Patent Application
20110049800
The present disclosure generally relates to document processing devices and methods for operating such devices. More specifically, the present disclosure relates to a substrate media transport system with reduced force nip to mitigate nip entrance disturbances that affect registration of a substrate media.
In document processing devices, accurate and reliable registration of the substrate media as it is transferred in a process direction is desirable. Even a slight skew or misalignment of the substrate media through an image transfer zone can lead to image and/or color registration errors. Such registration errors can occur as the substrate media passes through the nips.
Document processing devices typically include one or more sets of nip assemblies used to transport substrate media, such as sheets of paper, through the device. A nip assembly provides a force to the sheet as it passes through a nip to propel it through the document processing device. A nip assembly typically includes a drive wheel and an idler wheel in rolling contact with the drive wheel. One or more sets of drive wheels and idler wheels may be longitudinally aligned in order to form the nip therebetween. The driving wheel and the idler wheel may be urged together by a biasing device which in turn creates the nip force. The nip force is required such that the wheels properly engage the sheet as it passes through the nip. This nip force must be significant enough in order to eliminate slipping between the drive wheel and the sheet.
When a sheet being transported through the document processing device first engages the nip, the drive wheel and idler wheel are in rolling engagement with each other. As the sheet engages the wheels, at least one of the idler and drive wheels typically moves against the nip force in order to permit the sheet to enter the nip. The entering of the sheet, especially thick sheets, into the nip results in nip disturbances which negatively affect sheet registration. When a sheet enters a nip, the sheet must perform work in displacing the wheel of an amount equal to its thickness multiplied against the nip force. This work needs to be performed in the time it takes the sheet to fully enter the nip. The work required to move the wheel originates from a decrease in kinetic energy, i.e., speed, of the rotating nip components. The controls used to regulate the nip velocity typically cannot effectively mitigate the nip disturbances. Registration of the sheets, therefore, is compromised.
Accordingly it would be desirable to provide a substrate media transport system having nip assemblies that reduce the disturbance caused by substrate media entering the nips.
There is provided an apparatus for transporting substrate media including a nip assembly having a drive wheel operably connected to a drive mechanism for rotating the drive wheel, and an idler member disposed adjacent the drive wheel. The idler wheel and drive wheel forming a nip. The drive wheel and idler wheel are displaceable from each other to form a nip gap therebetween. A nip force generator is operably connected to the nip assembly. The nip force generator develops a first nip force upon entry of the substrate media into the nip and formation of the nip gap and develops a second nip force subsequent to the first nip force. The second nip force is greater than the first nip force.
There is also provided an apparatus for mitigating nip disturbances caused by substrate media entering the nip including a nip assembly having a drive member operably connected to a drive mechanism for rotating the drive wheel. The nip assembling further including an idler member is disposed adjacent the drive wheel. The drive and idler wheels being movable relative to each other to form a nip gap therebetween. A first force generating device generates a first nip force which acts upon the nip assembly upon an initial separation of the drive member and the idler member. A second force generating device selectively generates a second nip force which acts upon the nip assembly in response to a predetermined condition, the second nip force being greater than the first nip force.
There is still further provided a method of mitigating nip entrance disturbances including;
transporting substrate media toward a nip formed between a drive wheel and an idler wheel, the drive wheel and idler wheel being displaceable from each other by action of the substrate media to form a nip gap;
subjecting the substrate media to a first nip force upon entry of the substrate media into the nip and during displacement of the idler wheel from the drive wheel by the substrate media; and
subjecting the substrate media to a second nip force subsequent to the first nip force, the second nip force being greater than the first nip force.
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 “substrate of media” refers to, for example, paper, transparencies, parchment, film, fabric, plastic, or other substrates on which information can be reproduced, for example, in the form of a sheet or web.
A “nip” refers to a location in a document processing device at which a sheet is propelled in a process direction. A nip may be formed between an idler wheel and a drive wheel.
A “nip assembly” refers to components, for example and without limitation, a drive wheel and an idler wheel which form a nip.
A “drive wheel” refers to a nip assembly component that is designed to propel a sheet in contact with the nip. A drive wheel may include a wheel, roller or other rotable member. The drive wheel may have an outer surface including a compliant material, such as rubber, neoprene or the like. A drive wheel may be directly driven via a stepper motor, a DC motor or the like. Alternately, a drive wheel may be driven using a gear train, belt transmission or the like.
An “idler wheel” refers to a nip assembly component that is designed to provide a normal force against a sheet in order to enable the sheet to be propelled by the drive wheel. An idler wheel may include a wheel, roller or other rotatable member. The idler wheel may have an outer surface including a non-compliant material, such as plastic.
A “nip force” refers to a force acting upon substrate media when transported through a nip.
A “nip force generator” refers to a device, for example a mechanical, electro-mechanical, fluid power device, for exerting a nip force.
A “nip gap” refers to a space formed between a drive wheel and idler wheel of a nip assembly.
“Nip disturbances” refers to influences on nip components that affect desired operation of the nip assembly components.
With reference to
The drive wheel 20 may include an outer surface 32 having a compliant material such as rubber, neoprene or the like. The compliant material helps to grip the sheet 12 and permit the drive wheel 20 to move the sheet through the nip 21. The drive wheel 20 rotates about a drive shaft 34 and may be directly driven by a drive motor 36, such as a stepper motor, a DC motor or the like. A transmission device 38 may extend between the drive motor 36 and the drive wheel 20 for imparting motion to the drive wheel 20. The transmission device 38 may include a timing belt, gear trains or other transmission means known to those of ordinary skill in the art. The drive wheels 20 of each of the nip assemblies 16 may move in a coordinated manner to propel the sheets 12 through the nips 21 in a controlled manner.
When a sheet approaches the nip assembly 16, the idler wheel 18 is in rolling engagement with the drive wheel 20 and the wheels are held together by the nip force 17. In order for the nip assembly 16 to operate properly, the nip force may be high enough such that the sheet is propelled through the nip 21 without slippage. As the sheet engages the nip 21, the idler and drive wheels 18, 20 are separated from each other by the sheet 12 forming a nip gap 40. If the sheet 12 were to encounter a nip held together by a high nip force of the magnitude sufficient to prevent slippage, significant nip disturbances would be created detrimentally affecting registration and component wear. Thus, in accordance with the present disclosure, each nip 21 may be operated upon by a nip force generator 42 capable of producing a varying nip force.
With reference to
With reference to
Accordingly, the work performed by the sheet in forming the nip gap 40 is a function of the lower first nip force F1. Since the sheets entering the nips 16 only work against the lower nip force, nip entrance disturbances are greatly reduced. This helps to maintain proper registration of the sheets and also reduces damage to the sheets and the nip components. However, slippage of the sheets 12 passing through the nips 16 is also reduced since the second nip force F2 is applied and acts on the sheets 12 as the sheets are propelled through the nips 16.
It is further contemplated that the nip force generator may be capable of generating more that just the first and second forces. Multiple nip forces could be provided to control the operation of the nip assemblies 16 and the transfer of sheets 12 through the nips 21.
The nip force generator 42 may act on the idler wheel 18 and/or the drive wheel 20 to create the desired nip force. For purposes of description, the force generating device 42 will be described as operating on the idler wheel 18. With reference to
The first force generating device 54 may provide the first nip force F1 which holds the idler wheel 18 in rolling engagement with the drive wheel 20. The first force generating device 54 may develop a relatively low force sufficient to maintain contact between the idler wheel 18 and the drive wheel 20. For example F1 may be approximately 0.1 to 0.5 pounds. When a sheet 12 first encounters the nip 16 and separates the idler wheel 18 from the drive wheel 20, the sheet acts against the relatively low force, F1. The first force generating device 54 may include a spring 58 or other biasing device disposed between the pivot arm first end and a structure 60 such as a portion of a frame. As the sheet 12 enters the nip 16, the idler wheel 18 is pivoted against the low force F1. The formed nip gap 40 is enlarged until it eventually reached a size equal to the thickness of the sheet. At this point, further movement of the idler wheel 18 against the first nip force F1 ceases.
When the nip gap 40 equal the thickness of the sheet 12, the nip force generator 42 may engage the second force generating device 56 to develop the second nip force F2. The second force generating device 56 may be engaged in response to a signal generated when the idler wheel 18 has traveled a predetermined amount. Such a signal would be related to the nip gap size. Alternatively, engagement of the second force generating device 56 may be engaged after the sheet has reached a certain position or after a predetermined amount of time has elapsed after the sheet 12 has entered the nip 21. The second nip force F2, may be sufficient to allow the nip assemblies 16 to drive the sheet there through without slippage. For example, the second nip force F2 may be on the order of 1 to 3 pounds. However, other force values may be employed. The higher second nip force F2 is not generated until the nip gap 40 has reached the thickness of the sheet 12.
The second force generating device 56 may include an actuator 62 that has first and second operating states. The actuator 62 may be selectively energized to change operating states to apply the second nip force F2 at desired periods during the travel of the sheets through the nips 21. The actuator 62 may include, for example, a linear drive such as a solenoid or pneumatic cylinder. The actuator 62 may be operably connected to the pivot arm 50 such that it urges the idler wheel 18 and drive wheel 20 together creating the second nip force F2. The actuator 62 may be connected to the pivot arm 50 by a second biasing device 64. The second biasing device 64 may include a spring having one end attached to the actuator 62 and the other end connected to the pivot arm 50. Energizing the actuator 62 causes the spring to be pulled, thereby urging the idler wheel 18 toward the drive wheel 20 and developing the second nip force F2. With the nips compressed onto the sheets by the second nip force F2, the nip may propel the sheet through the nips 21 without slippage. Accordingly, by selectively energizing the actuator 62, the second nip force F2 may be selectively engaged and disengaged.
In alternative embodiment shown in
In sheet transport system 10 having multiple nip assemblies 16 as shown in
With reference to
Alternatively, the control of the nip force generator 42 may be responsive to a sheet position sensor 78. When the sheet is about to enter the nip, the nip force generator 42 may generate the first nip force F1. When the position of the sheet is sensed indicating that the sheet has fully entered the nip 21, the nip force generator 42 may berate the second nip force F2.
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. 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 following claims.
