US2227109A - Facsimile recording device - Google Patents

Description

Dec. 3 9 R. G. SHANKWEILER 2,227,109

FACSIMILE RECORDING DEVICE Filed March 10, 1938 FROM PAPER 1 SUPPLY ROLL 70 PRINTER AM H5]? f0 VOLTS AC INVEN TOR. R. s. s /A NKWEILER ATTORNEY.

Patented Dec. 31, '1940 UNITED STATES PATENT OFFICE FACSHHILE RECORDING DEVICE Ray G. Shankweiler, Philadelphia, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application March 10, 1938, Serial No. 195,031

Claims.

ing devices are well known in the art and such 5 devices are for the purpose of transmitting pictures, sketches, printed matter or the like from one station'to another, either by radio connection or by a line channel. Various methods of producing facsimile recordings at the receiving apparatus are known and have been used, one of which is the type in which carbon paper is used to provide a source of ink or coloring matter which is transferred to a clean sheet of recording paper in accordance with signals received from the transmitting station. In such a system, the

an electrolyte which, when applied to the record 25 ing paper, may be used to produce'markings or recordings on the paper by the application of an electric current. When such an electrolyte is used to produce recordings at a receiver, the conventional rotating helix and printer bar are used, but the system diiiers from the carbon paper process in that the printer bar maintains a uniform pressure with respect to the recording paper and helix and the facsimile reproduction is produced by controlling the amount of current which is caused to flow between the printer bar and the helix. In such a system the recording paper is made conductive by the presence of the electrolyte and the conductivity of the paper must be maintained within certain limits, otherwise the recordings are either pale or are considerably lacking in detail. In such receiving machines the recording paper is ordinarily fed from a supply roll to a tank or trough which contains the electrolyte for impregnating the pa- 5 per and from this trough the paper and the electrolyte which is absorbed thereby is fed to the recording mechanism of the facsimile receiver, at which point the paper is subjected to an electrical current in accordance with the received signals 50 to cause a reaction in the electrolyte to produce the facsimile recording. The spacing between the impregnating tank or point of immersion of the recording paper and the recording mechanism per se is ordinarily such that under normal atu mospheric conditions the conductivity of the paper upon reaching the recording mechanism will be proper. However, under certain conditions the ambient temperature and the humidity of the surrounding air may be such that the paper upon reaching the recording mechanismvis too dry to permit the production of satisfactory recordings. On the other hand, the temperature and humidity conditions may be such that the paper, upon reaching the recording mechanism, may be too wet, in which case the recording appears smeared 10 and considerable of the detail is lost.

One purpose of the present invention is, therefore, the provision of means whereby the conductivity of the recording paper in an electrolytic recording apparatus may be maintained proper 15 for producing satisfactory facsimile recordings.

A still further purpose of the present invention resides in the provision of means whereby changes in the moisture content of the recording paper during its passage from the impregnating tank to the recording apparatus pe se due to ambient temperatures and humidity conditions may be compensated for.

A still further purpose of the present invention resides in the provision of means whereby the conductivity of the recording paper is measured at the point of recordation, and means whereby the conductivity at that point may be controlled by such measurement.

Another "purpose of the present invention resides in the provision of means whereby the conductivity of the paper at the point where therecording takes place is measured between each successive picture line recorded.

Still another purpose of the present invention is the provision of means whereby a heater is positioned between the impregnation tank and the recording apparatus per se.

Still another purpose of the present invention is the provision of means whereby the heating device may be controlled automatically in accordance with the moisture or conductivity of thepaper at the point where the recording is made.

Still another purpose of the present invention resides in the provision of a simple yet reliable electrical circuit which may be utilized to automatically control the conductivity of the recording paper in an electrolytic facsimile recorder.

Still other purposes and advantages of the present invention will become more apparent to those skilled in the art from a reading of the following specification and claims particularly when considered with the accompanying drawing, wherein the single figure illustrates a preferred form of the present invention.

In the accompanying drawing is shown schematically the component parts of a facsimile recording apparatus. In mechanical construction the recorder is similar to that shown and described in the before mentioned patent to Young and includes a rotating drum or cylinder III which carries a helix ll about its periphery. There is also provided a printer bar 12 having an electrode l4 connected thereto for cooperation with the helix of the rotatable drum or cylinder I0. The drum is positioned for rotation about its axis so that upon each rotation of the drum the helix will produce one picture line in the facsimile recording. The treated paper upon which the facsimile recording is to be placed is fed between the helix and the printer bar in order that a dye will be electrically deposited or formed upon the paper in accordance with the amount of current which is permitted to flow between the printer bar and the helix in accordance with the signals which are received by the facsimile receiving apparatus.

The recording paper originates at a supply roll and passes over a guide roller l9 before it is immersed in the electrolyte tank 20. In the tank is placed the electrolyte solution 22 and a pair of guide rollers 23 and 24 for guiding the paper through the solution. Another guide roller 25 is also used to properly direct the paper after it has passed through the impregnation tank, the roller additionally functioning to remove any superfiuous electrolyte which may adhere thereto in the form of droplets. The paper is then directed to the recording apparatus per se but between the guide roller 25 and the printer bar electrode I4 is positioned a heating deviceZI. After the recording has been made the paper progresses to a pair of rollers 29 and 30 from which point it may again be wound on a roller or may be cut up into lengths according to the messages which are transmitted over the system. The rollers 29 and 30 also operate as feed rollers to pull the recording paper through the apparatus. These rollers are driven mechanically by some motor means (not shown), and are preferably rotated in conjunction with or in synchronism with the speed of rotation of the recording cylinder ill by means of an appropriate gear arrangement between the recording cylinder and the feed rollers.

Enclosing the impregnating tank 20 and the guide rollers associated therewith a housing may be so positioned that the recording paper will not be excessively afiected by extraneous temperatures and atmospheric conditions. The electrolyte 22 which is placed within the tank may be of any type which will produce proper and satisfactory electrolytic recordings when subjected to an electric current, and may, for example, be any one of the solutions or any modification of the solutions described in an application, Serial No. 178,743, of Myer Solomon filed December 8, 1937. The amount of moisture remaining in the paper at the time it reaches the printing point, as stated above, must be held within proper limits to ensure proper printing. The impregnating tank is therefore so situated that even under the driest atmospheric conditions the paper will be sufliciently wet by the time it reaches the printing point that proper recordings may be produced. Under other atmospheric conditions, drying the paper to the proper moisture content is therefore necessary and is accomplished by controlling the amount of heat which is applied to the element of the heating device 21. Since the resistance of the paper at the printing point is a function of its moisture content, it can be measured and used to control the heat supplied by the heater element which dries the paper to the proper moisture content. This is accomplished by providing a v for the recording drum. Attached to the support member 43 is a switch actuating arm 44, the arm being pivoted at the point 45. Positioned along the arm is a roller 41 for cooperation with the cam 42 and a spring 48 is provided for maintaining the roller or follower 41 in contact with the surface of the cam 42.

Since it is necessary that the conductivity or moisture content of the paper be determined, means are provided whereby the resistance of the paper at this point may be ascertained. Between each separate line of the recording there is normally a slight time delay and it is during this time delay that the resistance measurement is made. On the cam 42 there is therefore provided a recessed portion 50 which corresponds to the length of time during which no recording is being produced and during this time the resistance of the paper is measured.

Signals from the printer amplifier are supplied to the recording apparatus along conductor 52 the conductorterminating in a switch arm 53. Another switch arm 54 is provided for cooperation therewith, and during the time when a picture line is being recorded, switch arms 53 and 54 are in contact and the amplified signals are supplied to the recording point i4 by means of the conductor 56. The circuit is complete through the recording paper, the helix II, the drum l0, and the support member 43 to ground at 34. When the recording drum is rotated sufficiently to complete the recording of one picture line, the cam will be in such a position as to permit the roller 4! to cooperate with the recessed portion 50. The switch arm 54 is then permitted to come in contact with an additional switch arm 55 and the circuit from the printer amplifier to the recorder is broken since switch arm 54 is separated from the switch arm 53. The recording electrode l4 and the conductor 55 are then connected to the conductor 58.

The resistance measuring circuit and heater control arrangement consists of a transformer 60, the primary of which is connected to the usual -volt alternating current lighting circuit. The secondary of the transformer 50 is a high voltage center tap winding, the center tap SI of which is connected to ground. Connected between the conductor 62 and the center tap 5| is a discharge tube 64 comprising a cathode, a control electrode and an anode, the connection from the conductor 62 to the anode including a resistance 55 and a condenser 56. Connected between the conductor 63 and the center tap conductor 6| is a resistance 58 which operates as a potentiometer and along which a variable tap connection 59 is made. The connection 68 is connected to the control electrode of the discharge tube 64 by way of a resistance 10. It may, therefore, be seen that during alternate half-cycles of the alternating current when the conductor 62 is positive, a certain amount of current will flow through the discharge tube 64 in accordance with the setting of the adjustable point 69. During these half-cycles when the anode of the discharge tube 64 is positive the conductor 63 is negative, if the adjustable/connection 69 is moved toward the conductor 63 less and less anode current will flow through the resistance Slat these halt cycles,

and more anode current will be permitted to flow it the connection 68 is moved toward the ground conductor 6i. Connected also to the control electrode of the discharge tube 84 is the conductor 5! which, as stated above, during periods when no recording is made, is connected to the printer bar electrode ll of the recording apparatus. The recording drum or the facsimile receiving apparatus is connected to ground at 34 in order to complete the circuit for the printer signals and in order to complete the circuit for the resistance measuring means. It may be seen, therefore, that the resistance or the recording paper would present itself as a resistance conneted between the control electrode or the discharge tube 64 and ground so that the potential which exists uponthe control electrode of the discharge, tube 64 with respect to its cathode is determined by the resistance of the recording paper; or in other words, by the moisture content thereof. It the resistance of the paper is high the control electrode of the discharge tube 64 will be more negative than when the resistance of the paper is low, with the result that less anode current will be permitted to flow from the discharge tube 64. The condenser 66 is made relatively large and due to its storage eflect tends to hold the voltage which appears across the resistance 65 to substantially a constant value between each recording line; i. e., between successive resistance measurements of the paper.

Connected between the conductor 62 and the ground conductor BI is an additional electron discharge path including a tube 12, a resistance 13 and a condenser 14, the discharge tube and resistance being connected in series and the condenser being cc inected in parallel with the resistance. This diode will pass current during each alternate half-cycle, or in other words at each half cycle when the conductor 62 is positive with respect to the ground conductor 6 I. The amount or current passed by the discharge tube 12 is determined by the impedance of the tube 12 and the impedance of the resistor 13 and condenser 14 which are connected in series therewith.

Two discharge tubes 11 and 18 are also provided, one of these tubes being connected between the conductor 62 and the common conductor 6i while the other tube. 18, is connected between conductor 63 and the common conductor 6|. These tubes therefore conduct current alternately and the amount of current conducted by these tubes is controlled by the potential of the control electrodes of the tubes with respect to the potential of the cathodes thereof. Furthermore, connected in the common conductor 6| between the cathode of tube 12 and the cathodes of tubes 11 and 18 is the heating element of the heating device 21 so that all of the current which is drawn by the two tubes 11 and 18 flows through the heating device 21. The control electrodes of the tubes 11 and 18 are connected in parallel and are connected to the anode of a discharge tube 80, the cathode of which is connected to a point along the resistance 13 and the control electrode of which is connected to the anode of discharge tube 64. In order to maintain the control electrodes of tubes 11 and 18 at a proper initial potential with respect to the cathodes thereof, and in order that the anode circuit for tube 80 be complete, a resistance 82 is provided, the resistance being shunted by condenser 83.

The discharge tube 12 operates a hall-wave rectiller and the current passed therethrough produces a .potential drop across resistance 1! in the same direction as the voltage which appears across resistance 65. The purpose or the resistance 13 is to provide a. potential for balancing out the voltage developed across the resistance 65 for the min- B imum value or heating from the heating device 21. The connection from the cathode of the discharge tube to the resistance 13 is therefore adjusted to a point where substantially no heating will result when the paper is at its lowest permissible conductivity.

The connection from the cathode of tube llll to the resistance 13 is so adjusted that the voltage applied to the cathode of the discharge tube 80 is equal to the voltage applied to the control electrode thereof when the moisture content oi the paper is at its lowest limit without any heat being supplied by the heating device 21. For this condition, the discharge tube 80 draws full anode current through the resistance 82 which biases the control electrodes of the tubes 11 and 1| to cut-oil and as a result no current is permitted to flow through the heating element 21 (except for the small discharge current or the tube 80) As the moisture content of the paper increases, its resistance decreases and the current through the resistance 10 increases with the result that the bias of the control electrode of the discharge tube 64 becomes less negative resulting in an increase in the anode current of this tube. Because of this the voltage drop across the resistance 65 increases and becomes greater than the voltage drop across the resistance 13, so that the control electrode of the discharge tube 80 becomes negative with respect to its cathode and the plate current through the discharge tube 80 decreases. This allows the control electrodes of the discharge tubes 11 and 18 to become less negative, permitting anode current to' flow in each of the tubes with the result that the anode current produces a certain predetermined heating effect at the heating device 21 to suillciently dry the paper to bring the conductivity back to its normal condition and to establish a proper moisture content in the paper to produce satisfactory recordings.

In order to prevent the system from hunting a thermal lag is introduced in the heating element of the heating device 21. The extent or the thermal lag is determined by the size of the material on which the resistance wire of the heating element is wound and the required sizeot this core or element may be determined by experimentation. Various sizes of core may be used depending upon the material of which the core is constructed. Materials such as Bakelite," steel and copper have been successfully used as cores.

It is to be understood that although the system has been described somewhat specifically, various modifications and alterations may be made in the present invention without departing from the spirit and scope thereof, and it is desired that any and all such modifications be considered within the purview of the present invention except as limited by the hereinafter appended claims.

I claim:

1. In an electrolytic facsimile recording apparatus wherein a length of moisture absorbent material is used to receive the recording and whereinthe moisture content of the material is maintained within predetermined limits comprising a heating device, means for transporting the material to said heating device and recording apparatus, electronic tube means responsive to the conductivity of the material, and means responsive to said last named means for controlling the energy supplied to said heating device.

2. In an electrolytic facsimile recording apparatus wherein a length of moisture absorbent material is used to receive the recording and wherein the moisture content or the material is maintained within predetermined limits comprising a discharge tube, means for controlling the conductivity of said tube by the moisture content oi the material, an electric current heating device, means for varying the amount 01 current supplied to said heating device, and means for controlling said last named means by the conductivity of said tube.

3. A system for controlling the moisture content of a strip of recording material in an electrolytic recording apparatus comprising a source of current, an electron discharge device and a resistance connected across said source, said discharge devioe including at least a cathode, an anode and a control electrode, means responsive to the conductivity the material and connected to said cathode and control electrode for controlling the impedance of said discharge device, a heating device including a, resistance, a second discharge device including a cathode, an anode and a control electrode connected in series with said heating device, and means for controlling the impedance of said second discharge device by the potential drop across said first resistance.

4, A system for controlling the moisture content of a strip of recording material in an electrolytic recording apparatus comprising a source of current, an electron discharge device and a resistance connected across said source, said discharge device includingat least a cathode, an

anode and a control electrode, means connected to said control electrode for controlling the conductivity oi! said discharge device in accordance with the moisture content of said material to produce a potential drop across said resistance. a heating device including a resistance, a current limiting device connected in series with said heating device, and means responsive to the potential drop for controlling the impedance of said current limiting device.

5. In an electrolytic facsimile recording device comprising a pair oi recording electrodes, means for directing a length of recording paper between said electrodes, means for moistening said paper with a recording electrolyte, means for subjecting said recording p per to a signal current in a lineior-line manner to produce a recording, a soin'ce or current, an electron discharge device and a resistance connected across said source of current, said discharge device comprising a cathode, an anode and a control-electrode, means connected to said control electrode and to said cathode including said recording electrodes for controlling the conductivity of said discharge device to produoe changes in the current through said resistance in accordance with the conductivity of said paper as a function or the moisture content thereof, a heating device including a resistance for reducing the moisture content of said paper to a predetermined amount, a current limiting device connected in series with said heating device, and means responsive to the potential drop across said first named resistance for controlling the impedance of said current limiting device.

RAY G. SHANKWEILER.

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