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  
       [0001]     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  
       [0002]     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.  
         [0003]     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  
       [0004]     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  
       [0005]      FIG. 1  is a perspective view of an exemplary shaft driven media feeding apparatus with the top portion of the housing removed for clarity.  
         [0006]      FIG. 2  is a perspective view of an exemplary shaft driven media feeding apparatus with the top portion of the housing in place.  
         [0007]      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.  
         [0008]      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  
       [0009]      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.  
         [0010]      FIG. 2  illustrates one possible placement and design of upper housing  20  and lower housing  22 .  
         [0011]     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.  
         [0012]     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.  
         [0013]     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 )*[(N 1 *N 3 )/(N 2 *N 4 )] where N 1  represents the number of teeth on the bevel drive gear  12 , N 2  represents the number of teeth on the bevel gear  18   a , N 3  represents the number of teeth on bevel gear  18   b , and N 4  represents the number of teeth on bevel driven gear  14 .  
         [0014]     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.  
         [0015]     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.  
         [0016]     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.  
         [0017]     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.  
         [0018]     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.  
         [0019]     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.