Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1999-10-20
2001-05-29
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S117000
Reexamination Certificate
active
06237909
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to sheet material feed mechanisms. More specifically, the present invention relates to torque loading of sheet material feed rollers associated with imaging devices such as printers, copiers, and fax machines.
BACKGROUND OF THE INVENTION
Imaging systems such as printers, fax machines, and copiers are virtually omnipresent, and can be found in homes and offices worldwide. The development of such systems has facilitated improvements in communication that have in turn fostered a sea of change in the way people live and work. Telecommuting, paperless offices, and intra-office networks represent but a few examples of the advancements that have been made possible by modern imaging systems.
Since these systems have become crucial to everyday existence, their reliability and smooth operation is paramount. It is therefore vitally important to design imaging systems so that downtime and work interruptions are minimized. This can be a daunting challenge, given the relative complexity of systems in which sheet material must be infed, moved through the imaging process, and outfed in a matter of seconds.
It has been found that the difference in weight between smaller and larger sheet sizes, differences in weight between thicker and thinner sheets, and different sheet surface textures can present problems in sheet feeding throughout the imaging system. For each combination of these factors, successful transportation of sheet material depends upon applying the proper amount of applied force on the sheet with a feed mechanism such as a roller. The combination of forces is shown in FIG.
1
. When torque T is applied to the roller R, the combination of torque and normal force N produces a transport force P, which causes the sheet material to move. Accurate application of the applied force A transmitted through the roller R allows the system designer to produce the desired normal and transport forces appropriate for a particular sheet material.
The consequences of incorrect forces can be problematic. Using the infeed mechanism as an example, if the applied force is too low, sheets can have “no-pick” problems, where the transport force is insufficient to remove the sheets from the stack. At the other end of the spectrum, if the force is too great, the result may be “multi-feed” problems, wherein the transport force introduces several sheets into the feed mechanism simultaneously. Excess force can also cause deformation of one or more of the underlying sheets.
Among the known approaches to address these difficulties are systems which rely upon a method of sensing the height of a stack of sheet media, then placing the transport mechanism based on the sensed height of the media stack. Such systems are relatively complex, and do not directly control the normal force applied to the media stack when the pick mechanism operates. Further, known devices employ multiple sensing devices, one to sense stack height and another to sense transport mechanism position.
It can thus be seen that the need exists for a reliable and predictable way to transmit applied force to a feed roller associated with imaging devices such as printers, copiers, and fax machines.
SUMMARY OF THE INVENTION
These and other objects are achieved by providing a sheet material feed mechanism including a sheet material transport mechanism mounted for contact with a stack of sheet material. A force application mechanism is adapted and constructed to apply a variable normal force to the stack of sheet material through the sheet material transport mechanism. A displacable force detection assembly is mounted between the sheet material transport mechanism and the force application mechanism. Displacement of the force detection assembly corresponds to a normal force applied to the stack of sheet material through the sheet material transport mechanism.
The sheet material transport mechanism can be provided as a feed roller assembly. The feed roller assembly can include a driven roller in contact with the stack of sheet material. A drive roller can be operatively connected to the driven roller and the force application mechanism.
The force detection assembly can be provided as a motion-sensing device. The motion-sensing device can include a spring member having first and second ends, the first end of the spring member being secured to the force application mechanism. A sensor can be secured to the force application mechanism, with a sensor flag secured to the second end of the spring member. A normal force applied to the stack of sheet material through the sheet material transport mechanism causes a distance between the sensor flag and the sensor to vary.
The sheet material feed roller mechanism can include a control system adapted and constructed to monitor and control the sheet material feed roller mechanism. A connector assembly operatively connects the force detection assembly to the control system. The force application mechanism can be provided as a stepper motor.
The features of the invention believed to be patentable are set forth with particularity in the appended claims. The invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4084807 (1978-04-01), Terajima et al.
patent: 4934686 (1990-06-01), Ono et al.
patent: 5927703 (1999-07-01), Endo
patent: 404223939 (1992-08-01), None
patent: 405000743 (1993-01-01), None
patent: 405000744 (1993-01-01), None
Carter, Jr. Scott K.
Regimbal Laurent A.
Hewlett--Packard Company
Skaggs H. Grant
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