US3788873A - Fixing method utilizing intermediate heat transfer - Google Patents

Abstract

A METHOD FOR AFFIXING ELECTROSCOPIC TONER IMAGES ONTO A SUPPORT BY UTILIZING AN INTERMEDIARY AS A HEAT TRANSFER MEDIUM. A QUANTITY OF PARTICULATE MATERIAL IS HEATED TO A TEMPERATURE SUFFICIENT TO PRODUCE AT LEAST A PARTIAL MELTING OF THE PARTICULAR TONER MATERIAL TO BE FUSED AND THE TONER MATERIAL ON THE SUPPORT IS THEN CONTACTED WITH THE HEATED PARTICULATE MATERIAL TO INDUCE A TRANSFER OF THE THERMAL

ENERGY IN THE PARTICULATE MATERIAL TO THE TONER MATERIAL ON THE SUPPORT.

Description

R. H. DETIG 3,788,873

FIXING METHOD UTILIZING INTERMEDIATE HEAT TRANSFER Jan. 29, 1974 Original Filed 001;. so, 1969 FIG 2 V m M mw m "d H m R E O Ry B United States Patent Of 3,788,873 FIXING METHOD UTILIZING INTERMEDIATE HEAT TRANSFER Robert H. Detig, Old Tappan, N.J., assignor to Xerox Corporation, Rochester, NY.

Original application Oct. 30, 1969, Ser. No. 872,558, now Patent No. 3,623,710. Divided and this application Mar. 2, 1971, Ser. No. 120,143

Int. Cl. G03g 13/20, 15/70 US. Cl. 117-21 1 Claim ABSTRACT OF THE DISCLOSURE This application is a divisional application of Ser. No. 872,558 filed Oct. 30, 1969, now US. Pat. 3,623,710.

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

In order to permanently affix an electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the electroscopic toner ma-, terial 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 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 reflecting 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 effect 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 has the effect of evaporating and hence reducing the moisture content normally present within the paper material. This has the adverse eifect 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 problem involved in both electrographically' 3,788,873 Patented Jan. 29, 1974 ICC . formed images as well as xerographically formed images,

has been the obtaining of optimum quality reproductions. In the electrographic recording process wherein latent electrostatic images are deposited directly onto a dielectric material such as paper, which images are thereafter developed with an electroscopic toner material and in the xerographic process wherein a latent electrostatic image is formed on a photoconductive insulating material and then developed with an electroscopic toner material, the developed images thereafter being transferred to a sup- 1 port material such as paper, unwanted, scatter depositions of toner material are obtained in non-image areas of the reproduction. While this difficulty may generally be attributed to deficiencies in the particular development systern, the problem nevertheless exists, resulting in a reproduction having scattered depositions of unwanted toner particles in background of non-image areas along with the wanted larger deposits of toner material in the image areas of the reproduction.

It should therefore be appreciated that prior to fusing,

,all the toner material including that comprising the wanted image areas as Well as the unwanted background areas is loosely held, posing a difiicult problem of selectively removing the unwanted background areas without adversely affecting the Wanted image areas. At the same time, following fusing in the known fusing devices, all the powder has heretofore been permanently aifixed thereto so as to render the problem of selective removal of the background areas impossible. Efforts to remove this unwanted background deposition have heretofore generally been unsuccessful and accordingly the need to effect the elimination thereof has long been recognized.

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

It is a further object of the present invention to provide improved method and apparatus for permanently aflixing electroscopic toner material onto a support member-by the use of heat without adversely affecting the support material.

It 'is still another object of the present invention to provide method and apparatus for producing permanently afiixed electroscopic toner materials on a support in image configuration which are devoid of scattered toner particles in the background non-image areas.

It is still a further object of the present invention to provide method and apparatus for permanently affixing I a loose electroscopic powder image onto a support memberwithout producing an affixation of unwanted scattered particles of developer material in the background nonimage areas.

These and other objects of the invention are attained by heating a quantity of particulate material to a tem- BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic illustration of a system in which. the fusing arrangement as contemplated bythe present i1 1- vention is particularly adapted for use.

3 7, FIG. 2 is an enlarged schematic illustration of ing arrangement'illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention electroscopic toner images which are to be permanently aflixed to a support such as paper are contacted with a quantity of particulate material heated to a temperature suflicient to produce at least a partial melting of the toner material, which upon contact induces a transfer of the thermal energy in the particulate material to the toner material. As at least a partial melting of the toner images is thus produced, themelted toner material flows 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 affixing 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 from which it is fed into a feed apparatus generally 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 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 hearings 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 adaption of the type disclosed in Vyverberg Pat. No. 2,836,725 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 in which a two component developer material 27 which may be of the type disclosed in Walkup Pat. No. 2,63 8,416, 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 powder 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 fus- 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 suitable tensioning rolls 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 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 LMP3, 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 62, 63 and 64. 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 equally applicable to the use of support materials in the form of cut sheet stock.

The fusing apparatus 48 includes a container 67 which is open at the upper end thereof to permit the image bearing support surface 43 carrying the loose powder images 90 thereon into proximity with the fusing apparatus.

A plenum 68 is connected at the bottom of container 67 for a purpose which will hereinafter more readily be apparent. A wall or floor 69 at the bottom of container 67 forms a partition between the container 67 and plenum 68. Floor 69 includes a plurality of openings 69' therein which permit the passage of a pressurized gas from plenum 68 through openings 69' into container 67. It should be noted however, that the size of openings 69' in FIGS. 1 and 2 of the drawings have been exaggerated for purposes of clarity and in actual practice are of a quite small dimension of a microporosity nature.

A heating element 70 is located within container 67 adjacent wall 69. Heating element 70 may comprise a resistance heating element of the type which is generally well known. That is, that type of heating element which produces a generation of heat therefrom upon the passage of an electrical current through suitable conductors. Accordingly, heating element 70 is electrically connected to a source of electrical potential which when activated produces a heating of element 70 within container 67. Suitable control means may be provided in conjunction with heating element 70 to control or vary the quantity of heat generated by heating element 70.

Fusing apparatus 48 includes a quantity of particulate material '71 which is supported and contained within container 67. Particulate material 71 may comprise a variety of materials which are capable of absorbing and radiating heat. Among those materials which have been found to Work particularly well are sand particles, glass beads, and metal filings or chips. Additional materials in the form of particles which readily absorb and radiate heat may also be utilized in accordance with the present invention.

A brush cleaning arrangement 65 is positioned to contact support material 43 with the images 90 thereon after the support material 43 has passed from fuser 48. Brushes 65 are rotated by means of a motor 66 to remove any of the particulate material 71 which may be loosely adhering to support material 43 after passing through fusing apparatus 48. In addition, brush cleaning arrangement 65 may also remove any loosely adhering toner particles on support 43 as well as any of the particulate material 71 which may inadvertently adhere to the support material 43 after passing through fusing apparatus 48.

In operation, with heating element 70 activated by means of suitable electrical circuitry, heat is generated within container 67 and radiated from heating element 70. As heat is thus generated by heating element 70 the particulate material 71 within container 67 absorbs heat generated by heating element 70. As has been previously mentioned, the quantity of heat generated by heating element 70 may be regulated to the extent so as to impart a sufiicient quantity of heat to the particulate material 71 to at least partially melt the toner material in the image configuration 90 so as to fuse and permanently adhere to support 43.

With particulate material 71 being thus heated by heating element 70, a gas such as air for example, is introduced under pressure into plenum 68. As the pressurized air thus enters plenum 68, it passes through the microporous openings 69' in wall 69 to cause a random movement of the individual particles comprising particulate material 71 throughout the confines of container 67. As movement of the individual particles comprising particulate material 71 is thus introduced, the particulate material 71 assumes the form of a moving fluid within container 67 passing over the exposed surface of support 43 within container 67. As the particulate material 71 is thus fluidized it contacts the surface of web 43 with images 90 thereon to efiect the fusing operation.

In the dominant image areas 90, as the particulate material comes in contact therewith, heat is conducted from the individual particles which comprise particulate mate rial 71, as heat is thus conducted to the toner images a melting of the toner images is produced fusing the toner images onto support 43. In the non-image or background areas, where individual particles of the particulate material 71 contact support 43, little or no heat is conducted to support 43. This is due in large part to the fact that the support itself is a poor heat conductor and because there is an absence of substantial quantities of toner particles thereat. Hence little or no heat is transferred to support 43, in the non-image or background areas.

As particulate material 71 contacts support 43 the particulate material 71 has the additional feature of producing an abrasive action against support 43. This abrasive action exerted by the particulate material 71 against support 43 in the toner image areas 90 has little or no efiect upon removing the toner images 90 from the support 43 because of the good heat transfer characteristics exhibited between the particulate material 71 contacting toner images 90. However, in the non-image areas on support 43, the fluidized particulate material 71 produces a sufiicient abrasive action against support 43 to remove unwanted deposits of toner particles from support 43. This is believed to result from the fact that these small background areas are much less receptive to the absorbency of heat than the more dense image areas 90. However, for whatever reason, the fact remains that the image areas are fused to support 43 whereas toner particles in the nonimage areas remain unfused and are removed from support 43 by the abrasive action of particulate material 71.

In the preferred arrangement, sand granules may comprise the particulate material 71. However, as has been indicated, other suitable materials which readily absorb and conduct heat may also be utilized as the particulate material 71.

It should also be appreciated that a fluidization of the particulate material 71 within container 67 may be produced by means other than through the use of plenum 68 and the introduction of a compressed gas such as air. For example, a sonic transducer may be attached to container 67 which upon activation thereof produces a fluidization of particulate material 71 within container 67 in much the same manner as does the introduction of compressed gases through plenum 68.

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. A method for permanently aflixing electroscopic toner images onto a support comprising,

heating a quantity of solid particulate material in a reservoir to a temperature sufiicient to produce at least a partial melting of the particular toner material to be fused,

producing a fluidization of said heated solid particulate material within said reservoir, and

contacting said fluidized heated solid particulate material with a support having high density deposits of toner particles in image areas and low density unavoidably deposited randomly positioned powder particles in the non-image background areas for a time sufficient to produce at least a partial melting of the high density deposits of toner particles in the image areas.

References Cited UNITED STATES PATENTS 3,567,484 3/1971 White et a1. 117-21 3,383,775 5/1968 Jacob et a1 117-21 3,036,932 5/1962 Masarguppi et a1. 117-1 19.6 3,330,189 7/ 1967 Vil -1.7 3,448,970 6/ 1969 Kolibas 263-6 E 3,264,389 8/ 1966 Sims 117-21 2,726,166 12/ 1955 Greaves 263-6 E 3,623,710 11/1971 Detig 263-6 E WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant Examiner US. Cl. X.R.

117DIG. 6, 119.8; 118-59, 101

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