Many different kinds of hardcopy printing devices are available commercially today, and these include copiers, faxes and printers. Ubiquitous hardcopy printing devices such as printers are commonly found in homes and offices. Since the evolution of office automation, printers have been integrally connected with other office automation equipment like computers, workstations, print servers, or networks to provide hardcopy printing capability. With the advent of increased CPU processing speed and power due to fast-paced technological advancement, better computers, workstations and servers have also come into being. Thus, that complementing equipment such as printers too must have increased throughput in order to contribute to the overall productivity of any office automation system is inevitable.
Printers commonly use printing paper of various sizes, transparencies, or even postcards as print media. These media sheets are fed sequentially into these printers to receive print markings. In doing so, the throughput of the printer is thus limited, in part, by the rate at which the printer receives the media sheets. Many known methods are currently implemented in commercially available printers to handle and provide media sheets efficiently to these printers for printing.
An example of the implementation of such known methods is the pick-and-feed operation of many ink jet printers. A pick operation entails picking a single media sheet from a stack of media sheets and moving it along a media path through the use of a pick roller. A drive roller and a pinch roller, which cooperate to perform a feed operation, controls the positioning of the media sheet with respect to a printing head for receiving print markings. In some ink jet printers, the pick-and-feed operation is performed by the same roller serving both the pick and drive functions for cost reasons. From the perspective of performance however, a pick roller would require a different type of material from that of a driver roller. For high pick reliability, the pick roller should be made of soft rubber with high friction coefficient. Conversely, the rubber used for the drive roller should be hard so that it does not deform easily and thus is able to control the feeding of the media sheet accurately. Therefore the implementation of a common roller to perform both operations may not meet the need for both reliable and accurate media handling.
Some ink jet printers, on the other hand, make use of separate pick and drive rollers to achieve reliable and accurate media handling. This type of implementation, however, can present its own set of problems, especially during the design of a pick system for resiliently handling various sizes of media sheets. This set of problems can exist because such a pick system for multiple sized media sheets is usually susceptible to the occurrence of pick skew of the different sizes of media sheets. If the media sheet is skewed, then the print markings received on the media sheet will not be square to the page and the result will be aesthetically displeasing.
The present invention is intended to provide a solution to various prior art deficiencies, which include those present with the existing printing devices such as copiers, faxes or printers, to provide a cost effective and reliable media sheet pick operation within a media handling system.