Patent Application
20100102501
The present disclosure generally relates to document processing devices and methods for operating such devices. More specifically, the present disclosure relates to methods and systems for extending roll life in feed nips of a friction retard feeder.
Friction retard feeders are subsystems of a document processing system that are typically used to initiate reliable transport of a sheet from a tray to the remainder of the document processing system while preventing the transport of more than one sheet simultaneously. For example, in the case of a printer, scanner or other similar device, a friction retard feeder can be used to remove the top sheet of paper or other media from a paper tray so that it can be utilized by the remainder of the device while preventing underlying sheets from being transported. This reduces the possibility of jamming the device during operation.
Friction retard feeders are typically either active or semi-active in nature. An active friction retard feeder, such as is shown in
The active friction retard feeder operates on a differential friction principle by employing a feed roll 110 that has a high coefficient of friction with respect to the media and a retard roll 115 that has a coefficient of friction with respect to the media that is lower than that of the feed roll, but higher than the coefficient of friction between two sheets. As such, the feed roll 110 transports the top sheet in the process direction because it has a high coefficient of friction with the sheet. Moreover, the sheet has a coefficient of friction (due to the force imparted by the feed roll 110) to overcome the torque supplied by the slip clutch 120 causing the retard roll 115 to be driven by the feed roll. If more than one sheet is drawn from the stack, the sheets other than the top sheet contact the retard roll 115 which prevents transport in the process direction because the torque of the slip clutch 120 is not overcome by the friction between the two sheets. As a result, only a single sheet, the top sheet, is transported in a process direction at a time.
A semi-active friction retard feeder, as shown in
An alternate friction retard feeder (such as is shown in
Friction retard feeders are commonly incorporated into document processing systems that serve office and low end production markets because they have a low unit manufacturing cost and provide reliable feeding performance. One disadvantage of such feeders is that the feed and retard rolls wear out and need to be replaced frequently because of the shear forces on the elastomeric rolls due to drag forces and the force required to overcome the slip clutch torque. For document processing devices in low volume markets, this can be an acceptable limitation because of the limited amount of sheets which are passed through the feed nip. However, this disadvantage has restricted the use of friction retard feeders in higher volume markets.
Significant research has been performed in order to develop feed rolls that have a longer wear life. However, the effect of such research is limited by the fact that materials must also resist contamination from, for example, coated media, such as photo paper.
Before the present systems, devices and methods are described, it is to be understood that this disclosure is not limited to the particular systems, devices and methods described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope.
It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to a “nip” is a reference to one or more nips and equivalents thereof known to those skilled in the art, and so forth. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Although any methods, materials, and devices similar or equivalent to those described herein can be used in the practice or testing of embodiments, the preferred methods, materials, and devices are now described. All publications mentioned herein are incorporated by reference. Nothing herein is to be construed as an admission that the embodiments described herein are not entitled to antedate such disclosure by virtue of prior invention. As used herein, the term “comprising” means “including, but not limited to.”
In an embodiment, a sheet feeding system may include a feed roll, a retard system, a trailing edge retention system and a system for automatically and selectively separating the feed roll and the retard system. The feed roll may be configured to drive a first sheet of a stack of sheets in a process direction. The retard system may be configured to prevent one or more second sheets from being driven in the process direction. The trailing edge retention system may be configured to automatically and selectively retain one or more second sheets in the stack by applying a force to a trailing portion of at least one second sheet.
In an embodiment, a method of feeding a sheet from a stack in a document processing system that includes a nudger roll, a feed nip comprising a feed roll and a retard system, a take away nip, a plurality of sensors, and a trailing edge retention system may be performed. The method may include actuating the nudger roll to move a first sheet from a stack of sheets in a process direction, receiving a lead edge of the first sheet at the feed nip, moving, via the feed roll, the first sheet through the feed nip, actuating the trailing edge retention system to restrict movement of one or more second sheets in the stack of sheets, receiving the lead edge of the first sheet at a take away nip, automatically moving one or more of the feed roll and the retard system away from the first sheet, automatically moving one or more of the feed roll and the retard system back into a closed position, and automatically moving the trailing edge retention system away from the one or more second sheets.
Aspects, features, benefits and advantages of the present invention will be apparent with regard to the following description and accompanying drawings, of which:
The following terms shall have, for the purposes of this application, the respective meanings set forth below.
A “document processing device” refers to a device that performs an operation in the course of producing, replicating, or transforming a document from one format to another format, such as from an electronic format to a physical format or vice versa. Document processing devices may include, without limitation, printers (using any printing technology, such as xerography, ink-jet, or offset); document scanners or specialized readers such as check readers; mail handling machines; fabric or wallpaper printers; or any device in which an image of any kind is created on and/or read from a moving substrate.
A “nip” refers to a location in a document processing device at which a force is applied to a sheet by drive rollers to propel the sheet in a process direction. The “exit point” of a nip refers to the portion of the sheet path past the given nip. For example, a sensor that detects the lead edge of a sheet at the “exit point” of the feed nip, would detect a sheet after the lead edge passes the feed nip and before the lead edge enters the following nip.
As shown in
The nudger roll 405 is configured to transport only a top sheet 425 from the stack in a process direction. However, the nudger roll 405 may inadvertently cause one or more additional sheets, such as 440, to at least be partially transported towards the feed nip because of friction between the top sheet 425 and the other sheets.
As shown in
One or more of the feed roll 410 and the retard roll 415 may be moved away from or towards a process path (i.e., the path on which the top sheet 425 is transported) as part of the transport operation. For example, as shown in
The trailing edge retention system 420 may be used to further restrict sheets other than the top sheet, such as 440, from passing through the feed nip. The trailing edge retention system 420 may impart a force near a trailing edge of a sheet other than the top sheet, such as 440, when engaged, such as is shown in
The distance between the point at which the trailing edge retention system 420 contacts the remaining sheets, such as 440, and the trailing edge of the stack 450 (i.e., “A” in
The trailing edge retention system 420 may disengage after the feed nip closes, as shown in
In an embodiment, the trailing edge retention system 420 and a system that separates the feed nip (i.e., by moving one or more of the feed roll 410 and the retard roll 415) may utilize a common actuator. For example, a single step motor could be used to drive two cams, one of which would lift the trailing edge retention system 420, and one of which would move the retard roll 415 away from the feed roll 410. In an alternate embodiment, a motor could be used to drive cams that drive the nudger roll lift mechanism and at least one of the trailing edge retention system 420 and feed nip release system. Alternatively, separate solenoid actuators could be used to drive the trailing edge retention system 420 and feed nip release system.
In an embodiment, the trailing edge retention system 420 may be moved when sheets are loaded onto the stack. For example, if the stack is part of a tray that is pulled from a document processing device, the trailing edge retention system 420 may be located at a position that is directly over the stack, which could make it difficult to load sheets into the tray. As such, the trailing edge retention system 420 may be raised, lowered, rotated and/or otherwise moved as the tray is removed from the document processing device. In an embodiment, the trailing edge retention system 420 may be moved in response to the tray being removed from the document processing device, such as by using a triggering mechanism. For example, a spring loaded system may be used. The spring may be compressed when the tray is inserted into the document processing device, which may cause the trailing edge retention system 420 to be placed in a position from which it can restrict sheets as described above. Removing the tray from the document processing device may cause the spring to extend and move the trailing edge retention system 420 from its active position. Other methods for moving the trailing edge retention system 420 may be used within the scope of this disclosure.
A lead edge of the first sheet may be received 510 at a feed nip. The feed nip may include a feed roll and a retard roll, such as the ones described above in reference to
A trailing edge retention system may be actuated 520 to restrict movement of one or more second sheets in the stack of sheets. In an embodiment, actuation 520 of the trailing edge retention system may include generating a signal by a sensor located, for example, proximate to the exit point of a feed nip. The generated signal may indicate, for example, that the first sheet is present at the location of the sensor. In response to at least the generated signal, the trailing edge retention system may be moved into contact with one or more second sheets on a stack of sheets to restrict movement of the one or more second sheets.
The lead edge of the first sheet may be received 525 at the take away nip. The take away nip may include a take away roll and an idler roll, such as described above in reference to
One or more of the feed roll and the retard system may be automatically moved 530 from the first sheet. In an embodiment, movement 530 of the feed roll and/or the retard system may be performed by generating a signal by a sensor located, for example, proximate to the exit point of the take away nip. The generated signal may indicate, for example, that the first sheet is present at the location of the sensor. In response to at least the generated signal, the feed roll and/or the retard system may be moved 530 away from the first sheet. As a result, drag on the first sheet may be reduced.
In an embodiment, the feed roll and/or the retard system may be moved 535 towards the other in order to prepare for reception of a new sheet. In an embodiment, movement 535 of the feed roll and/or the retard system may be performed in response to the generation of a signal by a sensor located, for example, proximate to the exit point of a feed nip. The generated signal may indicate, for example, that the first sheet is not present at the location of the sensor. In response to at least the generated signal, the retard roll or feed roll could be moved to once again form a nip.
The trailing edge retention system may be automatically moved 540 from the one or more second sheets. In an embodiment, movement 540 of the trailing edge retention system may include generating a signal by a sensor located, for example, proximate to the exit point of a feed nip. T he generated signal may indicate, for example, that the first sheet is not present at the location of the sensor. In response to at least the generated signal, the trailing edge retention system may be moved 540 away from the one or more second sheets.
Significantly reduced wear on elastomer feed rolls and retard rolls may result from using a friction retard roll according to the principles described herein. The reduction in wear may result primarily because the feed nip is open for much of the feed cycle. In current active friction retard feeders, the retard roll works to separate the top sheet from the rest of the stack, but then continues to exert a force during the entire time that the sheet is being driven through the feed nip. In the disclosed embodiments, the retard/feed nip is opened after the top sheet reaches the take away nip, so that the retard and feed rolls are not being worn during much of the feed cycle. In particular, a retard roll may see the greatest improvement in wear reduction because it is not slipping against paper or rotating against the feed roll when the feed nip is open. In addition, a significant reduction in wear of the slip clutch of the retard system may also result because the feed nip is open for much of a sheet feeding cycle.
Table 1 provides information pertaining to the reduction of wear on the feed roll and retard roll for exemplary distances. If the distance between the feed nip and the take away nip is approximately 75 mm and the feed nip is released after approximately 20 mm of the sheet reaches the take away roll, the reduction in overall wear time on the feed roll 410 and the retard roll 415 for a standard 8.5″×11″ (216 mm×279 mm) sheet is approximately
For a 11″×17″ (279 mm×432 mm) sheet in the same system, the reduction in overall wear time on the feed roll 410 and the retard roll 415 is approximately
As such, a system developed in accordance with the principles taught in this disclosure could potentially more than double the life of the feed roll 410 and the retard roll 415 for letter sized paper and could potentially increase the roll life by a factor of approximately 4.5 for large format media. This reduction in wear rate means that the feed nip can feed a greater number of sheets before the rolls have to be replaced. This reduces service costs and run costs for the machine.
In addition, reduction in wear for a take away roll may result through use of a friction retard feeder designed according to the principles disclosed herein. Conventional feeders accelerate sheets to a higher velocity after the sheet reaches the take away roll. Because of this, an over-running clutch is typically included in the feed roll drive system that allows the feed roll to spin faster than it is being driven. However, the sheet must still overcome the feed roll drag force and the retard roll slip-clutch drag force in a conventional system. Because the feed nip is opened shortly after the sheet reaches the take away roll in the presently disclosed embodiments, the take away roll does not need to overcome the drag forces for a significant period of time when accelerating the sheet. Reducing the drag forces may reduce the risk of marking sensitive coated media from the rolls and requires less drive torque/power on the take away roll.
Additional benefits that may result include less marking of a coated media (both from the feed nip and from the take away roll force pulling the sheet around any baffles in the device) and less roll contamination because the nip is open for much of the sheet feed cycle. Roll contamination can cause a decrease in the coefficient of friction for the roll because the contaminant may cause the roll to slip with respect to a sheet that is being transferred. As the coefficient of friction is lowered, it becomes more likely that a second sheet will be transported through the feed nip to the remainder of the document processing system, causing a malfunction in a document processing operation.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. It will also be appreciated that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the disclosed embodiments.
