US2294148A - Method of and means for recording signals - Google Patents

Description

1942- B. L. KLINE EI'AL 27,294,148

METHOD OF AND MEANS FOR RECORDING SIGNALS Filed .Aug. 31', 1940 THIN ADHERENT FILM CONDUCTING BASE INVENTOR? B. L. KLIN M. A. RU DD Patented. Aug. 25, 1942 2,294,148 mmron or AND mums FOR nscoanmc SIGNALS Bernard L. Kline, Manhasset, N. Y.,.and Maurice A. Rudd, North Plainfleld, N. J., asslgnors to The'Westem Union Telegraph Company, New York, N. Y., a corporation of New York Application August 31, 1940, Serial No. 354,940 In Great Britain May 3, 1940 7 Claims.

This invention relates generally to a method of and means for electrical recording, and more particularly to recording on an electrosensitive blank various kinds of subject matter by means of telegraph facsimile or other types of electrical signals which are applied to selected elemental areas of the recording blank by means of an electrode that scans the surface of the recording blank for applying the signals to selected areas thereof. I

This 'application'is in part a continuation of our copending application, Serial No. 54,484, filed December 14, 1935.

Various methods of recording in facsimile by means of electrical signals and various types of recording mediums have heretofore been proposed, but in general the methods and recording blanks employed required special handling or treatment prior to their use, as in the case where wet recording papers were employed, or required heaters or other mechanisms controlled by signals which in turn operated to mark-the message sheet, or required special handling or development treatment after recording, and none of the devices or recording mediums heretofore proposed have enabled satisfactory recording to proceed at a sufficiently fast rate with relatively small amounts of energy whereby they are adapted for use with the currents and voltages ordinarilyemployed in telegraph recording systems, and none of the prior art methods and recording mediums has produced the sharp definition desired in facsimile recording consistent with producing records which may be scanned at a high rate of speed and with small values of currents and voltages.

For example, it is old to have paper tape impregnated with suitable electrically conducting solutions, said solutions being adapted to be decomposed by signal impulses so that a permanent record of the signal is made. Such recordings, however, are only suitable for relatively coarse work where no fine gradations of tonal values are necessary, such as in the reception of telegraphic signals in general and recording of various types of curves in connection with the performance of instruments. However, in the transmission of matter, particularly of pictures and the like, where half-tones are encountered, the range of tonal values extends from what might be termed paper method previously discussed, the capillary 55 action of the paper often results in a spreading of the record element so that satisfactory deflnition for precise work becomes an impossibility under normal high speed operation.

This invention provides a method of and means for recording which is remarkably free from the above objections. Thus, high speed of recording is a prime requisite due to the customary diversion of a telegraph or other signal transmitting means in connection therewith. The need of high speed operation is further enhanced by requirements'for sharp definition, and in picture transmission, increasing the number of lines to the inch increases the length of time required for the making of a record and, therefore, places a slow speed system at a further disadvantage. A further and desirable property of the record is the fact that the recording blanks may be stored under normal conditions for long periods of time without any substantial deterioration and are ready for use at all times. No supplementary treatment of the blanks is necessary apart from the reception of the signal impulses and the transformation of such signal impulses to record elements during the normal process of recording.

The invention in general makes use of the phenomenon of chemical disintegration by electric potentials and currents, the disintegration being generally accompanied by the absorption of electric energy. The substance to be disintegrated is preferably disposed as a thin adherent coating over a base material which for practical purposes may be considered as permanent and uninfluenced by the electric current. This base coating functions as one electrode surface for the entire record coating and also functions to provide a uniform color background which may be exposed to view over selective areas and to predetermined degrees to make up record elements. The material to be disintegrated preferably is of a color to contrast with the base material, which contrast may be as great or as small as the requirements dictate. It is evident that for bold outlines and where considerable picture contrast is required, the contrast between the disintegratable material and base material should be substantial. However, the tonal range of the record may be controlled by controlling the de gree of contrast between the base and disintegratable material.

An object of the invention is a method of and system for recording in which the foregoing disadvantages of the prior art methods are obviated,

and which produces sharp definition of the recorded image with a relatively small expenditure of energy and at a high rate of speed, and in which the energy is confined to sharply defined areas beneath a recording stylus or its equivalent at an given instant during the scanning operation.

Another object is an improved method of and system for recording on a blank having a coating or surface layer primarily composed of an opaque compound of contrasting color with respect to a conducting base sheet of the blank, and in which partial or substantially complete removal of the coating may easily be effected in the selected elemental areas by the marking currents applied thereto.

A further object of the invention is to effect marking on a, recording blank of the character described. which is dry and records in the absence of moisture, and is substantially unaffected by humidity, and in which complete recording may be effected with the blank in the same dry state as when the blank was made.

The invention further resides in the features of combination, construction and arrangement hereinafter described and claimed.

We have discovered that certain substances when firmly bound to the surface of a base of suitable conducting material may be removed therefrom by electrical energy applied locally, for example, by a recording stylus, to expose the base in varying degrees to delineate a record. We have further discovered that the ease with which these substances can be disintegrated and dissipated and hence removed to expose the surface of the base of the recording blank is substantially inversely proportional to their heats of formation. These substances, especially when embodied in the coating, should be opaque and have a contrasting color with respect to the base of the recording blank so that when they are removed therefrom, the surface of the recording blank will be visible to a greater or less degree.

As an example of such substances suitable for this purpose are metal compounds such as lead thiocyanate, mercuric sulphide, cadmium sulphide, zinc oxide, lead thiosulphate, and titanium dioxide, which in the order named have increasing heats of formation, halogen salts of metals and particularly the iodides of mercury, lead and copper, and opaque organic materials, such as the nickel salt of dimethyl-glyoxime and the complex Hansa yellow. That the phenomenon just stated does not necessarily depend upon a chemical change or a change of state of the particular substance appears from the fact that substances such as cadmium sulphide, zinc oxide and titanium dioxide cannot produce a black mark or record by chemical change but must be disintegrated and dissipated and thereby removed from a black or other contrasting color record surface to produce a contrastingly colored mark upon application of energy in accordance with the invention. Again, others of the named substances which are capable of undergoing chemical change to produce a mark by the resulting color change upon application of energy do so when energy is applied in substantially less amounts than that contemplated in practicing the present invention. For example, lead thiocyanate, lead thiosulphate and mercuric sulphide will produce marks by a color change. Lead thiosulphate and lead thiocyanate areconverted to colored chemical compounds which remain in the immediate neighborhood of the stylus upon application of electrical energy by the stylus. The mercuric sulphide undergoes an allotropic change upon application of electrical energy, as disclosed in the copending application Ser. No. 23,928, filed May 28, 1935, and in which the present applicants are coinventors. In some instances the change in color may be effected by a change in the content of water of crystallization. The conducting surface may be the surface of a piece of paper or other suitable base material made conducting in the manner described in the copending application of one of the applicants, Ser. No. 38,825, filed August 31, 1935, now Patent No. 2,251,742, issued August 5, 1941, or it may be paper or material of any kind which is made conductive during manufacture, as for example, black carbon bearing paper.

Referring to the drawing:

Fig. 1 is a perspective view of the recording medium and a simplified marking means illustrating the principle of the invention;

Fig. 2 illustrates diagrammatically a facsimile system embodying transmitting and recording means, the said system being of the type employing a receiver in which a telegraphic blank embodying the present invention is adapted to be used; and

Fig. 3 is a perspective view of a telegraphic blank embodying the invention.

Referring for the present to Fig. 1 of the drawing, reference character I0 designates a sheet or block of relatively good conductive material, preferably presenting a black surface. A pencil or stylus H is assumed to be movable in contact with the recording medium so that it may be placed at any point where a mark is desired. The platen and the stylus H are connected to a source I2 of electrical energy having sufiicient power to accomplish marking in the manner contemplated by the invention. The recording medium I4 is applied as a thin adherent film to the sheet Ill, which film may be removed in minute, sharply defined areas when the stylus is touched to the surface of the platen with the source l2 in operation. The sheet In is preferably of a flexible nature so that it may be rolled, as shown in Fig. 2, for application to the surface of the cylinder [3, of the reproducing device.

In the facsimile apparatus illustrated in Fig.

2, which may be of a conventional type, the scanning electrode or stylus l6, whose point bears on the surface of the blank 12 bearing conductive characters, is supported by a traveling carriage l1 adapted for longitudinal movement. The stylus I6 is caused to traverse the cylinder in a longitudinal manner by any suitable means and therefore the stylus point will describe a helical path as it moves over the surface of the transmitting blank and thus produce a scanning action. A transmitter of this nature is shown in application of R. J. Wise, Ser. No. 23,926, filed May 20, 1935, now Patent No. 2,153,858, issued April 11, 1939. Likewise in the receiving device shown at the right hand side of Fig. 2 of the drawing, the cylinder I3 is rotated and the receiving stylus 20 is advanced axially so that it traverses the blank with a helical movement covering all parts of the blank by a series of parallel lines. It will be understood that any suitable receiver or recording devicemay be employed and that axial movement may be imparted to the receiving blank as is done in graphic measuring devices.

Referring to Fig. 3, the body 2| of the recording blank which corresponds to the sheet In of reasonable limits.

surface covering to the base material and for all Fig. 1, may, as previously stated, comprise a sheet ofpaper or other suitable material made conducting by being impregnated with sodium nitrate dissolved in an alcohol of low volatility as disclosed in the copending application Ser. No. 38,825 referred to above and in the copending application of B. L. Kline, Ser. No. 30,555, filed July 9, 1935, now Patent No. 2,229,091, issued January 21, 1941, or it may consist of a black carbon bearing paper. The sheet of conducting paper 1l forming the body of the recording blank is preferably of such color that it will contrast with the recording substance which is to be applied to its surface in a manner later to be described.

If the paper layer 2! of the blank is of a kind which is not inherently conductive, it may be necessary to first apply the recording medium to its surface and thereafter to impregnate the back of the paper. By having the electrically conducting material, such as the sodium nitrate solution or carbon embodied in the recording blank adjacent to the recording surface layer, the recording may be accomplished by a small expenditure of energy, which is closely confined to the small area immediately beneath the recording stylus or its equivalent at any instant, and sharp definition of the recorded subject matter is obtained. The coating itself is of a character which readily is disintegrated and disslpated by the passage therethrough of a small marking current, the low heat of formation appearing to promote this ready disintegration and dissipation by small currents. The conductive base immediately beneath the coating provides a relatively good conducting path directly through the recording blank from the point of the stylus to the recording cylinder beneath the blank, and prevents dispersion of substantial amounts of marking current in and around the area of the blank beneath the stylus at any given instant, and thus spraying effects or other 'undesirable effects in the coating or recording blank at this point are eliminated, and blurring of the mark is obviated.

Inasmuch as the coating to be disintegrated represents the load-of the electric current, it is clear that the resistance of the record material should be concentrated in that region. In order to provide apermanent record, the material to be disintegrated may be formed in part from some suitable binder, such as lacquer, gelatin, starch, casein, cellulose derivatives, synthetic resins, and the like. The filler, such as above referred to, is preferably uniformly distributed in finely divided form throughout the binder.

Many of the fillers do not have a high degree of conductivity but generally have a lower resistance than the binder itself. By controlling the fineness of the grains of the filler and the dispersion1of this material throughout the binder, it is possible to control the electrical breakdown characteristics of the entire coating within This coating is applied as a practical purposes forms a unitary record blank. Inasmuch as the disintegrating properties of the entire coating are to be maintained at a uniform value-with the variations in disintegration being controlled by the intensity of current or potential, the thickness of the coating should be maintained at a substantially constant value throughout the useful area of the record. While the base material itself should have an electric resistance low in comparison to the resistance of the coating, which inherently is high, the resistance of the base material may have a substantial value.

- stable with respect to time and are also substantially unaffected by light, moderate changes of heat and moisture such as are present in the atmosphere and which are not unduly expensive.

The recording medium may conveniently be applied to the surface of the blank as an ink which is formed by powdering the material and grinding this powder with a linseed oil to a suitable consistency for application to the surface of the blank by a printing operation, or by grinding in a lacquer or other binder vehicle. It is within the scope of the invention to mix a pinrality of selected materials from the preferred group in formulating the ink or other coating mixture. In some circumstances of use it may be desirable to incorporate a trace of drier to aid in oxidation of the oil when in ink form. The powdered substance is not affected in any way by including the drier. Resinates, linoleates of lead, cobalt, manganese, etc., are standard driers and may be used when a drier is considered desirable or necessary.

The recording mediums of the present invention, as stated above, have low heats of formation, lying in the range of from 28,670 calories for lead thiocyanate to 217,400 calories for titanium dioxide. For purposes of producing the mark with the amount of electrical energy available for practical use, best results are obtained when materials are used, the heats of formation of which do not exceed 150,000 calories as an upper limit.

These chemical compounds when ground to a powder in a suitable vehicle may be disintegrated and removed from a conducting surface upon application of electrical energy, as shown by tests which involved weighing pieces of paper bearing a coating of the ink so formed before and after subjecting the ink to the application of electrical energy by a stylus similar to the stylus II.

The substances having lower heats of formation respond more quickly and are more easily removed by the application of electrical energy impressed by the stylus H. In all cases it is necessary to use more energy than is required to produce the allotropic change in mercuric sulphide as disclosed in the copending application Ser. No. 23,928 referred to above.

To improve the covering power of the coating mixture, any suitable opaque material may be added. Zinc oxide or titanium dioxide are preferred for this purpose. The zinc oxide is more suitable as it has a heat of formation of 84,350 calories and gives better definition in the received record even though it has a lower covering power than titanium dioxide. The heat of formation of titanium dioxide is given as 217,400 calories. Titanium dioxide when used in small amounts is suitable, but if too much of this opaque material is used, definition of the record may be impaired and an increase in the applied electrical energy is necessary.

In recording upon a blank embodying the present invention, the coating is removed immediately under the stylus, as current is passed therethrough, to expose the surface of the record blank beneath. The binders named above surround each particle of the filler, and prevent the filler from acting in the same manner as it would if exposed to air. It is possible that exposure to air would permit some oxidation resulting in the formation of other chemical compounds which may be colored and which may interfere with disintegration of the film in the manner contemplated.

Combinations of the materials which are comprised within the desired group have been proved to give a sharply defined record of a distinctive color contrast. As an example, a telegraphic blank having a greenish yellow backgrond is produced by mixing two parts of lead thiosulphate, two parts of cadmium sulphide and one part of titanium dioxide ground in a linseed oil to a suitable consistency for application by a printing operation to the surface of a black conductive base.

Variations in the color and opacity of the background and sharpness of the record may also be obtained by superimposing a plurality of films, each film containing the same material from the desired group or different materials selected/from the group.

From the foregoing disclosure of the invention it will be seen that there is provided a method of and system for effecting marking with a series of recording materials or substances adapted for the formation of ink films or other films and that record blanks covered by such films provide ready means for recording electrical signals. The blanks both before and after use in a recording apparatus may be handled without special precautions as they are not sensitive to ordinary variations of light and/or heat.

The thickness of the coating should be just sufficient to mask the base material and will vary with the opacity. The potential impressed across the coating should be just below the breakdown value so that superposed signal potentials will provide the differential necessary for effective operation. The character of potential appears to be immaterial and recording may be effected with either direct current or alternating current of frequencies ranging into the carrier spectrum.

What is claimed is: (v

1. The method of recording which comprises passing an electric current by conduction through selected elemental areas of a recording blank having a relatively good conducting base and .a relatively high resistance surface portion of a marking compound in a manner to cause disintegration and dispersion of the compound in said selected elemental areas without disintegrating or decomposing said compound in areas adjoining the selected elemental areas to provide sharp definition of the recorded subject matter.

2. In a facsimile system in which a conduct ing record support has positioned thereon a recording blank having a thinsurface coating of a material which is susceptible to dispersion when electrical marking potentials representative of writing, pictures or other subject matter to be recorded are applied successively to selected elemental areas of the coating by means of a scanning stylus, the method of producing sharp definition of the recorded subject matter by causing the energy developed by the marking potentials applied by the stylus to be concentrated and localized in each elemental area of said coating at the time immediately adjacent to the stylus. said method comprising the steps of providing in the body of said blank and adjacent to said surface coating a conducting path of low electrical resistance relative to the resistance of the path through the coating, impressing the marking potentials across the stylus and record support, causing relative scanning movement between the stylus and the surface of said coating,

and causing the concentrated energy developed in the scanned elemental areas of the coating to disperse the coating material in such areas to produce a facsimile record on the surface of said blank.

3. In a facsimile system in which a conducting record support has positioned thereon a recording blank having a thin surface coating of a material which is susceptible to dispersion when electrical marking currents representative of writing, pictures or other subject matter to be recorded are passed successively through selected elemental areas of the coating by means of a scanning stylus, the method of producing sharp definition of the recorded subject matter by causing the energy developed by the marking currents applied by the stylus to be concentrated and localized in each elemental area of said coating at the time immediately adjacent to the stylus, said method comprising the steps of providing in the body of said blank and adjacent to said surface coating a conducting path of low electrical resistance relative to the resistance of l the path through the coating, causing the marking currents to pass by conduction through those areas of the recording blank between the stylus and record support, causing relative scanning movement between the stylus and the surface of said coating, and causing the concentrated energy developed by the marking currents as they pass through the scanned elemental areas of the coating to disperse the coating material in such areas to produce a facsimile record on the surface of said blank.

4. A recording system comprising a source of electrical signal impulses, a recording blank including as a base a sheet of electrically conductive material, a thin adherent film intimately bound to said base and covering the same, said film and base having sensibly different appearances with the film being opaque and having a resistance high in comparison to that of the base but'being susceptible to breakdown and dispersion during recording, a stylus of good conducting material bearing upon said coating, means for imparting scanning movement of said stylus relative to said coating and means for impressing an electrical potential between said stylus and base material with said signal impulses superimposed upon said potential, said potential and signal impulses being sufliciently great to cause localized breakdown of said coating to expose the base material to varying degrees.

5. A facsimile recording system comprising a source of electrical signal impulses representative of writing, pictures or other subject matter to be recorded, a recording blank comprising a base and a surface coating intimately bound to said base and covering the same, said coating and base having sensibly different appearances with the coating being substantially opaque, said coating having a high electrical resistance but being susceptible to localized dispersion when electrical marking potentials are applied thereto, means including a stylus for applying electrical marking potentials to said coating in selected elemental areas thereof in response to the received signal impulses, means for causing said stylus to scan the surface of said coating during recording, and means for causing sharp definition of the recorded subject matter, said last named means including a continuous layer of electrically conductive material embodied in said base and adjoining said coating and substantially coextensive therewith, said conducting layer having low electrical resistance relative to the resistance of said coating and causing concentration of the energy developed by the marking potentials in those minute areas of said coating at the time immediately adjacent to said stylus during a scanning operation, and an electrode adjacent to said conducting layer for operatively connecting the conducting layer in circuit with said stylus.

6. A facsimile recording system comprising a source of electrical signal impulses representative of writing. pictures or other subject matter to be recorded, a recording blank comprising a base and a surface coating intimately bound to said base and covering the same, said coating and base having sensibly different appearances with the coating being substantially opaque, said coating having a high electrical resistance but being susceptible to localized dispersion when electrical marking currents are passed through the coating, means including a stylus for passing electrical marking currents through said coating by conduction in selected elemental areas thereof in response to the received signal impulses, means for causing said stylus to scan the surface of said coating during recording, and means for causing sharp definition of the recorded subject matter, said last named means comprising a continuous layer of electrically conductive material' embodied in said base and adjoining said coating and substantially coextensive therewith,

said conducting layer having low electrical resistance relative to the resistance of said coating and causing concentration of the energy developed by the marking currents in those minute areas of said coating at the time immediately adjacent to said stylus during a scanning operation, and an electrode adjacent to said conducting layer for operatively connecting the conducting layer in circuit with said stylus.

7. A facsimile recording system comprising a source of electrical signal impulses representative of writing, pictures or other subject matter to be recorded, a recording blank comprising a base and a thin adherent surface film intimately bound to said base and covering the same, said film and base having sensibly different appearances with the film being substantially opaque, said film having a high electrical resistance but being susceptible to localized dispersion when electrical marking potentials are applied thereto, means including a stylus for applying electrical marking potentials to said film in selected elemental areas thereof in response to the received signal impulses, means for causing said stylus to scan the surface of said film during recording, and means for causing sharp definition of the recorded subject matter, said last named means including a continuous layer of electrically conductive material embodied in said base and adjoining said film and substantially coextensive therewith, the .thickness of said fllm being just sumcient to mask the base material, said conducting layer having low electrical resistance relative to the resistance of said film and causin concentration of the energy developed by the marking potentials in those minute areas of said film at the time immediately adjacent to said stylus during a scanning operation, and an electrode adjacent .to said conducting layer for operatively connecting the conducting layer in circuit with said stylus.

. BERNARD L. KLINE.

MAUR CE A. RUDD.

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