US2807703A

US2807703A - Xerographic image fixing apparatus

Info

Publication number: US2807703A
Application number: US591466A
Authority: US
Inventors: Jr David D Roshon
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1956-06-14
Filing date: 1956-06-14
Publication date: 1957-09-24
Anticipated expiration: 1974-09-24
Also published as: BE558347A; FR1187000A; DE1063029B

Description

p 1957 D. D. ROSHON, JR 2,807,703

XEROGRAPHIC IMAGE FIXING APPARATUS Filed June 14, 1956 3 Sheets-Sheet 1 FIG; L

FIG; 2

UNFIXED TONERIMAGEX 14 13 RECORD CARD lNFRA-RED SOURCE I 1 GLAZING ACTION 16 I l *1 UNFIXED TONER IMAGE 13 RECORD :5- CARD I 3 INVENTOR.

DAVID D. ROSHON,.JR.

A 7' TORNEY p 1957 D. D. ROSHON, JR 2,807,703

XEROGRAPHIC IMAGE FIXING APPARATUS Filed June 14, 1956 5 Sheets-Sheet 2' R1 NE Sept. 24, 1957 D. D. ROSHON, JR

XEROGRAPHIC IMAGE FIXING APPARATUS 5 Sheets-Sheet 5 Filed June 14, 1956 United States Patent XEROGRAPHIC EMAGE FIXING APPARATUS David D. Roshon, In, Endicott, N. Y., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application June 14, 1956, Serial No. 591,466

4 Claims. (Cl. 219-45) This invention relates to xerographic record card printers in general, and in particular to the apparatus thereof for permanently affixing electroscopic toner images onto their respective print receiving record cards.

The present invention pertains to ways and means of selectively heating the electroscopic toner material depicting an image on a record card so as to raise the temperature of the toner to its fusing point while leaving the record card per se at a temperature sufficiently below the fusing point of the toner to be below the boiling point of water. As will be described in detail hereinafter, this is accomplished with the present invention by directing high intensity radiant energy, e. g., infrared radiation for a short period, onto the record card surface whereon the electroscopic toner image is supported, and by also preventing the transfer of heat energy from any source thereof by either conduction or convection so as to maintain the record card per so at a temperature below the boiling point of the moisture in the record card material. Thus, since the toner material has a larger radiant energy absorption coefficient than does the record card, the conversion of radiant energy to heat energy will for all practical purposes take place in the electroscopic toner image.

It might be well to bring out at the very outset of this specification that as used herein, the term electroscopic toner materia is to be understood as meaning any pigmented solid' matter, such as a finely divided powder for example, which may be used in printing. This would also include fluid-suspended particles which require to be fused to a print receiving material in order to be permanently aflixed thereto. Thus, for instance, electroscopic toner material would include thermoplastic compositions of the type described in the S. Solar copending U. S. patent application, Serial No. 516,314, that was filed on June 17, 1955, as well as the smoke particles referred to in the Huebner Patent No. 2,691,345 which issued on October 12, 1954. Furthermore, this would include so -called embossing powder into which has been mixed a dye. In addition to the foregoing, the term xerographic printing should be understood as meaning dry printing as distinguished from wet printing which is accomplished with fluid consistency materials, such as ordinary inks for example. Accordingly, xerographic, or dry, printing would require solid, or electroscopic toner image defining materials of the aforementioned type. This would also include the fluid-suspended pigment particles which require something more to he done to them, i. e., fusing, other than simply appiying the same to the surface of a print receiving material in order to produce a permanent imprint.

Heretofore, electroscopic toner images have been permanently afiixed to their respective image supporting, or print receiving, materials by any one of several known methods which, in general terms, include thefixing of toner images by heat, pressure and chemical solvent. These prior methods taken singly or in combination were found to be inadequate, however, when the so-called xerographic card printer was in the process of being developed. This machine which is disclosed and claimed in the copending U. S. patent application, Serial No. 556,176, filed by M. J. Kelly on December 29, 1955, is now known commerically as the IBM Type 938 Electrostatic Card Printer, and is one where electroscopic toner images are first caused to appear on the surface of an electrostatically charged electrophotographic drum, and are then transferred, one by one, onto related print receiving records such as well-known IBM record cards, for example. Subsequently, the toner images are permanently affixed to their respective print receiving records.

Each of the afore-mentioned prior methods of fixing electroscopic toner images, was found to be unsatisfactory for use in the card printer as stated hereinbefore for a variety of reasons. For example, pressure alone as ac complished by apparatus disclosed in the Hix et a1. copending U. S. patent application, Serial No. 419,392, filed on March 29, 1954, would not afrix electroscopic toner images onto their respective record cards satisfactorily. This was found to be the case even when the pressure applied was great enough (a) to cause severe record card dimensional changes such as in the record card thickness for instance, and (b) to adversely affect such record card parameters as surface friction, edge durability, stiffness, etc. On the other hand, heat fixing as performed heretofore in the Carlson Patent No. 2,357,809 which issued on September 12, 1944, for instance, was found to cause such a high quantity of moisture to be driven from each of the record cards as to cause severe changes in card length, card Width, etc., which, in turn, effected a severe record card warp and curl. As a result, the record cards were unacceptable for subsequent business machine use. The chemical fixing method which includes subjecting the toner images to the vapors of a chemical solvent therefor (see the Greaves Patent No. 2,726,166 which issued on Decemher 6, 1955), was found to have the advantage that it neither changed the various record card dimensions nor did it materially affect the moisture content of the record cards. As a result, the record card warping and curiing caused by the aforesaid oven-type heat fixing was avoided. The chemical fixing method has always been very undesirable from an engineering design standpoint, however, in view of the comparatively large amount of equipment needed. This should be evident from an examination of Fig. 1 in the afore-mentioned copending Kelly application. In addition thereto, the necessity of replacing the chemical solvent periodically is an equally undesirable task. Furthermore, there is always a possible toxic effect to machine operators and other personnel in the vicinity of the machine should a toxic chemical solvent be used.

It is therefore a primary object of this invention to provide an improved apparatus for permanently aflixing an electroscopic toner image onto a print receiving material.

Another object of this invention is to provide an apparatus for use in a high speed xerographic printer, whereby electroscopic toner images on record cards are permanently heat-fixed thereto without causing the record cards to warp.

Another object of this invention is to provide an electroscopic toner heat fixing apparatus forselectively raising the temperature of the toner image material to its fusing point while leaving the temperature of the toner image supporting material per se below the toner fusing temperature.

In line with the foregoing, another object of this invention is to provide an electroscopic toner heat fixing apparatus which is capable of fusing the image-depicting toner material on a record card while leaving a substantial portion of the original moisture in the record card so as not to cause the record card to warp.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a perspective view of a warped record card such as could be used to support an electroscopic toner image.

Figs. 2 and 3 are each views of a record card with a toner image thereon.

Fig. 4 is a schematic diagram of a repeatable flash tube radiant energy heat fixing circuit and apparatus.

Fig. 5 is an isometric view, with parts in section, of the electrostatic card printer radiant energy heat fixing device.

Fig. 6 is a somewhat diagrammatic view of the radiant energy heat fixing station used in the afore-mentioned electrostatic card printer which is described in the aforecited copending Kelly application.

Fig. 7 is a diagrammatic view of a radiant energy line focusing embodiment of the present invention.

As the description advances, the present invention will be described in detail. In order to avoid any unnecessary complexity as well as undue prolixity, this invention will be described in the light of well-known xerographic printers whereby a latent electrostatic image is developed by depositing on the surface of the plate wherein the image is stored electrically charged thermoplastic toner particles. The developed image as defined by these pigmented particles is then transferred onto a print receiving record card which has a lower infrared radiation absorption coefficient than does the toner image. Finally, the toner image is permanently affixed to its record card by the present invention.

ELECTROSCOPIC TONER U. S. patent application, Serial No. 516,314, filed by S.

Solar on June 17, 1955. Furthermore, a variety of elec troscopic toner compositions are available commercially from the Haloid Company of Rochester, New York. Two of these compositions which fuse at approximately 250 to 300 F., are known by the trademarks EXT-2 and EXT-75.

Hence, when the unfixed toner image is exposed to heat of sufficient intensity to fuse at least one constituent of the said toner image, enough of the toner will become molten and dissolve so that the solution thereof will penetrate into the fibers of the print receiving material. Upon subsequent cooling, the toner image will become indelibly fixed in the print receiving material.

RECORD CARDS AND WARPING THEREOF Record cards of the type used in connection with all record card controlled business machines must be kept within critical limits to assure good machine operation. That is, the physical dimensions of each record card. must be kept within very close tolerances. in addition thereto, the continuance of good machine operations, i. e., the avoidance of card jams, etc., makes it extremely important that these record cards be kept from warping or curling.

It should be clear at this point in the specification that record card distortion was the problem that existed prior to the time of the present invention whenever toner images were heat fixed onto their respective record cards. This was for the reason indicated previously that the oventype heat which was required to satisfactorily fix electroscopic toner images onto the record cards, would also cause severe moisture loss therefrom. This, of course, would result in card shrinkage both in length and in width. Thus, cards which were so heated were subject to severe warping and curling.

An acceptable record card warp test requires that at least three measurements be taken. Referring to Fig. 1, these include the diagonal warp measurement 10, the rightend top-bottom warp measurement 11, and the lower-edge top-bottom warp measurement 12. And, so long as none of these measurements exceeds approximately 0.15 inch, the record card 13 is considered to be free of warp or curl. Accordingly, it should be clear from the preceding portion of this specification that the purpose of the present invention is to selectively heat the electroscopic toner image material on a record card, to its fusing point while leaving the record card per se at a temperature suffieiently below the fusing point of toner to avoid record card warping. Stated in another way, the temperature of the record card material on the whole must be maintained below the boiling point of water so that a substantial portion of the original moisture content of a record card is not removed.

HEAT FIXING ELECTROSCOIIC TONER GeneraL-As stated previously, electroscopic toner images have heretofore been heat fixed onto print receiving record cards and webs. However, the heat sources used heretofore have almost without exception been of the variety for producing a so-called oven-heat type of fix. This latter heat fix operation causes the entire record card as Well as the electroscopic toner image supported thereby to be heated to the fusing point of toner by a heat transfer due to conduction and convection.

Radiant energy fixing.-Since electroscopic toner images can be indelibly heat fixed onto a record card by raising the temperature of the toner material to its melting point so that the molten toner will flow into the fibers of the print receiving material, and since the heat is applied to electroscopic toner and the toner supporting record card, it should be clear that the ideal heat fixing arrangement is one for applying heat selectively to only the toner image so as to fuse the same. That is, the record card per se would be at a sufficiently lower temperature than the fusing point of toner so that a substantial portion of the original moisture in the record card would remain therein.

Microscopic examination of the material 14 (Fig. 2) making up a toner image shows that the toner particles prior to fixing are arranged on a record card in more than one layer; and when exposed to the direct radiations 15 of an infrared source for an insufiicient period of time, the toner material 16 (Fig. 3) at only the surface of the image exhibits an extremely rapid glazing action. While in appearance this under-fixed image resembles an indelible toner image, this is not the case, of course, because only the outer layer thereof has been fixed. In fact, if the record card 13 were to be removed at this time from the radiant energy source 15, it should be apparent that the toner image would not be permanently bonded to the record card. Thus, additional heat energy is required after the initial glazing of the uppermost toner layer 16 to cause the toner image to be permanently affixed to its record card. This can be done by providing radiant energy of sutficiently high intensity for a sufficient period of time to fuse all of the material of the toner image. As a result, the layer of toner adjacent the record card 'as well as the toner material intermediate this layer and the topmost layer will be heated to the fusing point by conduction from the said top layer of toner subjected to the radiant energy.

Since present commercially available electroscopic toners are fixable at approximately 250 F. to 300 F.,

the heat fixing process can be associated with the removal of original moisture from the record card. Although for many printing applications this effect may not be too important, it is a most significant one, however, when associated with IBM record cards. As stated previous-1y, this is true because as the card is even momentarily heated to the toner melting point which is considerably above the boiling point of water, the resulting loss of record card moisture will cause card shrinkage and warping.

It is generally recognized that water is for the most part transparent to so-c'alled near infrared radiation, i. e., radiant energy of a wave length under 4 microns. Thus, when radiant energy such as near infrared radiation is used to heat-fix toner images on a record card, the moisture content of the record card will be transparent to this radiant energy. Accordingly, this portion of the radiant energy will not be converted into heat energy. Furthermore, since all toners are pigmented as are the aforementioned commercially available EXT-2 and EXT-75 toners, and since the record cards used as a print receiving material to support the toner images usually have glazed surfaces and are always lighter in color than the toner per se, the infrared radiations for the most part are reflected from the surface of the record cards, but are absorbed and converted into heat energy by the toner material.

TONER IMAGE INFMRED FIXING APPARATUS Three embodiments of toner image infrared radiation heat fixing apparatus will be described. Although these three embodiments differ considerably in structural appearance as well as in their operation, the underlying heat fixing principle thereof is the same. Briefly restated, this principle is one wherein a quantity of infrared radiant energy sufiflcient to fuse toner onto a record card is absorbed and transformed into heat energy by the said toner image. Furthermore, since the transfer of heat energy to the record card by conduction and convection is kept to a negligible rate by suitable means, and since the record card per se is made from paper stock which does not readily absorb radiant energy, the temperature of the record, card per se is kept at a lower value than the boiling point of water which is below the fusing point of toner. Accordingly, a substantial portion of the original record card moisture remains therein, whereby record card warping and curling is avoided.

Embodiment 1.-The embodiment shown in Fig. 6 is disclosed and claimed in the copending U. S. patent application, Serial No. 591,495, which was filed on June 14, 1956, by R. C. Allen et al. As brought out in this copending application, this apparatus is intended for use in the afore-mentioned copending Kelly application xerographic card printer. The record cards onto which the electroscopic toner images are transferred from the electrophotographic drum (not shown) of this printer, are moved past the toner image fixing station apparatus by feed rollers IMP-109 (Fig. 6). This fixing apparatus includes a plurality of infrared radiant energy generating lamps 416 which are so arranged as to span the entire length of a toner image on a record card. Furthermore, these lamps are energized electrically so that the temperature at the surface of each lamp is in the range of 2000 F. As a result, heat extracting, or so-called fixing station cooling, means are provided in order to avoid heating the toner image bearing record cards per se as they are moved past lamps 416, by the transfer of heat from these lamps due to conduction and convection, whereby the record cards would be caused to warp. With the apparatus shown in Fig. 6, the heat extracting means include a blower (not shown) operated by a suitable drive for moving a stream of air from an air intake opening 417 through various passages depicted by the arrows shown around the lamps 416 as well as

passages

418 and 419, to the air exhaust opening 421. This same blower is connected to the air flow tube 422 to aid in the withdrawal of heated air from around the card holding fins 423 (see also Fig. 5) at the toner image fixing station. The structure identified by reference numeral 475 includes an inverted V-shaped trough housing 480 within which there is located a hollow tube 424 having spaced fins 423 extending therefrom. This housing is completely enclosed except for the side thereof facing the lamps 416. As is brought out in the aforementioned copending Allen et al. application, the fins 423 are provided to hold each moving record card at a fixed distance from the surface of the lamps 416 by the negative pressure at the open slits in the fins.

Thus, as each record card bearing a toner image, is moved past the infrared radiation source lamps 416, a suflicient quantity of radiant energy is absorbed by the toner image to provide the proper amount of heat energy to fuse the said image. Since a negligible amount of radiant energy is absorbed by the record card per se, and since the heat transferred to the said card by conduction and convection is also negligible, the temperature of the record card is kept at a value sufficiently below the fusing point of toner, i. e., below the boiling point of water, to leave a substantial portion of the original moisture in the record card.

Embodiment 2.-The arrangement shown in Fig. 4 cmploys a repeating flash tube for heat fixing the toner image on a record card without causing the card to warp, by the radiant energy produced during a single tube flash. Referring to Fig. 4, a record card 13 having a toner image 14 thereon, is moved from hopper 7'0 by feed rollers 71 74 past flash tube 75 into stacker 80. There is interposed between the record card 13 and the said flash tube, which might be a commercially available General Electric Company Type FT-2l4 or Type FT-403 flash tube, a heat transfer barrier 76 for preventing heat transfer by conduction and convection from the flash tube 75 onto the record card 13. The aforesaid barrier 76 must, of course, be completely transparent to the infrared radiations emitted from the flash tube. Hence, barrier 76 could be a water filled glass jacket.

The flash tube 75 is caused to be energized whenever the switch 77 is closed. Hence, it should be apparent that a fully automatic flash fixing apparatus is withinthe scope of the present invention by providing card detecting means to operate switch 77. The card detecting means might be either a photoelectric sensing arrangement or a mechanically operated card lever 78 arrangement, as has been used previously in record card controlled machines, to cause switch 79 to operate whenever a record card is opposite flash tube '75. Switch 79, of course, would be connected in parallel circuit to switch 77.

The circuit diagram shown in Fig. 4 provides a flash tube operating potential of approximately 2000 volts. The primary winding of transformer $1 may be connected to a conventional 110 volt A. C. power supply 90, whereupon approximately 1400 volts will be impressed across the secondary winding of transformer 91. Thus, the peak voltage value that is applied across condenser C1 is in the neighborhood of 2000 volts, so that consequent upon the operation of switch 77, gas tube G1, preferably a Type 2050 thyratron tube, is caused to ignite and flash tube 75 is energized.

It is recognized that repetitive high speed flash tube operation, e. g., up to 10,000 flashes per second, is possible with certain known flash tube circuits. Most flash tubes presently available commercially may be flashed at repetitive rates up to about flashes per second when forced air cooling is used. Hence, it can be seen that with a high speed repetitive operation radiant energy generating flash tube, it should be possible to heat-fix the toner images 14 on each of a plurality of successively arranged record cards 13 caused to be advanced past the flash tube 75 at a high rate of speed.

Embodiment 3.Referring to Fig. 7, a record card 13 having a toner image 14 thereon, is moved by feed rollers fill--84 past a focusing reflective housing 35 having a tubular lamp 86 therein. The lamp 86 has a linear filament therein (not shown) which extends the complete length of the toner image. The housing 85 and the lamp 86 are so arranged that the radiant energy emitted from the lamp is focused in a line corresponding to the lamp filament just above the card feed path and directly onto the toner image 14-. Thus, the radiant energy is so focused and concentrated on the toner image, it is converted into heat energy for fusing the said image. If necessary, the housing 85 can be cooled by external means (not shown) so as to keep the transfer of heat energy therefrom by conduction and convection to a bare minimum.

SUMMARY Toner heat fixing methods known heretofore achieve the required liquid bonding between the electroscopic toner and the print receiving material to produce an indelibly fixed imprint. However, with the fixing methods known heretofore, i. e., the oven-type heating methods, the heat transfer by conduction and convection also causes a temperature rise in the print receiving material which corresponds to the temperature rise of the toner image. Such heating of the print receiving material, e. g., a record card, results in an excessive loss of moisture therefrom so as to cause card warping and curling. This can be avoided by the present invention which restricts the transfer of heat energy to the electroscopic toner by causing only infrared radiations to impinge upon the toner image and its supporting print receiving material. This limitation of the energy transfer process to radiant energ alone permits selective toner image heating by employing an electroscopic toner material which has a larger infrared radiant energy absorption coeficient than does the print receiving material.

In order to achieve successful selective heating, the transfer of energy must be accomplished during a short time interval. This can be done only by using a high intensity radiant energy source. Short duration pulses of radiant energy must be employed because (a) the toner image is directly in contact with the print receiving material whereupon heat can be transferred to the material rapidly by conduction, and (b) the toner which is at a higher temperature than the print receiving material will have a greater emissivity than the said material. Thus, in amplification of the foregoing, heat energy lost by the electroscopic toner image to the print receiving material simply means that more total energy must be applied so as to fix the toner image, with the result that more energy will be absorbed by the print receiving material before the toner can reach its fusing point. Consequently, the print receiving material will reach a higher temperature than it would have had the toner heat fixing process been carried out rapidly. Furthermore, with toner which has a high radiant energy absorption coefficient, there will be a greater re-radiation of energy which will cause a serious reduction in the degree of selective toner image heating.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to several preferred embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated in their operation may be made by those skilled in the art, without departing from the spirit of the invention. it is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

l. A device for use in a xerographic printer to permanently affix an electroscopic toner image onto a record card for supporting said image comprising electrical means effective when energized to emit infrared radiations, means for moving the record card past said electrical means, and record card detecting means for controlling the energization of said electrical means consequent upon the record card being opposite said electrical means, so that there are applied to the electroscopic toner image infrared radiations of a magnitude and for a time duration sufficient to fuse said electroscopic toner image but yet insuflicient to cause the record card to warp.

2. A device for use in a xerographic printer to permanently affix electroscopic toner images onto record cards for supporting respective ones of said images, comprising a normally inoperative source of infrared radiant energy, means for feeding record cards one by one in a manner such that said images are moved past said source, electrical means adapted to energize said source so that the intensity of infrared radiant energy emitted therefrom is suificient to fuse an electroscopic toner image, circuit means for operatively connecting said radiant energy source to said electrical means for a time duration sufficient to fuse an electroscopic toner image but yet insuflicient to cause the image supporting record card to warp, and card detecting means for rendering said circuit means operated once for each record card as the same is moved past said source of radiant energy.

3. A device for use in a xerographic printer to permanently aflix electroscopic toner images onto record cards for supporting respective ones of said images comprising a record card hopper, a record card stacker, means for feeding record cards one by one from said hopper to said stacker, a normally inoperative source of infrared radiant energy, electrical means adapted to energize said source so that the intensity of infrared radiant energy emitted therefrom is sufficient to fuse an electroscopic toner image, circuit means adapted to operatively connect said source to said electrical means for a time duration sufficient to fuse the electroscopic toner image but yet insufficient to cause the record card to warp, card detecting means operative in time relation with said feeding means and in response to a record card opposite said source, for rendering said circuit means operated once for each record card as the same is moved from said hopper to said stacker, and means for focusing infrared radiant energy from said source onto the electroscopic toner image of a moving record card.

4. A device for use in a xerographic printer to permanently affix an electroscopic toner image onto a record card for supporting said image comprising a source of heat energy for directing infrared radiations therefrom to the aforesaid toner image of a magnitude and for a time duration sufiicient to raise the temperature of the electroscopic toner to the fusing point thereof while leaving the temperature of the record card at a temperature below the fusing point of electroscopic toner, and other means for preventing the transfer of heat energy from said source by conduction or convection so as to main tain the record card at a temperature sumciently below the fusing point of electroscopic toner to prevent warping of the record card.

References Cited in the file of this patent UNITED STATES PATENTS 1,575,366 Johnson Mar. 2, 1926 2,448,830 Robbins et al. Sept. 7, 1948 2,551,582 Carlson May 8, 1951 2,573,881 Walkup Nov. 6, 1951 2,701,765 Codichini et al. Feb. 8, 1955 2,706,231 Tyler et al. Apr. 12, 1955