US20070102867A1

US20070102867A1 - Media feeding apparatus

Info

Publication number: US20070102867A1
Application number: US11/269,957
Authority: US
Inventors: Michael Leemhuis; Daniel Westhoff
Original assignee: Lexmark International Inc
Current assignee: Lexmark International Inc
Priority date: 2005-11-09
Filing date: 2005-11-09
Publication date: 2007-05-10

Abstract

A media feeding assembly capable of feeding media from a media source including a rotatable connecting shaft and a pick roller. Driving of the shaft may provide a driving and a normal force on the pick roller towards a media source.

Description

FIELD OF THE INVENTION

The present invention relates to a media feeding apparatus, and more particularly, to a shaft driven pick mechanism for use within an imaging apparatus that may supply a driving and normal force to pick media from a media tray.

BACKGROUND OF THE INVENTION

An image forming apparatus, such as an electrophotographic or inkjet printer, or even a duplicating apparatus, may include a media sheet supply system having a sheet feed assembly and a supply tray which may hold a plurality of media sheets, such as paper. The media sheets may be held in the supply tray until a print job is requested, and ideally are transported one by one within the apparatus for printing.
Such devices may utilize rollers to pick the media which rollers may commonly be sourced from, e.g., elastomeric type materials. Elastomeric materials in turn provide a useful surface to frictionally engage the media so that the media may be more efficiently conveyed from the media source to a selected media pathway within the image forming apparatus. Accordingly, it may be desirable to initially include an elastomeric material that maintains a relatively high coefficient of friction (COF) between the roller and media sheet. Over time, and depending upon the type of material utilized in the roller, surface finish, and cleaning chemicals utilized to clean the roller, it is common to see a reduction in the COF along with a reduction in media picking performance.

SUMMARY OF THE INVENTION

In one exemplary embodiment the present invention relates to a media feeding assembly capable of feeding media from a media source. The assembly may include a rotatable shaft and a pick device wherein driving of the shaft provides a normal force on the pick device towards a media source. In another exemplary embodiment the present invention again relates to a media feeding assembly capable of feeding media from a media source. The assembly may include a driven gear and a drive gear. Such gears may then be engaged with a pair of gears on either end of a connecting shaft having a length such that the number of gear meshes is two. The system efficiency of the assembly may then remain substantially constant and independent of connecting shaft length.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary shaft driven media feeding apparatus with the top portion of the housing removed for clarity.
FIG. 2 is a perspective view of an exemplary shaft driven media feeding apparatus with the top portion of the housing in place.
FIG. 3 provides a size comparison of a spur gear based media feeding apparatus v. a shaft driven media feeding apparatus illustrating the relative reduction in height of the shaft driven design.
FIG. 4 provides a partial cut-away sectional view of an exemplary shaft driven media feeding apparatus as engaged with media in a media feed tray.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary embodiment which identifies a shaft driven media feeding assembly 10. In this illustration, the upper portion of the housing 20 has been removed to expose the inner gearing for purposes of clarity and ease of description.
FIG. 2 illustrates one possible placement and design of upper housing 20 and lower housing 22.
The feeding assembly 10 may include a bevel drive gear 12 and a bevel driven gear 14. A connecting shaft 16 may then be positioned between such gears and each end of the shaft may include gears 18 a and 18 b, such as bevel gears. The bevel gears may therefore be used to adjust the speed, e.g., between drive gear 12 and bevel gear 18 a. The use of bevel gears 18 a and 18 b may also provide efficient transmission of power and motion between the angled intersection that may occur between bevel gears 18 a and 18 b with drive gear 12 and driven gear 14. As shown, bevel drive gear 12 in combination with bevel gear 18 a may transmit power to the connecting shaft 16 that is perpendicular to the drive shaft 21 (see FIG. 2). In the context of the present invention, it should be appreciated that any gearing that may be suitable to transmit power and/or motion from drive gear 12 to shaft 16 and to driven gear 14 is contemplated. This may therefore include, e.g., miter gears, helical gears and/or worm gears.
The assembly 10 may also include a one-way clutch 30, axle shaft 33 and pick devices such as pick rollers 34. The rollers may be formed from a suitable elastomeric material and may therefore provide a surface for frictional engagement with media to be picked. The gears 18 a and 18 b may also be positioned in the upper portion of the housing 20 by journal bearings (not shown). In addition, with reference to FIG. 2, the assembly may be engaged with a motor or other suitable source of power via the drive shaft 21 which as illustrated may be engaged with drive gear 12. In this manner, it should also be appreciated that assembly 10 may also pivot about drive shaft 21 to provide a normal force to media engaging pick roller 34. Such normal force and driving force may therefore automatically increase until the top sheet of media (i.e., the sheet of media engaging pick roller 34) moves. This may be termed an auto-compensating feature that may allow for the feeding of a wide range of paper weights, sizes and finishes from a single feeder, and which is quite advantageous with respect to expanding printer capability and performance. One example of an auto-compensating type system is disclosed in U.S. Pat. No. 5,527,026 whose teachings are incorporated herein by reference.
In addition, it is worth noting in FIG. 1 that the connecting shaft 16 may therefore employ what may be considered four bevel gears, i.e., bevel drive gear 12 engaging bevel gear 18 a and bevel gear 18 b engaging bevel driven gear 14. This provides that the number of gear meshes is always two. The feature of system efficiency (Eff) is reference to a loss in power as conveyed between the gears. This may be evaluated by measurement of an input torque and comparison to the output torque of the subject linkage after compensating for the gear ratio. In other words, the Eff=(Torque_out/Torque_in)*[(N₁*N₃)/(N₂*N₄)] where N₁represents the number of teeth on the bevel drive gear 12, N₂represents the number of teeth on the bevel gear 18 a, N₃represents the number of teeth on bevel gear 18 b, and N₄represents the number of teeth on bevel driven gear 14.
It may therefore be noted that this efficiency may now be relatively constant regardless of the length of shaft 16. This may therefore provide the benefit that designing a shaft 16 for an optimum length may only require a change in the housing components 20 and 22 and length of shaft 16. Accordingly, other components of the feeding assembly 10 may remain relatively similar. This may then allow for the feature that the feeding assembly 10 can serve as a standardized design which may reduce design, part and testing costs.
Such exemplary benefit (constant overall relative efficiency regardless of shaft length) may be highlighted by a comparison to the pick-arm 36 shown in FIG. 3. As illustrated, the pick arm 36 employs 6 spur gears and five gear meshes. In this case, if additional gears are added to extend pick arm length, the system efficiency will drop.
Accordingly, the gearing described herein provides the feature that the number of gear meshes is two together with the additional feature that the height of the arm relative to, e.g., a paper feeding tray (not shown) may be reduced. This may be illustrated in FIG. 3 which shows a spur gear type media feeding apparatus 36 in the background along with an arm bend location 40 in relative reduced size but which when brought forward and comparatively sized directly behind the shaft driven media feeding apparatus 10, confirms that the height of the arm 16 relative to a paper feeding tray (not shown) may be advantageously reduced. This exemplary benefit may then allow for the use of less vertical space in the printing device and may also avoid the need for relatively larger frames and covers.
The operation of the feeding assembly may now be described and may amount to the following sequence of steps, and attention is directed to FIG. 4. The drive gear 12 may first apply a counter-clockwise torque and bevel gear 18 a may be configured so that arm 16 experiences a counter-clockwise rotation which is configured to provide a clockwise rotation to pick roller 34. Assuming the pick roller 34 does not slip and start to rotate, the applied torque may supply an increased normal and driving force between the pick roller 34 and the top sheet of paper 42. That is, the normal force may be understood as a force which presses the pick roller 34 against the sheet of paper 42, as generally illustrated by arrow 46. This normal and driving force may continue until the paper 42 begins to feed. Once this occurs the pick roller 34 may then rotate in a clockwise direction as shown to drive the paper 42 forward in the general direction of arrow 44 on to a second drive roller (not shown). In addition, roller 47 may be supplied under tray 48 and may be designed to be contacted by roller 34 when the tray is empty. tray is empty. In addition, the roller 47 may be moveable vertically upward under the action of, e.g., a spring, and may pass through a hole in the tray (not shown). The pressure on roller 47 may prevent the assembly 10 from dry picking against the bottom of the paper tray 48 when no media is present.
The drive shaft design herein may also provide a reduced amount of backlash between input and output rotation of the gears. This may then reduce pick time variation of the feeder system which may cause inter-page gap variation. Maintaining a consistent inter-page gap may permit a smaller gap size which may allow the printer to use a relatively lower process speed for the same page per minute throughput.
The foregoing description is provided to illustrate and explain the present invention. However, the description above should not be considered to limit the scope of the invention as set forth in the claim appended hereto.

Claims

1. A media feeding assembly capable of feeding media from a media source comprising a rotatable shaft and a pick device wherein driving of said shaft provides a normal force on said pick device towards said media source.

2. The media feeding assembly of claim 1 further including a housing.

3. The media feeding assembly of claim 1 wherein said rotatable shaft has two ends, one end engaged to an angled drive gear and one end engaged to an angled driven gear.

4. The media feeding assembly of claim 3 wherein said pick device comprises a pick roller that is engaged to said shaft via said angled driven gear.

5. The media feeding assembly of claim 4 including an axle positioned between said pick roller and angled driven gear.

6. The media feeding assembly of claim 3, including a housing mounted for rotation on a pivot about said angled drive gear wherein driving of said input shaft places a torque on said housing about said pivot to force said pick device towards said media source.

7. The media feeding assembly of claim 1 wherein said media source comprises a media tray including a rotatable member positioned to extend through an opening in a bottom of said tray and biased toward said opening to contact said pick device when said tray is empty to permit rotation of said pick device when said tray is empty.

8. The media feeding assembly of claim 3 wherein said angled drive gear or angled driven gear comprises a bevel gear.

9. The media feeding assembly of claim 3 wherein said angled drive gear or angled driven gear comprises a miter gear.

10. The media feeding assembly of claim 3 wherein said angled drive gear or angled driven gear comprises a helical gear.

11. The media feeding assembly of claim 3 wherein said angled drive gear or angled driven gear comprises a worm gear.

12. A media feeding assembly capable of feeding media from a media source comprising:

a drive gear and a driven gear engaged with a pair of gears on either end of a connecting shaft having a length such that the number of gear meshes is two wherein the efficiency (Eff) of said assembly remains substantially constant and independent of said length of said connecting shaft after compensating for the gear ratio.

13. The media feeding assembly of claim 12 wherein the efficiency Eff of said assembly that remains substantially constant and independent of the length of said shaft after compensating for the gear ratio is calculated by the following equation:

Eff=(Torque_out/Torque_in)*[(N ₁ *N ₃)/(N ₂ *N ₄)]

where N₁represents the number of teeth on the drive gear, N₂and N₃represent the number of teeth on said gears on the end of said connecting shaft and N₄represents the number of teeth on said driven gear.

14. The media feeding assembly of claim 12 wherein a pick device is engaged to said shaft.

15. The media feeding assembly of claim 14 including an axle positioned between said pick device and said driven gear.

16. The media feeding assembly of claim 12 wherein driving of said shaft provides a normal force on said pick device towards said media source.

17. The media feeding assembly of claim 12 wherein said media source comprises a media tray including a rotatable member positioned to extend through an opening in a bottom of said tray and biased toward said opening to contact said pick device when said tray is empty to permit rotation of said pick device when said tray is empty.

18. The media feeding assembly of claim 12 wherein said drive gear or driven gear comprises a bevel gear.

19. The media feeding assembly of claim 12 wherein said drive gear or driven gear comprises a miter gear.

20. The media feeding assembly of claim 12 wherein said drive gear or driven gear comprises a helical gear.

21. The media feeding assembly of claim 12 wherein said drive gear or driven gear comprises a worm gear.