Patent Application
20060071390
This invention relates to imaging devices that feed variable length media over a paper path longer than the length of some of the media to be fed.
Printing devices utilizing a media tray under the device typically feed the media out of the tray to the rear and around a “C” shaped path to enter the imaging area and exit to the front of the device. This provides a very compact machine. Because of the varying lengths of media fed through such a device, some mechanism must be provided to accommodate the discrepancy between the length of short media and the path length. This conventionally is done by using a relatively large drive roller (or rollers) which move the media toward non-driven idler rollers to maintain contact with the media while it is being fed around the path and into the imaging area.
In a separate patent application recently filed and commonly owed with this application, an improved mechanical system to feed the documents is described and claimed which employs two autocompensating systems, one intermediate in the feed path. That system is described in detail here as this invention provides modes of use of that system which increase the speed of media through the “C” path for certain media.
This invention employs a mechanical system having a pivoting autocompensating feed roller located at an intermediate location in the feed path. (An autocompensating system comprises one or more feed rollers on a swing arm pivoted around a gear train which drives the feed roller.) Autocompensating systems are cost-effective and may be moved toward the media for feeding and off the media by reversing the torque to the gear train. An autocompensating system may be used to pick paper from the tray, and both autocompensating systems may be driven from one motor through different drive trains.
In basic operation the intermediate autocompensating system is moved away from the feed path until media is driven past that system. Then that system is applied to move the media while the tray autocompensating system is not driven. This assures feeding of short media, such as cards or photograph-sized media.
In accordance with this invention, modes are provided for standard-sized (non-short) media. In those modes the tray system drives the media, and the intermediate system is not employed. This avoids a pause in feeding while the intermediate autocompensating system is moved into the feed path and begins feeding. In its most cost-effective form, such a mode is operative only when the job data defines the media as sufficiently long or when an operator defines the media as sufficiently long. These alternatives add a minimum of structure to the printing system, as they involve only information received by an electronic controller of an imaging device. Alternatively, of course, the length of the media or the length of the bin holding media can be measured or obtained using sensors, as is readily done in this art.
The details of this invention will be described in connection with the accompanying drawings, in which
Imaging station 7 is located past nip rollers 9a, 9b which grasp paper 5 in the nip of rollers 9a, 9b and move it under printhead 3. Nip rollers 9a, 9b are stopped normally several times to permit printhead 3 to partially image sheet 5 by moving across sheet 5 (in and out of the view of
Nip rollers 9a, 9b push paper through the imaging station 7 where they enter exits rollers 11a, 11b, 11c, and 11d. Although rollers are by far the most common mechanism to transport the imaged sheet 5 out of the printer 1 to the user of the printer 1, virtually any grasping device can be used, such as a belt and pressing device or pneumatic suction device.
The printer of
A C-shaped paper guide 17 is made up of rear guide surface 17a and spaced, generally parallel, front guide surface 17b. Both surfaces have spaced ridges (shown for surface 17b as 17bb in
Pick roller 15a at tray 13 and drive roller 19a combine to move sheets 5 from tray 13 to nip rollers 9a, 9b. Drive roller 19a is effective to move short media into rollers 9a, 9b, when pick roller 15a is no longer in contact with the sheet 5.
Operational control is by electronic data processing apparatus, shown as element C in
Movement of parts in the printer is by one motor 30, shown in
Similarly, gear 32a meshes with idler gear 40 which meshes with a somewhat larger gear 42. Gear 42 has integral with it a central, smaller gear 42a (best seen in
As is evident from the gears trains, rotation of motor 30 counterclockwise as viewed in
With reference to
Assuming counterclockwise torque to gear 50 and clockwise torque to gear 60, so long as gear 56 of system 15 or gear 66 of system 19 is not rotating, the torque pivots bracket 58 or bracket 68 respectively and the force against a sheet 5 of drive roller 15a and 19a increases toward the maximum pivoting force which can be applied by motor 30. This force is immediately relieved when gear 56 rotates in the case of system 15 and when gear 66 rotates in the case of system 19. Such rotation occurs when a sheet 5 is being moved, and it is the increase in pivot force against the sheet until it is moved which constitutes autocompensating in the systems.
Opposite or no rotation from the feeding rotation of gears 50 and 60 relieve pivoting torque because the direction of pivot is away from the feeding position and therefore the gears 56 and 66 respectively are free to rotate. To prevent such rotation with respect to system 15, gear 50 is driven through a one-way clutch, (not shown), which may be a conventional ball-and-unsymmetrical-notch clutch or other clutch.
This mechanism is a slip drive. As shown in
As shown in
With spring 72 compressed, the turning of gear 66 turns spring 72 and the turning of spring 72 tends to rotate the entire housing 70, since well 74 is integral with housing 70. However, when further rotation is blocked, spring 72 simply slips.
When gear 66 is rotated in the reverse feeding direction, system 19 is moved away from the drive path of guide 17 as shown in
When gear 66 is rotated in the feeding direction, spring 72 adds somewhat to the downward force while slipping.
In basic operation, under control of controller C, motor 30 is driven to feed a sheet 5 from tray 13 by rotating autocompensating system 15 downward. Autocompensating system 19 is necessarily driven by the slip drive to move away from the paper feed direction. Accordingly, when a sheet 5 is being moved by system 15, system 19 is moved completely out of guide path 17, as shown in
In operation when the length of sheet 5 is not considered, the sheet 5 moves to encounter sensor arm 21 (
System 19 moves sheets 5 until they reach nip roller 9a, 9b and, preferably, become somewhat buckled. The buckling serves to align sheets 5. The remaining imaging operation may be entirely standard.
In accordance with this invention, a mode is provided in which longer sheets are fed to the nip rollers 9a, 9b by autocompensating system 15 alone. Autocompensating system 19 necessarily remains held out of the feed position because of the direction of rotation of motor 30. In a representative system, assuming acceleration and deceleration of rollers 15a and 19a of about 50 inches per second (ips) and maximum speed of 25 ips, feed time of media to nip rollers 9a, 9b is calculated to be reduced from about 370 milliseconds to about 320 milliseconds.
The sequence of such a mode is illustrated in
Decision 88 determines if a sheet 5 has reached the nip rollers 9a, 9b. If no, decision 88 is invoked again at short intervals. If yes, decision 88 invokes action 90, which continues normal printing by the nip rollers 9a, 9b.
As discussed, with a sheet 5 at nip rollers 9a, 9b, the nip rollers 9a, 9b first turn in reverse feed direction align to register sheet 5 and then turn to transport sheet 5 into the imaging station 7 for normal printing. Nip rollers 9a, 9b are proximate to imaging station 7 to permit all sheets to be fed into imaging station 7.
Determination of whether a sheet 5 has reached nip rollers 9a, 9b may be by any standard method such as by a sheet-presence sensor such as sensor arm 21 or by controller C tracking sheet movement.
If this speed move is the default mode, then misfeeds must be avoided by positively identifying media which is short. Accordingly, the feed mode preferably is positively invoked and the default is to use the intermediate roller is feeding all sheets. Since all of the operation discussed is necessarily under the control of the electronic control C, positive invoking of the speed mode may be by input by a human operator through a control panel (not shown) of the printer 1 or by controller C recognizing a media description in the data of a print job and invoking the speed mode just for that print job (print jobs typically have lead or “header” information and such information may definitively define media length). The print job may call for feeding from a tray reserved or unique to short media, thereby positively identifying the size of the media. The length of sheet may, of course, be measured by sensors and the size of a bin carrying sheets may be measured by sensors, which is well within the state of the art, but adds some complexity and costs to the imaging device. Where the length of the first sheet of a job is known, normally it can be assumed that all sheet of that job are of the known length.
A disadvantage of the speed mode is that the media is more positively guided when the intermediate feed is employed. This positive guidance can be used to position the media against one or more sensors or the like.
An additional advantage of a speed mode is quieter operation since reversing motor direction causes some clash of gears.
It will be recognized that this invention can take alternative forms, so long as an autocompensating system is used at least at the intermediate drive location.
