Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
1999-07-06
2001-02-27
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C074S462000, C464S158000
Reexamination Certificate
active
06193232
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to drive mechanisms for sheet material feed arrangements. Specifically, the invention relates to improved drive gear assemblies for sheet material feed rollers suitable for use in imaging systems.
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.
One common and recurring problem in imaging systems is document misfeed, which can result in sheet material such as paper getting lodged in the transport mechanism. This condition, often referred to as a “jam”, is a source of frustration for system users.
One cause of such jams is misalignment between elements of the sheet feed drive mechanism. As shown in
FIG. 1
, a typical drive mechanism D includes a driven friction tire arrangement F mounted on an upper shaft U. Support rollers S are mounted on a lower shaft L in proximity with the friction tires F. Transport force is imparted to the sheet material M as it passes between the friction tires F and the support rollers S.
As long as the upper shaft U and lower shaft L remain relatively parallel as shown in
FIG. 1
, the friction tires F contact the support rollers S with approximately the same force, and thus produce approximately the same transport force with little or no skew.
Unfortunately, the shafts are seldom parallel in practice. When the upper shaft U and lower shaft L are out of parallel alignment, as shown in
FIG. 2
, the friction tires F do not contact the support rollers S squarely. Consequently, the friction tires F and support rollers S will produce uneven transport forces, and therefore skew the sheet being transported.
In an attempt to mitigate this problem, gear wheel assemblies can be constructed as shown in
FIGS. 3 and 4
. The gear wheel assembly G includes an annular cylindrical gear wheel W. The gear wheel W has an internal gear tooth profile T on each end. A pair of toothed pinions P are mounted on a shaft A. The teeth of the pinions P are square, and are intended to mesh with the tooth profiles T to drive the gear wheel W. The pinions P have an external diameter substantially smaller than the internal diameter of the gear wheel W.
The pinions P do not allow a high degree of tolerance for misalignment. When the upper shaft U and lower shaft L are significantly out of parallel alignment, the individual pinions tend to “jump” a tooth, causing one pinion to be one or more teeth “ahead of” or “behind” the other. This situation places the gear wheel W in an asymmetrical position, resulting in a skewed sheet.
It can thus be seen that the need exists for a drive mechanism that will increase the reliability of sheet feed arrangements by minimizing skewing.
SUMMARY OF THE INVENTION
These and other objects are achieved by providing a gear wheel assembly in a sheet material feed mechanism. The gear wheel assembly includes an annular cylindrical gear wheel having an interior surface defining an interior diameter, with a plurality of gear teeth extending from the interior surface. A pinion is mounted for rotation within the gear wheel. The pinion includes an exterior surface defining an outer diameter, the outer diameter of the pinion being less than the inner diameter of the gear wheel. A plurality of gear teeth extend outwardly from the exterior surface of the pinion. The pinion gear teeth have arcuate contact edges adapted to drivingly engage with gear teeth of the gear wheel.
The contact edges of the pinion gear teeth can be provided with tapering radii of curvature, preferably tapering outwardly from the respective centers of the gear teeth. In an embodiment, the contact edges of the pinion gear teeth have a radius of curvature of 45 mm for a gear wheel having a diameter of 10.5 mm.
The gear wheel assembly can be configured so that there is a one-to-one correspondence of pinions to gear wheels in the sheet feed mechanism. At least one friction wheel can be mounted on the gear wheel shaft.
A method of maintaining parallelism between a gear wheel and a support roller assembly in a sheet material feed mechanism is also disclosed. In a first step, a gear wheel shaft having a longitudinal axis is provided. A pinion is then mounted for rotation with the gear wheel shaft, the pinion having a longitudinal axis coincident with the longitudinal axis of the shaft. A gear wheel having a longitudinal axis capable of non-parallel alignment with the longitudinal axis of the gear wheel shaft surrounds the pinion. A support roller assembly having a longitudinal axis and including at least one support roller is also provided. The pinion is then actuated to impart uninterrupted rotational movement to the gear wheel when the longitudinal axis of the gear wheel is parallel to the longitudinal axis of the support roller assembly and out of parallel alignment with the longitudinal axis of the pinion.
REFERENCES:
patent: 2114807 (1938-04-01), McCavitt
patent: 2638011 (1953-05-01), Smith
patent: 2687025 (1954-08-01), Wildhaber
patent: 3292390 (1966-12-01), Wildhaber
patent: 5927709 (1999-07-01), Greive
patent: 6059280 (2000-05-01), Yamauchi et al.
Carter, Jr. Scott K.
Michel Teodoro Ortiz
Regimbal Laurent A.
Hewlett--Packard Company
Skaggs H. Grant
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