Patent Application
20070216088
1. Field of the Invention
This invention relates to an apparatus for assuring media feeding, comprising: an impression drum having a media gripper; an input feed unit located substantially adjacent to the impression drum for feeding a sheet of media; and a servo motor operatively connected to the input feed unit such that a change in operating characteristics of the servo motor is detected if the sheet of media is properly retained by the gripper.
2. Description of the Related Art
Prior to the present invention, as set forth in general terms above and more specifically below, it is known, in the printing art to employ sensors at the entrance between the impression drum and the intermediate transfer drum in order to detect the media leading-edge position and timing. While this system is capable of detecting the leading edge and timing of the media, this solution requires additional sensors inside of the printing device. Also, the leading edge position and timing of the media are detected outside of the media grippers that can result in an inadequate detection of paper stick to blanket (PSTB). Finally, the sensors of this system may send faulty alarms due to dirt and paper dust adversely affecting the sensors. Consequently, a more advantageous system, then, would be provided if such sensors can be avoided.
It is also known, in the printing art to employ a pressurized system to determine if the media is located against the impression drum. In this manner, a vacuum is applied to the impression drum. If a sheet of media is located on the impression drum, a change in the vacuum properties is detected. While this system is capable of detecting the presence the media, this solution requires additional sensors inside of the printing device. Also, the system is not capable of detecting if the media is properly located within grippers. Finally, the vacuum sensors of this system may send faulty alarms due to vacuum ports becoming inadvertently clogged. Therefore, a further advantageous system, then, would be provided if such a vacuum system could be avoided.
It is apparent from the above that there exists a need in the art for a method and apparatus for assuring proper media feeding such that the proper retention of the media within the grippers can be detected without the use of sensors or other complicated systems so as to avoid paper stick to blanket (PSTB). It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.
Generally speaking, an embodiment of this invention fulfills these needs by providing an apparatus for assuring media feeding, comprising: an impression drum having a media gripper; an input feed unit located substantially adjacent to the impression drum for feeding a sheet of media; and a servo motor operatively connected to the input feed unit such that a change in operating characteristics of the servo motor is detected if the sheet of media is properly retained by the gripper.
In certain preferred embodiments, the input feed unit is a plurality of rollers that create a nip to feed the sheet of media towards the impression drum. Also, if a change in the torque on servo motor is detected then it can be assumed that the sheet of media is properly retained by the gripper. Finally, if a change in the velocity of the servo motor is detected, then it can be assumed that the media has not been properly retained by the grippers.
In another further preferred embodiment, a method and apparatus is presented for assuring proper media feeding such that the proper retention of the media within the grippers can be detected without the use of sensors or other complicated systems so as to avoid paper stick to blanket (PSTB).
The preferred method and apparatus for assuring media feeding, according to various embodiments of the present invention, offers the following advantages: ease-of-use; elimination of extraneous sensors; improved detection times; reduced printer downtime; decreased paper stick to blanket occurrences; and reduced blanket damage. In fact, in many of the preferred embodiments, these factors of elimination of sensors, improved detection times, reduced printer downtime, decreased paper stick to blanket occurrences, and reduced blanket damage are optimized to an extent that is considerably higher than heretofore achieved in prior, known method and apparatus for assuring media feeding.
The above and other features of the present invention, which will become more apparent as the description proceeds, are best understood by considering the following detailed description in conjunction with the accompanying drawings, wherein like characters represent like parts throughout the several views and in which:
The paper stick to blanket (PSTB) phenomenon is one of the main reasons for blanket (the soft material that is wrapped around the ITM drum) damage due to its interaction with jammed media. When PSTB occurs, the printer stops printing and the operator must then get to the blanket. The jammed media and any residual ink must be cleaned from the blanket. During this operation, the image may be fused to the blanket and then the operator is forced to replace the blanket. Also, in some cases, the jammed media may become bent and this bend may cause a mechanical defect in the blanket, which may also force the operator to place to blanket. It is to be kept in mind that under normal operating conditions, it takes about 30 milliseconds between the time the grippers are closed and the grippers reach the next drum. Clearly, media jamming is an issue and, even greater, is the concern of how to quickly determine that a media jammed has occurred in order to avoid undue amounts of lost downtime.
With this background in mind, apparatus 2 for assuring proper media feeding is illustrated in
With respect to
To demonstrate further proof of the concepts of the present attention,
The present invention can be embodied in any computer-readable medium for use by or in connection with an instruction-execution system, apparatus or device such as a computer/processor based system, processor-containing system or other system that can fetch the instructions from the instruction-execution system, apparatus or device, and execute the instructions contained therein. In the context of this disclosure, a “computer-readable medium” can be any means that can store, communicate, propagate or transport a program for use by or in connection with the instruction-execution system, apparatus or device. The computer-readable medium can comprise any one of many physical media such as, for example, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor media. More specific examples of a suitable computer-readable medium would include, but are not limited to, a portable magnetic computer diskette such as floppy diskettes or hard drives, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory, or a portable compact disc. It is to be understood that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a single manner, if necessary, and then stored in a computer memory.
Those skilled in the art will understand that various embodiment of the present invention can be implemented in hardware, software, firmware or combinations thereof. Separate embodiments of the present invention can be implemented using a combination of hardware and software or firmware that is stored in memory and executed by a suitable instruction-execution system. If implemented solely in hardware, as in an alternative embodiment, the present invention can be separately implemented with any or a combination of technologies which are well known in the art (for example, discrete-logic circuits, application-specific integrated circuits (ASICs), programmable-gate arrays (PGAs), field-programmable gate arrays (FPGAs), and/or other later developed technologies. In preferred embodiments, the present invention can be implemented in a combination of software and data executed and stored under the control of a computing device.
It will be well understood by one having ordinary skill in the art, after having become familiar with the teachings of the present invention, that software applications may be written in a number of programming languages now known or later developed.
Once given the above disclosure, many other features, modifications or improvements will become apparent to the skilled artisan. Such features, modifications or improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.
