US3667742A - Fixing arrangement - Google Patents

Abstract

APPARATUS FOR FUSING ELECTROSCOPIC TONER IMAGES ONTO A SUPPORT IN WHICH A PAIR OF ELASTICALLY DEFORMABLE SHELL MEMBERS OF A GENERALLY CYLINDRICAL CONFIGURATION ARE EACH SUPPORTED IN A DEFORMED GENERALLY ELLIPTICAL CONFIGURATION ABOUT A PAIR OF GENERALLY PARALLEL SPACED ROLLER MEMBERS WITH THE ROLLER MEMBERS BEING BIASED IN A DIRECTION GENERALLY ALONG THE MINOR AXIS OF THE RESPECTIVE ELLIPTICAL CONFIGURATION TO FURTHER DEFORM AT LEAST A PROTION OF THE ELLIPTICAL SURFACE OF ONE OF THE SHELL MEMBERS AGAINST AT LEAST A PORTION OF THE ELLIPTICAL SURFACE OF THE OTHER OF THE SHELL MEMBERS THEREBY PROVIDING AN EXTENDED NIP OR AREA OF CONTACT BETWEEN THE SHELL MEMBERS. A SOURCE OF HEAT ENERGY ASSOCIATED WITH AT LEAST ONE OF THE SHELL MEMBERS PRODUCES A HEATING OF THE SHELL MEMBERS TO AN ELEVATED TEMPERATURE AND AS THE HEATED SHELL MEMBERS ARE ADVANCED ABOUT THE ROLLER MEMBERS IN THE DEFORMED CONFIGURATION A SUPPORT MEMBER HAVING UNFUSED ELECTROSCOPIC TONER IMAGES THEREON WILL BE ADVANCED THEREBETWEEN TO PRODUCE AT LEAST A PARTIAL MELTING OF THE TONER IMAGES ON THE SUPPORT WITHIN THE EXTENDED NIP AREA.

Description

June 6, 1972 R C KAMQLA 3,667,742

FIXING ARRANGEMENT Filed Dec. 28, 1970 2 Sheets-Sheet 1 INVENTOR. ROMAN C. KAMOLA ATTORNEY June 6, 1972 R. c. KAMOLA 3,567,742

FIXING ARRANGEMENT Filed Dec. 28, 1970 2 Sheets-Sheet 2 tates Patent US. Cl. 263-6 E 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for fusing electroscopic toner images onto a support in which a pair of elastically deformable shell members of a generally cylindrical configuration are each supported in a deformed generally elliptical configuration about a pair of generally parallel spaced roller members with the roller members being biased in a direction generally along the minor axis of the respective elliptical configuration to further deform at least a portion of the elliptical surface of one of the shell members against at least a portion of the elliptical surface of the other of the shell members thereby providing an extended nip or area of contact between the shell members. A source of heat energy associated with at least one of the shell members produces a heating of the shell members to an elevated temperature and as the heated shell members are advanced about the roller members in the deformed configuration a support member having unfuscd electroscopic toner images thereon will be advanced therebetween to produce at least a partial melting of the toner images on the support within the extended nip area.

BACKGROUND OF THE INVENTION This invention relates generally to the aflixing of electroscopic toner material to a support member and more particularly to permanently affixing electroscopic toner material in an image configuration onto a support by the use of heat.

In order to permanently afiix or fuse an electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the electroscopic toner material to a point at which at least one of the constituents of the toner material is caused to melt. This action causes molten droplets of the toner material to form which molten droplets are absorbed to some extent in the fibers of the support member which in many instances constitutes paper so as to produce a permanent afiixation of the toner material on the support. Thereafter, as the toner material is cooled, solidification of the toner material occurs causing the toner material to be firmly bonded to the support material.

In both the electrographic recording art as well as the xerographic art, the use of heat for fixing toner images onto a support is old and well known. For example, one of the oldest and perhaps the most common heat fixing or fusing arrangements heretofore, has been the use of a resistance heating element which is supported in a refleeting device adjacent the support material. However, since in most such applications, the support material generally constitutes paper, such radiant heating devices have had an adverse affect on the support material itself. That is, in such fixing arrangements in order to insure sufficient fusion of the toner material to the paper, the temperature therein has been such as to elevate the temperature of the paper as well as the toner beyond a point so as to have deleterious effects on the paper. For example, in most radiant fusing devices, not only is the temperature of the toner material in image configuration elevated, the temperature of the paper support also is elevated which 3,667,742 Patented June 6, 1972 "ice has the effect of evaporating and hence reducing the moisture content normally present within the paper material. This has the adverse affect of causing the paper to become brittle, as well as warping or inducing a curl therein. Accordingly, such radiant fusing arrangements have heretofore been found generally unacceptable in many applications.

Another approach to fusing electroscopic toner images onto a support has been passing the support with the toner images thereon between a pair of opposed heated roller members. In this type of arrangement the toner images contact the heated surface of a roller member within the nip therebetween which produces a conductive heating of the toner image within the nip.

In this type of arrangement however, because of the very small contact area between roller member and image within the nip, a relatively high pressure contact between roller and image must be maintained if adequate heating of the image area is to be obtained. 'In addition, in such arrangements, it is generally necessary to maintain the surface of the roller member at a fairly high temperature level to insure proper melting of the toner image within the relatively short time of contact. While this type of direct contact roller fuser has in many applications served as a most effective fusing arrangement it nevertheless has certain shortcomings largely due to the limited contact area provided between the roller members and the toner images, and the pressures and temperatures required to produce adequate fusion of the toner images.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide improved apparatus for affixing electroscopic toner material onto a support material.

It is a further object of the present invention to provide improved apparatus for permanently affixing or fusing electroscopic toner material onto a support member by the use of heat without adversely alfecting the support material.

It is still another object of the present invention to provide an improved direct contact fusing apparatus.

It is still another object of the present invention to provide a direct contact fusing device having an extended contact nip.

It is still a further object of the present invention to provide a direct contact fusing device having a low initial warm up time.

It is yet a further object of the present invention to provide a highly efiicient direct contact fusing device while preventing offset of the toner images.

It is yet a further object of the present invention to provide a direct contact fusing device having an extended nip of contact which is adapted for simultaneous fusing of images on both sides of a support sheet.

These and other objects of the invention are attained by a first elastically deformable shell member of a generally cylindrical configuration, a pair of roller members supported internally of said first shell member in a generally parallel spaced relationship to each other to elastically deform said shell member thereabout into a generally elliptical configuration, a second elastically deformable shell member of a generally cylindrical configuration, a pair of roller members supported internally of said second shell member in a generally parallel spaced relationship to each other to elastically deform said second shell member thereabout into a generally elliptical configuration, means operatively associated with said pairs of roller members for biasing said roller members in a direction generally along the minor axis of the respective elliptical configurations to further deform at least a portion of the elliptical surface of one of the shell members against at least a portion of the eliptical surface of the other of the shell members'to provide an extended nip between said shell members, heat generating means operatively associated with at least one of said shell members for heating said shell member to an elevated temperature, and means operatively associated with said shell members and said roller members for advancing said shell members about said roller members in the deformed configuration to transport a support member having unfused electroscopic toner images thereon through the extended nip between said shell members to produce at least a partial melting of said toner images on said support member.

' Other objects of the invention will become readily apparent to those skilled in the art in view of the following detailed disclosure and description thereof, especially when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of a system in which the fusing arrangement as contemplated by the present invention is particularly adapted for use.

FIG. 2 is an enlarged schematic illustration of the fusing arrangement illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT According to the present invention electroscopic toner images which are to be permanently affixed to a support such as paper are contacted between a pair of members in an extended nip which are heated to a temperature sufficient to produce at least a partial melting of the toner material. Within the area of contact, a transfer of the thermal energy in the heated members to the toner material occurs. As at least a partial melting of the toner images within the extended contact area is thus produced, the melted toner material fiows to a certain extent into the fibers of the support material which after cooling readily adheres in a permanent manner to the support material.

Although the invention will be described with particular reference to toner images which are formed through the now well-known xerographic process, it will be readily appreciated by those skilled in the art that the fusing arrangement as contemplated by the present invention is also readily adaptable for permanently afiixing electroscopic toner images onto a support which have been produced by means of an electrographic recording or electrostatic printing process.

Referring to FIG. 1, in which a xerographic reproducing apparatus has been schematically illustrated, an original copy to be reproduced is placed on a support tray 10 from-which it is fed into a feed apparatus generally a designated 11. On the feed apparatus the original is moved on an endless belt 12 driven by motor 13 to pass the optical axis of projection lens system 14 that is illuminated by a projection lamp LMP-l. The image of the original is reflected by mirror 15 through an adjustable objective lens 16 and then reflected by mirror 17 downwardly through a variable slit aperture assembly 18 and onto the surface of a xerographic plate in the form of a drum 19.

'Xerographic drum 19 includes a cylindrical member mounted in suitable bearings in the frame of the machine and is driven in a clockwise direction by a motor 24 at a constant rate that is proportional to the transport rate of the original, whereby the peripheral rate of the drum surface is identical to the rate of movement of the projected radiation image. The drum surface comprises a layer of photoconductive material on a conductive backing that is sensitized to exposure by means of a corona generating device 25 which may be an adaptation of the type disclosed in Vyverberg Pat. No. 2,83 6,725 that is energized from a suitable high potential source.

The exposure of the drum to the radiation image discharges the photoconductive layer in the areas struck by radiation, whereby there remains on the drum a latent electrostatic image in image configuration corresponding to the radiation image projected from the original. As the drum surface continues its movement, the electrostatic latent image passes through a developing station 26 at which a two-component developer material 27 which may be of the type disclosed in Walkup, Pat. No. 2,638,- 416, is cascaded over the drum surface by means of developing apparatus 28.

In the developing apparatus, developing material is carried up the conveyor 29, driven by suitable drive means from the motor 30, and then released onto chute 31 whereby it is cascaded down over the drum surface. The toner component 32 of the developer that is consumed in developing is stored in dispenser 33 and is dispensed in amounts controlled by gate 34.

After developing, the xerographic powder image passes a discharge station 41 at which the drum surface is illuminated by lamp LMP-2, whereby residual charges on the non-image areas of the drum surface are completely discharged. Thereafter, the powder image passes through an image transfer station 42 at which the power image is electrostatically transferred to a moving support surface 43 by means of a second corona generating device 44 similar to corona charging device 25', mentioned above.

The moving support surface 43 to which the powder image is transferred may be of any convenient type, such as paper, and may be obtained from a supply roll 45, fed over guide roll 46 and over tensioning roll 47, being directed into surface contact with the drum in the immediate vicinity of transfer corona generating device 44. After transfer, the support surface 43 is separated from the drum surface and guided through the fusing apparatus as contemplated by the present invention generally designated 48, wherein the powder image is permanently affixed thereto. Thereafter, the support surface may be fed over a further'system of guide and tensioning rolls such as 49 and onto a take-up roll '52 that is driven by motor 53.

After separation of the support surface 43 from the drum, a corona generating device 54 directs electrostatic charge to a residual powder image on the drum surface. Thereafter, the xerographic drum surface passes through a cleaning station 55 at which the surface thereof is brushed by a cleaning brush assembly 56, rotated by a motor 57, whereby residual developing material remaining on the drum surface is removed. The drum surface then passes through a second discharge station 58 at which it is illuminated by fluorescent lamp LMP-3, whereby the drum surface in this region is completely flooded with light to remove any electrostatic charge that may remain thereon. Suitable light traps are provided in the system to prevent any light rays from reaching the drum surface, other than the projected image, during the period of drum travel immediately prior to sensitization by corona generating device 25 until after the drum surface has com pletely passed through the developing station 26.

During operation of the xerographic apparatus, the image bearing support surface 43 carrying the loose powder images is moved through the fusing apparatus in a path accorded by the interrelation of rollers 47 and 49. While the support material 43 with the toner images 90 thereon has been shown and described as being in the form of an elongated web it will be appreciated by those skilled in the art that the fusing arrangement as contemplated by the present invention is equallyapplicable to the use of support materials in the form of cut sheet stock.

The fusing apparatus 48 includes an insulating shell or jacket 60 which surrounds and encloses the active elements of the fusing assembly. Openings 73 and 74 at either side of insulating shell 60 in the direction of support travel permit support member 43 with toner images 90 thereon to pass through the fusing assembly with a minimal loss of heat energy from the active elements of the fusing apparatus. Insulating shell 60 may be composed of any suitable material which has a low conductivity and emissivity of thermal energy.

The active elements of fusing apparatus 48 include shell members 61 and 62 and roller members 63-64 and 65-66 respectively associated therewith. Shell members 61 and 62 are preferably formed from any suitable elastically deformable material which has a high conductivity and emissivity of thermal energy. Suitable materials include spring steels, stainless steels or alloys having high fatigue strength. Shell members 61 and 62 in the normal undeformed condition are of a generally cylindrical configuration, the walls of which are thin in relation to the size of the cylinder thus providing a low mass per unit surface area of the shell members.

Roller members 63-64 and 6566 are likewise preferably formed from any suitable material which has a high conductivity and emissivity of thermal energy. Suitable materials include heat treated steels, stainless steels or alloys having high fatigue strength. Roller members 63-64 and 65-66 like shell members 61 and 62 are of a generally cylindrical configuration and have wall thicknesses which are relatively thin in relation to the size of the respective cylinders. However, unlike shell members 61 and 62, roller members 63-64 and 6566 are, relatively speaking, rigidly non-deformable about their respective central axes and maintain their general cylindrical configuration under an applied pressure. Shell members 61 and 62 on the other hand are elestically deformable about their respective axes while remaining non-deformable through the dimensional thickness of the respective walls.

The roller members 63-64 and 6566 are supported internally of the respective shell members 61 and 62 in a generally parallel spaced relationship to each other by any suitable support means which permits rotational movement of the respective roller members about their respective central axes. By way of example, roller members 63-64 and 6566 may be rotatably journaled at either end thereof in suitable frame plates operatively attached to either end of insulating jacket 60.

Roller members 63-64 and 6566 in their mounting arrangement are spaced from each other within the respective shell members 61 and 62 a distance suflicient to elastically deform the respective shell members from the normal cylindrical configurations against the normal elasticity of the shell material into generally elliptical configurations about the respective roller members. iRoller members 63-64 and 6566 in their mounting arrangements are also biased or pressed in directions extending generally along the minor axes of the respective elliptical configurations to further deform at least a portion of the elliptical surface of one of the shell members against at least a portion of the elliptical surface of the other of the shell members to provide an extended nip or area of contact between the shell members 61 and 62 as may be seen from FIG. 2 of the drawings.

Across the extended nip or area of contact between shell members 61 and 62 a pressure will be exerted as a result of the deformation of the shell members 61 and 62 from the normal cylindrical configuration. It will be appreciated that by carefully balancing physical properties of materials from which the shell members 61 and 62 are formed with appropriate wall thicknesses of the shell member, a wide latitude in pressures across the nip may be obtained. It will also be appreciated that with a proper choice of materials and relative dimensions, substantially uniform pressures may be obtained throughout the nip or extended area of contact.

To provide a heating of the toner images to be fused within the nip or extended area of contact, the active elements of the fusing apparatus 48 are heated to an elevated temperature by suitable heat generating means. In the embodiment as illustrated in FIG. 2, a source of heat energy such as quartz lamps 67 and 68 are located inwardly of shell members 61 and 62 and extend as do shell members 61 and 72 in the lateral direction a distance sufiicient to encompass the width of support material 43 onto which images are to be fused. Lamps 67 and 68 are operatively connected to a source of electrical energy and are adapted upon energization to produce a heating of shell members 61 and 62 and roller members 63-64 and 6566 to elevated temperatures sufficient to produce at least a partial melting of toner images on support member 43 which are passed through the nip or contact area between shell members 61 and 62. Suitable temperature responsive means such as heat sensor 72 may also be provided to operatively control the enerization of quartz lamps 67 and 68 and thereby maintain the temperature of the active elements of fusing apparatus 48 at a predetermined optimum level. In the embodiment of FIG. 2 only one such sensing element 72 has been illustrated which is supported internally of roller member 64. However, it will be appreciated by those skilled in the art that additional sensing devices such as 72 may also be utilized to operatively control the energization of quartz lamps 67 and 68 to thereby maintain the active elements of fusing apparatus 48 within predetermined operating temperature ranges.

In the embodiment of fusing apparatus 48 as illustrated in FIG. 2, shell members 61 and 62 are preferably coated with a thin layer of material such as polytetrafiuoroethylene. This coating of polytetrafiuoroethylene or like material provides a fuser contact surface having a relatively high repellancy for the toner particles as images are passed through the fusing apparatus 48. This polytetrafluoroethylene coating therefore serves to prevent offsetting of the tacky or partially molten images onto shell members 61 and 62 as the images 90 pass through fusing apparatus 48. A light film of a suitable release agent may also be applied to the surfaces of polytetrafluoroethylene coated shell members 61 and 62 to further prevent against offsetting of the toner images 90 onto the surfaces of shell members 61 and 62. To this end, a light film of silicon oil for example, may be applied to the surfaces of shell members 61 and 62 by means of belts or ribbons 69 and 70 which are impregnated with the release agent. In the embodiment of FIG. 2, belts or ribbons 69 and 70 are disposed transversely to the direction of movement of shell members 61 and 62 and support member 43. As shell members 61 and 62 are driven about the roller members 63-64 and 6566 a film of the release agent from belt members 69 and 70 Will be deposited on the surfaces of shell members 61 and 62. Suitable means may also be provided for indexing belt members 69 and 70 over the surfaces of shell members 61 and 62 to maintain an adequate supply of the release agent to shell members 61 and 62.

In the embodiment of FIG. 2, shell members 61 and 62 are driven in their deformed configuration about roller members 63-64 and 6566 to transport a support member 43 having toner images 90 thereon through the fusing apparatus 48. In the embodiment of FIG. 2, roller member 65 is driven in a counterclockwise direction by means of a suitable drive arrangement exterior to the insulating shell 60. This may be accomplished by various combinations of gearing, belts, chain, etc. to drive roller member 65 at a predetermined rotational speed. In the embodiment as illustrated in FIG. 2, roller member 65 includes a plurality of sprocket teeth 71 which are spaced about the periphery of the roller member 65 to impart movement to shell members 61 and 72. In the preferred arrangement, a first set of sprocket teeth 71 are located adjacent one end of roller member 65 and a second set of sprocket teeth 71 are located adjacent the other end thereof. Sprocket teeth 71 on roller member 65 mesh with suitably arranged apertures in roller member 63 to drive roller member 63 in a clockwise direction as seen in FIG. 2. Sprocket teeth 71 on roller member 65 also mesh with suitably arranged apertures along the edges of shell members 61 and 72 to provide a positive driving force to shell members 61 and 62 in the directions as shown about idler rollers 64 and 66 respectively. Thus as roller member 65 is driven from a source external to the fuser assembly 48, shell members 61 and 62 will *be driven about roller members 63-64 and 65-66 respectively to transport support material 43 having unfused electroscopic toner images thereon through the fusing assembly. As will be appreciated however, other equivalent drive arrangements may be employed for driving shell members 61 and 62 about roller members 63-64 and 65-66 in the deformed configuration.

From the foregoing arrangement it will be appreciated that as shell members 61 and 62 of fusing apparatus 48 are driven in the directions as shown in FIG. 2, a support member 43 having images 90 thereon to be fused will be transported through the extended nip or area of contact between shell members 61 and 62. -It should also be appreciated that as a result of the extended nip or area of contact that lies between opposite roller pairs 64-66 and 63-65, fusing of the toner images may be produced at relatively lower contact pressures and at relatively lower temperatures than has heretofore been possible in more conventional contact fusers. It should also be appreciated that as a result of the relatively low mass per unit area of shell members 61 and 62 and roller members 63-64 and 65-66 the fusing apparatus 48 requires a very short initial warm up time within which the active elements of the fusing apparatus reach optimum fusing temperature. It should also be appreciated that because of the relatively low mass per unit area of the active elements of the fusing apparatus, the fusing apparatus therefore is characterized by a quick thermal response time which enables an accurate control between optimum fusing temperature limits. It should be further appreciated that as a result of the substantially uniform pressure which is exerted within the extended area of contact, an optimum heat transfer relationship is provided which continues over a longer period of time than has heretofore been possible with conventional 'contact fusers. Finally, it will be further appreciated that the fusing apparatus as contemplated by the present invention is ideally adapted for fusing images which are not only placed on one side of the support member but which are also placed on both sides of the support member, in a simultaneous manner.

While the invention has been described with reference to a preferred arrangement, it will be generally understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention.

What is claimed is:

1. Apparatus for fusing electroscopic toner images onto a support comprising,

a first elastically deformable shell member of a generally cylindrical configuration,

a pair of roller members supported internally of said first shell member in a generally parallel spaced relationship to each other to elastically deform said shell member thereabout into a generally elliptical configuration,

a second elastically deformable shell member of a generally cylindrical configuration,

a pair of roller members supported internally of said second shell member in a generally parallel spaced relationship to each other to elastically deform said second shell member thereabout into a generally elliptical configuration,

means operatively associated with said pairs of roller members for biasing said roller members in a direction generally along the minor axis of the respective elliptical configuration to further deform at least a portion of the elliptical surface of one of the shell members against at least a portion of the elliptical surface of the other of the shell members to provide an extended nip between said shell members,

'heat generating means operatively associated with at least one of said shell members for heating said shell member to an elevated temperature, and

means operatively associated with said shell members and said roller members for advancing said shell members about said roller members in the deformed configuration to transport a support member having unfused electroscopic toner images thereon through the extended nip between said shell members to produce at least a partial melting of said toner images on said support member.

2. Apparatus according to claim '1 further including,

applicator means for applying a quantity of offset preventing material to the surface of said shell members.

3. Apparatus according to claim 1, said heat generating means including,

a first source of heat energy supported internally 0 said first shell member adapted when energized to heat said first shell member to an elevated temperature,

a second source of heat energy supported internally of said second shell member adapted when energized to heat said second shell member to an elevated temperature, and

means responsive to the temperature of said shell members for controlling the energization of said sources of heat energy.

4. Apparatus for affixing electroscopic toner images onto a support comprising,

a first generally cylindrically shaped thin shelled member formed from a heat conductive material of high elasticity,

a first pair of roller members supported for rotation about their respective axes internally of said thin shelled member, said roller members being spaced from each other in a generally parallel relationship to elastically deform said thin shelled member thereabout in a generally elliptical configuration,

a second generally cylindrically shaped thin shelled member formed from a heat conductive material of high elasticity,

a second pair of roller members supported for rotation about their respective axes internally of said thin shelled member, said roller members being spaced from each other in a generally parallel relationship to elastically deform said thin shelled member thereabout in a generally elliptical configuration,

fmeans operatively associated with said first and said second pairs of roller members for biasing said roller members in. a direction generally along the minor axes of the elliptical configurations of said thin shelled members to further deform at least a portion of the elliptical surface of one of the thin shelled members against at least a portion of the elliptical surface of the other of the thin shelled members to provide an extended nip between said first and said second thin shelled members,

heat generating means operatively associated with at least one of said thin shelled members for heating said thin shelled member to an elevated temperature, and

means operatively associated with said thin shelled members and said roller members for driving said thin shelled members about said roller members in the deformed configuration to advance a support member having unfused electroscopic toner images on said support through the extended nip therebetween to produce at least a partial melting of said toner images on said support.

5. Apparatus to claim 4, said heat generating means including,

. a first source of heat energy supported internally of said first thin shelled member adapted when energized to heat said first thin shelled member to an elevated temperature,

a second source of heat energy supported internally of said second thin shelled member adapted when energized to heat said second thin shelled member to an elevated temperature, and

means responsive to the temperature of said thin shelled members for controlling the energization of said sources of heat energy.

6. Apparatus according to claim 5 further including,

applicator means for applying a quantity of ofiset 10 preventing material to the surface of said thin shelled members.

References Cited UNITED STATES PATENTS 3,498,592 3/1970 Moser et a1. 263-6E 3,539,161 11/ 1970 Byrne 2636 E 3,578,797 5/1971 Hodges 263--6 E X 0 3,584,195 6/1971 Vince 263-6 EX CHARLES J. MYHRE, Primary Examiner

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