US3796183A

US3796183A - Free floating pressure biasing apparatus for cleaning roll fuser

Info

Publication number: US3796183A
Application number: US00254269A
Authority: US
Inventors: R Thettu
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1972-05-17
Filing date: 1972-05-17
Publication date: 1974-03-12
Anticipated expiration: 1991-03-12
Also published as: NL7306855A

Abstract

A free floating pressure biasing apparatus for applying predetermined pressure on cleaning roll devices cleaning residual toner particles from the heated fuser roll of a heated pressure fusing system in an electrostatic copy machine. Two springs, one heavy and one light or low rate, are employed in a housing urging the cleaning roll devices against the heated fuser roll. During the non-fusing condition the pressure is low to insure proper temperature due to biasing from a low rate spring. During the fusing operation both springs act against the cleaning roll devices to maintain an effective cleaning operation. A modified embodiment of the apparatus including an additional spring normally urging the cleaning rolls away from the fuser roll surface during the non-fusing operation.

Description

1451 Mar. 12, 1974 FREE FLOATING PRESSURE BIASING APPARATUS FOR CLEANING ROLL FUSER [75] Inventor: Raghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: May 17, 1972 [21] App]. No.: 254,269

LOADING MECH.

319L466 12/!966 Ascr cl al. 263/6 3,409,280 I H1968 Spring et al 2,781,705 2/1957 Crumrimc et :11...

2,661,716 l2/l953 Minkow 3,449,548 6/1969 Adamck ct al. i. 1 18/637 Primary ExaminerMervin Stein Assistant Examiner-Leo Millstcin 5 7 ABSTRACT A free floating pressure biasing apparatus for applying predetermined pressure on cleaning roll devices cleaning residual toner particles from the heated fuser roll of a heated pressure fusing system in an electrostatic copy machine, Two springs, one heavy and one light or low rate, are employed in a housing urging the cleaning roll devices against the heated fuser roll. During the non-fusing condition the pressure is low to insure proper temperature due to biasing from a low rate spring. During the fusing operation both springs act against the cleaning roll devices to maintain an effective cleaning operation. A modified embodiment of the apparatus including an additional spring normally urging the cleaning rolls away from the fuser roll surface during the non-fusing operation.

5 Claims, 8 Drawing Figures PATENTEB l 2 m4 SHEEI 2 [IF 4 FIG. 2

FREE FLOATING PRESSURE BIASING APPARATUS FOR CLEANING ROLL FUSER This invention relates to fusing systems and in partic ular to a free floating pressure biasing apparatus for maintaining predetermined pressure on cleaning devices for cleaning toner particles from the fuser roll of a heated pressure fusing system.

In the practice of xerography as described in U.S. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic surface is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where the light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image can then be developed by contacting it-with a finely divided electrostatically attractable material such as a powder..The powder is held in image areas by the electrostatic charges on the layer. Where the charge field is greatest, the greatest amount of powder is deposited; where the charge field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the document or object being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably affixed thereto to form a permanent print.

One typical device for fixing the toner particles to the backing sheet is by a heated pressure fuser roll system in which the copy sheet is passed through the nip of a Teflon coated heated fuser roll and a backup roll as described in US. Pat. Nos. 3,256,002 and 3,268,351. In such fusing systems, care must be taken to remove unwanted toner particles from the heated fuser roll prior to its Contact with the copy being fused. If care is not taken to keep the fuser roll free of toner particles, these toner particles can build up on the face of the fuser roll and degrade the quality of the fix by removing the fusing properties on the surface of the roll contacting the copy sheet and toner images. Furthermore, such unwanted toner particles can be released from the fusing roll upon its subsequent contact with the toner image to fuse toner particles to the copy sheet in non-imaged areas.

It has been found that with high-speed duplicating machines in present use that cleaning rolls having a toner coated conformable surface may be used effectively to clean residual toner from the heated fuser roll as described in copending application Ser. No. 221,569, filed on Jan. 28, 1972 and commonly assigned herewith. The apparatus of the present invention is for the purpose of enabling a free floating constant force loaded biasing on the cleaning roll such that proper temperature on the cleaning roll is maintained even during the non-fusing operation.

It is therefore an object of the present invention to improve heated pressure fusing systems.

It is another object of the present invention to enhance cleaning of a heated fuser roll.

It is another object of the invention to provide cleaning rollers which conform with fuser roll surfaces being cleaned and maintain uniform contact therewith.

It is still another object of the present invention to prevent uneven cleaning of fuser rolls.

It is still another object of the present invention to as sure cleaning of fuser rolls by cleaning rollers which will not stick to the fuser rolls.

It is still another object of the present invention to minimize unnecessary maintenance of copier/duplicator systems.

'lhese and other objects of the instant invention are obtained by a new and'improved cleaning roller assembly which comprises one or more cleaning rollers having a conformable surface which is urged into predetermined pressure contact-with a heated fuser roll surface during the fusing operation but is in free floating contact with the roll surface during non-fusing opera tion to prevent sticking during the cleaning operation.

Further objects of this invention together with additional features and advantages thereof will become apparent from the following detailed description of the embodiment of the invention when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic representation of an automatic xerographic reproducing machine incorporating a heated pressure fusing system utilizing the improved cleaning roller assembly of the present invention;

FIG. 2 is a side elevational view of the heated pressure fusing system and improved cleaning roller assemy;

FIG. 3 is an isometric view of the cleaning roller assembly with parts broken away to illustrate certain details;

FIGS. 4 (a) 4 (0) show side sectional views of the free floating pressure biasing mechanism in sequence of operation according to the present invention;

FIG. 5 is an end view of the cleaning roller assembly; and

FIG. .6 is a side sectional view of a modified embodiment of the pressure biasing mechanism.

Referring now to the drawings as shown in FIG. 1, an embodiment of the invention is a suitable environment such as an automatic xerographic reproducing machine. The automatic xerographic reproducing machine includes a xerographic plate or surface formed in the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing journaled in a frame to rotate in a direction indicated by the arrow. The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations.

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

a charging station A which the uniform electrostatic charge is deposited onto the photoconductive plate;

an exposure station B at which light or radiation pattern of copies to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copies to be reproduced;

a developing station C at which xerographic developing material including toner particles have an electrostatic charge opposite to that of the latent electrostatic image is cascaded over the latent electrostatic image to form a powdered image in configuration of the copy being reproduced;

a transfer station D which the powdered image is electrostatically transferred from the plate surface to a transfer material such as paper which is then passed through heated pressure fusing system having a cleaning roller assembly as will be described hereinafter; and

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

For further details of the xerographic processing stations, above reference is made to copending application Ser.'No. 838,902 filed July 3, 1969.

Referring now in particular to FIG. 2 there is shown details of the heated pressure fusing system which includes a heated fuser roll .16 and a backup pressure roll 18. Fuser roll 16 is a hollow circular cylinder with a metallic core 20 and a'Teflon layer 22. A quartz lamp 24 serves as a source of thermal energy and is located at the center of the fuser roll. Power to the lamp is controlled by a thermal sensor generally called a thermistor contacting the periphery of the fuser roll as described, for example, in U.S. Pat. No. 3,357,249. The backup roll 18 is also a circular cylinder and is made up of a metal core surrounded by a thick rubber layer 32 and also a'Teflon layer 34 to prevent soaking silicone oil into rubber layer 32 and subsequent swell- When the two

rollers

16 and 18 are engaged as shown in FIG. 2 the applied load deforms the rubber in the pressure roll to provide the nip with a finite width. The copy sheet 40 electrostatically bearing the toner images 42 on the under side is brought into contact with the nip of the rolls with the toner image contacting the fuser roll 16. For a given temperature of the fuser roll, the fusing rate will depend upon the contact arc length of the support material against the dwell time, i.e., the time. the toner images remain between the fuser roll 16 and the backup roll 18. Dwell time can be varied either by changing the surface velocity of the rolls or by varying the contact arc length and holding the speed of the roll the same. Contact arc length depends on the softness of the rubber on backup roll 18 and on the amount of pressure between the

rolls

16 and 18. The mechanism for driving the rolls'and for lowering and raising the rolls into contact can be accomplished by any suitable means, such as a mechanical camming device.

As a sheet of material is advanced between the

rolls

16 and 18 the toner images on the support material will contact the peripheral heated surface of the roll 16 whereby the toner images become tackified and in this tackifled condition the toner will tend to offset on this roll except that it is partially prevented from doing so by the Teflon coating on the roll. However, it is by the wicking apparatus of the present invention which is successful in applying a thin film of offset preventing liquid suchas silicone oil to the Teflon surface 22 of the fuser roll 16 such that toner ofiset is prevented as will be described hereinafter.

An oil dispensing apparatus 45 includes wicking assembly 48, an oil pan for maintaining a supply of silicone oil 51 and an applicator roll 52. The oil pan is loaded against the heated fuser roll 16 by a spring action mounting (not shown) as details of the mounting form no part of the present invention. Applicator roll 52 is used to convey a thin film of oil to the bottom face 55 of the wicking assembly as the applicator roll is rotated in the direction shown by the arrow. Desirably, the applicator roll 52 is driven by an oil dispensing motor 58 which is energized during the fusing operation for a period depending upon the number of copies being produced. It should be understood that cleaning roller apparatus 10 can be used to clean dry fuser rollers as well as oil wetted fuser rolls as described above. For example the cleaning roller apparatus could be used to clean any contamination of the surface of the dry fuser roll as described in U.S. Pat. Nos. 3,539,161 and 3,498,596.

Cleaning roller apparatus 10 maintains the working heated surface of fuser roll 16 in a toner-free condition thereby preventing unwanted residual toner particles from being redeposited upon subsequent copies as they are fused. The cleaning roller apparatus of the invention cleans any residual 'toner particles adhering to the surface of the heated fuser roll continuously and uniformly during the cleaning operation. The cleaning roller apparatus includes a plurality of cleaning rollers and 71 which are constructed so as to have a soft and conformable surface to insure proper contact with the relatively hard exterior of the heated fuser roll 16.

Cleaning rollers

70 and 71 are mounted on a movable holder or carriage 73. Carriage 73 is biased by a free floating constant force loading mechanism 75 according to the present invention which enables the carriage to be capable of applying a uniform load both when the cleaning rollers are fully contaminated with toner particles or freshly installed and enable free floating of the assembly during non-fusing operation.

Referring now to FIG. 3, there is shown the free floating constant force mechanism 75 which includes a pair of free floating pressure biasing assemblies 78 movably supported on frame 79 and actuatable by actuating assembly 81 including shaft 83 carrying camming members 85. For purposes of explanation it is deemed sufficient that only one of the free floating pressure biasing assemblies 78 be described in detail.

Referring now to FIGS. 4(a) 4(0), there is shown details of the freefloating pressure biasing assembly which includes a housing 101, enclosing an outer shaft member 103 extending between a retaining ring 109 received in the groove 110 of the housing and a spacer member 114 whose movement is restricted by a shoulder portion 112 formed -in the housing 101. Spacer member 114 carries a plurality of hardened precision balls 115 which are received in pockets 116 formed in spacer member 114. Balls 115 are free floating within the spacer member 114 and enable the outer shaft member 103 to move freely towards the left and right as long as a wedge shaped friction ring member 117 is not in contact with balls 115.

A low rate of compression spring 122 is held between a bearing member 128 carried in housing 101 and a step portion 129 on outer shaft 103. When the outer shaft 103 is moved towards the left, the spring 122 is compressed as best shown in FIG. 4(a) Bearing member 128 is trapped between the housing 101 and the retaining ring 109. As a result the outer shaft member 103 can move freely to the left and right.

It will be noted that friction ring member 117 is shaped as a conical wedge portion 136 on one side and as a stepped shoulder 146 on the other side. By this arrangement the friction ring member may be free float ing between the outer shaft member and the housing unless the housing is moved to the right by actuating cam member 85 as shown in FIG. 4(1)), causing the wedge portion 136 to engage balls 115. If this occurs, a relatively heavy spring 137 bears against friction ring member 117 causing outer shaft member 103 to lock as shown in FIG. 4(a). It will now be appreciated that a heavy biasing pressure is exerted against carriage 73 and thus the cleaning rollers achieve proper conformability during the cleaning operation.

In operation the cleaning rollers during the nonfusing mode of operation are in a floating state against the action low rate spring 122. This mode of operation enables the cleaning rolls to be in kissing contact with the surface of the fuser roll and insures proper temperature of the toner laden surface of the cleaning rollers such that the toner is soft and, therefore, ideal for cleaning the fuser roll surface. As the residual toner starts to build up on the cleaning rollers their diameter increases and hence the cleaning rollers gradually push against spring 122, which gradually increases the load on the cleaning rollers. For example, when the rollers have grown in size to about three quarters of an inch diameter from about one half inch diameter, there is an increase of about one quarter pound pressure. It will be appreciated that there is always a gap betwen the balls 115 and the friction ring member 116 due to the spring 122 always acting against the bearing 128 which carries with it housing 101 to maintain the positive separation of the halls and the friction ring member.

During the cleaning mode of operation, housing 101 is moved towards the right or towards the fuser roller, causing spring 122 and heavy spring 137 to compress. Spring 137 pushes the friction ring member 116 against the balls 115 thereby causing the outer shaft 103 to lock. As a result a much higher load is transmitted to the cleaning rollers as required for the cleaning process. When the actuating assembly is released, the balls in the friction ring member are separated and only spring 112 maintains the cleaning rollers in freefloating contact with the heated fuser roller to effect proper temperature on the cleaning roller surface during the non-fusing operation.

it has been found that it is desirable to retract the cleaning roll apparatus away from the fuser roll under certain circumstances as, for example, in the case of cleaning dry or non-oil wetted fusing systems. This may be easily achieved by insertion ofa spacer member 151 and a spring member 153, as shown in FIG. 6. It will be appreciated that during the fusing operation that heavy loading by spring 122 and spring 137 is still maintained, which enables buildup of contamination on the cleaning rollers.

It will now be appreciated that due to the unique free floating pressure biasing apparatus of the present invention, the toner buildup on the cleaning rollers will not adversely affect the loading characteristics against the heated fuser roll. Moreover, the cleaning rollers are at all times maintained into pressure contact with the heated fuser roll to insure proper operating temperatures so that residual toner may adhere to the cleaning rollers.

What is claimed is:

1. In a fusing system for fusing toner images in an electrostatic copying machine in which a heated roll surface is used to fix the toner images to copy sheet material and cleaning rollers contact the heated roll surface for cleaning toner offset onto the heated roll surface, an improved pressure biasing apparatus acting on the cleaning rollers, comprising carriage means supporting at least one cleaning roller in contact with the heated roll surface to be cleaned,

pressure biasing means for urging said carriage means towards theheated roll surface at a predetermined pressure,

said pressure biasing means including slidable shaft means movable from a first position in which said cleaning roller is in a free floating condition low pressure contact with the heated roll surface to a second position in which the cleaning roller is maintained in relatively high pressure contact against the heated roll surface, and

actuating means for moving said shaft means from the first position to the second position during the fusing operation.

2. Apparatus to claim 1 wherein said slidable shaft means is acted on by a relatively light spring means when in said first position and by relatively heavy spring means when, in said second position.

3. Apparatus according to claim 2 wherein said shaft means is carried in a housing displaceable upon actuation by said actuating means for locking said slidable shaft means into relatively high pressure contact against said heated fuser roll.

4. In a fusing systemfor fusing toner images in an electrostatic copying machine in which a heated roll surface is used to fix the toner images to copy sheet matcrial and cleaning rollers contact the heated roll surface for cleaning toner offset onto the heated roll surface, an improved pressure biasing apparatus acting on the cleaning rollers, comprising carriage means supporting at least one cleaning roller in contact with the heated roll surface to be cleaned,

pressure biasing means for urging said carriage means towards the heated roll surface at a predetermined pressure, said pressure biasing means including slidable shaft means movable from a first position in which said shaft means is in a free floating condition to a second position in which the shaft means is maintained in pressure contact against the heated roll surface,

actuating means for moving said shaft means from the first position to the second position during the fusing operation,

wherein said slidable shaft means is acted on by a relatively light spring means when in said first position and by relatively heavy spring means when in said second position,

wherein said shaft means is carried in a housing displaceable upon actuation by said actuating means for locking said slidable shaft means into relatively high pressure contact against said heated fuser roll, and

wherein said housing includes a friction member engaging ball members carried on said slidable shaft means.

5. In a fusing system for fusing toner images in an electrostatic copying machine in which a heated roll surface is used to fix the toner images to copy sheet material and cleaning rollers contact the heated roll surface for cleaning toner offset onto the heated roll surface, an improved pressure biasing apparatus acting on the cleaning rollers, comprising carriage means supporting at least one cleaning roller member in contact with the heated roll surface to be cleaned, pressure biasing means for urging said carriage means towards the heated roll surface at a predetermined pressure, said pressure biasing means including slidable shaft means movable from a first position in which said shaft means is in a free floating condition to a second position in which the shaft means is maintained in pressure contact against the heated roll surface, actuating means for moving said shaft means from the first position to the second position during the fusing operation wherein said slidable shaft means is acted on by a relatively light spring means when in said first position and by relatively heavy spring means when in said second position,

wherein said housing is further acted on by additional spring means normally urging said housing in a dircction away from said heated roll surface during the non-fusing operation.

Claims

1. In a fusing system for fusing toner images in an electrostatic copying machine in which a heated roll surface is used to fix the toner images to copy sheet material and cleaning rollers contact the heated roll surface for cleaning toner offset onto the heated roll surface, an improved pressure biasing apparatus acting on the cleaning rollers, comprising carriage means supporting at least one cleaning roller in contact with the heated roll surface to be cleaned, pressure biasing means for urging said carriage means towards the heated roll surface at a predetermined pressure, said pressure biasing means including slidable shaft means movable from a first position in which said cleaning roller is in a free floating condition low pressure contact with the heated roll surface to a second position in which the cleaning roller is maintained in relatively high pressure contact against the heated roll surface, and actuating means for moving said shaft means from the first position to the second position during the fusing operation.

2. Apparatus to claim 1 wherein said slidable shaft means is acted on by a relatively light spring means when in said first position and by relatively heavy spring means when in said second position.

4. In a fusing system for fusing toner images in an electrostatic copying machine in which a heated roll surface is used to fix the toner images to copy sheet material and cleaning rollers contact the heated roll surface for cleaning toner offset onto the heated roll surface, an improved pressure biasing apparatus acting on the cleaning rollers, comprising carriage means supporting at least one cleaning roller in contact with the heated roll surface to be cleaned, pressure biasing means for urging said carriage means towards the heated roll surface at a predetermined pressure, said pressure biasing means including slidable shaft means movable from a first position in which said shaft means is in a free floating condition to a second position in which the shaft means is maintained in pressure contact against the heated roll surface, actuating means for moving said shaft means from the first position to the second position during the fusing operation, wherein said slidable shaft means is acted on by a relatively light spring means when in said first position and by relatively heavy spring means when in said second position, wherein said shaft means is carried in a housing displaceable upon actuation by said actuating means for locking said slidable shaft means into relatively high pressure contact against said heated fuser roll, and wherein said housing includes a friction member engaging ball members carried on said slidable shaft means.

5. In a fusing system for fusing toner images in an electrostatic copying machine in which a heated roll surface is used to fix the toner images to copy sheet material and cleaning rollers contact the heated roll surface for cleaning toner offset onto the heated roll surface, an improved pressure biasing apparatus acting on the cleaning rollers, comprising carriage means supporting at least one cleaning roller member in contact with the heated roll surface to be cleaned, pressure biasing means for urging said carriage means towards the heated roll surface at a predetermined pressure, said pressure biasing means including slidable shaft means movable from a first position in which said shaft means is in a free floating condition to a second position in which the shaft means is maintained in pressure contact against the heated roll surface, actuating means for moving said shaft means from the first position to the second position during the fusing operation wherein said slidable shaft means is acted on by a relatively light spring means when in said first position and by relatively heavy spring means when in said second position, wherein said shaft means is carried in a housing displaceable upon actuation by said actuating means for locking said slidable shaft means into relatively high pressure contact against said heated fuser roll, and wherein said housing is further acted on by additional spring means normally urging said housing in a direction away from said heated roll surface during the non-fusing operation.