Patent Application
20090212489
The present application is directed to alignment systems and methods for use in an image forming apparatus and particularly to systems and methods that move a media sheet against a reference edge as the media sheet moves along a media path.
Image forming apparatus' include a media path for moving media sheets from an input area, through a transfer area, and ultimately to an output area that is usually on an exterior of the apparatus. The input area may include a variety of constructions, including but not limited to an input tray. A pick arm may be pivotally positioned to contact a top-most media sheet in the input tray. The pick arm is activated and drives the top-most media sheet from the input tray and along the media path. The media path may also include one or more nips formed between opposing rolls. The nips may function to drive the media sheets along the media path and/or to align the media sheets. The transfer area includes one or more imaging units that transfer an image onto the media sheets.
The media sheets should move along the media path in a consistent fashion. This is necessary to ensure the media sheets are located at the transfer area at the precise time to receive the images. The media sheets should also be aligned by the time they reach the transfer area. Proper alignment ensures the images are positioned at the correct position on the media sheets. A misaligned media sheet at the transfer station may result in a print defect as the image is not centered or otherwise located on the media sheet.
The media path should also be constructed in a manner to prevent media jams. The media jams are frustrating to the user as it requires intervention to clear the jam and restart the image formation process. Further, media jams may damage the media sheets and/or the image forming apparatus.
The present application is directed to systems and methods to align a media sheet in a media path of an image forming apparatus. In one embodiment, the system may include an input area with an alignment edge to initially laterally align the media sheet. The media sheet may then move through an alignment nip which is constructed to laterally move the media sheet against a reference edge. The media sheet moves along the reference edge and becomes aligned prior to moving to a transport belt. The media sheet may then move through one or more transfer nips to receive one or more images.
The present application is directed to systems and methods to align a media sheet moving along a media path.
To better understand the context of feeding media sheets,
In use, a media sheet is moved from the input tray 20 and moved into the media path 30. The alignment nip 40 is formed between a drive roll 41 and a backup roll 42 to align the media sheet prior to passing to a transport belt 50 and past a series of image forming stations 103. A print system 142 forms a latent image on a photoconductive member 61 in each image forming station 103 to form a toner image. The toner image is then transferred from the image forming station 103 to the passing media sheet.
Color image forming devices typically include four image forming stations 103 for printing with cyan, magenta, yellow, and black toner to produce a four-color image on the media sheet. The transport belt 50 conveys the media sheet with the color image thereon towards a fuser 124, which fixes the color image on the media sheet. Exit rolls 126 either eject the print media to an output tray 128, or direct it into a duplex path 129 for printing on a second side of the media sheet. In the latter case, the exit rolls 126 may partially eject the print media and then reverse direction to invert the media sheet and direct it into the duplex path 129. A series of rolls in the duplex path 129 return the inverted print media to the primary media path for printing on the second side.
A first alignment of the media sheets occurs within the input tray 20.
After leaving the input tray 20, the media sheet moves further along the media path 30 and into the alignment nip 40 as illustrated in
The drive roll 41 may be connected to a shaft 48 that is driven by a motor 49. Motor 49 drives the drive roll 41 in a forward direction to move the media sheet further along the media path 30. The drive roll 41 may be constructed from a soft durometer material. In one specific embodiment, the drive roll 41 is constructed to have a hardness of between about 50-70 shore A. The size of the drive roll 41 may vary, and in one embodiment includes a diameter of about 15-17 mm.
The backup roll 42 is positioned against the drive roll 41 to form the alignment nip 40. A spring 45 may be operatively connected to the backup roll 42 to create a nip force with the drive roll 41. In one embodiment, the spring 45 creates a nip force of about 0.5-2 lbs. In one embodiment, the backup roll 42 is harder than the drive roll 41. The nip force may result in slight deformation of the drive roll 41.
In one embodiment, the motor 49 may be unidirectional. In addition to driving the rolls 41, 42 forward, the motor 49 may also drive the rolls backward. In one embodiment, the rolls 41, 42 are driven backwards to form a buckle in the media sheet to remove any skew in the media sheet.
The reference edge 31 is a flat surface used for aligning an edge of the media sheet as the media sheet moves along the media path 30. The reference edge 31 is positioned between the input tray 20 and the transport belt 50. In one embodiment, a downstream end 32 of the reference edge 31 is spaced upstream from an upstream end of the transport belt 50. The reference edge 31 may include a gentle lead-in from a bottom of the reference edge 31 to the media path 30 to prevent damage to the media sheet during alignment.
As best illustrated in
In use, the media sheet is initially loaded into the input tray 20. Once loaded, the biasing mechanism 21 abuts against the first side of the media sheet and aligns the second side of the media sheet against the edge 22. The media sheet is ultimately picked from the input tray 20 by the pick arm 23 and roll(s) 24 and moved along the media path 30. The media sheet moves into the alignment nip 40. The position of the backup roll 42 causes the media sheet to be moved laterally as it is driven forward along the media path 30. The lateral movement causes the second side of the media sheet to contact and align against the reference edge 31. In one embodiment, the media sheet is moved laterally about 1 mm as it moves through the alignment nip 40 and against the reference edge 31.
The media sheet is further driven along the media path 30 and into contact with the transport belt 50. The media sheet then moves through one or more of the transport nips 61 formed between the transport belt 50 and the photoconductive members 61 at each respective transfer roll 59.
In one embodiment, the media sheet is still moving through the alignment nip 40 as the media sheet moves through one or more of the transfer nips 60. The transfer nips 60 may move the media sheet at a slower speed than the alignment nip 40. This speed differential prevents the alignment nip 40 from placing any tension on the media sheet as it moves through the one or more transfer nips 61. In one embodiment, the media sheet may form a buckle upstream from the first transfer nip 61.
In one embodiment, a transfer nip force is formed between the photoconductive member 61 and the transport belt 50 where it is supported by the transfer roll 59. The transfer nip force may be greater than an alignment nip force formed between the rolls 41, 42 at the alignment nip 40.
In one embodiment, the backup roll 42 is positioned at a non-parallel angle relative to the reference edge 31. In another embodiment, the backup roll 42 is parallel with the reference edge 31 and the drive roll 41 is positioned at a non-parallel angle relative to the reference edge 31.
One type of input area for initially aligning the media sheet is an input tray 20 as discussed above. Another input area includes a multi-purpose feeder 120 as illustrated in
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
