Patent Application
20080075477
The present application is directed to methods of moving a media sheet within an image forming device. A media path extends through the device for moving the media sheets to receive a toner image. One or more sensors are positioned along the media path to detect the position of the media sheets and signal a controller that oversees the media sheet movement. The speed of the media sheet may be varied to ensure the media sheet moves along the media path at a proper speed to ensure adequate image formation. The sensor may be activated when the media sheet moves at a first speed, and deactivated when the media sheet moves at a second speed. The controller receives a signal from the sensor indicating the orientation of the media sheet. The controller may adjust the speed of one or more sections of the media path based on these signal or signals.
The image forming device 10 may include a laser printer (mono or color), facsimile, copier, or combination of two or more of these devices which is often referred to as an all-in-one device. The device 10 may be sized to fit on a workspace, such as a desktop. The device 10 may further include accessible work areas for the user to insert and remove media sheets, replace components within the device, and clear media jams from within the device.
A first toner transfer area 83 includes one or more imaging units 84 that are aligned horizontally extending from the front 81 to a back 85 of the body 80. Each imaging unit 84 includes a charging roll, a developer roll, and a rotating photoconductive (PC) drum 86. The charging roll forms a nip with the PC drum 86, and charges the surface of the PC drum 86 to a specified voltage such as −1000 volts, for example. A laser beam from a printhead contacts the surface of the PC drum 86 and discharges those areas it contacts to form a latent image. In one embodiment, areas on the PC drum 86 illuminated by the laser beam are discharged to approximately −300 volts. The developer roll, which also forms a nip with the PC drum 86, then transfers toner particles from a toner reservoir 87 to the PC drum 86 to form a toner image. The toner particles are attracted to the areas of the PC drum 86 surface discharged by the laser beam. In one embodiment, the toner reservoirs 87 each contain one of black, magenta, cyan, or yellow toner.
An intermediate transfer mechanism (ITM) 60 is disposed adjacent to each of the imaging units 84. In this embodiment, the ITM 60 is formed as an endless belt trained about support rollers 61. The ITM 60 may be constructed from a variety of materials including polyimide, Ethylene TetrafluoroEthylene (ETFE), nylon, thermoplastic elastomers (TPE), polyamide-imid, and polycarbonate alloy. During image forming operations, the ITM 60 moves past the imaging units 84 in a clockwise direction as viewed in
The ITM 60 rotates and collects the one or more toner images from the imaging units 84 and then conveys the toner images to a media sheet at a second transfer area. The second transfer area includes a second transfer nip 91 formed between one of the rollers 61 and a second transfer roller 92. In other embodiments as illustrated in
A media path 40 extends through the device 10 for moving the media sheets. Media sheets are initially stored in the input tray 71 or introduced into the body 80 through a manual feed 41. The sheets in the input tray 71 are picked by a pick mechanism 42 and moved into the media path 40. In this embodiment, the pick mechanism 42 includes a roller positioned at the end of a pivoting arm. The roller rotates to move the media sheets from input tray 71 towards the second transfer area. In one embodiment, the pick mechanism 42 is positioned in proximity (i.e., less than a length of a media sheet) to the second transfer area with the pick mechanism 42 moving the media sheets directly from the input tray 71 into the second transfer nip 91. For sheets entering through the manual feed 41, one or more rollers are positioned to move the sheet into the second transfer nip 91.
The media sheet receives the toner image from the ITM 60 as it moves through the second transfer nip 91. The sheets with toner images then move along the media path 40 and into a fuser nip 43. Fuser nip 43 is formed between a pair of rollers or belts 44, 45 that apply heat and pressure to adhere the toner images to the media sheet The fused media sheets then pass through exit rollers 46 that are located downstream from the fuser nip 43. Exit rollers 46 may be rotated in either forward or reverse directions. In a forward direction, the exit rollers 46 move the media sheet from the media path 40 to an output area. In a reverse direction, the exit rollers 46 move the media sheet into a duplex path 47 for image formation on a second side of the media sheet.
The second transfer nip 91 and fuser nip 43 also each function to move the media sheet along sections of the media path 40. Therefore, the speeds of the nips 91, 43 are controlled to maintain the proper speed to ensure toner transfer at the second transfer nip 91 and adequate fusing at the fuser nip 43. The speed of the media sheet as it moves along the media path 40 may vary. By way of example, a first speed may be necessary for moving the media sheet through the second transfer nip 91, and a second faster or slower speed is necessary for moving through the fuser nip 43. In one embodiment, the distance between the nips 91, 43 is less than the length of the media sheet. Therefore, the media sheet is in contact with both nips 91, 43 at the same time. The speed of the nips 91, 43 should be carefully controlled to ensure the media sheet moves at the required speed through each section without affecting the speed of the sheet as it moves through the other section.
Sensors S1, S2, are placed along the media path 40 to determine the position and orientation of the media sheet. In one embodiment, one or both sensors S1, S2 include an actuator arm positioned within the media path 40. Movement of the media sheet along the media path 40 causes the actuator arm to be pushed aside which either actuates a switch, or is sensed by an emitter/receiver combination as described below. In another embodiment, one or both sensors S1, S2 are optical sensors that detect a leading edge or trailing edge of the media sheet when passing the sensor location. The sensors S1 and/or S2 include an emitter that transmits a signal and a receiver that receives the signal. The signal is interrupted when the media sheet passes past the sensor thus indicating the location. One embodiment of a sensor includes a light-emitting diode as the emitter and a phototransistor as the receiver.
In one embodiment, a first sensor S1 is placed on the media path 40 between the second transfer nip 91 and the fuser area 43, and second sensor S2 is positioned downstream from the fuser area 43. The sensors S1, S2 may be the same, or may be different. Additional sensors may be placed along the media path 40 as necessary. Each sensor S1, S2 is operatively connected to the controller 20 and provides the controller 20 with information regarding the media sheets
Controller 20 may further be operatively connected to an encoder 26 and a motor 25 that drives one or both rollers 92, 69 at the second transfer nip 91. Encoder 26 is operatively connected to the controller 20 and ascertains the revolutions and rotational position of the motor 25. Each revolution of the motor 25 equates to a predetermined amount of movement of the media sheet through the second transfer area 91. Controller 20 may also be operatively connected to motor 23 and encoder 24 at the fuser area 43. Motor 23 drives one or both members 44, 45 as the media sheets move through the fuser area 43 and to the discharge rollers 46.
The position of the media sheets along the media path 40 is tracked by the controller 20 using one or more of the sensors S1, S2, motors 25, 23, and encoders 26, 24. After the media sheet passes through the second transfer area 91, the leading edge trips sensor S1. At this time, controller 20 registers the position of the media sheet. As the media sheet continues to move along the media path 40, incremental positions are calculated by monitoring the feedback from the encoder 26 to determine the distance the sheet has moved since being detected by the sensor S1. Controller 20 continues to track the media sheet in this manner until the leading edge of the media sheet moves through the fuser nip 43 and trips sensor S2. At this time, controller 20 again registers the position of the leading edge of the media sheet. Continued movement of the media sheet may be obtained by monitoring feedback from one or both encoders 26, 24. After the trailing edge of the media sheet passes beyond sensor S1, the incremental position may then be determined exclusively by monitoring the feedback from encoder 24. In another embodiment, the incremental location is determined by monitoring the number of steps taken by one of the motors 25, 23 since the media sheet has last moved through a sensor S1, S2. One embodiment of monitoring the movement of the media sheets along the media path is disclosed in U.S. Pat. No. 6,330,424, assigned to Lexmark International, Inc., and herein incorporated by reference.
The media sheet M is moved further along the media path 40 as illustrated in
The leading edge LE moves through the fuser nip 43 and actuates sensor S2 as illustrated in
When the leading edge LE actuates sensor S2, controller 20 increases the speed of the fuser nip 43. As illustrated in
Controller 20 further prevents the media sheet M from being pulled at an excessive speed by the fuser nip 43 to cause print defects at the second transfer nip 91. Therefore, controller 20 may slow the speed of the fuser nip 43 after the sensor S1 moves to the non-actuated position. This reduction in speed again causes the slackened area B to reform. Formation of the slackened area B above a predetermined amount again activates the sensor S1. Reforming and dissipation of the slackened area B may continue as the media sheet M moves through the nips 91, 43, Controller 20 may continue to vary the speed of the fuser nip 43 as long as the media sheet M remains along the media path 40. In one embodiment, the controller 20 maintains the increased speed of the fuser nip 43 until the trailing edge TE moves beyond the second sensor S2.
Eventually, the trailing edge TE moves beyond the sensor S2 as illustrated in
In another embodiment, the leading edge LE is moved from the second transfer nip 91 into the fuser nip 43 without activating the sensor S1. The speed of the fuser nip 43 is maintained to prevent the media sheet M from buckling and activating the sensor S1. While the media sheet M is within the fuser nip 43, the speed of the fuser nip 43 may be slowed therefore causing a buckle B to form that eventually activates the sensor S1. The speed of the fuser nip 43 may then be selectively changed between speeds to decrease or eliminate the buckle B, and then let the buckle B reform.
The embodiment described above includes first and second sensors S1, S2 positioned along the media path M. In another embodiment, a single sensor S1 is positioned along the media path 40 as illustrated in
Controller 20 determines the position of the media sheet based upon the initial actuation of the sensor S1, and tracking the speeds of the nips 91, 43. The leading edge LE is initially determined upon the actuation of sensor S1. The incremental position of the leading edge LE is determined by tracking the speed of the nips 91, 43. After the controller 20 has determined that the media sheet M is within the fuser nip 43, the speed of the fuser nip 43 may be increased. The speed and extent of time is determined by tracking the activation of the sensor S1. Adjustments to the speed of the fuser nip 43 may continue as the media sheet M moves along the path 40.
In one embodiment, controller 20 maintains the speed of the second transfer nip 91 at a relatively constant speed. The speed of the fuser nip 43 is adjusted to prevent the media sheet from being pulled or hindered during the movement which may cause a print defect in other embodiments, controller 20 may vary the speed of the second transfer nip 91 as the media sheet M is within the nip 91.
In the embodiments described above, the sensor S1 is actuated when contacted by the media sheet M, and deactivated when the media sheet M moves away. In other embodiments, sensor S1 may be actuated when the sheet M moves away, and deactivated during contact with the sheet M.
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.
