US20090026693A1

US20090026693A1 - Sheet Separating Mechanism And Sheet Feeding Apparatus Having The Same

Info

Publication number: US20090026693A1
Application number: US11/828,359
Authority: US
Inventors: Boo Siong Sean Lim
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2007-07-26
Filing date: 2007-07-26
Publication date: 2009-01-29

Abstract

A sheet separating mechanism for a sheet feeding apparatus includes a separation wall configured to face a stack of media sheets and a media guide attached to a top end of the separation wall. The separation wall includes an inclined surface that confronts the leading edges of the media sheets in the stack and a separation strip disposed on the inclined surface. At least one flat spring having a deflectable free end and a friction pad adhered to the free end is removably attached to the media guide. The separation strip and the friction pad are arranged such that, during a sheet feeding operation, the separation strip defines an initial separation surface and the friction pad defines a second separation surface downstream from the initial separation surface in the sheet feeding direction.

Description

FIELD OF THE INVENTION

The present invention generally relates to a sheet separating mechanism for separating sheets from a stack of media sheets and a sheet feeding apparatus having the same.

BACKGROUND

Conventional image forming devices, such as inkjet printers, laser-jet printers, copiers, and facsimile machines, normally include a sheet feeder for automatically feeding individual sheets, one by one, from a stack of media sheets to an image forming unit. To prevent individual sheets in the stack from adhering to one another during the sheet feeding operation, conventional sheet feeders are provided with some sort of sheet separating mechanism. Because there are a variety of media types in the market with different coefficients of friction and thicknesses, the separation force needed for separating different types of media sheets may not be the same. As such, it is desirable to have a reliable and simple sheet separating mechanism that can handle a large variety of media types.

SUMMARY

The present invention provides a sheet separating mechanism for a sheet feeding apparatus that can function reliably with different types of media. This sheet separating mechanism includes a separation wall configured to face a stack of media sheets and a media guide attached to a top end of the separation wall. The separation wall includes an inclined surface that confronts the leading edges of the media sheets in the stack and a separation strip disposed on the inclined surface. At least one flat spring having a deflectable free end and a friction pad adhered to the free end is removably attached to the media guide. The separation strip and the friction pad are arranged such that, during a sheet feeding operation, the separation strip defines an initial separation surface and the friction pad defines a second separation surface downstream from the initial separation surface in the sheet feeding direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a sheet feeding apparatus having a sheet separation wall according to an embodiment of the present invention.

FIG. 2 is a perspective view of the sheet feeding apparatus shown in FIG. 1.

FIG. 3 is an enlarged perspective view of the sheet separation wall shown in FIG. 1.

FIG. 4 is a perspective view showing a portion of the sheet feeding apparatus where a flat spring with a friction pad is located.

FIG. 5A is a perspective front view of the flat spring with a friction pad according to one embodiment.

FIG. 5B is a perspective back view of the flat spring shown in FIG. 5A.

FIG. 6 is a cross-sectional view illustrating the function of the flat spring in the sheet feeding apparatus.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view of a sheet feeding apparatus 10 according to an embodiment and FIG. 2 is a perspective view thereof. The sheet feeding apparatus 10 may be incorporated into an image forming device, such as an inkjet printer, a facsimile device, or a multi-function printer with facsimile/scanning/copying functions. Referring to FIG. 1, the sheet feeding apparatus 10 includes an input tray 11 having a support surface 11 a, on which a stack M of media sheets (herein after referred to as “media stack”) is placed, and a sheet separation wall 12 at one end. The sheet feeding apparatus 10 further includes a pickup mechanism 20 which includes a pickup roller 21 rotatably mounted to a pick arm 22. Referring to FIG. 2, the pick arm 22 is pivotally mounted on a drive shaft 23. A conventional drive source, e.g. a motor (not shown) is operatively connected to the drive shaft 23 to rotate the same. The drive shaft 23, in turn, is operatively coupled to the pickup roller 21 via a conventional driving mechanism (not shown) to indirectly rotate the pickup roller 21. The pickup roller 21 is arranged so as to contact the uppermost sheet of the media stack M and can be driven to urge the sheets from the media stack M, one by one, towards and along the sheet separation wall 12. Connected to a top end of the separation wall 12 is a media guide 13 for guiding a sheet towards a media path P. Referring to FIGS. 1 and 2, a set of turn rollers 30 is mounted adjacent to the media guide 13. The turn rollers 30 are mounted on a roller shaft 31 (FIG. 2) and are rotatably driven to advance a sheet from the media stack M into the media path P. In a typical imaging cycle, an uppermost sheet is picked from the media stack M in the input tray 11 by the pick roller 21 and transported to an image forming zone (e.g. print zone) along the media path P.
Referring to FIG. 3, the sheet separation wall 12 includes a plurality of wall sections 12 a mounted on a support frame 12 b. Each wall section 12 a has an inclined surface that faces the media stack M and forms an obtuse angle relative to the support surface 11 a of the input tray 11. In other embodiments, the wall sections 12 a are integrally formed with the support frame 12 b as a single unitary structure. A separation strip 14 is disposed on one of the inclined surfaces 12 b. The separation strip 14 is made of a material that has a coefficient of friction that is sufficiently high enough to facilitate separation of the uppermost sheet from the underlying sheets, yet low enough to allow the uppermost sheet to be moved by the pick roller 21 along the inclined surfaces. In one embodiment, the separation strip 14 is formed of an elastomer, such as a natural or synthetic rubber. Although only one separation strip 14 is shown in FIG. 3, it should be understood by those skilled in the art that additional separation strips may be disposed on other wall sections 12 a. The sheet separation wall 12 is configured to facilitate the separation of the uppermost sheet from the underlying sheets when multiple sheets from the media stack M are moved by the pick roller 21 towards the separation wall 12. Collectively, the inclined surfaces of the separation wall 12 constitute a separation surface against which the leading edges of the sheets from the media stack M are urged into engagement.
As shown in FIG. 3, the media guide 13 is configured to have a plurality of spaced apart extensions 13 a. A plurality of flat springs 15 are attached to the media guide 13 at spaced apart locations with the number of flat springs 15 corresponding to the number of turn rollers 30. Referring to FIG. 4, each flat spring 15 is removably attached to the media guide 13 at a location between adjacent extensions 13 a. Adhered to each flat spring 15 is a friction pad 16. Each flat spring 15 is positioned such that the friction pad 16 is in pressing contact with a corresponding turn roller 30.
Referring to FIG. 5A and FIG. 5B, the flat spring 15 has two arms 15 a and a deflectable free end 15 b. The arms 15 a are configured to removably attach (i.e. clip) the flat spring 15 onto the media guide 13. The friction pad 16 is adhered onto the deflectable free end 15 b. The flat spring 15 may be formed from stainless steel sheet. The friction pad 16 is formed of a friction material (e.g. cork material) with a coefficient of friction that is lower than that of the turn roller 30 but is higher than that of the media sheets. The friction pad 16 should not erode the turn roller as the friction pad is being biased against the turn roller, but the friction pad should provide enough friction to prevent multiple sheets from being fed into the media path P.
During a sheet feeding operation, an uppermost sheet is urged towards the separation wall 12 by the pick roller 20 so that the leading edge of the uppermost sheet engages and slides along the inclined surfaces of the sheet separation wall 12, including the separation strip 14. The separation strip 14 facilitates the separation of the uppermost sheet from underlying sheets of the media stack M by applying friction to the leading edges of the sheets. The uppermost sheet is then pinched between the friction pads 16 and the turn rollers 30 by the biasing force from the free ends 15 b of the flat springs 15. Subsequently, the uppermost sheet is fed into the media path P in the direction towards an image forming zone within the image forming device.
In certain instances, despite the presence of the separation wall 12 with the separation strip 14, multiple sheets are shifted upward along the separation wall 12. This may be the result of some underlying sheets sticking to the uppermost sheet that has been successfully separated from the media stack M. The friction pads 16 are designed to provide an extra safeguard against multiple-sheet picking and further reduce the likelihood of multiple sheets being fed into the media path P.
Referring to FIG. 6, the free end 15 b of the flat spring 15 is deflectable away from the turn roller 30 (in the direction shown by arrow R) as needed to accommodate media sheets of different thicknesses. If two or more sheets are about to be fed together into the media path P by the turn rollers 30, the movement of the adjacent underlying sheet S2 is retarded by friction against the friction pad 16 thereby allowing the upper sheet S1 to be advanced forward as depicted in FIG. 6. As such, during a sheet feeding operation, the separation strip 14 on the separation wall 12 defines an initial separation surface and the friction pads 16 collectively define a second separation surface for retarding the movement of any underlying sheet that may have advanced beyond the separation wall 12.
The sheet separating mechanism of the present invention functions effectively in preventing multiple-sheet feeding for different types of media. The flat spring design takes up little space and is inexpensive to produce. Because the flat spring is removable, its position can be changed according to the operation requirements of a particular sheet feeding apparatus.
While particular embodiments of the present invention have been described, it will be understood by those skilled in the art that modifications and substitutions can be made without departing from the scope of the invention as set forth in the following claims.

Claims

1. A sheet separating mechanism for separating individual sheets from a stack of media sheets during a sheet feeding operation, said sheet separating mechanism comprising:

a separation wall configured to face a stack of media sheets, said separation wall comprising an inclined surface that confronts the leading edges of the media sheets in the stack and a separation strip disposed on said inclined surface;

a media guide attached to a top end of the separation wall for guiding the movement of a sheet; and

at least one flat spring attached to said media guide, said flat spring having a deflectable free end and a friction pad adhered to the free end,

wherein the separation strip and the friction pad are configured to apply friction to the leading edges of the sheets coming into contact therewith, and

wherein the separation strip and the friction pad are arranged such that the separation strip defines an initial separation surface and the friction pad defines a second separation surface downstream from the initial separation surface in a sheet feeding direction.

2. The sheet separating mechanism of claim 1, wherein said separation strip is formed of an elastomer.

3. The sheet separating mechanism of claim 1, wherein said friction pad is formed of a cork material.

4. The sheet separating mechanism of claim 1, wherein said flat spring is removably attached to said media guide.

5. The sheet separating mechanism of claim 4, wherein said flat spring is configured to have two arms for clipping onto the media guide.

6. The sheet separating mechanism of claim 1, wherein said flat spring is made of stainless steel.

7. The sheet separating mechanism of claim 1, wherein said media guide comprises a plurality of spaced apart extensions and said flat spring is positioned between adjacent extensions.

8. A sheet feeding apparatus for supplying sheets, one by one, from a stack of media sheets in a sheet feeding direction, said sheet feeding apparatus comprising:

a support surface for supporting a stack of media sheets;

a separation wall having an inclined surface that forms an obtuse angle relative to said support surface and a separation strip disposed on said inclined surface, said separation strip being configured to apply friction to the leading edges of sheets coming into contact therewith;

a rotatable pick roller operable to urge an uppermost sheet in the stack of media sheets towards and along the separation wall;

a media guide attached to a top end of the separation wall;

a plurality of turn rollers mounted adjacent to the media guide; and

at least one flat spring having a deflectable free end and a friction pad adhered to said free end, said friction pad being configured to apply friction to the leading edges of sheets coming into contact therewith,

wherein said flat spring is attached to said media guide and positioned such that said friction pad is in pressing contact with one of the turn rollers.

9. The sheet feeding apparatus of claim 8, wherein the free end of the flat spring is deflectable away from said one of the turning rollers to accommodate media sheets of different thicknesses.

10. The sheet feeding apparatus of claim 8, wherein said separation strip is formed of an elastomer.

11. The sheet feeding apparatus of claim 8, wherein said friction pad is formed of a cork material.

12. The sheet feeding apparatus of claim 8, wherein said flat spring is removably attached to the media guide.

13. The sheet feeding apparatus of claim 12, wherein said flat spring is configured to have two arms for clipping onto the media guide.

14. The sheet feeding apparatus of claim 8, wherein a plurality of said flat spring are attached to said media guide, each flat spring being positioned such that the friction pad thereon is in pressing contact with a corresponding turn roller.