US 3706491 A
The backup roll of a roll fuser for fixing xerographic images is periodically cleaned by passing plain paper through the fuser roll couple at a slow rate while the backup roll is heated above a toner melt temperature. Roll cleaning is accomplished automatically by providing a xerographic document copier with a special slow rate operating cycle wherein image production is inhibited so that plain paper is fed through the roll couple in accordance with the cleaning method.
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Description (OCR text may contain errors)
United States Patent Furman et al.
FUSER ROLL CLEANING METHOD AND APPARATUS FOR PERFORMING IT Inventors: Rudolph S. Furman, Lexington;-Jerrold F. Zimmer, Versailles, both of Ky.
International Business Machines Corporation, Armonk, NY.
Filed: Dec. 16, 1971 Ap'pl. No.: 208,736
U.S. c1...' ..3ss/133, 15/1.5, 263/6 E,
- 355/3 Int. Cl....., ..G03g 15/00 Field of Search ..355/3, l4, l5, 17, I33;'
1451 Dec. 19, 1972 [:56] References Cited UNITED STATES PATENTS 3,588,445 6/l97l Hopkins ..2l9/2l6 X 3,649,992 3/1972 Thettu ..l5/l.5
Primary Examiner-John M. Horan Assistant Examiner-Alan A. Mathews Attorney-E. Ronald Coffman et al.
[ ABSTRACT The backup roll of a roll fuser for fixing xerographic images is periodically cleaned by passing plain paper through the fuser roll couple at a slow rate while the backup roll is heated above a toner melt temperature. Roll cleaning is accomplished automatically by providing a xerographic document copier with a special slow rate operating cycle wherein image production is inhibit ed so that plain paper is fed through the roll couple in accordance with the cleaning method.
7 Claims, 2 Drawing Figures PATENTEU DEC 19 m2 FIG. 1-
FUSER ROLL CLEANING METHOD AND APPARATUS FOR PERFORMING IT BACKGROUND OF THE INVENTION Xerographic images are commonly formed by a pigmented thermoplastic resin powder that is electrostatically deposited onto a suitable support sheet, usually paper. The powder image can be fixed to the support sheet by various techniques including radiant heat, conductive heat, and solvent vapor. One of the most efficient fixing techniques suitable for high speed operation is the so-called roll fuser which employs direct conductive heat transfer to the toner powder from the surface of a roll held in pressure contact therewith by a backup roll. By proper control of heat transfer to the toner and selection of roll surface materials, it is possible to fuse the xerographic image without transferring significant toner particles to the surface of the hot fusing roll. Although the backup roll of the roll fuser couple is ordinarily not in contact with the toner particles of a xerographic image it has been found that toner material will accumulate on the backup roll over relatively long periods of time, such as thousands of cycles. A main source of the toner material that accumulates on the backup roll is minute amounts of residual toner floating in the air space within the machine covers. Small amounts of toner may also be left on the fusing roll and from there transferred to the backup roll at times when the rolls are in direct mutual contact. While it is preferred to separate the roll couple in the absence of copy paper positioned therein, it is difficult to completely prevent all contact between the rolls of the fusing couple at the beginning and end of a fusing operation on cut sheet copy.
Roll fusers also are used efficiently for fusing copy on a sheet that has previously fixed copy on its reverse side. Although the reverse side image will not be disturbed by the fusing of the second side image, if the backup roll temperature is maintained sufficiently low, minute amounts of toner from the reverse side image will be picked up by the backup roll as a further contribution to the toner accumulation thereon.
Excessive accumulation of toner on the backup roll of the fuser couple will soil the reverse side of the copy sheet and, in extreme cases, can cause the copy sheet to stick to the backup roll and create a paper feed failure.
Disclosure of the Invention We have determined that the backup roll of a roll fuser couple can be conveniently and efficiently cleaned by passing plain paper or other absorbent sheet material through the roll fuser couple while the couple operates at a relatively low speed. Whereas in ordinary fusing operation, the peripheral speed of the fuser rolls prevents the transfer of substantial heat to the backup roll; in our cleaning method, the lower roll feed rate allows the backup roll to be heated into the toner melting temperature range. Thus, as the plain paper passes through the fuser roll, the accumulated toner on the backup roll surface will become soft and mobile and thus will adhere to the plain paper rather than the backup roll surface. The slow speed also allows cleaning of the heated roll, if required.
The method of our invention can be implementedin an automatic xerographic document copier with a minimum of changes. The document copier will inelude plain paper feed forcopying purposes, and it is only necessary to inhibit the image production process of the copier to allow the plain paper to be fed through the fusing roll couple. By changing the drive speed of the fusing roll couple, significantly more heat will be transferred to the backup roll to accomplish the cleaning cycle. Accordingly, an operator control is provided to select operation that inhibits image production and provides for a low speed paper movement but otherwise operates the copier in accordance with its usual cyclically performed functions. I
. These and other features, objects, and advantages of our method and the apparatus for implementing it will be apparent to those skilled in the art from the following description of an illustrative embodiment of our inventive concepts wherein reference is made to the accompanying drawings of which:
FIG. 1 is an elevational side view partly in cross section of a fusing-roll couple in which our method can be performed, and
FIG. 2 is aside elevational schematic view of a xerographic document copier illustrating the implementation of our method into the automatic processes of the copier.
A contact roll fuser mechanism 10, as shown in FIG. 1, comprises a fusingroll couple 11 defining a nip 12 therebetween-that is aligned with a paper delivery table or feed plate 13. Unfixed copy-in the form of a sheet of toner receptive support material such as paper 20 bearing an unfused thermoplastic toner particle image 21 thereon is passed along the paper table 13 to the nip l2 and through the nip to exit table 14.
The roll couple 11 includes a fuser roll 15 and a resiliently deformable backup roll 16 which'mutually cooperateto form a contact area 12a at the nip 12 by deformation of the backup roll 16 due to the pressure 7 applied between the rolls. A heat source 17 is mounted within the fusing roll 15 and preferably comprises a tungsten filament quartz envelop radiant heat lamp. The heat transferred by conduction from the roll 15 is a function of roll speed, heat source power, and the contact dwell time as controlled by the arc of contact area 12a. The fusing roll 15 ordinarily operates with a high surface temperature of between 300 and 400 F.
Fusing roll 15 has an external surface covering 18 of a material selected for its low surface energy or nonadhesive characteristics. Certain elastomers and polymers have been found suitable for this purpose and are commercially available. By controlling the heat from source 17 and the contact area 12a, ordinary fusing is performed by direct heat conduction to the particles of image 21 with a minimum of heat transfer to the paper 20 and backup roll 16. In fact, the backup roll 16 ordinarily operates with a surface temperature of about 200 F. The heat transferred to the toner particles of image 21 is controlled to produce a toner viscosity that tends to cause the toner to adhere completely to the paper 20 and to separate completely from the hot fusing surface 18.
The fusing roll 15 is driven clockwise in FIG. 1 by a motor or other power means 30 through a chain or belt connection 31. Typically, the surface speed of roll 15 will be about 10 inches per second or faster.
The backup roll 16 is made of a relatively thick elastomeric material having an external surface 19 about 0.1 4 0.4 inches. The backup roll 16 is mounted on support arms. structure 32' and is positionable from its position as shown to a retracted position by operation of cam 33 and spring 34 to be separated from the fusing roll when copy is not being fused. It is necessary, however, to bring the rolls 15 and 16 together slightly before the leading edge of sheet and to maintain them in contact slightly beyond thetrailing edge of the sheet 20. This necessity-makes it'possible fuser roll surface 18 andbe transferred to the backup roll surface 19in spite of the. low adhesion characteristics of both surfaces.
The rolls 15 and 16 are normally driven by motor 30 at ahigh rate of speed, for example,'15 inches per second, that is generally comparable to the speed at which an image is placed on the paper 20 by associated electrophotographic development apparatus. At this relatively high speed, most of the heat is transferred to the toner 21 and some heat is transferred to the paper 20. It is desired to minimize the heat transfer to paper 20 as this heat is, for the most part, wasted. It is further desired to further minimize transfer of heat to the backup roll 16 since this also would be a waste of heat and further would make the roll couple unsuitable for fusing copy on support paper '20 having a previously formed and fixed thermoplastic image on the reverse side thereof. I I
After several thousand copies have been fused by the rollcouple 11, it will be found that toner particles have accumulated on the surface 19 of the backup roll 16.
These toner particles may soil the back side of copy x for minute residual toner material 22 to remain on the V paper '20 or, in extreme cases, may cause the copy paper to tend to stick-to the backup roll 16 and create a I paper feed failure. To clean the fusing roll 15 and especially the backup roll 16 in accordance with our invention, motor speed control 35 is provided by which the fusing roll 15 and backup roll 16 can be driven at a relatively low speed, e.g., 0.5 1.5 inches per second,
compared to normal fusing speed of about 10 inches per second or greater. While the speed control 35 shown in FIG. 1 is in the form of an electrical motor controller, those skilled in the art will recognize that other speed change means, such as gear shifting or a selective drive belt system, could be employed. With the roll couple 11 moving at slow speed, an untoned sheet of copy paper 20 or other absorbent material is 'times if necessary to move substantially all of the accumulated toner from the backup roll 16.
Inasmuch as document copy machines are .constructed to be operated with. a minimum of. expert maintenance, attention, it is useful to embody a roll fuser cleaning system into the automatic processes of the machine. A typical xerographic type copy reproducing machine 50 is shown in FIG. 2 and includes a xerographic copy surface or drum 51 that is rotatably mounted to traverse a series of image production processing stations. The copy process is initiated by depression of a start bar or key 40 that moves past a latch member 41 to allow the latch member to pivot clockwise to an active position where its latching surface 42 trips the start bar .40 and a switch 43 is closed to initiate rotation of the copy drum 51 through operation of .drive motor 30. Sequence control mechanism 44 operates in timed relation to copy drum 51 to cause automatic functioning of the various machine operations. The image production process begins at charge corona 52 where a uniform electrostatic charge is applied to surface 51. This uniform charge is selectively discharged by an imagingstation 53 and then is passed to an image development unit 54 where the actual physical toner image is created. The development station can be of several types, one preferred type being a simple bucket conveyor that delivers a mixture of developer carrier. and toner powder to an elevated location above the surface 51 and allows this mixture to cascade 'overthe surface 51. The image production is completed by transferring the powder image thus created on surface 51- to sheet paper 20 that is fed in synchronism with the surface 51 froma roll 23 and sheet cutter knives 55. Thus, operation is performed by transfer corona 56 that attracts the image 21 from the surface 51 and places it on the upper surface of the plain paper 20 without disturbing its image configuration. The paper 20 is then separated from the surface 51 and is fed onto feed plate 13 and into the nip 12 of roll fuser 10 substantially like that shown in'FIG. 1. After the image 21 has been fused,'the finished copy is passed directly into-an exit pocket 57 where it can be removed by the machine operator. The copy process is completed by continuing the copy surface 51 passed a cleaning station 58 to its starting point at the charge corona 52. When thecopy process'is complete as indicated by a suitable mechanical sensing of the machine operation, a control link 45 is operated to withdraw latch 41 retransfer switch 43, and enable the key 40 to be restored to its unoperated position by a spring 46. r
To automate the roll cleaning process, we have provided a manually operable auxilliary'start key or cleaning-cycle-select control member 60 that is depressed by the operator to slow the paper feed, disable the image production mechanismand initiate a cycle of machine operation. The key 60 includes a pair of detent grooves 61a and 61b that alternately cooperate with a spring biased detent 62 to define a normal inactive key position as shown or a displaced active position upon key depression. Key 60 includes an extension ,63 that overlies a tab 64 on the key 40 so that key 40 is depressed automatically upon depression of key 60. This action insures the initiation of machine operation and provides for automatic termination of operation once a cycle has been completed. Key 60 further transfers an interconnecting control switch 65 from a high speed control contact 66 to a low speed control contact 67 to thereby cause the motor 30 to operate ata relatively low speed. Paper 20 thus will be fed and processed passed the surface 51'at a low speed and will be fed to the contact fuser at the same low speed.
Key 60 further acts through a connecting link 68 to disengage a clutch 69 between the motor 30 and a drive shaft 59 of the developer unit 54 to prevent cascading of developer material over the surface 51. With the developer unit 54 disconnected, image production is effectively inhibitedJThus, the machine will operate through a conventional copy cycle with the parts moving at a reduced speed and without the deposition of toner onto the paper 20 being fed from roll 23. As the paper passes through the roll fuser 10, toner will be withdrawn from fuser roll and especially the backup roll 16 as described in connection with FIG. 1.
If the copy machine is provided with a multiple cycle counter, several plain sheets of paper 20 can be automatically fed as necessary to provide a complete and thorough cleaning of the fuser backup roll.
Those skilled in the art will recognize that the foregoing illustrative embodiments of our invention represent but a single preferred implementation of our inventive concepts and that various modification, deletions, substitutions, and additions can be made to the apparatus shown without departing from the spirit and attained benefits of our inventive concepts. Accordingly, the scope of protection sought by LettersPatent is to be defined solely by the appended claims.
1. The improved method of operating a contact fuser having cooperating members that provide contact surfaces for receiving support members bearing thermoplastic toner particle images therebetween, wherein one of said surfaces is maintained at high temperatures and the thermoplastic particle image on ya support member is engaged under pressure by said one surface for a relatively short first period of time and wherein the improvement comprises the step of:
cleaning said contact surfaces of residual thermoplastic toner material by contacting said surfaces against a toner receptive member with said one surface at a high temperature for a second period of time that is substantially longer than said first period of time.
2. Fuser mechanism for fixing thermoplastic toner particle images to a support member and having a roll couple forming a nip therebetween, each roll of said couple having an external surface of low surface energy material, roll heating means directly thermally connected with only a first roll of said couple for maintaining the external surface of said first roll at high temperature, and power means operatively connected to said roll couple for rotating the rolls thereof, wherein the improvement comprises:
speed change means associated with said power means for causing said rolls to be driven at a normal relatively fast speed or selectively alternatively at a relatively slow speed,
means for delivering a sheet of toner receptive material into the nip of said roll couple, and
manually operable control means connected with said speed change means for selecting said relatively slow speed whereby said sheet and the second roll of said cop le are heated by said first roll, and toner materia on said first and second rolls is transferred to said sheet. 3. In a copy reproducing machine having a supply of copy material, image producing means for generating a thermoplastic toner particle image on a sheet of said copy material, a fusing roll couple'for fixing the thermoplastic toner particle image to said copy material, and manually initiatable control means for producing an automatic sequence of operations including feeding a sheet of said copy material to said image producing means, producing the said image onto the sheet, and passing the sheet bearing the image to said roll couple, each roll of said couple having an external surface of low surface energy material, heating means directly thermally connected only with the one roll of said couple that engages said toner particle image for maintaining the external surface of said one roll at high temperature, and power means connected to said roll cou- .ple for rotating the rolls thereof, wherein the improvement comprises:
a cleaning-cycle-select control member having a nor mal inactive position and a displaced active position,
speed change means associated with said power means for causing said rolls to be driven at 21 normal relatively fast speed and further being controlledly connected withvsaid clean-cycle-select control member for causing said rolls to be driven at a relatively slow speed in response to said control member being positioned in its displaced position, and
further means responsive to said control member being positioned in its displaced position for inhibiting operation of said image producing means,
whereby operation of said copy reproducing machine .with said control member in its displaced position delivers a sheet of said copy material without an image thereon to said roll couple while said roll couple is moving at said relatively slow speed.
4. Fusing mechanism as defined in claim 3 wherein the other roll of said couple is heated only by conduction of heat from said one roll.
5. Fuser mechanism as defined in claim 2 wherein said relatively slow speed is about 10 percent or less of said relatively fast speed.
6. Fuser mechanism as defined in claim 2 where said low surface energy material is silicone rubber.
7. Fuser apparatus as defined in claim 2 wherein at least one roll of said couple is significantly deformable when placed in pressure cooperation with the other of said rolls whereby an area of contact between said rolls is created at the nip.