US2572549A - Sheetsxsheet z - Google Patents

Description

Oct. 23, 1951 D. D. WHITE ET A1. 2,572,549

VOLTAGE: MODULATED MARKING FLUID DEPOSITION DEVICE Filed May 5, 1947 2 SHEETS-SHEET 1 A-rrrs Oct. 23, 1951 A Q D, WHITE ET AL 2,572,549

VOLTAGE MODULATED MARKNG FLUID DEPOSITION DEVICE Filed May 5, 1947 2 SHEETS-SHEET 2 Patented Oct. 23, 1951 VOLTAGE MODULATED MARKING FLUID DEPOSITION DEVICE Desmond Deverell White, Frank Ronald Osborn, and Stefan Reich, Elstree, England, assignors to Dufay-Chromex Limited, London, England,

a British company Application May 5, 1947, Serial No. 746,174 In Great Britain September 12, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires September 12, 1965 2 Claims. 1

This invention relates to improvements in apparatus for electric recording by deposition of dye, pigment, other colouring matter or the like of a suitable nature, and particularly to apparatus for using a modulated current to produce on a paper sheet or similar receiving surface deposits of liquids containing particles of dye, pigment, ink or other colouring matter (herein referred to as colour units) of area or amount or density varying proportionally with the modulated electric control. An illustrative example of the use to which this invention may be put is the production of prints on paper or the like from an original photograph or like picture, e. g. the production of three-colour prints from a three-colour photographic transparency.

It is an object of this invention to provide apparatus for electrical recording, that is simple in design and effective and speedy in operation.

According to the invention the apparatus comprises the following combination of elements:

A stylus located adjacent the recording surface, means for supplying coloring matter to the stylus surface at a pressure insuillcient for the projection of the coloring matter from the stylus, means for setting up an electrical potential gradient between said stylus and the desired point of deposition on the recording surface and means for varying the intensity of potential gradient. The setting up of the potential gradient causes particles to be drawn from the stylus, disintegrated and deposited on the receiving surface, and by controlling the intensity of the potential gradient the intensity of the deposition of the coloring matter may be controlled.

Considering the simple case of a rotatable metallic drum carrying on its surface a sheet of paper which is to receive from a device of the general character of a pen a record the character of which is determined by an electric signal," i. e. by a modulated electric current or voltage, the liquid-depositing device, stylus or "pen does not touch the paper but is held at a slight distance therefrom while the drum is rotated. The modulated electric control current is led to an amplifier which gives an output of suitable voltage. This output is electrically connected to the liquid in the liquid-depositing device which terminates in a point which provides an exposed particle of liquid which therefore lies in the electric eld between the liquid and the metallic drum (which may be earthed) and the liquid particle attains such an electric charge that it is disintegrated into a ne mist which is directed..

by the-electric eld on to the paper surface. The

liquid contains a dye, pigment or lnk and considering the particle at the outlet at any instant, the characteristic of this invention is that the area or amount or density of the record produced on the paper from that particle is proportional to the value at that instant of the modulated voltage.

Turning to the construction of the liquid-depositing device or pen, this may comprise va tube of ilne bore ground externally to a. point at its outlet end. An insulated iibre (say of glass) passes through said bore and carries a bead at its extremity (external to the outlet orifice) which bead forms an outlet valve. This tube may be arranged vertically and above the receiving surface with the point downwards and close to the paper or alternatively the tube may be arranged below the receiving surface with the point upwards. In either case the bead has a lm of the liquid on its surface. The modulated current from some transmitting device is led to an amplifier which gives an output of a suitable voltage. There is an electric conductor leading from the output of the amplier to the depositing device. It may lead to a metal wire dipping into the liquid with the interposition of a suitable limiting resista-nce if necessarv. Alternatively, the conductor from the amplifier may lead to a metallic sleeve on the outside of the tube or jet. The tube may itself be of metal which will act as a conductor. It may or may not be provided with a tip of insulating material made of glass, plastic or other suitable substance. If the liquid is a dye dissolved in butyl alcohol, the voltage from the amplifier may vary between 1,000 and 4,000 volts. The operation is a peculiar one. The metallic drum carrying the paper being earthed or at a xed voltage, there is an electric eld between the liquid and the drum. A lm of liquid spreads over the bead and the liquid is drawn to a point by the electric field and the electric charge on the liquid particle at this point is sutil-f cient to cause the particle to disintegrate and a minute spray or mist of the liquid is formed and is directed to the paper. The position of the bead in relation to the nozzle may be manually adjusted through the fibre which carries the bead or alternatively the position of the bead in relation to the nozzle (i. e. the extent of opening of the outlet valve) may be controlled from the amplifier so as to take care of extensive changes in the modulated output.

In one form of liquid-depositing device a pointed member somewhat of the shape of a rifle bullet but having external capillary grooves run- The position of the pointed member or nose in relation to the receiving surface may be varied by the electric control, but this system of .control of the colour units is not preferred.

Where the original is a colour transparency .1:

and it is desired to produce a colour print, the receiving drum is operated as above describedbut there are three or more separate scanning beams,

three or more separate photocells of appropriate sensitivity, three or more separate electric circuits and three or more separate depositing devices, the disposition of these parts .in relation to the drums being such as to ensure the proper relationship of the three deposits both in relation to the original andto one another.

It is -Weilknown that when using an ampliner .of a modulated current it is possible to inject In thecase where the electric control 'is eiec-ted by the use of a photo-electric cell activated by an optical scanning device, the invention ensures that the area or amount of the deposited colour unit is responsive to the modulation of -the'scanning 'light by the original.

'In one modification of this invention whether the liquid-depositing device or pen be hollow (like a sty'lographic pen) or has external capillary grooves, `the spray discharge may be focussed on to `the receiving surface by suitably disposed electrodes carrying control potentials -actinggon the minute particles of the mist to determine their course (in a manner analogous to that in which avbeam .ofrelectrons Vin a cathode ray tube is 4focussedon a screen or on an exit pupil) Again l the liquid-depositing device or pen (and particularly the nose or pointed end) may be surrounded by a conducting sleeve or shroud to stabilize theelectric eld or to assist in determining its shape.

Y When a highly concentrated solution of dye is used, the conducting sleeve or shroud may be used for v(,:onduct-ing over the liquid-depositing device, :a gas, v(e. g. air or carbon-dioxide) saturated with a vapour of Vthe solvent being used, to prevent evaporation of the dye-containing solvent.

It has been stated above that an amplifier may be used inthe electric control system. Such an amplifier may be provided with means for limiting the upper and lower values of the output voltage.

It is desirable to prevent the accumulation on the receiving paper of undesired electric charges andthe paper may be treated to control itselectric conductivity. Thus 'itfmay be impregnated with a solution of a salt (e. g. lithium chloride) or with a hygroscopic agent such vas glycerine. The vconductivity of the liquid to be deposited may also be controlled.

A"lo'niaintain a check on the vlight and shade in the deposited picture, the picture as it is formed may be optically scanned and an electric .fsignaP generated by the scanning device (e. g'. 'bythellscf a-,photo-.electriccelh is fedbackfto the amplifier in such a Way as to correct automatically any errors in reproduction.

The nature of this linvention and the manner in which the same is to be performed will be appreciated from the following description of examples, reference being made to the accompanying drawings, in which:

. Figure 1 is a diagram of a reproducing arrange- Y ment;

VFigure 2 is a sectional elevation of one form of liquid-depositing device;

,Figure 3 is a side elevation and Figure 4 an end elevation of a modified form of liquid-depositing device; and

Figure 5 is a sectional elevation of a shrouded form of liquid-depositing device.

Referring to Figure l, a projection lamp I2 is used to produce a, beam of light which passes through a lens system I3 to bring the beam to a fine point at the transparency I4. The transparency I4 is mounted on a Arotary drum 'I5 carried on a 4horizontal Yshaft I6 which can be `rotated and axially moved at rates suitable for scanning, thus giving helical scanning. The rotary drum I4 may be of glass or transparent plastic which gives the minimum of interference to this scanning beam or the drum may be metal with orices at those places where the original picture lies. After Ypassing Vthrough the trans# parency the light beam is collected by a lens system ITI and focussed on to Athe sensitive Vportion of a photoelectric cell i8 which gives an electric output proportional to the intensity of the light falling on it and the current from `the cell is led through conductors lasuitablyscreened from .external influences to an amplifier 20.'(D..C. or A. C.) which produces an output of highvoltage which varies proportionally to the intensity of the light falling on the cell. This outputled by conductor .2| to a lliquid depositing deviceZ-.Z of the type above described. The ,papercr like receiving surface 23 is mountedon an earthed metallic drum 24 which is rotated and moved axially identically with the scanning drumV I5. Preferably vthe metallic `drum 24 `for the receiving `sheet 23 is mounted on the same shaft I6 asthe scanning drum il '.5 and therefore partakes of iden-4 tical movements. The important fact is-thatthe area or amount or density `of the colour -unit or deposit on the paper at any instant is proportional to the electric voutput from the amplifier and the reproduction which is built up on V.the paper is la faithful reproduction of the original.

Referring to Figure 2, the liquid-depositing de# vice or pen 22 comprises a tube 30 -offine bore ground external-ly to a point -3I at its'foutlet end. An insulating libre 32, -say of glass, passes through said bore `and Vcarries a bead '33' at its extremity, which bead forms an outlet valve.

Referring to Figures 3 and 4, the liquid-.dei positin'g device 22 may comprise a pointed mem-'- ber or nose 4Q having line external grooves or channels 4l leading to the point 42 and the liquid may 'be :retained by capillary action. Such a pointed `member or nose may have its axis horizontal or inclined slightly downwards towards the point.

Referring to Figure '5, the pen '50 is surrounded by a shroud 51 which may be of electrically-conducting material so as to stabilise the electric field. This sleeve or shroud k5l is pro-v vided with an inlet conduit 52 so that a gas (e'. g. air or carbon dioxide) saturated with the vapour ofthe solvent being used may be 'conductedover the liquid-depositing device to prevent undue evaporation of the dye-containing solvent.

We claim:

1. Electric recording apparatus comprising a recording surface, yan electrode located behind said surface, a stylus located adjacent to and in front of said surface, means for supplying coloring matter to the stylus surface at a pressure insufficient for the projection of the coloring matter from said stylus, said stylus being an electrically conducting pointed member having fine external grooves or channels leading to the point, in which channels the liquid coloring matter is retained by capillary action, means for setting up an electric potential difference between said stylus and said electrode, and means for varying said potential difference, whereby the particles of said coloring matter are attracted from said stylus surface :and are disintegrated and the coloring matter is deposited in intensity on said surface in accordance with said variable potential difference.

2. Electrical recording apparatus comprising in combination, a recording surface, a liquid-depositing device for supplying coloring matter 'o0 the recording surface, means for producing a continuous relative movement between the liquid depositing device and the recording surface whereby the liquid depositing device traces a, line over the recording surface, said device having a tip which is located out of contact with but close to the recording surface and which is fed with liquid cloring matter through a capillary opening, means for feeding the liquid coloring matter to the liquid depositing device, means for setting up a high voltage potential gradient between the recording surface and the liquid depositing device sumcient to project coloring matter from the tip of the liquid depositing device on to the record- 'ing surface across the intervening gap, and means controlled by the said modulated electric current for varying the intensity of the said potential across the gap between the tip of the liquid depositing device and the recording surface in accordance with the intensity of the modulated electric current, whereby the intensity of deposit of the said liquid coloring matter varies from l point to point along the line traced by the liquid depositing device on the recording surface.

DESMOND DEVERELL WHITE. FRANK RONALD OSBORN. STEFAN REICH.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS

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