutting the separating roller28. Further, the peripheral surface of the feed roller24can feed the topmost sheet P out by rotating while abutting the stack of sheets P stacked on the presser plate14.

First cams30are fixed to both end portions of the supporting shaft22. The first cams30have arc-shaped portions30awhich are fan-shaped and whose eccentric radii are larger than the radius of the feed roller24.

A driven gear32is mounted to one end portion of the supporting shaft22. A portion of the outer periphery of the driven gear32is toothless. A driving gear34, which is driven to rotate by an unillustrated motor, can mesh with the driven gear32. When the sheets P are to be fed, the driving force of the driving gear34is transmitted to the driven gear32at a predetermined timing by an unillustrated control device, such that the supporting shaft22, the feed roller24, the core rollers26and the first cams30rotate one time in the direction of arrow A (seeFIGS. 3A through 3D).

As shown inFIG. 1, flanges36which project upward are formed at positions of the both sides of the presser plate14which positions oppose the first cams30. Second cams38are rotatably supported by rotating shafts39at the flanges36. First cam followers40, which can abut the first cams30, are provided so as to project out at end sides of the flanges36, at the sides of the second cams38which sides are opposite the sides in the feeding direction. Concave portions42are formed beneath the first cam followers40. The second cams38can enter into the concave portions42when the second cams38are rotating.

Second cam followers44are mounted to the base18beneath the concave portions42of the first cam followers40. As shown inFIG. 3A, due to the second cams38abutting the second cam followers44, the second cams38are held in a state (posture) in the direction of abutting the first cams30. Rollers46are provided at the regions of the second cams38which regions abut the first cams30. Convex and concave portions may be formed in the peripheral surfaces of the rollers46in order to prevent slippage between the rollers46and the first cams30. As shown inFIG. 3A, when the arc-shaped portions30aof the first cams30, whose eccentric radii are large, abut the portions of the second cams38where the eccentric radii are large, the presser plate14is pushed downward to its lowermost position.

Because the coil springs20push the presser plate14upward, the second cams38abut the second cam followers44in addition to abutting the first cams30.

When the first cams30rotate in the direction of arrow A, components of force which rotate the second cams38in the opposite direction so as to counteract this, are applied to the second cams38so that the second cams38rotate in the direction of arrow B (seeFIG. 3C).

As shown inFIG. 2, pins48project at the inner sides (the feed roller24sides) of the second cams38. L-shaped receiving portions50, which are structured by the flanges36and the first cam followers40, are provided at the presser plate14. When the second cams38rotate in the direction of arrow B, the pins48are received in the receiving portions50, and rotation of the second cams38is restricted due to the self-weights thereof.

In this sheet supplying device10, the number of sheets P which can be stacked on the presser plate14(the number of sheets which can be accommodated) is about 250 sheets for regular paper, and about 200 sheets for thick paper.

Hereinafter, operation of the sheet supplying device10will be described with reference toFIGS. 3A through 6C.

As shown inFIG. 3A, when the sheets P are not being fed, the arc-shaped portions30aof the first cams30abut the portions of the second cams38where the eccentric radii are large, so as to push the presser plate14downward in the direction of resisting the urging forces of the coil springs20. Pressing forces F in the direction of the arrow and due to the urging forces of the coil springs20are applied to the first cams30. At this time, the presser plate14is positioned at its lowermost position, and the sheets P (not illustrated) stacked on the presser plate14are set apart from the feed roller24.

As shown inFIG. 3B, when the first cams30rotate in the direction of arrow A due to the rotation of the supporting shaft22, components of force in the direction opposite the rotating direction are applied to the second cams38which are abutting the first cams30, and the second cams38rotate in the direction of arrow B while abutting the second cam followers44. The rollers46of the second cams38are abutting the first cams30, and the first cams30rotate smoothly due to the rollers46.

As the second cams38rotate, the eccentric radii of the abutting regions thereof become shorter, and the presser plate14is pushed upward by the urging forces of the coil springs20. Due to the rotation of the supporting shaft22, the feed roller24and the core rollers26as well rotate in the direction of arrow A.

As shown inFIG. 3C, when the first cams30rotate 40° in the direction of arrow A, the second cams38rotate in the direction of arrow B while abutting the second cam followers44, and the presser plate14rises up smoothly. At this time, the second cams38enter into the concave portions42of the first cam followers40while rotating.

As shown inFIG. 3D, when the first cams30rotate 42.5° in the direction of arrow A, the second cams38rotate further in the direction of arrow B while abutting the top portions of the second cam followers44, and the presser plate14is raised upward by the urging forces of the coil springs20. When the second cams38rotate further in the direction of arrow B and the pins48of the second cams38engage with the receiving portions50, further rotation of the second cams38is impeded.

As shown inFIG. 4A, when the first cams30rotate 50° in the direction of arrow A, the angular positions of the second cams38do not change because the pins48are engaged with the receiving portions50. Accordingly, the second cams38come away from the second cam followers44. The presser plate14rises further due to the abutment of the first cams30and the second cams38. Then, due to the rotation of the supporting shaft22, the feed roller24and the core rollers26also rotate further in the direction of arrow A.

The presser plate14rises until the topmost portion of the stack of sheets P stacked on the presser plate14abuts the feed roller24. Then, the stack of sheets P abuts/engages with the feed roller24, and due to the feed roller24rotating while abutting the topmost sheet P, the sheet P is fed out. At the conveying direction downstream side of the sheet P, the reverse surface side of the sheet P contacts the separating roller28at a predetermined pressure. Due to the friction between the sheet P and the separating roller28, feeding of the sheets P in an overlapping manner is prevented, and a single sheet P is conveyed.

When a small number of the stacked sheets is conveyed, as shown inFIG. 4B, when the first cams30rotate in the direction of arrow A by 64.43°, the second cams38abut bearing portions30bof the first cams30, and the presser plate14reaches it uppermost position.

When the presser plate14is at its uppermost position, the first cam followers40provided at the presser plate14are positioned rearward of the supporting shaft22(i.e., at the side opposite the feeding direction side of the supporting shaft22), such that the first cam followers40are prevented from interfering with the supporting shaft22. Thereafter, as shown inFIGS. 4C and 4D, when the first cams30rotate in the direction of arrow A, the second cams38slidingly contact the bearing portions30bof the first cams30, and the presser plate14is held at its uppermost position.

As shown inFIG. 5A, when the first cams30rotate 250.79° in the direction of arrow A, due to the distal ends of the arc-shaped portions30aabutting and pressing the first cam followers40, the presser plate14is pushed in the direction against the urging forces of the coil springs20(i.e., is pushed downward).

As shown inFIG. 5B, when the first cams30rotate 270° in the direction of arrow A, the second cams38abut the second cam followers44due to the lowering of the presser plate14. Then, the pins48of the second cams38separate from the receiving portions50, and the second cams38rotate in the direction of arrow C while abutting the second cam followers44.

As shown inFIG. 5C, when the first cams30rotate 290° in the direction of arrow A, due to the arc-shaped portions30apushing the first cam followers40, the presser plate14is lowered, and the second cams38rotate in the direction of arrow C by abutting the second cam followers44.

As shown inFIGS. 5D and 6A, when the first cams30rotate further, the arc-shaped portions30apress the presser plate14downward while the arc-shaped portions30aslide along the first cam followers40, and the second cams38rotate further in the direction of arrow C by abutting the second cam followers44.

As shown inFIG. 6B, when the first cams30rotate 340° in the direction of arrow A, the arc-shaped portions30amove away from the first cam followers40and abut the second cams38.

As shown inFIG. 6C, due to the first cams30rotating 360° in the direction of arrow A (i.e., due to the first cams30rotating one time), while the first cams30and the rollers46abut one another, the second cams38are rotated to their initial positions, and the presser plate14is pushed downward to its lowermost position.

In the present sheet supplying device10, by rotating the first cams30and the second cams38respectively, the presser plate14is raised and lowered. Therefore, the stroke of the presser plate14can be made to be large, and the first cam followers40and the supporting shaft22do not interfere with one another when the presser plate14is at its uppermost position. Therefore, even if the first cams30are made to be small, the sheet P accommodating capacity can be increased, and the sheet supplying device10can be made to be compact.

SECOND EMBODIMENT

Hereinafter, a second embodiment of a sheet supplying device relating to the present invention will be briefly described with reference toFIGS. 8A and 8B.

Note that the same reference numerals are applied to members and portions which were described in the first embodiment, and repeat description will be appropriately omitted.

In a sheet supplying device70shown inFIGS. 8A and 8B, springs74, which urge the second cams38in the direction of arrow B, are wound around rotating shafts72of the second cams38. Ones of ends of the springs74are attached to the second cams38, whereas the other ends are attached to the flanges36.

In this way, as the presser plate14rises, the second cams38rotate in the direction of arrow B in a state of abutting the second cam followers44. On the other hand, when the presser plate14falls, the second cams38rotate in the direction resisting the urging forces of the springs74(i.e., in the direction of arrow C) due to the second cams38abutting the second cam followers44.

In this way, by the simple structure of providing the springs74which urge the second cams38, the behavior of the second cams38at times when the presser plate14is moving upward and downward can be stabilized.

THIRD EMBODIMENT

Hereinafter, a third embodiment of a sheet supplying device relating to the present invention will be described briefly with reference toFIGS. 9A,9B,10A, and10B.

Note that the same reference numerals are applied to members and portions which were described in the first and second embodiments, and repeat description will be appropriately omitted.

In a sheet supplying device80shown inFIG. 9B, second cams82are rotatably supported at the presser plate14via the rotating shafts39. Springs such as in the second embodiment are not provided at the second cams82.

Second cam followers84, which abut the second cams82and rotate the second cams82in a given direction, are provided beneath the concave portions42of the first cam followers40.

Third cam followers86are provided at positions which oppose the second cam followers84, with the second cams82therebetween. The third cam followers86restrict rotation of the second cams82in the direction of moving away from the second cam followers84.

The surfaces of the third cam followers86which surfaces abut the second cams82have configurations which curve along the loci of rotation of the second cams82. The third cam followers86can make the second cams82rotate continuously in the given direction.

The second cam follower84and the third cam follower86are formed as an integral part and mounted to the base (seeFIG. 1).

Next, operation of the present sheet supplying device80will be described.

As shown inFIG. 9A, the second cams82abut the second cam followers84and the third cam followers86at the both sides. The portions of the second cams82where the eccentric radii are large abut the portions of the first cams30where the eccentric radii are large. At this time, the presser plate14is positioned at its lowermost position against the urging forces of the springs20.

When the first cams30rotate in the direction of arrow A due to the rotation of the supporting shaft22, components of force in the direction opposite to the direction of rotation of the first cams are applied to the second cams82. The second cams82rotate in the direction of arrow B while abutting the second cam followers84. At this time, because the abutment surfaces of the third cam followers86are formed in configurations which curve along the loci of rotation of the second cams82, the second cams82rotate continuously without joggling. As the second cams82rotate, the presser plate14rises smoothly.

As shown inFIG. 9B, due to the rising of the presser plate14, the second cams82separate from the second cam followers84. At this time, the rotation of the second cams82is restricted by the pins and the receiving portions (which are not illustrated) (seeFIG. 2). Then, due to the rotation of the first cams30, the presser plate14rises up to its uppermost position.

As shown inFIG. 10A, when the first cams30rotate further in the direction of arrow A, the first cams30abut the first cam followers40and push the presser plate14downward. Due to the lowering of the presser plate14, the second cams82abut the second cam followers84, and the second cams82rotate in the direction of arrow C (seeFIG. 10B).

As shown inFIG. 10B, as the presser plate14is lowered, the second cams82abut the third cam followers86, and rotation of the second cams82in the direction of arrow C is restricted. Due to the first cams30separating from the first cam followers40and abutting the second cams82, the presser plate14is lowered to its lowermost position.

In this sheet supplying device80, the third cam followers86are disposed at positions opposing the second cam followers84with the second cams82therebetween. Therefore, rotation of the second cams82in the direction of moving away from the second cam followers84can be restricted. As a result, the second cams82rotate so as to smoothly follow the second cam followers84. Due to such a structure, even if the springs74(seeFIGS. 8A,8B) of the second embodiment are not provided, similar effects can be achieved.

Note that, instead of mounting the second cam follower84and the third cam follower86as an integral part to the base (seeFIG. 1), the second cam follower and the third cam follower may be structured as separate parts, and the third cam follower may be mounted to the presser plate14.

FOURTH EMBODIMENT

Hereinafter, a fourth embodiment of a sheet supplying device relating to the present invention will be described in detail with reference toFIGS. 11 through 13C.

Note that the same reference numerals are applied to members and portions which were described in the first embodiment, and repeat description will be appropriately omitted.

As shown inFIGS. 11 and 12A, in a sheet supplying device160, a supporting shaft166is rotatably provided at a main body frame301. Oval first cams150and rod-shaped members156, which are longer than the portions of the first cams150where the eccentric radii are large, are fixed to the supporting shaft166. As shown inFIG. 11, the free end of the rod-shaped member156is bent inwardly and forms an abutment portion156awhich abuts the first cam follower40of the presser plate14.

Oval second cams154are rotatably supported at the presser plate14by the rotating shafts39. The second cams154abut second cam followers164which are mounted to the main body frame301(not shown inFIGS. 12A through 12C), and are urged in the direction of arrow B by unillustrated springs.

As shown inFIG. 11, long holes159,161which extend in the vertical direction are formed in the first cam follower40and the main body frame301. A rotating shaft158of an oval third cam152is slidable in the vertical direction along the long holes159,161. The third cams152can abut second cam followers162which are mounted to the main body frame301(not shown inFIGS. 12A through 12C). The third cams152are urged in the direction of arrow C by springs which are not shown.

The first cams150are driven to rotate in the direction of arrow A due to the rotation of the supporting shaft166. The third cams152and the second cams154are driven cams which rotate following the rotation of the first cams150.

As shown inFIG. 12A, the supporting shaft166of the first cams150and the rod-shaped members156is a different shaft than the supporting shaft22of the feed roller24, and can be driven to rotate separately from the feed roller24.

Next, operation of the present sheet feeding device160will be described with reference toFIGS. 12A through 12CandFIGS. 13A through 13C.

As shown inFIG. 12A, the presser plate14is pushed downward to its lowermost position due to respective portions of the first cams150, the third cams152, and the second cams154, at which portions the eccentric radii are large, abutting one another and the abutment portions156aof the rod-shaped members156abutting the first cam followers40.

As shown inFIG. 12B, when the first cams150rotate in the direction of arrow A, accompanying this rotation, the rod-shaped members156also rotate, and the abutment portions156aseparate from the first cam followers40. As the first cams150rotate, the third cams152rotate followingly in the direction of arrow C (which is the urging direction of the unillustrated springs) while abutting the second cam followers162. As the third cams152rotate, the rotating shafts158begin to slide along the long holes159.

As the third cams152rotate, the second cams154rotate in the urging direction of the unillustrated springs (the direction of arrow B) while abutting the second cam followers164. Due to such rotation of the first cams150and the third cams152and the second cams154, the presser plate14rises upward due to the urging forces of the springs20.

As shown inFIG. 12C, when the first cams150rotate further in the direction of arrow A, the third cams152rotate further in the direction of arrow C, and the rotating shafts158slide in the long holes159. Accompanying this, the second cams154also rotate in the direction of arrow B. When the third cams152and the second cams154have respectively rotated 90°, rotation thereof is restricted due to the unillustrated pins and receiving portions.

Due to the portions of the first cams150, the third cams152, and the second cams154, at which portions the eccentric radii are small, abutting one another, the presser plate14rises to its topmost position. At this time, the first cam followers40do not interfere with the abutment portions156aof the rod-shaped members156and the supporting shaft166of the first cams150. When the presser plate14is raised, the sheets P are supplied by the feed roller24(seeFIG. 1).

Thereafter, as shown inFIG. 13A, when the first cams150rotate in the direction of arrow A, the abutment portions156aof the rod-shaped members156abut the first cam followers40, and push the presser plate14downward against the urging forces of the springs20.

As shown inFIG. 13B, when the first cams150rotate further in the direction of arrow A, the first cams150abut the third cams152, and the third cams152abut the second cam followers162, and the third cams152rotate in the direction of arrow E which is opposite to the urging forces of the springs (not shown). Together therewith, the rotating shafts158of the third cams152are slid along the long holes159. The second cams154, which are abutting the third cams152, abut the second cam followers164and rotate in the direction of arrow D which is opposite to the urging forces of the springs (not shown).

As shown inFIG. 13C, when the first cams150have rotated one time in the direction of arrow A, the rotating shafts158of the third cams152slide along the long holes159, and the portions of the first cams150, the third cams152, and the second cams154, at which portions the eccentric radii are large, abut one another. In this way, the presser plate14falls to its lowermost position.

In the present sheet supplying device160, the presser plate14is raised and lowered by the combination of the three cams. Therefore, even if the eccentric radii of the respective cams150,152,154are not made to be large, the stroke of the presser plate14can be made to be large. Therefore, the sheet P accommodating capacity can be increased, and the device can be made compact overall.

FIFTH EMBODIMENT

Hereinafter, a fifth embodiment of a sheet supplying device relating to the present invention will be described in detail with reference toFIGS. 14A,14B andFIGS. 15A,15B.

Note that the same reference numerals are applied to members and portions which were described in the first and fourth embodiments, and repeat description will be appropriately omitted.

As shown inFIG. 14A, first cams170are provided so as to be rotatable by a supporting shaft176at the main body frame (not illustrated) of a sheet supplying device180. The supporting shaft176is driven to rotate separately from the supporting shaft22of the feed roller24. Second cams174are rotatably supported by rotating shafts182at the presser plate14. The second cams174can abut the second cam followers164. Springs for urging in a given direction are not provided at the second cams174.

Third cams172are rotatably supported by rotating shafts178between the first cams170and the second cams174, so as to abut the first cams170and the second cams174. The rotating shafts178can slide vertically along long holes (not illustrated) provided in the main body frame. The third cams172can abut the second cam followers162. Springs for urging in a given direction are not provided at the third cams172.

The first cams170are driven to rotate 90° in opposite directions (the direction of arrow A and the direction of arrow D), due to the rotation of the supporting shaft176. The third cams172and the second cams174are driven cams which rotate followingly accompanying the rotation of the first cams170.

Next, operation of the present sheet supplying device180will be described.

The presser plate14is pushed downward to its lowermost position due to the respective portions of the first cams170, the third cams172, and the second cams174, at which portions the eccentric radii are large, abutting one another.

As shown inFIG. 14A, when the first cams170rotate in the direction of arrow A, the third cams172rotate followingly in the direction of arrow C while abutting the second cam followers162. Together therewith, the rotating shafts178start to slide. Due to the rotation of the third cams172, the second cams174rotate followingly in the direction of arrow B while abutting the second cam followers164. Due to the rotation of the first cams170and the third cams172and the second cams174, the presser plate14rises upward due to the urging forces of the springs20.

As shown inFIG. 14B, at the time when the first cams170rotate 90° in the direction of arrow A due to the rotation of the supporting shaft176, when the third cams172followingly rotate90° in the direction of arrow C, the rotation of the third cams172is restricted due to the pins and the receiving portions which are not shown. Accompanying the rotation of the third cams172, the second cams174also followingly rotate90° in the direction of arrow B, and the rotation of the second cams174is restricted due to the pins and the receiving portions which are not shown.

Due to respective portions of the first cams170, the third cams172, and the second cams174, at which portions the eccentric radii are small, abutting one another, the presser plate14rises to its topmost position. When the presser plate14is raised, the sheets P are supplied by the feed roller24(seeFIG. 1).

Thereafter, as shown inFIG. 15A, when the first cams170are driven to rotate in the direction of arrow D (the direction opposite to the direction of arrow A) by the supporting shaft176, the lowering of the presser plate14due to the rotation of the first cams170begins. At this time, the third cams172and the second cams174remain stopped because their rotation is restricted.

As shown inFIG. 15B, when the first cams170rotate further in the direction of arrow D, the third cams172abut the second cam followers162, and thereby rotate followingly in the direction of arrow E.

Moreover, due to the second cams174abutting the second cam followers164, the second cams174rotate followingly in the direction of arrow F, and push the presser plate14downward.

The presser plate14moves downward to its lowermost position due to the first cams170rotating further in the direction of arrow D, and the portions of the first cams170, the third cams172, and the second cams174, at which portions the eccentric radii are large, abutting one another.

In the present sheet supplying device180, the presser plate14can be moved upward and downward by the combination of the three cams. Therefore, even if the eccentric radii of the respective cams170,172,174are not made to be large, the stroke of the presser plate14can be made to be large. Therefore, the sheet P accommodating capacity can be increased, and the device can be made compact overall.

EMBODIMENT OF THE IMAGE FORMING DEVICE

Lastly, an embodiment of an image forming device, to which the sheet supplying device10of the first embodiment is applied, will be described in detail with reference toFIG. 7.

The process cartridge204, in which an image forming section has been integrally formed into a unit, is provided in the present image forming device200. A photosensitive body drum216, which rotates in a given direction, is provided at the interior of the process cartridge204. A charging roller218, which charges the photosensitive drum, a developing roller220, which develops an electrostatic latent image formed on the photosensitive body drum, and a transfer roller222, which transfers the developed toner image on the photosensitive body drum onto the sheet P, are disposed at the periphery of the photosensitive body drum216from the rotating direction upstream side. A cleaning member224, which cleans the surface of the photosensitive body drum after transfer, is provided at the downstream side of the transfer roller222in the rotating direction of the photosensitive body drum216. An exposure device214, which illuminates image light onto the photosensitive body drum216, is provided in the image forming device200between the charging roller218and the developing roller220.

The sheet supplying devices10of the present invention, in which the sheet-shaped sheets P are stacked, are provided in two levels, one above the other, at the lower portion of the image forming device200. Feeding cassettes206,208, in which the sheets P of respectively different sizes can be accommodated, are disposed at the sheet feeding devices10so as to be able to be pulled out to the exterior thereof. The feed rollers24, which remove and convey the sheets P one-by-one as described above, are provided at the sheet P removing positions of the feeding cassettes206,208.

Two sets of conveying rollers210,211and conveying rollers212,213are provided which convey the sheets P, which have been supplied from the feed rollers24, to a position opposing the photosensitive body drum216and the transfer roller222. A fixing unit250, which is provided with a heat roller252and a pressure roller254, is installed at the downstream side of the transfer roller22in the conveying direction of the sheets P. A discharged sheet tray230, to which the sheets P are discharged after fixing, is provided at the downstream side of the fixing unit250.

An opening/closing cover232is provided at the image forming device200. By opening the opening/closing cover232, the fixing unit250can be installed in the image forming device200. When the fixing unit250is installed in the image forming device200, simultaneously therewith, a connector of the fixing unit250and a connector of the image forming device200are joined together. By closing the opening/closing cover232, the image forming device200is set in a state in which operation is possible.

In this image forming device, an electrostatic latent image is formed on the surface of the photosensitive body drum216due to the photosensitive body drum216being charged by the charging roller218and image light being illuminated thereon from the exposure device214. The electrostatic latent image is developed by the developing roller220, such that a toner image is formed on the photosensitive body drum216.

The sheet P is supplied from the feeding cassette206of the sheet supplying device10due to the rotation of the feed roller24, and the sheet P is conveyed by the conveying rollers210,211and the conveying rollers212,213to the position opposing the photosensitive body drum216and the transfer roller222. Then, the toner image on the photosensitive body drum216is transferred onto the sheet P by the transfer roller222. Due to the application of heat and pressure between the heat roller252and the pressure roller254of the fixing unit250, the toner image on the sheet P is fused such that the image is fixed on the sheet P. Thereafter, the sheet P on which the image has been formed is discharged out to the discharged sheet tray230.

In the image forming device200in which the sheet supplying device10of the first embodiment is incorporated, when the presser plate14is raised up and the sheet P is supplied by the rotation of the feed roller24, the presser plate14and the supporting shaft22of the feed roller24do not interfere with one another, and the accommodating capacity of the sheets P can be increased even if the first cams30are not made to be large. Namely, the sheet supplying device10, and accordingly, the image forming device200, can be made to be compact.

Note that, instead of the sheet supplying device10of the first embodiment, any of the sheet supplying devices of the second through fifth embodiments can be incorporated into the image forming device. In this way, the sheet P accommodating capacity can similarly be increased, and the image forming device can be made to be compact.