US3003404A - Machine for effecting electrostatic printing - Google Patents

Description

-1 1,951 K. A. METCALFE ETAL 3,003,404

MACHINE FOR EFFECTING ELECTROSTATIC PRINTING Filed Nov. 29, 1957 2 Sheets-Sheet 1 Oct. 10, 1961 K. A. METCALFE Erin. 3,

MACHINE FOR EFFECTING ELECTROSTATIC PRINTING Filed Nov. 29, 1957 2 Sheets-Sheet 2 United States Patent. l cc 1 3,003,404 I, 7 microns FOR momma ELECTROSTATIC Kenneth Archibald Metcalfe, Graymore, South Australia, and Robert John W t, South lnyneham, South or! to the Commonwealth invention relates to a machine for elfecting elecprinting and in particular it relates to a machine of the type in which numbers of copies are produced in a rapid sequence. Printing machines of various types are already well known and it is for instance common in printing to produce printed matter on a web of paper by passing the paper beneath inked rollers and then severing the sheets from the web to provide the individual sheets.

The method of transferring the image from an inke roller consists either in inking higher partstof the roller or to use an oilset method in which the roller has a flat surface portions of which are rendered receptive to the printing medium while others are not.

The present invention has been designed to produce continuous printing in this manner but the printing is effected by electrostatic means and can be carried out either on a continuous web which is subsequently out if desired or it can be carried out on individual sheets carried through the printing process by a suitable belt or the like.

Briefly, the invention contemplates a machine comprising means to charge a photo-conductor surface, and to form an image pattern thereon, developer means to contact said photoconductor surface with a body of liquid developer to produce a printed image on said surface, and means to move material to be printed through the 3,003,404 Patented Oct. 10,1961

After the web 2 passes through the charging zone 4 it is taken through the image forming zone 8 where a light source 9, and a negative 10 produce a xerographic image on the web, the zone 8 in the case of FIGS. 2 and 3 comprising a roller 11 over which the web 2 passes, and a second roller 12 which is arranged as a cylinder and whichcarries the negative 10 on its periphery, a slot 13 in a cylindrical shield 14 directing a narrow band of light through the negative 10 and onto the web where it is confined between the rollers 11, and 12.

This transforms the light image from the negative 10 to anelectrostatic image onthe web 2 by regulating thelelectrical pattern by the well known method of bleeding away the. chargeat those points etfected by the appropriate light intensities of the image.

\ The web 2 which now carries the electrostatic image said machine to receive the said printed image there- FIG. lis a schematic view of an embodiment showing a web of photo-conductor paper andv the disposition ofthe mechanism in relation thereto,

FIG. 2 is a detail schematic view of a form of continuous exposure device,

FIG. 3 is a perspective view of a machine with the one end and the cover plates omitted, and

FIG. 4 is a view corresponding to FIG. 1 but showing a modified device in which the print istransferred from a photo-conductor roller to a plain paper web.

Referring first to the embodiment shown in FIGS. 1, 2 and 3.

A supply reel 1 containing a continuous web 2 of 7 paper orthe like is disposed adjacent the feed end of the machine and the web is taken from the supply reel vl overa'guide roller 3 (not shown in FIGQI) to an electrostatic charging zone 4' which comprises a plate having asen'es of points 6 to which the necessary high voltage is applied. A backing member 'Iis provided on the other side of the sheet 2 to insure'that effective charging of the coated surface on the web 2 will take place. The web 2 is, of course, coated with a photo-conductor, and charging and the subsequent operations are carried out in the absence of light.

thereon then passes into the developer zone '15 which comprises a tank 16 of liquid developer which basically consists of a liquid having a resistivity sufliciently high that it will not destroy .the electrostatic image on the web 2 and having suspended init a coloring medium or. pigment which is selective to the imagefcharge on theweb, the web passing around a developing roller 17 onto which developer is fed by a distributor pipe 18 under control of a valve 19, the roller -17 serving as a developing roller in that it causes a concentrated field to. be formed as the web passes around it and thereby insures rapid and highly effective printing of the image,

the web with the now fully developed image thereon then passing through a drying zone 20 where the pigment which has been deposited on the, web in accordance with the electrostatic image will be dried, the web being finally taken up on the reel 21. I p

The printing roller 17 is mounted on arms 22 at each end mounted on hinge pins 23, springs '24 urging the arms 22 to force the developer roller 17 against a drive roller: 25 which insuresadequate contact of the web 2 with the developer roller 17 and also. draws the web 2 forward at a controlled rate.

I Drive is obtained from the motor 26 and gear box.27, a belt 28 engaging a double pulley 29 on the shaft of the gear box 27 and the pulley 30 on the shaft 31 of the roller 25.

Take-npis by means or the belt 32 between the pulley 29 and the pulley 33 on the shaft 34 of the take-up on the shaft 34 as required but maintains the necessary tensionon the web 2. I

. iA drain tank 36 catches any surplus developer from the developer zone.

The described are mounted on a base 37 which has side plates 38, only the further one being shown in FIG; 3, and a cover plate (not shown) encloses the mechanism to exclude light from the path throughcharging zone 4'to the developing zone 15.

box 39 represents the 109 8 for. the mechanism which would be electrically coupled to the plate 5 and the backing member I.

-FIhesupply reel 1 and the take-up reel 21 can have the'u shafts and engaged respectively in slots 41 and 42 in the side plates, while the roller 12 may have its shaft-{43 carried in a slot .44 so that the. roller 12 rests on the web 2 where it passes over the roller -11.v 'The shaft 43 supports the lamp 9 and the shield 14 non-rotationally, but the roller 12 is free to rotate thereon throngh'the medium of the bearing 45 and spiders 46.

Referring now to the embodiment shown in FIG. 4.

g In supply reel 1 feeds the web 2 to the take-up reel 21. 7

Alight source 9 again illuminates a drum 12 on which the negative or light-controlling member is carried, the

3 light from the source 9 passing through the slot 13 in the shield 14 but instead of the modulated light putting the pattern on the web 2, the electrostatic image is formed on the photo-conductor coating 50 of the drum 51 which rotates in synchronism with the drum 12, the drum 12 being in contact with the drum' 51 if that is desired or mechanical synchronizing means being supplied between the drums 12 and 51 if that is preferred.

The photo-conductor layer 50is charged by the plate 5 to which a high potential is applied, the plate having points 6 to aid the discharge, the drum 51 acting as the backing member 7 used in the earlier described embodiment.

This then charges the photo-conductor layer just prior to the image being formed thereon.

The developer tank 16 is provided with a control valve 19 and it wets the developer roller 17 so that at this locality on the drum 51 the image is developed but as the drum rotates in the direction of the arrow, the image is immediately transferred to the web 2 by contactwhere the web 2 is pressed to the coating 50 of the drum 51 by the roller 25. y

In this way ordinary printing paper or other suitable web material may be used without it having to be specially coated, the drum 51 serving as the means on which the electrostatic image is formed, the coating 50 on it receiving a charge from the plate 5 which is modified by the bleeding away of the charge under control of the negative on the drum 12 under influence of the light from the source 9 passing through the slot 13 in the shield 14, the electrostatic image being then developed by the wetted developer roller 17 and while in a wet condition being transferred to the web 2 by pressure of the roller 25.

Provided the drums 12 and 51 are synchronized, printing can continue in this manner indefinitely and it has been found in fact that after the drum 51 has been well inked, the application of the developer which can be modified printing ink, will take place selectively and when this happens the drum 12 can be swung out of the way and printing continued.

The obvious advantage of this form of device is that the web 2 need not be specially treated and the process is thereby cheapened and brought into the sphere where it is suitable for printing newspapers or periodicalsor the like, as well as having direct application to photocopying of office documents or the like.

From the foregoing it will be realised that 'a continuous printing process is provided in which the material being printed is fed first past a charging locality and then through the image imposing locality and then through a liquid development zone where intensified printing is effected because of the use of a developer roller and-then through a drying locality, this producing a permanent printed image in an extremely rapid and satisfactory manner.

It is not necessary that the medium for effecting the change of the electrostatic pattern on the paper or the like be light means as .it is possible to vary the electrostatic charge on appropriate parts of the treated surface by contact means or it is possible to dispense with the pre-charging of the coated material .and to charge it directly with the pattern which is to be printed, the pre-charging merely forming a convenient method where the image is to be produced by light rays or the like which bleed away those portions of the charge not required in producing the electrostatic image pattern.

As' shown in FIG. 4, the image can be applied to a transfer surface by electrostatic means and this electrostatic image can then be transferred to the web or material'to be printed by direct contact betweenthe materials. It is also possible to vary the electrostatic charging device so that instead of producing a complete charge over the whole of the surface, the charge is initially produced only in accordance with the pattern which is to be printed, this being possible by shielding or intensifying and similar effects.

It will of course be realized also that the system outlined need not be limitedto a single pass through a developer as it can be duplicated so that color work can be produced in a continuous manner, and in this connection it is interesting to mention that two colors can easily be produced by providing a positive and a negative image on the material to 'be printed and then developing with two differently colored pigments selective to the different charge patterns so that in a single pass at least two colors can be applied without any difficulty.

A further feature of interest is that it is possible to carry sheets of electrostatic printing paper or the like on the web by causing the paper to adhere to the web due to the charge which is given to the paper, so that it is then a simple matter to carry the paper on the web through the complete process as it Will'be held to the web firstly by the electrostatic charge and during andafter development by the physical contact with the web particularly where a developer roller is used. While the paper will, in its wetted form, adhere to the web, immediately it is dried by evaporation of the volatile liquid of the developer the paper will be freed to be stacked or received in any normalconvenientmanner.

The machine will of course be arranged so that where there is sensitivity to light of the image this portion of the process will be carried out in the absence of light, and it may also be desirable to isolate sections of the machine such as the chargingtmeans and the developer sections because the developer may be of an inflammatory nature and it would therefore have to be guarded against arcing or similar effects at the charging locality, such an isolating plate being indicated by the reference'nu'meral 54. The development could be effected within a chamber in which a gas is also held which will suppress any tendency of combustion of the volatile developer.

From the foregoing it will be clear that repetition printing can be carried out in a quick and simple manner by means of the machine using electrostatic effects for printing and utilizing a liquid developer having the character of quick deposition in an extremely fine form and ready drying and fixing of the printed image, the 'permanence of this method and the freedom from subsequent deterioration being just as high as with ordinary ink printing because the pigment which is electrostatically deposited can have a nature similar to the pigment used 'in ink printing and as the solvent which has the high electrical resistivity and which supports the pigment in the developing solution can be any of the appropriate highly volatile solvents, removal of the solvent can be very rapid to leave the printed picture in a dry and permanent form. a

When transferring the image from the surface 50 of the roller 51 in the system shown in FIG. 4, an electrical charge may be used to cause transfer, or to assist transfer, of the developed image from the surface 50 to the web of paper or the like, using appropriate polarities and backing plates for the paperor the'like but it will be realized that a wet image can be readily transferred by direct contact between rollers or the like even without electrostatic aiding means, this being further aided if necessary by having the surface 50 of such a nature that drying of the pigment forming the image is slowed down due to lack of aborption of solvent or the like.

We claim: e e A machine for effecting electrostatic printing on a paper web having aphoto-conductivesurface comprising a main supporting frame, a supply reel carrying, said paper web rotatably supported on said frame, a take-up reel, means to drive said take-up reel, rollers on said frame to keep the paper web on a processing path between the said supply reel and take-up reel, an electrical charg- 8 devi at a Gherging station on said frame along said processing path to charge said photo-conductive surface, a clear hollow rotary drum on said frame positioned to be contacted by said paper web after the paper web leaves the charging station to form an exposure station, means on said drum to secure a negative thereto, said negative being held in close proximity to the paper web, a shield disposed in said drum havinga slot therein facing the photo-conductive surface on the said paper web, a light source in the said drum to project a continuous image through the negative onto the said photo-conductive surface, a roller to press the web to the said drum at said slot, a developer roller rotatably supported on said frame to contact said photo-conductive surface and forming a developing station after said exposure station, means to supply liquid developer to said developer roller, which is selectively deposited on said paper web according to the image charge, a drive roller sandwiching said web against said developer roller, means urging said drive and developer rollers together whereby an intimate contact between said web and developer roller is assured and said web driven along said path, and a drying station after said developer station including heating means also 6 supported on said frame to dry said developed image be fore the web is taken up on the take-up roller.

References Cited in the file of this patent "UNITED STATES PATENTS 2,041,153 Shiraefi et a1 May 19, 1936 2,041,478 Niederle May 19, 1936 2,357,809 Carlson Sept. 12, 1944 2,520,504 Hooper Aug. 29, 1950 2,549,546 Thomas Apr. 17, 1951 2,551,582 Carlson May 8, 1951 2,576,047 Schafiert Nov. 20, 1951 2,624,652 Carlson Ian. 6, 1953 2,709,716 Haller May 31, 1955 2,811,465 Greig Oct. 29, 1957 2,878,120 Mayer et a]. .Ma.r. 17, 1959 2,892,709 'Mayer June 30, 1959 FOREIGN PATENTS 201,301 Australia Mar. 19, 1956 755,486 Great Britain Aug. 22, 1956 1,147,162 France June 3, 1951

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