US20070152397A1

US20070152397A1 - Image forming systems with gimbaled retard feeder device

Info

Publication number: US20070152397A1
Application number: US11/320,431
Authority: US
Inventors: Henry Bober; Linn Hoover; Alan Francis
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 2005-12-29
Filing date: 2005-12-29
Publication date: 2007-07-05

Abstract

An image forming system may include a photoreceptor, a sheet feeding apparatus and a retard feeder device that includes a feed roll, retard roll and nudger roll. The retard feeder device transfers a sheet of paper from the sheet feeding apparatus, through the sheet imaging media registration system and on to the photoreceptor. The retard roll is mounted in a loading bracket to allow the Retard Rollers to be loaded against the Feeder Rollers. The loading bracket is mounted on a pivot pin so that the retard rollers can pivot to maintain equal pressure against both feed roll. A retard feeder device may include a bracket, a feed roll assembly that includes two tires, a retard roll assembly that includes two tires and a nudger roll assembly. The retard roll loading bracket is fastened to a pivot pin so that the retard rollers can pivot to maintain an equal pressure between the tires of the retard roll assembly and the tires of the feed roll assembly.

Description

BACKGROUND

The disclosure relates to image forming systems, and more particularly to a retard feeder device that may be used in the image forming systems.
Retard feeders may be used in image forming systems to advance or separate an image receiving medium, such as a substrate or sheet of paper, from a storage device or tray that holds the image receiving medium. The retard feeder may include individual rolls. For example, the retard feeder may include a feed roll assembly, retard roll assembly and a nudger roll assembly. The feed roll assembly is positioned opposite the retard roll assembly, and each roll assembly often may include either two rollers or tires or a single wide roller. The feed and retard roll assemblies contact each other forcibly to create a nip. The nudger roll assembly is forcibly positioned on top of a stack of paper and frictionally nudges the top sheet [or sheets] into the Feeder-Retard Roller Nip. The feed roll assembly is driven so that they advance the sheet of paper out of the media supply tray. The retard roll is not driven in a semi-active retard feeder, but the retard roll may include a drag clutch. Maintaining an equal load between the two Feeder and Retard Tires is essential to maintaining reliable feeding operation and minimizing media skew or rotation.
The drag clutch establishes a well controlled frictional drag torque on the retard roll assembly. It permits the retard roller assembly to rotate when enough frictional drive force is place on the retard roll by a sheet of paper or other like imaging media being driven through the Feeder-Retard Roller Nip. This is the case when a single sheet of imaging media has entered the Feeder-Retard Nip. The single sheet is fed with the feeder roll assembly while the retard roll assembly is rotated by the passing of the single sheet. If not enough friction is placed on the retard roll, the retard roll does not rotate and it will frictionally hold back or ‘retard’ the sheet. This is the case when two or more sheets of imaging material enter the Feeder-Retard Nip. Thus, the drag clutch may operate as a drag brake. For a single sheet of paper to through the Feeder-Retard Nip, the Feed Roller Drive Force on the sheet must be capable of overcoming the Retard Drag Torque. However, if two sheets of paper, e.g., a multi-feed, are advanced from the paper tray through the Feeder-Retard Nip, the Retard Drag Torque will hold back or retard the bottom sheet(s) as long as the Drag Force on the Retard Roll is greater than the sheet to sheet friction.

SUMMARY

The feed roll assembly, retard roll assembly and the nudger roll assembly of the retard feeder device are generally positioned parallel to each other but the feed and retard roller assemblies need to be precisely parallel to each other because they are loaded against one another to create the nip. The parallel alignment of the feed roll assembly and retard roll assembly is extremely important because equal pressure must exist between both pairs of feed and retard roller tires or both sides of a single wide roll nip so that paper is fed into a image forming system from a storage device with very limited skew. Minimizing skew is important so as to not over stress the Registration & Deskew System, located in the Image Forming System.
In order to acceptably align the feed roll assembly axis and retard roll assembly axis to each other, and create the equal pressure in both feed/retard roll nips, the composition or Durometer of conventional rollers or tires may be altered or reduced to allow the tire deformation to adjust for a lack of parallel alignment and produce an appropriately balanced nip pressure across both feeder/retard tire nips. However, when the tires are formed of harder or higher Durometer to provide better wear resistance and roller life, the alignment of the feed and retard roll assemblies becomes more sensitive and unequal pressure may still exist between the feed and retard roll tire nips. Moreover, some materials used for the tires are expensive and difficult to manufacture accurately enough to produce the necessary parallelism. If a uniform pressure, or nip force, does not exist between both feed roller and the retard roller assemblies, a non uniform drive force will be produced by the two feeder/retard tire nips. This imbalanced drive force can cause print media skewing or rotation. The low drive force can also allow the retard roller assembly to slip or even stall, causing the leading edge of a sheet entering the feeder/retard tire nip to stub on the stalled retard roll and misfeed. A paper jam results from the misfeed because when the leading edge of the print media or paper stubs on the stalled retard roller tires, it rolls over or folds under and does not enter the feeder/retard tire nip.
Thus, in accordance with various exemplary embodiments, a retard feeder device may be connected to a gimbal, e.g., a pivot pin, to allow the retard roll assembly to pivot into parallel alignment with the feeder roll assembly and create uniform pressure between the two sets of tires. Using the gimbal allows longer life higher Durometer materials and/or less expensive manufacturing processes to be used for the tires because the gimbal ensures proper alignment and equal pressure between the feed and retard roll assemblies.
In various exemplary embodiments of the disclosure, an image forming system may include a photoreceptor, a Registration-Deskew station and a sheet feeding apparatus such as a retard feeder device. Such a retard feeder device will include a feed roll assembly, a retard roll assembly and a nudger roll assembly. The retard feeder device transfers a sheet of paper from the sheet feeding apparatus storage tray to the Registration-Deskew Station and then to photoreceptor for imaging. The retard roll is mounted to a retard roller assembly loading bracket and forcibly positioned against the feed roller assembly.
A retard feeder device may include a bracket, a feed roll assembly that includes either two widely spaced tires or a single wide tire, a retard roll assembly that includes either two widely spaced tires or a single wide tire and a nudger roll assembly. The retard roll loading bracket is fastened to a gimbal or pivot pin so that the retard roll assembly pivots into parallel alignment with the feeder roll assembly to maintain an equal pressure between the tires of the retard roll assembly and the tires of the feed roll assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the systems and methods according to the invention will be described in detail, with reference to the following figures, wherein:
FIG. 1 shows an exemplary diagram of an image forming system that includes a retard feeder device;
FIG. 2 shows an exemplary diagram of the retard feeder device positioned on a feed head frame;
FIG. 3 shows an exemplary detailed diagram of the retard feeder device; and
FIG. 4 shows an exemplary system without a gimbaled retard pivot.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an exemplary diagram of an image forming system 100 that includes a retard feeder device. The system includes a belt 10 having a photoconductive surface 12 deposited on a conductive ground layer 14. The photoconductive surface 12 may be made from a photo responsive material, for example, one including a charge generation layer and a transport layer. The conductive layer 14 may be made from a thin metal layer or metallized polymer film that is electrically grounded. The belt 10 moves in the direction of arrow 16 to advance successive portions of photoconductive surface 12 sequentially through the various processing stations disposed about the path of movement thereof. The belt 10 may be entrained about a stripping roller 18, tensioning roller 20 and drive roller 22. The drive roller 22 may be mounted rotatably in engagement with belt 10. A motor 24 rotates roller 22 to advance belt 10 in the direction of arrow 16. The roller 22 may be coupled to a motor 24 by suitable means, such as gears and/or a drive belt. The belt 10 may be maintained in tension by a pair of springs (not shown) resiliently urging the tensioning roller 20 against the belt 10 with the desired spring force. The stripping roller 18 and tensioning roller 20 may be mounted to rotate freely.
A portion of the belt 10 may pass through a charging station A. At the charging station A, a corona generating device 26 may charge the photoconductive surface 12 to a relatively high, substantially uniform potential. After the photoconductive surface 12 of the belt 10 is charged, the charged portion may be advanced through an exposure station B.
At the exposure station B, a controller or electronic subsystem (ESS) 28 may receive the image signals representing the desired output image and process the signals to convert them to a continuous tone or gray scale rendition of the image that is transmitted to a modulated output generator, for example, the raster output scanner (ROS) 30. The controller 28 may be a self-contained, dedicated minicomputer. The image signals transmitted to the controller 28 may originate from a computer, thereby enabling the image forming system 100 to serve as a remotely located printer for one or more computers. The image forming system 100 may serve as a dedicated printer for a high-speed computer. The signals from the controller 28, corresponding to the continuous tone image desired to be reproduced by the printing machine, may be transmitted to the ROS 30.
After the electrostatic latent image has been recorded on the photoconductive surface 12, the belt 10 advances the latent image to a development station C where the toner, in the form of liquid or dry particles, is electrostatically attracted to the latent image using commonly known techniques. At the development station C, a magnetic brush development system 38 may advance charged developer material into contact with the latent image. A magnetic brush development system 38 may include two magnetic brush developer rollers such as 40 and 42. The rollers 40 and 42 may advance charged developer material into contact with the latent image. The developer rollers may form a brush of carrier granules and toner particles extending radially outward. The latent image on Belt 10 attracts toner particles from the carrier granules forming a toner powder image thereon. As successive electrostatic latent images are developed, toner particles are depleted from the developer material. A toner particle dispenser 44 dispenses toner particles into a developer housing 46 of the development system 38.
As shown in FIG. 1, after the electrostatic latent image is developed, the toner powder image present on the belt 10 advances to the transfer station D. A print sheet 48 is advanced to the transfer station D by a sheet feeding apparatus 50. The sheet feeding apparatus 50 may include a retard feeder device 80 that includes a feed roller assembly 81, retard roll assembly 82 and nudger roller assembly 83. The nudger roll 83 may contact the uppermost sheet of paper in the stack 54 and the roller assembly rotates to advance the uppermost sheet of paper from the stack 54 to the feed roll assembly 81 and retard roll assembly 82. The feed roller assembly 81 and retard roller assembly 82 may separate any double fed sheets before forwarding the sheet into the Registration-Deskew Station 205. The Registration-Deskew Station may incorporate a set of clutched stalled Nip Rollers 210 and a Buckle Chamber 215. After being deskewed, the fed sheet is driven into a chute 56. The chute 56 may direct the advancing sheet of support material into contact with photoconductive surface 12 of belt 10 in a timed sequence so that the toner powder image formed thereon contacts the advancing sheet at the transfer station D. The transfer station D may include a corona generating device 58 that sprays ions onto the back side of sheet 48 in order to attract the toner powder image from photoconductive surface 12 to sheet 48. After transfer, the sheet 48 continues to move in the direction of arrow 60 onto a paper transport or conveyor (not shown) which advances the sheet 48 to a fusing station E.
The fusing station E may include a fuser assembly 62 that permanently affixes the transferred powder image to the sheet 48. The fuser assembly 60 may include a heated fuser roller 64 and a back-up or pressure roller 66. The sheet 48 passes between the fuser roller 64 and back-up roller 66 with the toner powder image contacting the fuser roller 64. In this manner, the toner powder image is permanently affixed to the sheet 48. After fusing, the sheet 48 advances through the chute 68 to output tray 72 for subsequent removal from the printing machine by the operator.
After the print sheet is separated from photoconductive surface 12 of belt 10, the residual toner/developer and paper fiber particles adhering to photoconductive surface 12 are removed there from at the cleaning station F. The cleaning station F may include a rotatably mounted fibrous brush in contact with the photoconductive surface 12 to disturb and remove paper fibers and a cleaning blade to remove the nontransferred toner particles. Subsequent to cleaning, a discharge lamp (not shown) floods the photoconductive surface 12 with light to dissipate any residual electrostatic charge from the image remaining thereon prior to the charging thereof for the next successive imaging cycle.
FIG. 2 shows an exemplary diagram of the retard feeder device 80 positioned on a feed head frame 90. As shown in FIG. 2, a gimbal pivot pin 91 is positioned on the feed head frame wall 92 in between the feed head frame wall 92 and the retard feeder device 80. A traditional feed head frame 90 could include retard assembly carrier pivot ears on the feed head frame wall 92. They may be altered or removed so that the gimbaled bracket 94, the retard carrier bracket 95 and the retard roller assembly, 82 from FIG. 1, is allowed to pivot on the pivot pin 91. By using the gimbal pivot pin 91, the Gimbal Bracket 94 and the retard roll assembly 82 is allowed to pivot. The pivoting motion of the retard roll assembly 82 allows the retard roller assembly to be parallel to the feeder roller assembly. This ensures equal pressure between the tires of the feed roller assembly 81 and the tires of the retard roller assembly 82, which reduces sheet skew and misfeeds as the individual sheets of paper are fed into an image forming system 100 from the stack 54.
In accordance with various exemplary embodiments, the gimbal pivot pin 91 may be positioned on the feed head frame wall 92 as shown in FIG. 2. The pivot pin 91 may be fastened to the feed hard frame wall by any known fastening means, and the retard carrier bracket 95 of the retard roll assembly 82 located within the retard feeder device 80 may be axially retained on the pivot pin 91 using a pin thrust fastener 93. The gimbal bracket 94 may be formed of, for example, aluminum or plastic. The retard roll assembly 82 is mounted in the retard carrier bracket 95 which is pivotally secured to the gimbal bracket 94. The carrier pivot axis 96 is perpendicular to the gimbal pin axis 91. The retard carrier bracket 95 and the retard roller assembly 82 are spring loaded to develop the required nip force between the feeder and retard roller assemblies, so that it develops equal pressure on both of the retard roller assembly tires. Because the pivot pin 91 is fastened to the feed head frame wall 92 perpendicular to the rotational axis of the feed and retard roller assemblies 81 & 82, the pivot pin 91 allows the retard roll assembly 82 to rotate in a direction shown by arrows A in FIG. 3 to correct or eliminate any gap between feed roller assembly tires 81 a and retard roller assembly tires 82a. The gimbal pivot pin 91 must be positioned on the feed head frame wall 92 symmetrically to and vertically above the combined Center of Gravity 97 of the gimbaled parts [the gimbal bracket 94, retard carrier bracket 95 and the retard roll assembly 82] to ensure stability and to provide the necessary uniform pressure between the individual feed and retard tires [81 a/82 a, 81 b/82 b].
For example, the gimbal pivot pin 91 must be positioned central between the two feed rolls 81 a-b so that its longitudinal axis points toward the paper stack 54 and be parallel to the plane of the paper sheets. If the gimbal pivot pin axis is not equidistant between the individual tire nips, the nip loads will not be equal. The gimbal pivot pin 91 allows the gimbal bracket 94, the retard carrier bracket 95 and the retard roll assembly 82 to align with the feed roll assembly 81 and apply equal nip force to both sets of tires. If the retard roll assembly 82 is not nominally balanced, the off center weight may load one roller more than another. Thus, a balance weight 87, e.g., a counterweight, may be included as shown in FIG. 3 to offset an asymmetric moment from the drag clutch 84. The balance weight 87 also forces the center of gravity back to the pivot pin 91 axis. The drag clutch 84 is attached to the retard carrier bracket 95. The drag clutch is rotationally coupled to the retard roll assembly 82 using gears 86 a-b. The balance weight 87 may be attached to the retard carrier bracket 95.
FIG. 3 shows an exemplary detailed diagram of the retard feeder device. The retard feeder device 80 self-aligns or pivots to contact both feed roller tires with both retard roller tires with a uniform pressure. As shown in FIG. 3, the retard feeder device 80 may include the feed roll assembly 81, retard roll assembly 82 and nudger roll assembly 83. The feed roll assembly 81 may include feed roller tires 81 a-b, and it may be positioned above the retard roll assembly 82. The retard roll assembly 82 may include retard roller tires 82 a-b. The feed roller tires 81 a-b and retard roller tires 82 a-b may be formed to resemble tires and they may be composed of urethane, silicon or other suitable high coefficient of friction materials. The drag clutch 84 limits the retard roll assembly 82 the media retarding frictional drag torque and rotate when enough friction force is placed on the retard roll assembly 82. If not enough friction force is placed on the surface of the retard roll assembly 82, the retard roll assembly 82 does not rotate. Thus, the drag clutch 84 may operate as a drag brake. The feed roll assembly 81 may be driven by a motor (not shown) and suitable gears or belts (not shown). As power is applied to the motor, the motor drives or rotates the feed roll assembly.
As shown in FIG. 4, without the gimbaled retard pivot feature, the retard roller assembly 82 is uniformly contacting the feed roll assembly 81, possibly indicating a high spot on one of the tires, preventing uniform contact on both nips. However, a gap 88 exists between the feed roller tire 81 b and retard roller tire 82 b because the eccentric tire 81 a pushes down on the retard roller assembly 82 and the retard carrier bracket 95. The gap 88 indicates a loss of nip pressure between the feed roller tire 81 b and retard roller tire 82 b caused by the feed roll assembly 81 and retard roll assembly 82 centerlines being rigidly fixed and unable to accommodate high tire spots, tire eccentricities or tire diameter differences. In other words, the feed roll 81centerline to the retard roll 82 centerline side to side spacing remains fixed. The eccentric tire contact on one side temporarily increases the nip center distance on both sides, decreasing or totally eliminating contact on the other tire nip. This creates an unbalanced nip force between the two feed-retard nips.
With the gimbaled retard pivot, the retard roll assembly 82 self-aligns or pivots to contact both feed roller tires with both retard roller tires with uniform pressure,. The uniformity of the nip pressure is improved and the gap shown in FIG. 4 is eliminated. Thus, sheet skewing and paper jams that occur in conventional devices are significantly reduced or eliminated by providing a uniform pressure across both feed-retard tire nips.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims

1. An image forming system, comprising:

a photoreceptor;

a sheet feeding apparatus; and

a retard feeder device that includes a feed roll assembly, a retard roll assembly and a nudger roll assembly, the retard roll assembly including a retard roll tire nip, the feed roll assembly including a feed roll tire nip,

the retard feeder device transferring a sheet of paper from the sheet feeding apparatus to a registration-deskew station and on to the photoreceptor; and

the retard roll assembly mounted on a gimbal pivot pin so that the retard roll assembly pivots into alignment with the feed roll assembly to maintain equal pressure between both of the feed and retard roll tire nips.

2. The image forming system of claim 1, wherein the retard roll assembly pivots either in a clockwise or counter-clockwise direction around the gimbal pivot pin.

3. The image forming system of claim 1, wherein the gimbal pivot pin is positioned in between a feed head frame and the retard feeder device.

4. The image forming system of claim 3, the retard roll assembly comprising a carrier bracket, wherein a gimbal bracket is connected to the carrier bracket and is fastened to the pivot pin using a fastener.

5. The image forming system of claim 4, comprising a drag clutch attached to the carrier bracket of the retard roll assembly.

6. The image forming system of claim 5, wherein the drag clutch allows the retard roll assembly to overcome a frictional drag torque of the retard roll assembly and rotate when a sufficient friction force is place on the retard roll assembly.

7. The image forming system of claim 5, comprising a balance weight connected to the carrier bracket of the retard roll assembly, the balance weight offsetting an asymmetric moment from the drag clutch and forcing a center of gravity back to an axis of the gimbal pivot pin.

8. The image forming system of claim 7, wherein the feed roll assembly and retard roll assembly are formed as feed roll and retard roll tires, respectively, and the retard roll assembly having the carrier bracket is spring loaded so that the retard roll assembly develops equal pressure on the feed and retard roll tires.

9. The image forming system of claim 7, wherein the feed roll assembly and retard roll assembly are formed as tires composed of urethane, silicon or a high coefficient friction material.

10. The image forming system of claim 9, wherein the nudger roll assembly contacts the sheet of paper and rotates to advance the sheet of paper to the feed roll assembly and retard roll assembly from the sheet feeding apparatus.

11. A retard feeder device, comprising:

a feed head frame;

a feed roll assembly that includes either two tires or one wide roller;

a retard roll assembly that includes a carrier bracket, a gimbal bracket, and either two tires or one wide roller; and

a nudger roll assembly,

the retard roll assembly fastened to a gimbal pivot pin so that the retard roll assembly pivots to maintain an equal pressure between the tires or roller of the retard roll assembly and the tires or roll of the feed roll assembly.

12. The retard feeder device of claim 11, wherein the retard roll assembly including the carrier bracket and the gimbal bracket is fastened to the pivot pin using a fastener.

13. The retard feeder device of claim 12, wherein the retard roll assembly pivots either in a clockwise or counter-clockwise direction around the gimbal pivot pin.

14. The retard feeder device of claim 13, wherein the retard roll assembly having the carrier bracket is connected to gimbal pivot pin using the gimbal bracket.

15. The retard feeder device of claim 11, comprising a drag clutch connected to the carrier bracket.

16. The retard feeder device of claim 15, wherein the drag clutch allows the retard roll assembly to overcome frictional drag torque and rotate when a sufficient frictional force is place on the retard roll assembly.

17. The retard feeder device of claim 16, comprising a balance weight connected to the carrier bracket, the balance weight offsetting an asymmetric moment from the drag clutch and forcing a center of gravity back to an axis of the gimbal pivot pin.

18. The retard feeder device of claim 17, the feed roll assembly comprising tires, wherein the retard roll assembly is spring loaded so that the retard roll assembly develops equal pressure against the feed roll assembly tires.

19. The retard feeder device of claim 18, wherein the tires are composed of urethane, silicon or a high coefficient friction material.

20. The retard feeder device of claim 19, the retard roll assembly including a retard roll nip, the feed roll assembly including a feed roll nip, wherein the nudger roll assembly contact a sheet of paper and rotates to advance the sheet of paper to the feed roll and retard roll nips from a stack of paper.