Sheet feeding or delivering – Delivering – With transfer means between conveyor and receiver
Reexamination Certificate
1998-08-31
2001-02-13
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Delivering
With transfer means between conveyor and receiver
C271S185000, C271S184000, C271S303000, C271S305000
Reexamination Certificate
active
06186496
ABSTRACT:
The present invention relates to feeding substrates through an electrophotographic printing machine. More particularly, the invention relates to compiling sheets into a set of printed sheets.
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet.
High speed copying machines are becoming increasingly popular. These machines have a capacity or output capacity of say, for example, over 60 copies per minute. These machines are able to use single cut sheets of paper of various size such as A4, 8½×11, or 8½×14 inch copy sheets. These machines may be of the light lens, xerographic machine or may be a printer with digital input. Single, cut sheet printing machines are now available at speeds around 200 cpm.
The present invention relates to an improved sheet inverting system, and more particularly, to an inverter adapted to be placed within the normal paper path of a copier while providing improved handling of variable size sheets, as well as, curled sheets within the inverter.
As xerographic and other copies increase in speed, and become more automatic, it is increasingly important to provide higher speed yet more economical, reliable and more automatic handling of both the copy sheets being made by the copier and the original document sheets being copied. It is thus desired to accommodate sheets which may vary widely in size, weight, thickness, material, condition, humidity, age, etc.
These variations change the beam strength or flexural resistance, as well as, other characteristics of the sheets. Yet, the desire for automatic and high speed handling of such sheets without jams, misfeeds, uneven feeding times, or other interruptions increases the need for reliability of all sheet handling components. A sheet inverter is one such sheet handling component with particular reliability problems and sheet handling size and capability limitations.
Although a sheet inverter is referred to in the copier art as an inverter, its function is not necessary to immediately turn the sheet over (i.e., exchange one face for the other). Its function is to effectively reverse the sheet orientation in its direction of motion. That is, to reverse the lead edge and trail edge orientation of the sheet.
Typically, in an inverting device, the sheet is driven or fed by feed rollers or other suitable sheet driving mechanisms into a sheet reversing chute. By then, reversing the motion of the sheet within the chute and feeding it back out from the chute, the desired reversal of the leading and trailing edges of the sheet in the sheet path is accomplished.
Depending on the location and orientation of the inverter in a particular sheet path, this may, or may not, also accomplish the inversion (turning over) of the sheet. In some applications for example, where the (inverter) is located at a corner of a 90° to 180° inherent bend in the copier sheet path, the inverter may be used to actually prevent inverting of a sheet at that point, i.e., to maintain the same side of the sheet face-up before and after this bend in the sheet path. On the other hand, if the entry and departing path of the sheet, to and from the inverter, is in substantially the same plane, the sheet will be inverted by the inverter. Thus, inverters have numerous applications in the handling of either original documents or copy sheets to either maintain, or change, the sheet orientation.
Inverters are particularly useful in various systems of pre- or post-collation copying, for inverting the original documents, or for maintaining proper collation of the sheets. The facial orientation of the copy sheet determines whether it may be stacked in forward or reverse serial order to maintain collation. Generally, the inverter is associated with a by-pass sheet path and gate so that a sheet may selectively by-pass the inverter, to provide a choice of inversion or noninversion.
Typically, in a reversing chute-type inverter, the sheet is fed in and then wholly or partially released from a positive feeding grip or nip into the inverter chute and then reacquired by a different feeding nip to exit the inverter chute. Such a temporarily loss of positive gripping of the sheet by any feeding mechanism during the inversion increases the reliability problems of such inverters.
As noted above, many inverters, particularly those utilizing only gravity, have reliability problems in the positive output or return of the sheet at a consistent time after the sheet is released in the inverter chute. Those inverters which use chute-drive rollers or other drive mechanisms of the type disclosed in U.S. Pat. No. 3,416,791 have a more positive return movement of the sheet, but this normally requires a movement actuator (collector solenoid) for the drive or and either a censor or a timing mechanism to determine the proper time to initiate the actuation of this drive mechanism so that it does not interfere with the input movement of the sheet, and only thereafter acts on the sheet to return it to the exit nip or other feed-out areas.
Further, inverter reliability problems are aggravated by variations in the condition or size of the sheet. For example, a preset curl in the sheet can cause the sheet to assume an undesirable configuration within the chute when it is released therein and interfere with the feed-out.
Further, copiers are typically required to utilize a wide range in sheet or media thickness or weight. For example, printing machines are required to utilize the lightest media (13# bond and lower) while also being able to utilize heavy, thick media such as index paper (110# weight or greater). Being able to invert paper with such a wide range of weight and stiffness is very difficult.
During the process of inverting a sheet, the sheet is directed toward an inverting chute along an inverter entry path. After the chute has been reversed, the sheet leaves the reversing chute through an inverter exit path. The leading edge of the sheet must be directed into the inverting chute and the leading edge of the sheet must be directed into the inverter exit path after the sheet has been reversed in the reversing chute.
A movable gate is typically used to direct the sheet into the inverting chute at the inverter entry path and to direct the sheet into the inverter exit path after it has been reversed in the inverting chute. A movable gate is typically used to direct the sheet into the inverting chute and to direct the sheet further into the inverter exit path. Typically, the movable gate is moved from a first position to a second position through the use of either a solenoid and cam device or a motor device.
The use of solenoid or motor devices to move a gate results in reliability and speed limitations because of the mechanical motions of the solenoid or motor. Further, the motion of the solenoid or motor must be timed with the entry of the sheet into the inverter chute and exit of the sheet from the inverter chute. These timing issues require either further slowdown of the process
Attridge David M.
Marasco Joseph
Miller Jonathan R
Ryan Andrew D.
Walsh Donald P.
Xerox Corporation
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