Patent Application
20120001383
This invention relates to a paper-handling system and, more specifically, to a novel assembly for controlling skew correction or changing the position of sheets traveling in a sheet transport path.
While the present invention can be used in any suitable paper or media transport or non-marking system, it will be defined for purposes of clarity as used in an electrophotographic marking system.
In such marking systems such as xerography or other electrostatographic processes, a uniform electrostatic charge is placed upon a photoreceptor belt or drum surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the belt or drum photoreceptor surface. The toner may be in dry powder form or suspended in a liquid carrier. The charged toner, being electrostatically attached to the latent electrostatic image areas, creates a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to an intermediate transfer belt or to a final support material such as paper.
Prior to imaging, a plurality of paper (or other media) sheets are fed from a paper stack to a paper transport system. It is essential to producing an optimum image that each sheet fed to the imager and developer stations be in precise alignment especially in high speed marking systems. This may include deskewing or side registration of sheets being initially fed in to be printed, duplexing and/or sheets being outputted to a stacker, finisher or other output modules. Paper-handling systems of this type are known in the art such as those disclosed in U.S. Pat. Nos. 6,173,952 and 7,090,215. These patents are incorporated by reference into the present disclosure.
Nip (contact between idler and drive rollers) releases are important in proper aligning of paper sheets both before and after the imaging steps. Typically, in the prior art, the support structure required for nip separation consists of one or more separate parts independent of the loading element which generally is some form of a spring. Actuated nip releases currently make use of complicated designs to deliver the functions of support and force separately that are required for drive nips. The increased complexity of prior art nip separation assemblies has led to high cost and low reliability that frequently fails in the field. Most, if not all, of the prior art nip separation assemblies do not last for the life of the marking machine.
The present invention incorporates the use of combined functions by using a passive/fixed flat spring configuration as the primary or sole source to produce a load while simultaneously providing a nip support and mounting.
The present invention provides a low cost actuated idler assembly by which the functions of “breaking” a drive/idler roll nip as well as applying the required drive roll normal force is simplified and cost reduced over traditional designs by incorporating the support and normal force functions through the use of a single leaf spring. As earlier noted in the prior art, the support structure required for nip separation consists of one or more separate parts independent of the loading element which is usually some form of spring. This invention uses a leaf spring as the only source to apply the nip normal force when the drive roll and idler are in contact (forming a nip) and uses the leaf spring as the follower for a cam system to separate the drive roll and idler. As the cam rotates, it contacts the leaf spring follower which applies a force on the idler roll shaft separating it from the drive roll. This invention demonstrates a convenient way to combine functionality of a single part of a design to provide drive roll/idler separation. It reduces the cost of traditional nip separation design schemes while at the same time substantially improving reliability of such a function. The flat leaf spring of this invention should have a suitable thickness depending upon the specific desired application.
As above noted, current nip release designs make use of complicated combinations of nip loading and support systems to provide an actuated nip assembly. This present invention takes advantage of the properties available with a flat spring. Those properties are first the ability to provide a semi-rigid support platform for holding the idler nip and second the ability to provide a normal force to the nip. The uniqueness lies in combining the two functions of nip normal loading and nip idler support. By incorporating a load-producing structural support, the flat spring, the nip loading and the idler placement can be accomplished with a much reduced complexity and cost.
In the present invention, by combining the attributes of support and force application, the nip idler complexity is significantly reduced over said prior art devices leading to lower cost and improved reliability.
Prior art actuator design involves specific and usual complexity of an actuated nip assemble. These designs consistently lead to faults due to tolerance allocation issues as well as failures with each of the parts within the system. The current nip release and its frequent replacement and high cost of the system makes reliable replacement assemblies a highly desirable forward step in the art.
This invention includes use in any paper-handling system and the changing or correcting the orientation of the sheets traveling in a sheet transport path. In a marking system, sheets being fed to be marked or printed, sheets being fed for duplex printing, sheets being sent to a stacker and sheets outputted to a finishing station or other modules are all included within the scope of this invention. As set forward in the disclosure for clarity and understanding, the sheet registration system of this invention has been described herein in reference to pre-imaging paper feeding in electrostatic marking systems, both color and monochrome.
There have been related sheet registration systems used in the prior art, however, none of them combine simplicity and effectiveness with acceptable associated costs. In U.S. Pat. No. 7,422,211 B2 (Dejong), a closed loop registration method is disclosed which improves on lateral registration and deskew systems such as that disclosed in U.S. Pat. No. 6,173,952. While somewhat effective, both processes involve relatively expensive components especially in high speed marking systems and have short useful lives and lack somewhat in reliability.
The present invention provides an improved, reliable, less complicated and longer life system for selectively opening sheet feeding nips of a paper path of a marking system when necessary for alignment or to correct paper jams. Plural sheet feeding nip sets may be easily opened with selective control by use of stepper motors, sensors and controllers. This invention uses a passive/fixed flat spring support to produce a load while simultaneously providing a nip support and mounting. The nips may be opened when desired by rotating idler roller shafts to rotate one or more cams directly mounted on the shafts. The cams (preferably oval shaped) are directly in contact with the flat spring support and move the spring and idler roll in a contact position with a drive roll or in a retracted position from the drive roll.
Three different drive roller-idler roller nips may be used in one embodiment to form three possible positive steering nips when those idlers are closed against the cams as shown in the embodiment of
In
In
A. greatly reduced part count and complexity from current designs for sheet handing assemblies;
B. significantly lower costs;
C. improved reliability;
D. maintains function of allowing for 2 different nip stances;
E. eliminates multiple part tolerance build up issues that plague prior art marking machines; and
In summary, this invention provides a sheet handling assembly for correcting and controlling sheet skew comprising a drive roll, an idler roll, a flat leaf spring, and a cam mounted on a cam shaft to form a cam system. The flat leaf spring alone is configured to supply combined functions of both a support and force or load upon the idler roll.
The assembly has a plurality of sensors each in contact with a controller and a stepper motor wherein the controller is configured to actuate idler roll nip separation by causing the stepper motor and the cam system to separate the idler roll from the drive roll. The cam system is configured to act upon the flat leaf spring to separate the drive roll and the idler roll and thereby provide nip separation. As the cam rotates, it is configured to contact the flat leaf spring which is configured to apply a force on the idler roll separating it from the drive roll.
The flat leaf spring is attached at one end to a fixed frame and attached on an opposite end to a shaft of the idler roll and is configured to apply a nip normal force to the idler roll when the idler roll and drive roll are in contact, and is configured to use the flat leaf spring as a follower for the cam system to separate the drive roll and idler roll. It is preferred that the flat leaf spring have any suitable thickness depending upon the desired usage and structure.
The cam is preferably oval shaped having a longer and shorter oval section and is configured to rotate upon the cam shaft and as it contacts the flat leaf spring is configured to lift the idler roll out of contact with the drive roll. The cam shaft is connected on one terminal end to a stepper motor, the stepper motor in electrical or mechanical connection to a system controller, the controller configured to control individually all nip separation in the assembly.
Also provided by the present invention is a method of controlling the flow of sheets through a sheet handling assembly. This method comprises providing a drive roll in contact with an idler roll to form a nip thereby, then connecting a flat leaf spring on one first end to the idler roll, and on a second opposite end to a fixed frame. The method continues by locating a cam on a shaft in contact with the flat leaf spring between the first and second ends of the flat leaf spring. The cam is then rotated to contact the flat leaf spring and move it and to raise and lower the idler roll from contact with and out of contact with the drive roll.
The cam has an oval configuration where when a longer side or section of the oval cam contacts the flat leaf spring it causes contact of the idler roll with the drive roll. The cam has an oval configuration where when a short side or section of the oval cam contacts the flat leaf spring, it causes a lift or release of the idler roll from contact with the drive roll. The flat leaf spring is a sole source of integrating nip loading and support to the sheet handling assembly. The cam shaft is connected on one end to a stepper motor; the stepper motor is controlled by a system controller to thereby individually control all nip separation in the assembly.
It will be appreciated that variations 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.
