Electrophotographic printing machine

Sept. 24, 1957

Filed March 29, 1954

c. j. fitch 2,807,233

ELECTROPHOTOGRAPHIC PRINTING MACHINE

Sheets-Sheet 1

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INVENTOR.

BY

CLYDE J. FITCH attorney

Sept. 24, 1957

Filed March 29, 1954

C. J. FITCH

ELECTROPHOTOGRAPHIC PRINTING MACHINE

2,807,233

Sheets-Sheet 2

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INVENTOR.

CLYDE J. FITCH

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ATTORNEY

Sept. 24, 1957

c. j. fitch 2,807,233

ELECTROPHOTOGRAPHIC PRINTING MACHINE

Filed March 29, 1954

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Sheets-Sheet 3

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ATTORNEY

United States Patent Office

2,807,233

ELECTROPHOTOGRAPHIC PRINTING MACHINE

Clyde J. Fitch, Endicott, N. Y„ assignor to International

Business Machines Corporation, New York N Y a corporation of New York ’ ’’

Application March 29,1954, Serial No. 419,314

Claims. (Cl. 118—637)

This invention relates to electric printers in general and to the print transfer apparatus thereof in particular

In keeping with electric printers in general, and with electrophotographic printers in particular, the embodiment of this invention pertains to apparatus for effecting a transfer of a visible image from an image carrying member, to a print receiving material, such as a web of paper for example, and has for its purpose to provide an improved image, or print, transfer apparatus by which selective electric printing may be effected.

To amplify the foregoing, the embodiment of this invention pertains to so-called xerographic machines capable of making a duplicate of information appearing on source records, such as record cards for example, on a print receiving strip by means of a transfer or printing process. As is well known to persons familiar with the electrophotographic printing art, xerography is a term applied to a printing process in which electrostatic latent images are rendered visible by a suitable electrically charged toner powder, the resulting powder image thereafter being transferred and fixed to a print receiving mdiviTcii·

Another broad object of this invention is to provide a selective printing electric printer whereby only selected information appearing at a certain place, or places on a source record, is transferred from the source record onto a copy record.

Another object of this invention is to provide an electrophotographic printer having an improved image .^apparatus associated therewith for transferring y electric power only select electrically charged powder images.

More specifically, another object of this invention is to provide a xerographic printer having an image transrer apparatus associated therewith which is capabfe of SS&amp;SS* “ *·*· ^,r”^{!ter or} vX7^{S a}.1^lmage touwfer apparatus which requires lower voltages than used heretofore.

thXnn ^{of the} invention will be pointed out in the ° ^{10WlnS descn},^{pflon a}nd claims and illustrated in the accompanying drawings, which disclose, by way of whidi^Phas^thh^ee^PnnC1Pf^le °^f₁^{the invention a}nd the best m^de,

Fig. 1 IS a somewhat diagrammatic view of an electrophotographic printer utilizing a shifting transfer roller apparatus at the image transfer station.

Fig. 2 is a somewhat diagrammatic view of an electrovoltages than used heretofore.

2,807,233

Patented Sept. 24, 1957 photographic printer utilizing an electric pulse controlled transfer apparatus at the image transfer station.

Fig. 3 is a flow diagram depicting generally the operations required in order to place the image of source record information upon a print receiving a copy record.

Fig. 4 is a somewhat diagrammatic view of the transplane^^of ^associated mechanism taken along the

Fig. 5 is a somewhat diagrammatic view of the transer apparatus and associated mechanism taken along the plane 5—5 of Fig. 2.

Referring to Fig. 1, record cards 20 to be operated on are stacked m hopper 21, and are fed, one by one ^{by a c}°^nventlonal picker (not shown) of the type in Patent No. 2,448 830 issued to J. J. Robbins et al^each card cycle out of card hopper 21 to stacker 22. Successive pairs of feed rolls 23 and 24 cause cards 20 to be advanced during successive card cycles past the optical projector apparatus 25. ^p

26^Awb.&gt;h^atA ^{25 includes a sin}S^le W ray projector 26 which throws a concentrated band of parallel light ber^S27^POnT^{the COastricted center} &amp; the aperture in mem5®^r.²⁷· Inasmuch as the reflecting surface of a mirror 28 is over the aperture of member 27, the light band is 29^UXn°thT^n8e “^{POn th}f ^{SUrfaCe of xer}°S^raphic drum andXrroS. “θ ^{PreSent betWeen member 27}.As is shown in Fig. 3, each of the record cards 20 is shown to include printed information which is represented and identified by block 30. Due to the fact that the surface of each card 20 has a light rejecting property as the cards are fed past projector 25 (see also Fig 1)’ and between member 27 and mirror 28, light rays’ are directed onto the surface of drum 29 except when the fiedbv^Sth^nC1Uf^{ed With}“ ^{the printed} information identified by the reference numeral 30, are not brought into alignment with the aperture of member 27. It may tight X ^{hM hat apparatus 25} “dudes a conventional light scanning means for transferring the image of the £Z2»?ⁿdXS^or“^,,i‘^&gt;n ““«’ tat.ion in a counterclockwise direction, said shaft 31 being driven by an electric motor 34 (^ee also S 4) CTltoder^P« ^dt^{m 29}.^ln.^cIudes an electrically conducting cylinder 35 and a printing element, or plate 36 in the lav™ °^f ~?.^el j^CtncaJ^Iy insulating or non-conducting image metal οΓΧΧ™ a T^{Wd by a sheet of any} flexible « a conductive material 37 that enables its eing flexed around and attached to the cylinder 35 the sheet 37 being secured to the cylinder in any of the cS iffig X^WS ί ^{attaChing a ΡΓίηώ}* ^pla* ‘ο a suJpoX It k n^{h d} ’ ^aSK^{by means of suitabIe} clamping devices It is necessary however, that the backing sheet 37 of the th^eM^la?^{erplate 36 is} in good electrical contact with the electrically grounded drum shaft 31. The electrically as plate 36 whJh^tOCOndactlve insulating material, such XI κ ⁶’ Y^{h h may have a} Powder image produced thereon by electrostatic charging, exposure and powder v lopment, after which the powder image can be made thl / Permanent print image by transferring and fixing the developed powder image onto a print receiving material such as paper strip, or web, 38. &amp;

2.807,233 ⁴ tached to cam follower arms 46 which are also fixed to shaft 47 whereon cam follower roller 48 is mounted. Web feed control arms 49 having feed roller 50 attached thereto are also fixed to shaft 47 so that arms 45, 46 and 49 act in unison. The afore-mentioned arms are pivotally mounted upon shaft 54, the said shaft having idler roller 55 rotatably mounted thereon, and being fixed in printing machine support frames, such as frame 53 for example. As is shown in Fig. 1, web 38 is fed from reel 56 past drag rollers 57, around idler roller 55 and transfer roller 40, between fixing rollers 58, feed rollers 50 and 59, and rollers 60, to reel 61.

In order to produce a permanent image, it is necessary to fix onto the print receiving material, such as web 38 15 for example, those powder images that are transferred thereto. One means for fixing powder images utilizes a line pressure such as is afforded by the pressure fixing rolls 58 (Fig. 1) and 158 (Fig. 2). A sufficient line pressure for example 500 pounds per lineal meh of con20 tact, will cause the toner powder to flow into the fibers of the web material. An oil pad 68 (Fig. 1) and 168 (Fig. 2) is provided to remove any excess powder which will cling to the upper fixing roller.

As long as powder images are to be transferred from 25 plate 36 onto web 38, the generally T-shaped unit comprised of arms 45, 46 and 49, will be positioned under the urging of springs 43 so that transfer roller 40 causes web 38 to engage plate 36. In addition, this generally T-shaped unit is positioned so that roller 50 maintains 30 the web in contact with continuously rotating drive roller 59 in order to cause the web to advance. It is necessaiy to point out that roller 59 is spring-biased in an upward direction so that there is assurance of good contact, between transfer roller 40 and drum 29 during the periods that rollers 50 and 59 are in contact. In order to disable printing, i. e., to prevent the transfer of charged powder images, cam 62 is rotated so as to engage, roller 48 which, in turn, causes arms 45, 46 and 49 to pivot in a counterclockwise direction. Hence, transfer roller 40 will be moved away from drum 29, and web feed roller 50 will be moved away from drive roller 59, to thereby disable the friction-drive applied to web 38 by rollers 50 and 59. In addition, transfer roller 40 is moved a sufficient distance to carry the web into engagement with braking member 65 whereby web 38 is stopped immedi⁴⁵ ately by the braking action.

In order to remove any toner powder which remains on the surface of plate 36 prior to the incremental areas thereof becoming charged again by ion-source unit 32, a rotating plush roller 66 is provided. This roller is po5θ sitioned within a housing 67 for retaining the powder removed by the counterclockwise rotating action of the roller, from the xerographic drum plate 36.

A comparison of the electrophotographic printers shown in Figs. 1 and 2 will reveal a similarity between ³³ many elements thereof. Hence, for purposes of clarity and simplicity, those elements in the printer of Fig. 2 which are similar to corresponding elements in the printer shown in Fig. 1, will be identified by a 100 series reference numeral corresponding to the reference numeral used m ⁶⁰ Fig. 1. That is, for example, the xerographic drum of the printer shown in Fig. 1, is identified by the reference numeral 29, and the xerographic drum of the printer shown in Fig. 2 is identified by the reference numeral 129.

Referring to Fig. 2, record cards 120 to be operated on ⁶⁵ are stacked in hopper 121, and are fed, one by one, each card cycle out of card hopper 121 to stacker 122. Successive pairs of feed rolls 123 and 124 cause the record cards to be advanced during successive card cycles past the optical projector apparatus 125. .

Apparatus 125 includes a single light ray projector 126 for directing a band of light rays upon the constricted center of the aperture in member 127, to thereby effect a conventional light scanning operation whereby the image of the printed information on the record card is trans75 ferred to the surface of the xerographic drum 129.

Ο

With the feeding of record cards 20 from hopper 21 to stacker 22, xerographic drum 29 is caused to rotate at a speed which is correlated to the record card feed speed, by means of drive shaft 31. As successive incremental areas of the light sensitive photoconductive plate 36 are . moved past ion-producing unit 32, the aforesaid plate is electrostatically charged by the ion-producing source. Carlson Patent No. 2,588,699 may be referred to for a complete showing and description of the afore-mentioned . electrophotographic charging apparatus.

Consequent upon the exposure of the surface of plate 36 to the image of a record card 20, said image being caused by the light rays which are directed from projector apparatus 25, those electrically charged incremental areas of plate 36 onto which light rays are directed, are discharged, and those areas not illuminated by light rays remain charged. This, of course, is for the reason that plate 36 is a photoconductive insulating material which is in electrical contact with conductive backing sheet 37, said sheet 37 being electrically connected to grounded shaft 31. Hence, after photoconductive plate 36 is exposed to the light image of a record card, an electrostatic latent image of the record card will remain on plate 36, this electrostatic latent image being one wherein the “dark” characters within printed information image areas identified by reference numeral 30 (Fig. 3) cause charged characters within image areas identified by reference numeral 30« which correspond to the afore-mentioned dark characters, and wherein the light image areas corresponding to the record card surface are no longer charged. .

Continued rotation of the xerographic drum in a counterclockwise direction causes the image portions 30« of plate 36 (Fig. 3) to be moved into developing chamber 39 A similar chamber is utilized in the apparatus of Schaffiert Patent No. 2,576,047. The electrically charged toner powder in chamber 39 will flow onto plate 36 and over the electrostatic latent image, and will move downwardly thereover due to gravity in a continuous stream, thus being evenly distributed over the image layer. The surplus toner powder which does not adhere to the electrostatic latent image formed on plate 36, falls into a receiving receptacle within chamber 39 so as to cause the powder to be completely retained within the chamber housing. The powder image that is formed on the image plate 36 visibly defines the electrostatic latent image, i. e., the powder will cling only to the “dark” printed information image areas having an electric charge thereThe powder in chamber 39 may be a finely powdered dye, pigment, carbon or other black or colored substance, or in some cases a white powder such as zinc oxide. A suitable electroscopic developer powder, or toner, is described in Copley Patent No. 2,659,670

Continued rotation of drum 29 causes the powder image on plate 36 to move out of chamber 39 and into the transfer, or printing, station having transfer roller 40 thereat. The transfer roller comprises an inner-metallic portion 41 and an outer portion 42 of very resilient or yielding material having a high electrical resistance, as for example, a layer of soft semi-conducting rubber. The transfer roller requires a resilient outer portion so as to compensate for mechanical irregularities of the xerographic drum surface, and to prevent mechanical damage to the photoconductive surface thereof. The conductive rubber is preferably a very poor conductor of electricity, and may have an electrical resistivity of approximately 10⁶ ohms per cubic centimeter. The resistance value is not too critical and it may be greater than the aforementioned value. However, the resistance value is preferably not less than 10^s ohms per cubic centimeter.

Transfer roller 40 is biased by springs 43 (see also Fie. 4) in the direction of photoconductive plate 36 so that web 38 is sandwiched therebetween. The transfer roller is supported by the shaft 44 thereof which, in turn, is journaled in arms 45. The latter arms are each at40

2,807,233 _v 5 . Xerographic drum 129 is mounted on a shaft 131 which is driven by an electric motor 134 (see also Fig. 5) in a counterclockwise direction. The aforesaid drum includes ttoe ¹nh^^1CaU^^C°°^dUC-^{ting Cylinder 135 and a sen}sie photoconductive insulating printing plate 136. This mtHn^1Sf^{Camed by a Sheet of any flexible} metal or other conductive material 137 that enables its being flexed around and attached to the cylinder 135.

With the feeding of record cards from hopper 121 bv shaft 31 ^lhe T??· ^{drUm is Caused to rotate}JJr/¹ X^{a Speed whlch ls} correlated to the record caid feed speed As successive incremental areas of the hjit sensitive photoconductive plate 136 are moved past an Η.?-^{10 17}°’ X® πί⁰¹⁶⁸³¹'¹ P^Iate is caused to have an electrical, charge placed thereon. The charging roller tfonto? 7 ^lnner'^m®‘^anic P^ortion 171 and an outer portion172 of very resilient or yielding material having a high duetto⁰³¹ X^1Stanae’ ^{as for} example, a layer of soft condaetmg rubber Inasmuch as this charging roller is sub‘-ηίιηΐΐν similar to the upper cylindrical member or 20 roll used in the electrical printing apparatus described to rt k°^Pe|' f^at/^{nt N}°- ²’⁵²⁰’⁵⁰⁴’ reference may be had to this patent for more detailed information.

^{Upt&gt;n the ex}P^osur^e of the surface of plate lAtnn ™^age °^f/ ^reC°^{rd card 120}’ ^an electrostatic 25 and fn h²⁶ ’^{S CaUSed t0} -^{remain there0D in} ‘he manner, rowtnn X ™^asons’ mentioned hereinbefore. Continued lotation of the xerographic drum 129 in a counterclockwise direction causes the electrostatic latent image-exposed norfions of plate 136 to be moved into developing 30 chamber 139 wherein the electrically charged tone! Powdei is permitted to flow onto plate 136 and over the electrostatic latent image. As a result thereof, a powder image which visibly defines the electrostatic latent image is formed on tne surface of plate 136. Further rotation 35 °f_a(JX°^2raphlc drum causes the powder image on Plate 136 to· move out of chamber 139 and into the transter, or printing, station having transfer cylinder 175 tnereat.

Transfer cylinder 175 includes end wheels 176 (see 40 _:also Fig. 5) and 177, and a conductive roller 178 The diameter of roller 178 is smaller than the diameters of end wheels 176 and 177 by an amount such that a gap of approximately 0.002 inches exists between plate 136 “Ud web 138 In order that the web does not rub against the drum surface during print suppress time, it is necesX ^dlameter of roller 178 is smaller than the diameter of the end wheels by an amount greater than twice the thickness of the web. Roller 178 is rotatably web ns °” ^{Shaft 179 in Order that} Ceding of thnXl³A^{may be} X^{pped durln}g noil-print periods even hough the xerographic drum is caused to continue rotat- g. The wheels 1/6 and 177 are journaled and arranged m such a manner as to be electrically separated from shaft 79 which, as shown m Fig. 2, is used to supply electric power to conductive roller 178, and the cylinder shaft is biased m a direction towards drum 129 by conventional means so that the end wheels ride on the peripheral surΙ ΐ ^drUm' ^{As 1S shown}&gt; web 138 is fed from reel 156 past drag rollers 157, around rollers 160 and 178 be^{rollers 158}’ ^{feed roIlers 150 and} 159&gt; to’reel 161. in order to remove any toner powder which remains fteSf be^rfr °^{f P}l^a‘^{e 13}Λ ^{ΡΓί0Γ t0 the} -crernema ^{b ra}.^ln? ^char8^ed again by charging cylinder 170, there is provided a rotating plush roller 166. This roller is positioned within a housing 167 for retaining the of fli^erron^m0V_f^{ed by}u,^{the counterclockwi}se rotating action of. the roller, from the xerographic drum plate 136.

..Image transfer apparatus

Referring to Fig. 1, transfer roller 40 is connected to a source of positive potential, e. g., 1000 volts, via wire 70 The ^Υ °^perated r^{VitCh 71 and/or cam conta}cts Cl. The insulating image plate 36, carried by the conductive supporting plate 37, is charged negatively, whereas he 75 toner powder which produces the image by adherence to the plate 36, is charged positively by triboelectric action of the carrier material to which the electroscopic powder particles adhere until separated therefrom by the stronger attrachve force of the negatively charged insulating image Plate 36. Inasmuch as backing sheet 37 is electrically connected to grounded shaft 31, an effective condenser is obtained at the transfer station wherein backing sheet 37 and transfer roller 40 serve as plates thereof, and insulating plate 36 along with web 38 act as the dielectric thereot. , he afore-mentioned positive potential applied to transfer roller 40 is sufficient to cause an electric field to exist between the transfer roller 40 to backing plate 37. This electrostatic field or potential gradient causes the powder adhering to plate 36 to transfer onto web 38 whereafter the transferred powder on web 38 is fixed thereto by pressure rollers 58. In order to disable printing i. e to prevent the transfer of charged powder images,’ cam 62.is rotated so as to engage cam follower roller 48 which, in turn, causes arms 45, 46 and 49 to pivot in a counterclockwise direction. This, as stated previously causes transfer roller 40 to be moved away from xerographic drum 29, and web feed roller 50 to be moved away from drive roller 59. The resulting air space defined by the outer peripheries of plate 36 and transfer roller 40 is sufficient to preclude a transfer of the powder from xerographic drum 29 onto web 38. Inasmuch as the generally upward movement of roller 50 disables the friction-dnve that is applied to web 38 by rollers 50 and 59 and since the shifting of transfer roller 40 is of such a na« -° ^brakeJ^v.^{eb 38 b}y means °f braking member 65, web 38 is stopped immediately.

I ^t0. ^Flg· ².’ ^{a suitable} positive potential, e. g., +2 JOO volts, is applied to the conductive roller 178 of transfer cylinder 175 via line 177. Hence, roller 178 is electrified so that a resulting ion-stream transfers the toner powder adhenng to plate 136 onto web 138, and cXT,^fer °' P°^werj^{s effective} «° long as cam contacts C„ are closed In order to disable the printing operation, • e., the transfer of powder images, cam contacts C2 are roUer 1« ^C°^ncurrently therewith, web feed drive roUer 159 s stopped so as to stop the feeding of web 138 The drag load applied to web 138 by rollers 157 158’ 160, 50 and 159, is sufficient to prevent X^’thS eter ShT “n / ^{(see als}° ^Fig· ^{5) has a diam}eter which is smaller than that of end wheels 176 and 177 cylinder 175 need not be shifted away from xero&lt;ranhic ^d™^I2’ XS iXfSg

It is necessary to point out at this time that the descrinιοη thus far pertains to a positive-to-positive printer However, a reverse image printer may be had simpto bv -mploying a reversal developer powder so that the charge on the powder image is reversed, and by connecting the transfer roller or cylinder to a voltage that is negative mav range ‘ f ° ^{Xerographic drum}- A suitable voltage X. ^{egatlVe 1000 Volts t0 ne2ative} 2000

In order to avoid undue complexity and prolixity a positive-to-positive printer will be described for illusfra five purposes only. This is not to be construed as a limt

Operation ^The. ^prlnted i^nformation which is to be transferred to le print receiving web is identified in the illustrated em“&gt; “ !^y’^ed· b« „_ea „_οχ _M “ records because the double reversal effected bv the nm jecfion of the image onto plate 36 (Fig. 1) for example “ t Sr ssz ir^,er, °' p”*™· ί™»» weo js, causes the information transferred to the web thXXXeorli ^Same °^{rder iS infOTmation} ™

2,807,233 plate 136 so that either the web or the plate may be stopped during a movement of the other without creating a rubbing action therebetween.

In summation, apparatus have been shown and described whereby selective electrophotographic printing is effected in order to transfer onto a print receiving material only select information in a predetermined place, or places, of a source record. And while there have been shown and described and pointed out the fundamental novel features of the invention as applied to preferred embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated and in their operation may be made by those skilled in the art, without departing from the 15 spirit of the invention. It is the intention, therefore, to.be limited only as indicated by the scope of the following claims.