Systems and methods for reducing registration errors in translating media shaft drive systems

Systems and methods for positioning a sheet in a feed path including at least one sheet drive roller driven in a rotational direction by a drive shaft in which the drive shaft translates in a lengthwise direction along the axis of the drive shaft. A power shaft rotates about the same axis as the drive shaft and is driven by a power source that is fixedly mounted in the system. The power shaft is fixed to the drive shaft by a flexible coupling that allows the drive shaft and the power shaft to move relative to one another in the lengthwise direction along the axis while maintaining corresponding rotational motion between the power shaft and the drive shaft.

This disclosure relates to sheet registration systems in image forming devices, and specifically to systems and methods for reducing sheet registration errors in translating media shaft drive systems.

BACKGROUND

Sheet aligning mechanisms in image forming devices use a variety of methods for registering sheets in process (forward), lateral (side-to-side), and skew (rotation) directions. Precise registration is important for reliable and accurate image production and/or reproduction.

Sheet handling and registration systems today can perform all three registration functions nearly simultaneously and with sheets moving along a paper path at a controlled speed, without sheet stoppages. This is otherwise known as in-process sheet registration, or more colloquially, sheet registration “on the fly.” The requirement advantageously to conduct sheet printing operations at ever increasing speeds challenges conventional sheet handling and registration systems. An ability to achieve a desired sheet skew rotation, sheet lateral movement, and forward sheet speed adjustment during ever briefer time periods presents unique challenges in various systems.

Conventional systems use two high-power servo-motors or step motors for driving a laterally spaced pair of separate sheet driving nips. Motors mounted on transversely-movable carriage assemblies with respect to the feed path to achieve both skew and lateral adjustment add significant proportional weight to the carriage. This additional weight makes it difficult to control rapid movement as may be required for lateral adjustment.

SUMMARY

Related methods remove the motors from the traversing carriage. This reduces the weight of the carriage, allowing quicker and more accurate lateral response.

A current solution, however, has its drawbacks. These systems in which drive motors are separate from the carriage carrying the drive shaft and drive nips use elongated gears that communicate drive power from the drive motors to a drive shaft. A relatively long gear on the drive shaft moves laterally across a smaller gear connected to a fixed motor. Such designs can suffer from backlash and/or transitional delay between the gears due to clearances between teeth of the gears and/or wear of the gears and mounting hardware. Even small clearances or other gaps can translate to undesirable deviations in sheet registration, imprecise translation of drive forces and/or backlash.

FIG. 9depicts a related system in which a narrow sear70is mated with a traversing gear80that is fixed to a drive shaft16. Carriage12moves relative to the drive motors20in the direction indicated by arrow D. In such a system, clearances between the individual teeth of gears70and80may allow for inaccuracies in the translation of drive forces and/or undesirable backlash. Further, as the gears70and80wear, these effects may be increased, thus requiring replacement of the parts in order for effective functioning of the registration device.

In such systems, attempts to reduce clearance and/or backlash by increasing contact pressure in the gear system also increases functional forces that restrain the lengthwise movement of the gears. The effects of such frictional forces can be significant, particularly in light of the gear structure that, for every lengthwise movement of the drive shaft16in the axial direction, a frictional movement of equal distance is created along the teeth of gear70.

In view of the foregoing, it would be desirable to provide systems and methods whereby backlash would be reduced and/or communication of drive forces enhanced between power shafts and drive shafts in sheet handling and registration systems while motors driving such shafts remain stationary.

Disclosed systems and methods may provide a translating shaft drive system for use in sheet handling and registration systems that allow the system to translate while the drive motors remain stationary, thus allowing relatively low carriage mass and fast carriage return times, while providing reduced backlash and resultant registration errors. This may be accomplished via a coupling that fixes a drive shaft to a power shaft in a rotational direction while allowing relative movement between the shafts in a lengthwise direction.

Disclosed systems and methods may include couplings with structures that reduce frictional movement within, or at connection points of, the coupling caused by relative movement of the shafts in a lengthwise direction while maintaining accurate position in a rotational direction.

In various exemplary embodiments, the coupling may comprise at least two pieces that are joined to each other at ends of the pieces. At least one of the pieces may be fixed to a drive shaft and at least another of the pieces may be fixed to a power shaft.

In various exemplary embodiments, the pieces may be substantially rectangular and joined together at short sides of the pieces. Additionally, the pieces may be substantially flat.

In various exemplary embodiments, the pieces may be substantially circular and joined together substantially along the circumference of the pieces. Additionally, either or both of the pieces may include a concave portion on the mating surface.

In various exemplary embodiments, the coupling may include at least two bending links, each bending link having two ends. Each of the two ends of the respective bending links is fixed in the rotational direction to one of the respective power shaft or drive shaft. In various exemplary embodiments, the structure of the coupling may be such that relative movement of the shafts in a lengthwise direction causes negligible frictional movement in the coupling in the lengthwise direction.

In various exemplary embodiments, the coupling may comprise at least one flexible substantially hollow structural member fixed to the drive shaft or the power shaft and/or one compressible torsionally-rigid substantially solid structural member.

These and other objects, advantages and features of the systems and methods according to this disclosure are described and/or are apparent from, the following description of exemplary embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

Although embodiments of disclosed systems and methods are designed in view of specific exemplary use in a translating shaft drive system for sheet handling and registration units in image forming devices, and specifically xerographic image forming devices, the disclosed systems and methods are equally applicable to any shaft drive systems in which radial stiffness is provided while allowing low-friction axial motion of the system particularly with respect to one or more fixedly mounted drive systems.

FIG. 1illustrates a first exemplary embodiment of a translating shaft drive system according to this disclosure. The system1places a sheet into proper alignment or registration for downstream processing. As shown inFIG. 2, the exemplary system1may include a registration unit10that in turn may include a carriage12having two drive rolls14. The drive rolls14may be driven by drive motors20. The rotary output of each motor20may be transmitted to a power shaft18by a suitable power transmission unit such as, for example, belts22, or the drive motors20may be directly connected to power shaft18in a configuration that is not shown.

The power shafts18may in turn transmit power to drive shafts16via couplings24. As depicted inFIG. 1, couplings24may be formed by joining two pieces52formed of relatively thin sheets of material such as, for example, metal, at or near the ends of the pieces52. The power shaft18and drive shaft16may each be fixed in a rotational direction to a center portion of a piece52, respectively. As such, a rotational correlation of the power shaft18to the drive shaft16is intended to be maintained (seeFIG. 3).

It should be appreciated that, although depicted with two pieces52, exemplary embodiments of the coupling may include more than two pieces, joined in similar fashion. For example, four pieces52could be joined in the form of an X, with two pieces52fixed to the power shaft18and two other pieces52fixed to the drive shaft16(seeFIG. 9). It should also be appreciate that the depicted pieces52are exemplary and not limiting to the shape, size or configuration of pieces or couplings contemplated by this disclosure. For example, individual pieces may vary in shape and size and/or be combined with other disclosed structural components of exemplary couplings without departing from the scope of this disclosure.

Referring back toFIG. 1, drive rolls14are fixedly mounted on each of the drive shafts16. Adjacent to, and in pressure contact with, drive rolls14may be rotatably mounted by suitable means nip rolls26. The nip rolls26may be commonly coaxially mounted for rotation about the axis of a cross shaft30which is mounted on the carriage12. The roll pairs26,14may engage a sheet by nip28and drive it through the registration unit10.

The carriage12may be mounted for movement transversely of the direction of feed, as indicated by arrow A, while the motors20are otherwise fixedly mounted.

The structure depicted inFIG. 1allows the carriage12to move transversely through a range without moving the motors20or power shafts18. Couplings24also accurately translate the power provided by power shafts18to drive shafts16and drive nips14while providing negligible impediment to the movement of the carriage12in the transverse direction A.

FIG. 2illustrates a second exemplary embodiment of a translating shaft drive system according to this disclosure. Similar components to those depicted, inFIG. 1are labeled in like manner inFIG. 2. As shown inFIG. 2, a second exemplary coupling joining power shaft18to drive shaft16is depicted. Two bending links40are shown. Each bending link40may include rigid members44,48, which may translate the power provided by power shafts18to drive shaft16and drive nips14while providing negligible impediment to the movement of the carriage12in the transverse direction A. A more detailed view of aspects of exemplary coupling are depicted inFIGS. 4-6.

According to this second embodiment, and as shown inFIG. 4, one end of each rigid member44may be fixed in a rotational direction to power shaft18. Such fixing may be accomplished via press fitting pins50, as depicted inFIG. 6. This may fix ends of each rigid member44to the power shaft18in a rotational direction, represented by arrow B. The other of the ends of each rigid member44may be similarly joined to a cooperating end of each rigid member48, as depicted inFIGS. 4 and 5. The other of the ends of rigid members48, opposite the cooperating ends joined to rigid members44, may be fixed to the drive shaft16in a similar manner to the fixing of each rigid member44to the power shaft18. Thus, accurate translation of the rotation of power shaft18may be communicated to drive shaft16while still allowing translational movement of power shaft18and drive shaft16in the direction indicated by arrow C inFIG. 4.

FIG. 7illustrates a third exemplary embodiment of a coupling for use in a translating shaft drive system according to this disclosure. In this embodiment, the pieces of the coupling are two substantially circular flexible cups62,64. The cups62,64are connected to power shaft18and drive shaft16, respectively, and joined substantially around the circumference of the cups. Compression or expansion of either or both of the cups62,64allows translational movement of power shaft18and drive shaft16while still accurately communicating rotation of power shaft18to drive shaft16via the torsional rigidity of the cups62,64.

FIG. 8illustrates a fourth exemplary embodiment of a coupling for use in a translating shaft drive system according to this disclosure. In this embodiment, the coupling includes a structural portion54, fixed to the drive shaft and the power shaft, formed of a flexible, substantially hollow, spheroid, or a compressible torsionally-rigid substantially solid spheroid. It should be appreciated that these shapes are exemplary and not limiting of the shapes, configurations or combinations that disclosed embodiments may include. Compression or expansion of the structural portion54allows translational movement of power shaft18and drive shaft16while still accurately communicating rotation of power shaft18to drive shaft16via the torsional rigidity of the structural portion54.

It should be appreciated that, in depicted exemplary embodiments, frictional movement of individual components within, or at connection points of, the coupling caused by translational movement of the drive shaft16is less than the distance of the translational movement. For example, as depicted inFIG. 2, a rigid member44, attached to the power shaft18and a second rigid member48, may rotate relative to the power shaft based on translational movement of the drive shaft16. However, the distance of any frictional movement between the contact surfaces of the rigid member44and the power shaft18is less than the distance of the translational movement of drive shaft16. Other exemplary couplings may facilitate relative movement of the drive shaft and the power shaft in a longitudinal direction along the axis with negligible, or no, frictional movement in the coupling (see FIGS.3and7-9).

The couplings depicted inFIGS. 1-9, may enhance translation of drive forces and/or reduced backlash over related systems as depicted inFIG. 10described above.

It should be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined and/or used in many other different systems or applications. Individual exemplary coupling components may be combined in a variety of manners with other disclosed exemplary coupling components without departing from the scope of this disclosure. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, and are also intended to be encompassed by the following claims.