US3190643A

US3190643A - Sheet guiding apparatus

Info

Publication number: US3190643A
Application number: US176529A
Authority: US
Inventors: Gordon P Taillie
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1962-03-01
Filing date: 1962-03-01
Publication date: 1965-06-22
Anticipated expiration: 1982-06-22

Description

2 Sheets-Sheet 1 Filed March 1, 1962 FIG. 1

INVENTOR. GORDON P. TAILLIE A T TORNEV June 22, 1965 G. P. TAILLIE 3,190,643

SHEET GUIDING APPARATUS Filed March 1, 1962 2 Sheets-Sheet 2 INVENTOR.

GORDON P. TAILLIE B %"M4g .4 rromvsy United States Patent Yorlr Filed Mar. 1, 1962, Ser. No. 176,529 2 Claims. (Cl. 2711-45) This invention relates to the field of Xerography and, particularly, to an improved apparatus to hold paper copy as it is removed from the Xerographic drum and while it it is passing through a fuser.

More specifically, the invention relates to improved paper guiding or hold-down apparatus for use in Xerographic reproduction machine, wherein the support surface, usually paper, to which an image of the copy being reproduced is transferred, contacts a xerographic drum containing an electrostatic charge and then passes to an other utilization apparatus, for example, a fusing or fixing device. Although the invention is considered to have general application as a paper guide, it is particularly useful in Xerographic reproduction machines wherein images are produced on a paper by means of a powder that, preceding and immediately after fusing, are imperrnanent and must be handled in such a manner that the powder image will not be smeared or obliterated.

In the process of Xerography, for example, as disclosed in either Carlson Patent 2,297,691, issued October 6, 1942, or in Carlson Patent 2,357,809, issued September 12, 1944, a Xerographic plate, comprising a layer of photoconductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This eX- posure discharges the plate areas in accordance with the radiation intensity which reaches them and thereby cre ates an electrostatic latent image on or in the plate coating.

Development of the image is effected with developer material which comprises, in general, a mixture of a suitable pigmented or dyed electroscopic powder, hereinafter referred to as toner, and a granular carrier material, which functions to carry and to generate triboelectric charges on the toner. More exactly, the function of the granular material is to provide mechanical control to the powder, or to carry the powder to an image surface and, simultaneously, to provide almost complete homogeneity of charge polarity. In the development of the image, the toner powder is brought into surface contact with the photoconductive coating of the Xerographic plate and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic image is usually transferred to a support or transfer material to which it may be fixed by any suitable means, usually an electric heat fuser.

In automatic Xerographic machine, the Xerographic plate usually is in the form of a rotating cylindrical drum. An electrostatic charge is placed on the Xerographic drum for the purpose of transferring toner material to the paper support surface. This electrostatic charge also attracts the paper support surface causing tacking of the support surface to the drum. The copending application of Hunt et al., filed August 1, 1960, Serial No. 46,463, Patent No. 3,009,415, discloses a machine of the type described herein, Where sheets of a paper support surface are fed seriatim by means of an endless chain, to a rotating xerographic drum, through a fusing device, around a paper support roll and onto a receiving tray.

As the drum rotates, the paper support surface moves synchronously therewith and is drawn off the drum by a papergripper mounted on an endless chain. The endless chain is driven synchronously with the xerographic drum so that, theoretically, the paper support surface should be drawn off the drum immediately after contacting the drum. However, variances in manufacturing tolerances frequently cause some degree of slack be tween the support surface and the drum. In addition, as the paper support surface is removed from the drum, the unsupported trailing edge is free to move in any direction. Therefore, unless the paper support surface is held in a flat flow path the tacking effect of the paper to the drum will cause the paper to follow the drum surface upwards out of its normal flow path and interfere with the normal operation of other components of the machine or disturb the powder image on the paper support surface. Also, as the support surface leaves the drum there is a certain degree of electrostatic charge that adheres thereto, and unless prevented by guides or hold-down means, will cause the support surface to jump out of its normal flow path to any grounded body in the near proximity. Further, the heat produced by the fuser causes the support surface to curl and rise out of its normal flow path. All the conditions are capable of disturbing the powder image on the support surface unless means are provided to hold the support surface in a flat flow path.

The paper support surface, after leaving the Xerographic drum, is drawn through a heat fuser and then around a support roll to effect a change in direction. The support surface must be held reasonably flat as it passes through the heat fuser or the proper degree of heat will not be applied. Any buckling or curling will cause the support surface to receive excessive heat, producing dis coloration or scorching. If the electrostatic charge on the paper caused the paper to be grounded by the heat fuser, the possibility of fire could result.

The natural rigidity of the paper support surface and the rigidity produced by the drying effect of the heat fu-ser causes the paper support surface to rise out of a flat flow path as it is drawn around the support roll at the rear of the fuser. This condition is particularly evident as the unsupported trailing edge of the support surface is passing through the fuser. Unless guided or held in a flat position, the trailing edges of the support surface could extend upward into the heating elements of the fuser, creating an inflammable condition.

Since the powder image on the support surface is in an impermanent condition before entering the heat fuser and immediately after leaving the fuser, conventional paper guides or hold-down devices can not satisfactorily be used. Conventional devices such as fiat springy strips of metal or cylindrical rollers would hold the support surface in position but would pass over the powder image and remove powder from the support surface and smear the image over the support surface.

It is therefore the primary object of this invention to provide improved apparatus that will, in an automatic xerographic reproduction unit, hold a paper support surface in a fiat position while passing through the machine and not smudge, smear or remove a significant amount of toner powder from the support surface.

It is a further object of this invention to provide an improved guide or hold-down device that will maintain a support surface in a flat position while that support surface is passing through a heat fuser.

It is a further object of this invention to provide an improved paper guide or hold-down device that is economical to produce, easily assembled in a machine and effective for use on a variety of sizes of paper.

These and other objects of the invention are attained by means of a thin circular disc cut with teeth or star-like points about its periphery and rotatably mounted on flexible wire brackets along the flow path of the transfer surface. The discs are located immediately above the sup- Patented June 22, 1965 port surface and guide or hold the support surface in its predetermined flow path. By this arrangement, there is provided a guide or hold-down device that contacts the support surface by a series of small points and does not smear or remove the powder image from the support surface.

The invention is disclosed in the appended drawings, in which:

FIG. 1 is a schematic representative of an automatic xerographic reproduction machine embodying the present invention;

FIG. 2 is a perspective View of a'portion of the machine of FIG. 1, with portions broken away to more clearly show the present invention; and,

PEG. 3 is an enlarged perspective view of the invention.

As shown in FIG. 1, the xerographic apparatus com-.

prises a xerographic plate including a photoconductive layer of light-receiving surface on a conductive backing and formed in the shape of a drum, generally designated by numeral 9. The drum is journaled in the frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally, as follows:

A charging station, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum.

An exposure station, at which a light or radiation pattern of copy to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof and thereby form a latent electrostatic image of the copy to be reproduced;

A developing station, at which a xerographic developing material including toner particles having an electrostatic charge opposite to that of the electrostatic latent image are cascaded over the drum surface, whereby the toner particles adhere to the electrostatic latent image to form a xerographic powder image in the configuration of the copy to be reproduced;

A transfer station, at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or support surface; and,

A drum cleaning and discharge station, at which the drum surface is first charged and then brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The drum charging apparatus 1t consists of a corona discharge device containing an array of one or more corona discharge electrodes that extend transversely across the drum surface. The electrodes are energized from a high potential source and are substantially enclosed by a shielding member. As the drum rotates past the charging apparatus, a uniform electrostatic charge is placed on the photoconductive surface.

After the drum surface is electrostatically charged, it passes the exposure station 8 where a light image of the copy to be reproduced is flashed onto the drum surface. This exposure station may consist of any one of a number of optical projection systems. The system shown utilizes a projector 11 containing a movable carriage for transporting a film holder in light projecting relation to the moving light sensitive surface of the Xerographic drum and a projection lamp LMPll. The lamp LMPll projects a light image of the film through a lens system onto an objec mirror 12 mounted in a light shield 13. The image is reflected from the mirror 12 through an aperture onto the surface of the rotating drum 9. As the light image from projector llll is flashed on thedrurn, the electrostatic charge on the photoc'onductive surface A is discharged in the areas exposed to light resulting in an electrostatic image configuration of the copy being reproduced.

The drum continues to rotate past the developer station C, where the electrostatic image is developed into a visible powder image. The developing apparatus consists of' a developer housing ldcontaining a supply of developer material 15 at the bottom thereof and an endless belt 15 with spaced buckets 17 mounted on the outer periphery. The belt is mounted for rotation by means of a motor (not shown) through drive shaft 19. As the belt 16 is rotated, the buckets 17 pick up developer material from the bottom of the developer housing and deposit it on the drum surface. The developer material cascades over the drum surface depositing toner particles on the areas containing an electrostatic charge. The excess developer material falls back to the bottom of the developer housing for reuse. The toner material used in the developing process is replaced by means of toner dispenser 2t Positioned adjacent the developing station is the image transfer station D where the Xerographic powder image is transferred to a suitable support surface 53, usually paper. In the embodiment illustrated, there isshown a paper sheet feed mechanism whereby a. sheet of paper is held by one of two paper grippers 21 mounted on an endless chain 22. The chain 22 is mounted on sprockets 23 and driven in substantially synchronous relation to the xerographic drum 9, whereby the paper support surface is carried from the paper feed-in station 24 into surface contact with the xerographic drum. The paper is tacked to the xerographic drum by the electrical charge on the drum surface and moved synchronously therewith.

The paper support surface has a tendency to follow the drum causing a bulge 8'!) in the paper support surface, and, unless restricted, comes in contact with corona 3d.

The powder image on the drum is transferred to the paper by means of corona transfer device 25 located at or immediately after the point of contact. The corona transfer device 25 is substantially'the same as corona charging device it? located at the charging station A. The paper gripper Zll draws the paper away from the drum surface as the chain continues past the image transfer station. The' paper is then drawn through a heat fuser 26 whereby electrical heating elements R1, R2 and R3 heat the paper and permanently fix the powder image thereto.

Glass rods 71, mounted in brackets 83 (FIG. 2) run transversely across the width of the support surface beneath the fuser 25. The glass rods provide support and proper positioning of the support surface.

The chain 22 continues to carry the paper from the fuser as around a support roll located on shaft 32 concentrically with sprocket 81, through

pressure rollers

27 and 28, where the paper gripper Z1 releases the paper and returns to the feeding station 2 to repeat the process. The paper passes through

pressure rollers

27 and 28, and is deposited in the paper receiving tray 29.

After the image has been transferred to a support surface, the drum continues to rotate on past the cleaning station E. A corona pro-cleaning device 30, mounted on bracket 52, similar to the corona charging device It is located adjacent to transfer station D. This corona precleaning device sprays an electrostatic charge on the drum surface to loosen all residual toner material remaining on the drum surface after the image transfer station. Brush 31 contacts the drum surface and removes the excess toner. The drum is then exposed to light from lamp LMPZ contained in housing 32 to remove any residual electrostatic charge remaining on the drum.

There is a dust hood 33 that encompasses approximately two-thirds of the area of the brush 31 for the purpose of collecting dust particles removed from the xerographic drum. For removing dust particles from the brush and dust hood an exhaust duct 34- is arranged to cover a slot that extends transversely across the dust hood 33 and is connected to a filter bag 35 in a filter box 36. Motor driven fan units 37 connectedto the filter box produce a flow of air through the filter box drawing air through the areas surrounding the xerographic drum and the dust hood. The air entrains powder particles removed from the drum by the brush as the air flows through the dust hood. Powder particles are separated from the air as it flows through the filter bag so that only clean air reaches the motor fan unit.

Referring now to FIG. 2, there is shown two supporting

side walls

50 and 51 of the automatic xerographic reproduction machine. The paper gripper 21 mounted on drive chain 22 is shown in FIG. 2, in position approaching fuser 26. Directly in front of the fuser is a bracket 52, which supports corona cleaning device 30. Bracket 52 is rigidly mounted on support members 53 which are secured to back wall 54 of the xerographic machine. In order to guide the paper support surface as it passes through the machine, the invention provides a series of star-Wheel assemblies 55 secured to brackets 52 and 56.

As shown in the illustrated embodiment, there are four star-wheel assemblies at the front of the fuser and two at the rear with uniform spacing across the maximum size support surface. The number and spacing of the starwheel assemblies shown, is not to be construed as a limiting factor. Actually the number used and their relative spacing is determined by the various sizes of paper to be used in the machine with care taken to insure that the smallest size paper will be guided by at least two starwheels in front of the fuser and at least one at the rear.

The star-Wheel assemblies 55 and 57 are shown in FIG. 3, and consist of a bracket 61) which rotatably supports star-wheel 61 on end and is adapted, at the opposite end, to receive screws 70 (as shown in FIG. 2). Bracket 66 is pre-shaped so that star-wheel 61 will be approximately above the support surface when assembled, however, bracket 60 is flexible so that minor adjustments may be made after installation. The star-Wheel end of bracket 60 is bent at a right angle to contain a positioning washer 62, star-wheel 61 and securing washer 63. Washers 62 and 63 are provided to properly position stanwheel 61 and permit free rotation of the star-wheel. Any standard fastening means may be used to hold the washers and the star-wheel on bracket 60, such as a lock nut, peen-ing the end, or any suitable clamping device. Star-wheel 61 is formed of thin material cut in a substantially star-like configuration. The points 64 of the star-wheel lie in a circular path about the center of the wheel so that the wheel will rotate when moved across a surface, but only the points 64 will touch the surface.

In operation, paper gripper bar 21 receives the paper support surface 58 at paper feed station 24. The paper support surface is carried past and in contact with drum 9. Gripper bar 21 draws the support surface ofi drum 9 and under front star-Wheel assembly 55. As the support surface leaves the transfer point D, it tends to follow the drum upward out of its path of flow and into contact with star-wheel assemblies 55 which are positioned approximately above the normal flow path of the paper.

The points 64- come into contact with the paper support surface and cause the starwheel to rotate over the support surface. The star-wheel effectively holds the paper in position and prevents it from following the rotation of the drum. As the star-wheels pass over the paper, the points '54 touch a very small percentage of the surface.

By way of example, typewritten copy usually has an image coverage on the paper of about 5% so that the chance of a point 64 touching the powder image is very small. When the points do touch the image they pick up an insignificant and almost unnoticeable amount of powder material.

Rear star-wheel assemblies 57 come in contact with paper 58 as it leaves the fuser 26. At this point, the image on the support surface has been heated, but is not necessarily fused into a permanent state, so that it is still necessary to hold the support surface in position without disturbing the image. The support surface passes around a support roll, which is concentric with sprocket 81. The natural rigidity of the support surface resists the bending effect and tends to lift the trailing portion of the support surface upwards toward the fuser. Star-Wheels 57 contact the support surface and hold it in a relatively fiat position, in proper fusing relation to the heating elements.

The paper gripper 21 after releasing the support surface returns to feed position 24 and starts the procedure anew. A series of glass rods 71 are positioned under the fuser running transversely with the width of the support surface. These glass rods 71 support the paper and prevent the trailing edge from falling as it passes off the drum 9, thus positioning the paper relative to the fuser and heating elements R1, R2 and R3.

While the present invention as described herein, has been shown in use with an electric resistance type heat fuser, it is not intended to be limited thereby and may be used with any type fusing device. Though the present invention, as described herein, has been carried out in a specific embodiment, it is not desired to be limited thereby, but it is intended to cover the invention broadly within the scope of the appended claims.

What is claimed is: 1. In a xerographic reproducing apparatus including a sheet material conveyor system comprising a pair of endless chains and a gripper mechanism mounted on said chains to grasp the leading edge of a sheet of material and convey it through a path past various xerographic processing stations, at xerographic drum containing a powder image to be transferred to the sheet material and positioned to come into contact with sheet material carried by the gripper mechanism of the conveyor, an electrostatic discharge device positioned beneath the xerographic drum at the point the xerographic drum contacts the sheet material in the conveyor system and adapted to apply an electrostatic charge to the opposite surface of the sheet material from that in contact with the xerographic drum so that the powder on the xerographic drum will be attracted to the sheet material, and a heat fuser positioned adjacent to the conveyor at a point past the xerographic drum to bond the powder to the sheet material, the improvement comprising a plurality of thin disc shaped members with a series of extended points about the periphery mounted on support brackets at positions along the conveyor with the points of the disc shaped members immediately above the sheet material carried by the conveyor,

the disc shaped members being rotatably mounted on the brackets so that upon contact with the sheet material they will rotate across the surface of the sheet material making contact only with the extended points about the periphery whereby the sheet material is held in the flow path of the conveyor without causing damage to the powder image on the surface of the sheet material.

2. In a xerographic reproducing apparatus including a sheet material conveyor system comprising a pair of endless chains and a gripper mechanism mounted on said chains to grasp the leading edge of a sheet of material and convey it through a path past various xerographic processing stations, a xerographic drum containing a powder image to be transferred to the sheet material and positioned to come into contact wih sheet material carried by the gripper mechanism of the conveyor, an electrostatic discharge device positioned beneath the xerographic drum at the point the xerographic drum contacts the sheet material in the conveyor system and adapted to apply an electrostatic charge to the opposite surface of the sheet material from that in contact with the xerographic drum so that the powder on the xerographic drum will be attracted to the sheet material, and a heat fuser positioned adjacent to the conveyor at a point past the xerographic 7 8 drum to bond the powder to the sheet material, the imtended points about the periphery whereby the sheet provement comprising: material is held in the flow path of the conveyor at least two assemblies of thin disc shaped members Without causing damage to the powder irnage on the with a series of extended points about the periphery surface of the sheet material.

of said members,

a R C" the mi each assembly mounted on support brackets along the efermces lied Dy Em my conveyor with the points of the disc shaped members UNITED STATES PATENTS immediately above the sheet material carried by the 110,244 12/70 Kellberg 271-74 X conveyor, 324,939 8/85 Hyde et a1 101420 one of said assemblies mounted adjacent the Xerographic 10 544,074 8/95 Whitlock 10l,420 X drum, 7 1,342,117 6/ 20 KnoWles 101-420 another of said assemblies mounted immediately fol- 2,227,635 1/41 E kl d t 1, 101 350 lowing the heat fuser, 2,576,047 11/51 Schaffert.

the disc shaped members being rotatably mounted on the brackets so that upon contact with the sheet 15 SAMUEL COLEMAN P'lmmy Exammer' material they will rotate across the surface of the ROBERT A. LEIGHEY, RAPHAEL M. LUPO, sheet material, making contact only with the X- Examiners.

Claims

1. IN A XEROGRAPHIC REPRODUCING APPARATUS INCLUDING A SHEET MATERIAL CONVEYOR SYSTEM COMPRISING A PAIR OF ENDLESS CHAINS AND A GRIPPER MECHANISM MOUNTED ON SAID CHAINS TO GRASP THE LEADING EDGE OF A SHEET OF MATERIAL AND CONVEY IT THROUGH A PATH PAST VARIOUS XEROGRAPHIC PROCESSING STATIONS, A XEROGRAPHIC DRUM CONTAINING A POWDER IMAGE TO BE TRANSFERRED TO THE SHEET MATERIAL AND POSITIONED TO COME INTO CONTACT WITH SHEET MATERIAL CARRIED BY THE GRIPPER MECHANISM OF THE CONVEYOR, AN ELECTROSTATIC DISCHARGE DEVICE POSITIONED BENEATH THE XEROGRAPHIC DRUM AT THE POINT THE XEROGRAPHIC DRUM CONTACTS THE SHEET MATERIAL IN THE CONVEYOR SYSTEM AND ADAPTED TO APPLY AN ELECTROSTATIC CHARGE TO THE OPPOSITE SURFACE OF THE SHEET MATERIAL FROM THAT IN CONTACT WITH THE XEROGRAPHIC DRUM SO THAT THE POWDER ON THE XEROGRAPHIC DRUM WILL BE ATTRACTED TO THE SHEET MATERIAL, AND A HEAT FUSER POSITIONED ADJACENT TO THE CONVEYOR AT A POINT PAST THE XEROGRAPHIC DRUM TO BOND THE POWDER TO THE SHEET MATERIAL, THE IMPROVEMENT COMPRISING A PLURALITY OF THIN DISC SHAPED MEMBERS WITH A SERIES OF EXTENDED POINTS ABOUT THE PERIPHERY MOUNTED ON SUPPORT BRACKETS AT POSITIONS ALONG THE CONVEYOR WITH THE POINTS OF THE DISC SHAPED MEMBERS IMMEDIATELY ABOVE THE SHEET MATERIAL CARRIED BY THE CONVEYOR, THE DISC SHAPED MEMBERS BEING ROTATABLY MOUNTED ON THE BRACKET SO THAT UPON CONTACT WITH THE SHEET MATERIAL THEY WILL ROTATE ACROSS THE SURFACE OF THE SHEET MATERIAL MAKING CONTACT ONLY WITH THE EXTENDED POINTS ABOUT THE PERIPHERY WHEREBY THE SHEET MATERIAL IS HELD IN THE FLOW PATH OF THE CONVEYOR WITHOUT CAUSING DAMAGE TO THE POWDER IMAGE ON THE SURFACE OF THE SHEET MATERIAL.