US3844179A

US3844179A - Gear drive for electrophotographic printing machine

Info

Publication number: US3844179A
Application number: US00370181A
Authority: US
Inventors: C Hawley
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-06-14
Filing date: 1973-06-14
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29
Also published as: FR2233535A1; SE7406924L; BE816382A; FR2233535B1; CA1007075A; DE2426176A1; IT1015035B; NL7408013A; JPS5034245A; AR203483A1; CH578699A5; BR7404813D0; GB1467714A

Abstract

An apparatus in which a pair of gear members include alternate resilient and rigid portions producing flexure in each of the gears so that backlash is minimized.

Description

United States Patent 1191 I Hawley 1 Oct. 29, 1974 GEAR DRIVE FOR 3,361,002 1/1968 Staehlin 74/409 ELECTRQPHOTOGRAPHIC PRINTING 3,406,583 10/1968 Baier 74/411 MACHINE D FOREIGN PATENTS OR APPLICATIONS [75] Inventor Charles Hawley Webster 1,319,233 1/1963 France 74/461 [73] Assignee: Xerox Corporation, Stamford,

Conn' Primary Examiner-Leonard I-I. Gerin [22] Filed: June 14, 1973 Attorney, Agent, or FirmI-I. Fleischer; C. A. Green; 21 Appl. No.: 370,181 Ralabate [52] US. Cl. 741/409 5 ABSTRACT [51] Int. Cl. F16h 55/18 1 Field of Search An apparatus in which a pair of gear members include 74/461 alternate resilient and rigid portions producing flexure in each of the gears so that backlash is minimized.

[56] References Cited 8 Claims, 3 Drawing Figures summit PATENTEU "CT 29 I974 GEAR DRIVE FOR ELECTROPHOTOGRAPHIC PRINTING MACHINE The foregoing abstract is neither intended to define the invention disclosed in the specification, nor is it intended to be limiting as to the scope of the invention in any way.

BACKGROUND OF THE INVENTION shafts which require close tolerances between their center to center distances. This insures that when the gear members mesh with one another backlash therebetween is minimized. Backlash is the amount by which the width of a tooth space exceeds the thickness of the engaging tooth on the pitch circles thereof. In order to minimize backlash, it is frequently necessary to specify the distance between centers of the shaft members extremely precisely. Control of the tolerances between shaft members insures that backlash or relative movement between gears is minimized. When the shaft members are arranged to be removed readily from the electrophotographic printing machine it is frequently not feasible to have tightly toleranced distances between respective centerlines. This is particularly true in the case of an electrophotographic printing machine wherein the photoconductive drum and transfer roll are readily removed therefrom and yet have to rotate in synchronism with'one another. By way of example, in the case of multi-color electrophotographic printing a cut sheet of support material is secured to the transfer roll for recirculation thereon. Successive single color toner powder images are transferred to the cut sheet of support material from the photoconductive drum. The photoconductive drum and the transferroll rotate at substantially the same angular velocity enabling successive toner powder images to be superimposed in registration with one another on the sheet of support material. A common drive motor rotates the photoconductive drum and transfer roll through a gearing arrangement. It has been found that it is highly desirable to minimize backlash between the gears driving both the photoconductive drum and the transfer roll to prevent relative movement therebetween. Relative movement between the photoconductive drum and transfer roll may produce errors in registration between successive toner powder images. In' the past, relative movement has been controlled by precisely tolerancing the center to center-distance between the photoconductive drum shaft and the transfer roll shaft. Finally, the respective gears on the heretofore mentioned shafts are precisely machined to minimize backlash therebetweemln fact, frequently it has been necessary to provide for an interference fit between the respective gears to reduce relative movement therebetween, i.e. backlash.

It has been found that in order to produce a satisfactory multi-color image of any original document, it isnecessary to superimpose successive single color toner powder images on one another in registration. Hence, this requires exceedingly close tolerancesbetween the respective shaft members to minimize backlash between the respective gears. However, it is also highly desirable to remove the photoconductive drum and transfer roll readily from the printing machine in order to simplify the maintenance thereof. The foregoing objectives conflict with one another in that the requirement for a tightly toleranced center to center distance between the shaft members may prevent the ready removal of the photoconductive drum and transfer roll from the printing machine.

Accordingly, it is aprimary object of the present invention to improve meshing gear members so that backlash therebetween is minimized while maximizing the permissible shaft to shaft centerline tolerance.

SUMMARY OF THE INVENTION Briefly stated, and in accordance with thepresent invention, there is provided an apparatus rotating a first shaft member at a substantially predetermined angular velocity relative toa second shaft member with substantially no relative movement therebetween.

In the present instance, the apparatus includes a first gear member mounted on the first shaft member and a second gear member mounted on the second shaft members. Preferably, the first gear member includes a plurality of resilient portions equally spaced between rigid portions thereof. The resilient portions are disposed at substantially about a preselected radius on the first gear member. Similarly, the second gear member includes a plurality of resilient portions equally spaced between rigid portions thereof. In like manner, the resilierit portions are located at substantially about a preselected radius on the second gear member. The first gear member meshes with the second gear member in a contact zone such that the shaft members rotate at the predetermined angular velocity with substantially no relative movement therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIG. 1 schematically illustrates an electrophotographic printing machine embodying therein the features of the present invention;

FIG. 2 is a perspective view showing the gearing arrangement of the FIG. 1 printing machine; and

FIG. 3 is an elevational view depicting one of the FIG. 2 gears.

While the present invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION 7 For a general understanding of the disclosed multicolor electrophotographic printing machine in'which the present invention may be incorporated, continued reference is had to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. Turning now to FIG. 1, the various components of the multi-color printing machine are illustrated schematically therein. Although the gearing arrangement of the present invention is particularly well adapted for use in this type of an electrophotographic printing machine, it should become evident from the following discussion that it is equally well suited for use in a wide variety Qfmachines, and is not necessarily limited to the particular embodiment shown herein. 1

As depicted in FIG. 1, the electrophotographic printing machine employs a drum having a photoconductive surface 12 secured to and entrained about the exterior circumferential surface thereof. Drum 10 is mounted rotatably on the machine frame and driven at' a substantially constant angular velocity, in the direction of arrow 14, by drive motor 16 (FIG. 2). As drum 10 rotates, photoconductive surface 12 passes sequentially through a series of processing stations. Drive motor I6 rotates drum 10 at a predetermined speed (in this case 9.6 revolutions per minute) relative to the other operating mechanisms of the printing machine. U.S. Pat. No. 3,655,377 issued to Sechak in 1972 demagnetic brush developer units". A typical magnetic scribes a suitable photoconductive surface. A timing disc (not shown) mounted on one end of the shaft of drum 10 cooperates with the machine logic to synchronize the various operations with the rotation of drum 10. In this way, the proper sequence of events is produced at the respective processingstations.

Initially, drum 10 rotates photoconductive surface 12 through charging station A. At charging station A, a corona generating device, indicated generally at 18, extends longitudinally in a transverse direction across photoconductive'surface 12. This enables corona generating device 18 to'spray ions onto photoconductive surface 12 to produce a relatively high, substantially uniform charge thereon. Preferably, corona generating device 18 is of the type described in U.S. Pat. No. 2,778,946 issued to Mayo in 1957.

After photoconductivesurface 12 is charged to a substantially uniform potential, drum 10 is rotated to exposure station B. At exposure station B, a color filtered light image of original document 20 is projected onto charged photoconductive surface 12. Exposure station B includes a moving lens system, generally designated by the reference numeral 22 and a color filter mechanism shown generally at 24. A suitable moving lens system is disclosed in U.S. Pat. No. 3,062,108 issued to Mayo in I962. Original document 20, such as a sheet of paper, book, or the like is placed face down upon transparent viewing platen 26. As shown in FIG. I, lamps 28 are adapted to move in a timed relationship with lens 22 and filter mechanism 24 to scan successive incremental areas of original document 20 disposed upon platen 26. In this manner, a flowing light image of original document 20 is projected onto the charged photoconductive surface 12. During the exposure process, filter mechanism 24 interposes selected color filters into the optical light path of lens 22. The appropriate filter operates on the light rays transmitted through lens 22 to record an electrostatic latent image on photoconductive surface 12, corresponding to a preselected spectral region of the electromagneticwave spectrum, hereinafter referred to as a single color electrostatic latent image.

Drum 10 next rotates to development station C. At development station C, three individual developer units, generally indicated by the

reference numerals

30, 32 and 34, respectively, are arranged to render visible the electrostatic latent image recorded on photoconductive surface 12. Preferably, each of the developer units are of a type generally referred to in the art as brush developer unit utilizes a magnetizable developer mix which has carrier granules and toner particles therein. Generally, the toner particles are heat settable. In operation, the developer mix is continually brought through a directional flux field to form a brush thereof.

The electrostatic latent image recorded on photoconductive surface 12 is brought into contact with the brush of developer mix. Toner particles are attracted from the developer mix to the latent image. Each of the respective developer units contain appropriately colored toner particles corresponding to the complement of the spectral region of the wave length of light transmitted through filter 24. For example, a color filtered electrostatic latent image is developed by depositing green absorbing magenta toner particles thereon. Blue and red filtered latent images are developed vwith yellow and cyan toner particles, respectively.

After development, the now visible toner powder image is advanced to transfer station D. At transfer station D, the toner powder image adhering electrostatically to photoconductive surface 12 is transferred to a sheet of final support material 36. Final support material 36 may be, amongstothers, plain paper or a sheet of thermoplastic polysulfone material. A transfer roll, shown generally at 38, secures support material 36 releasably thereto for movement in a recirculating path therewith. Transfer roll 38 is adapted to rotate in synchronism with drum 10 (in this case at substantially the same angular velocity therewith). This is achieved by the gearing arrangement of the present invention. Gear member 40 mounted on shaft member 42 of drum l0 drives gear member 44 mounted on shaft member 46, of transfer roll 38. The gearing arrangement disclosed in FIG. 1 will be more fully discussed with reference to FIG. 2. Inasmuch as a plurality of toner powder images are transferred from photoconductive surface 12 to support material 36, each image transferred thereto must be superimposed in registration with the prior one. The relationship of gear 40 to gear 44, i.e. the backlash therebetween directly affects image registration. Preferably, registration between successive images should not exceed about 0.006 inches of misalignment. Image transfer is achieved by .electrically biasing transfer roll 38 to a potential having sufficient magnitude and the proper polarity to attract electrostatically toner particles from the latent image recorded on photoconductor surface 12 to support material 36. It should be noted that gear 40 rotates in the direction of arrow 14 and therebydrives gear 44, which in turn rotates transfer roll 38, in the direction of arrow 48. U.S.

align the advancing sheet and move it to transfer roll 38 where gripper fingers 62 secure it thereto. After a plurality of toner powder images have been transferred from photoconductive surface 12 to support material 36, gripper fingers 62 separate support material 36 from the surfaceof transfer roll 38. This permits stripto be advanced on endless conveyor 66 to fusing station Continuing now with the description of the formation of a muIti-color copy, at fusing station E, fuser 68 generates sufficient heat to permanently affix the toner powder image to support material 36. One type of suitable fuser is described in US. Pat. No. 3,498,592 issued to Moser et al. in 1970. Support material 36, with the toner powder image affixed thereto, is, thereupon, advanced by

endless belt conveyors

70 and 72 to catch tray 74. Catch tray 74 is arranged to permit the machine operator to readily remove the completed copy from the printing machine.

The last processing station in the direction of rotation of drum 10, as indicated by arrow 14, is cleaning station F. As heretofore indicated, a preponderance of the toner particles are transferred to support material 36, however, some residual toner particles remain on photoconductive surface 12. At cleaning station F, these residual toner particles are removed from photoconductive surface 12. The residual toner particles are inigenerating device (not shown) adapted to neutralize upper surface 82a is disposed closely adjacent to the root diameter of the gear teeth. Similarly, gear 44 includes a plurality of resilient portions 84 thereon. Resilient portions 84 are arcuate apertures orslots 84 which extend preferably over an arc of about 52 /,the arc may range from about 45 to about 60. In this case,

four slots 84 are shown in gear 44. Each slot 84 is preferably about 1 inch in width and has the uppermost surtially brought under the influence of a cleaning corona the remaining electrostatic charge on toner particles and photoconductive surface 12. Thereafter, the neutralized toner particles are cleaned from photoconductive surface 12 by rotating fibrous brush 76. Brush 76 is positioned in contact with photoconductive surface 12. One type of suitable brush cleaning device is described in US. Pat. No. 3,590,412 issued to Gerbasi in 1971.

It is believed that the foregoing description is sufficient to illustrate the general operation of a multi-color electrophotographic printing machine utilizing the teachings of present invention therein. Referring now to FIGS. 2 and 3 for the specific subject matter of the present invention, FIG. 2 depicts gear 40 mounted on shaft member 42 attached to photoconductive drum l0 and gear 44 mounted on shaft member 46 attached to transfer roll 38. As shown in FIG. 2, drive motor 16 rotates gear member 48. Coupling 80 connects shaft 46 to shaft 78 which rotates transfer roll 38 in the direction of arrow 48. Drive motor 16 is mounted in line and coupled directly to the transfer roll shaft 78. Flexible coupling 80, Le. a metal bellows, is provided between transfer roll shaft 78 and drive shaft 46. Bellows coupling 80 is preferably made from a steel having a torsional stiffness of about 750 inch-pounds/per degree to prevent image mis-registration.

Identical gears

40 and 46 are mounted on the transfer roll shaft 46 and photoconductive drum shaft 42. Preferably, gears 40 and 44 and 48 are tooth plastic gears.

Gears

40 and 44 preferably have a pitch diameter of 5.73 inches and a circular pitch of 0.375 inches. Drive motor 16 is a synchronous speed motor which rotates transfer roll 36 in the direction of arrow 48at 9.6 revolutions per minute. Hence, gears 40 and 44 also'rotate at 9.6 revolutions per minute in the directions of arrows l4and 48, respectively.

Gear 40 includes a plurality of resilient portions 82 (in this case four) disposed about an arc thereon. Resilient portions 82 are arcuate apertures or slots in gear 40. Slots 82 extend in an arc preferably ranging from about 45 to 60, the preferred are being about 529?. The width of slots 82 preferably is about 1 inch and face 84a thereof closely adjacent to the root diameter of the gear teeth of gear member 44.

In operation, the angular rotation of gear 40 is synchronized with the angular rotation of gear 44. Since both gear 40 and gear 44 rotate at the sameangular ve locity, i.e. 9.6 revolutions per minute, the contact zone will remain substantially unchanged between each of the gears. Hence, resilient portions 84 on gear 44 is disposed to pass through the contact zone when rigid portions 86 of gear 40 passes therethrough. Similarly, rigid portions 88 of gear 44 passes through the contact zone when resilient portions 82 of gear 40 pass therethrough. Hence, a rigid portion on one of the gears is always aligned with a resilient portion on the other of the gears. In this way, the gear member having the resilient portion passing through the contact zone flexes so as to eliminate backlash or relative movement between each of the gears. Since each of the gears is substantially identical, gear 40 will be discussed in detail, with reference to FIG. 3.

Turning now to FIG. 3, gear 40 is shown therein as including four slots 82 thereimGear 40 has 48 teeth and a pitch diameter of 5.73 inches with a circular pitch of 0.375 inches. Each slot 82 preferably extends over an arc of 52%", the arc may range from about to about The width of slot 82 is preferably about 1 inch. Each slot 82 is equally spaced about gear 40 on substantially equal radii thereon. Rigid portions 86 are interposed between slots 82. In operation, each slot 82 is adapted to be located opposed from a rigid portion of the other gear as the two meshed gears pass through the contact zone. In this manner, the gear having the slot passing through the contact zone flexes to eliminate backlash between each of the gears. This flexing continues to occur with regard to alternate gears. Initially gear 40 may flex as the slot therein passes through the contact zone and subsequently gear 44 may flex as the slot therein passes through the contact .zone. Hence, one of the gears is continually flexing as its re spective slot passes through the contact zone. This flexure or deflection of each of the gears on a substantially continuous basis eliminates backlash and relative movement between each of the gears. Hence, it is feasible to utilize a pair of shaft members having a comparatively loose tolerance between centers while substantially eliminating backlash through the use of the gear members of the present invention.

In recapitulation, it is evident that the gear members of the present invention cooperate with one another to substantially eliminate relative movement therebetween. This enables the center to center distance of the respective shaft members to be toleranced loosely. Thus, it is feasible to readily remove the transfer roll and photoconductive drum while substantially eliminating backlash therebetween. In this manner, the requisite image registration between successive toner powder images transferred to the sheet of support material is maintained. This facilitates the servicing of a multicolor electrophotographic printing machine while tives, modifications and variations that fall within the.

spirit and broad scope of the appended claims.

What is claimed is:

1. An apparatus rotating a first shaft member at 'a substantially predetermined angular'velocity relative to a second shaft member with substantially no relative movement therebetween, including:

a first gear member mounted on the first shaft memher, said first gear member having a plurality of resilient portions equally spaced between substantially rigid portions at substantially about a preselected radius thereon; and

a second gear membermounted on the second shaft member and meshing with said first gear member in a contact zone, said second gear member having a plurality of resilient portions equally spaced between substantially rigid portions and at substantially about a pre-selected radius thereon, said first gear member being adapted to mesh with said second gear member such that each of the resilient portions of said first gear member pass through the contact zone when each of the rigid portions of said second gear member pass therethrough.

2. An apparatus as recited in claim 1, wherein the resilient portions of said first gear member include a plurality of substantially equally spaced arcuate apertures extending over a preselected arc in the region of the root diameter of said first gear member.

3. An apparatus as recited in claim 1, wherein the resilient portions of said second gear member include a plurality of substantially equally spaced arcuate apertures extending over a preselected arc in the region of the root diameter of said second gear member. a

4. An apparatus as recited in claim 1, wherein said first gear member and said second gear member are preferably made from a plastic material.

5. An electrophotographic printing machine of the type having a photoconductive drum mounted on a first shaft member arranged to rotate at a predetermined angular velocity relative to asecond shaft member having a transfer roll mounted thereon, including:

a first gear member mounted on the first shaft member, said first gear member having a plurality of resilient portions equally spaced between substantially rigid portions at substantially about a preselected radius thereon;

a second gear member mounted on the second shaft member and meshing with said first gear member in a contact zone, said second gear member having a plurality of resilient portions equally spaced between substantially rigid portions at substantially about a pre-selected radius thereon, said first gear member being adapted to mesh with said second gear member such that each of the resilient portions of said first gear member pass through the contact zone when each of the rigid portions of said second gear member pass therethrough; and

means for rotating one of the shaft members so that said gear member associated therewith drives said gear member associated with the other shaft member, thereby rotating the photoconductive drum and transfer roll at the predetermined velocity with substantially no relative movement therebetween.

6. A printing machine as recited in claim 5, wherein the resilient portions of said first gear member include a plurality of substantially equally spaced arcuate apertures extending over a preselected arc in the region of the root diameter of said first gear member.

7. A printing machine as recited in claim 5, wherein the resilient portions of said second gear member in= clude a plurality of substantially equally spaced arcuate apertures extending over a preselected arc in the region of a root diameter of said second gear member.

8. A printing machine as recited in claim 5, wherein said first gear member and said second gear member are, preferably, made from a plastic material.

Claims

1. An apparatus rotating a first shaft member at a substantially predetermined angular velocity relative to a second shaft member with substantially no relative movement therebetween, including: a first gear member mounted on the first shaft member, said first gear member having a plurality of resilient portions equally spaced between substantially rigid portions at substantially about a pre-selected radius thereon; and a second gear member mounted on the second shaft member and meshing with said first gear member in a contact zone, said second gear member having a plurality of resilient portions equally spaced between substantially rigid portions and at substantially about a pre-selected radius thereon, said first gear member being adapted to mesh with said second gear member such that each of the resilient portions of said first gear member pass through the contact zone when each of the rigid portions of said second gear member pass therethrough.

3. An apparatus as recited in claim 1, wherein the resilient portions of said second gear member include a plurality of substantially equally spaced arcuate apertures extending over a preselected arc in the region of the root diameter of said second gear member.

5. An electrophotographic printing machine of the type having a photoconductive drum mounted on a first shaft member arranged to rotate at a predetermined angular velocity relative to a second shaft member having a transfer roll mounted thereon, including: a first gear member mounted on the first shaft member, said first gear member having a plurality of resilient portions equally spaced between substantially rigid portions at substantially about a pre-selected radius thereon; a second gear member mounted on the second shaft member and meshing with said first gear member in a contact zone, said second gear member having a plurality of resilient portions equally spaced between substantially rigid portions at substantially about a pre-selected radius thereon, said first gear member being adapted to mesh with said second gear member such that each of the resilient portions of said first gear member pass through the contact zone when each of the rigid portions of said second gear member pass therethrough; and means for rotating one of the shaft members so that said gear member associated therewith drives said gear member associated with the other shaft member, thereby rotating the photoconductive drum and transfer roll at the predetermined velocity with substantially no relative movement therebetween.

7. A printing machine as recited in claim 5, wherein the resilient portions of said second gear member include a plurality of substantially equally spaced arcuate apertures extending over a preselected arc in the region of a root diameter of said second gear member.