Cathode ray telautograph
United States Patent 2227083

The invention relates to a novel apparatus for transmitting letters, drawings, sketches and the like with the aid of a cathode ray tube. The object of the invention is to provide an arrangement having a cathode ray tube with two deflection systems for deviating the produced electron ray in...

Erich, Handrick
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The invention relates to a novel apparatus for transmitting letters, drawings, sketches and the like with the aid of a cathode ray tube.

The object of the invention is to provide an arrangement having a cathode ray tube with two deflection systems for deviating the produced electron ray in two different directions extending preferably at right angles to one another. A resistance layer is provided as is also an electrically conductive point or stylus by means of which the image is drawn upon the resistance layer before being transmitted. The deflection systems of the cathode ray tube are conductingly connected with the said resistance layer and are arranged in a bridge circuit fed from a direct current source so that movements of the point over the resistance layer may cause corresponding movements of the electron ray over the fluorescent screen of the tube.

The invention may best be explained by referring to the drawing wherein like reference characters represent like parts and wherein: Figure 1 shows schematically a preferred form of the present invention; Figure 2 shows a detail modification of a portion of Figure 1; Figure 3 shows one system for suppressing the cathode ray beam under certain circumstances, and Figure 4 shows a modification of the system shown in Figure 3.

In Figure 1, item I represents schematically a tube having four deflection plates. Each pair of deflection plates is bridged by resistors, namely one of the plate pairs by the resistors 10 and I i and the other pair of plates by the resistors 12 and 13. The centers of the resistors bridging the pairs of deflection plates have connections to the negative pole of a direct current source 2 while the other pole has the point or stylus 6 consisting of conductive material, connected thereto across a relay winding 9. This point serves for drawing a picture on the resistance layer 3 of which a part 4 is a smooth plate suited for writing or drawing the picture to be transmitted with the arrangement. To this end, four contacts 7 are arranged upon the resistance plate 3 in a uniform distribution in the vicinity of the border of 3 of which each is connected to a respective plate of the deflection systems of the tube I. A pair of deflection plates is connected with opposite contact electrodes 7.

Now, if the writing member or stylus 6 comes in contact with a point of the resistance layer I 3 the direct current source 2 passes a current through the deflection plate resistances, the writing member 6 and the resistance layer 3 placed in a bridge circuit. The current in the different branches of the bridge then depends on the resistance existing between the contact point of the writing member and the individual contacts 7; in other words it depends upon the position of the writing member on the layer 3. Hence, potentials appear at the resistors 10, II, 12, 13 which are applied to the pairs of deflection plates thus effecting a displacement or deflection of the electron ray beam of the tube on the screen to a point which corresponds to the position of the writing member on the resistance layer. If for instance the writing point is situated in the center of 4, the potentials appearing at opposite ends of the resistors 10 and II are equal in intensity and accordingly the beam is not deflected. The same is true as regards the potentials at resistances 12 and 13. Therefore, the electron ray impinges the center of the fluorescent screen without having been deflected. If, however, the writing point is in the vicinity of one of the electrodes 7, the potentials at the resistors 10, II, 12 and 13 are such that they effect a maximum adjustable displacement of the electron ray determined by the magnitude of the direct current source.

Hence, as the writing member moves over the layer 4, the electron ray carries out corresponding movements on the fluorescent screen, i. e., the pictures drawn by the writing member are rendered visible on the fluorescent screen and transmitted thereto. The images appearing on the fluorescent screen therefore are sufficiently true to scale, but it should be borne in mind in this connection that the fidelity of the transmission is the higher, the smaller the surface 4 and the greater the symmetry of the latter with respect to all contacts 7. But if it is desired to have the surface 4 as large as possible, it is advisable to provide a resistance layer which varies all over in its thickness from point to point instead of having the same thickness so that distortions of the picture due to the transmission will be compensated. Figure 2 shows an example of a modification of the arrangement according to the invention.

An elastic metal foil is spanned between the mounts 15 and 16 above the resistance layer 3 and the table 4. This foil carries a piece of writing paper 14. The tensioned foil takes the place of the writing member 6 in that for instance the mounts 15 and 16 are connected to the direct current source 2. Now when writing on the paper 14 by any desired instrument the foil is pressed M5 against the resistance layer 3 so that a current can pass through the bridge circuit and which produces potentials at the deflection plates in the manner described.

The relay I serves for controlling the beam intensity, and accordingly the brilliance of the tube, at writing, in fact if the writing organ touches the resistance layer, the relay is actuated and short circuits a negative biasing potential placed at the beam intensity control electrode of the tube, said potential preventing the appearance of the luminous spot on the screen when the apparatus is out of operation.

The control of the cathode ray beam may best be explained by referring to Figure 3 of the drawing wherein a portion of the circuit of Figure 1 is shown. Figure 3 shows also the arrangement of the cathode ray tube serving for recording and transmitting of the images produced by stylus 6. The cathode ray tube is indicated by I. Its cathode is indicated by 21. In front of the cathode the control electrode 22 is arranged, and succeeding this electrode, an electron lens 23, a cylinder 24 and an anode 25 are located. The plate is succeeded by two pairs of deflecting plates 26. A direct potential source 28 is provided for producing the anode potential and the partial potentials required for the other electrodes, a voltage divider 27 being inserted in the circuit of said direct potentfal source. The positive pole of battery 28 is grounded so that plate 25 is also at ground potential. Control electrode 22 is connected to the negative pole of 28 through a resistance 28. Resistance 29 is bridged by a switch 30 which, on the one hand, is connected to that end of resistance 29 which is directly connected to the control electrode 22. As can be seen from Figure 3 the control electrode 22 is negatively biased in regard to cathode 21 so that the cathode ray is not able to produce an electron beam and a spot on the luminescent screen of tube I. The potential between the control electrode and the cathode may amount to approximately 1-2 v., for example. When relay winding 9 exerts attracting power due to operation of stylus 6, it closes switch 30 and, consequently, a less negative potential in regard to the cathode is imparted to the control electrode, for instance, a potential of only 4 v. Thus a cathode ray beam is produced 60 and the tube is ready for operation.

According to Figure 4, relay actuating means consists of elements 31 to 39, 31 being a resistance, 32 an electron tube with plate33, control grid 34 and cathode 35, 36 indicating a battery biasing 5 control grid 34 negatively in regard to cathode 35 to such an extent that the tube cannot pass any current. 38 indicates the plate battery and I represents a current-sensitive electromagnetic relay of lower sensitivity which, for instance, exerts attracting power at a current of 30 ma. and more, and closes switch 30 according to Figure 3.

The whole arrangement represents a device for amplifying the current passing through 31 producing a corresponding control potential at resistance 31 which makes the grid more positive to such an extent that a strong current Is passed by the tube. In this case, a much stronger current flows through the plate circuit of tube 32 than through resistance 31 so that a less sensitive relay I is operated by the plate current than may be operated directly. This arrangement is preferably used when it does not appear suitable to feed the current of approximately 1 ma. flowing through stylus 6 directly to an electromagnetic relay of corresponding sensitivity as in Figure 3.

The subject matter of the application is particularly well suited for the direct transmission at distance of script, drawings, signatures (in banks for instance), for reducing the scale of drawings or enlarging, and the like. When transmitting such configurations this extremely simple apparatus will be preferreed as compared with the known complicated television arrangements which serve for transmitting moving images having many details.

As regards the manufacture of transmission apparatus according to the Invention, it is advisable to make the entire apparatus exclusive of the tube so that it may be connected to any desired cathode ray tube.

I claim: 1. A cathode ray telautograph system comprising a cathode ray, means in said tube for developing a beam of electrons, means for deflecting the beam in substantially mutually perpendicular directions, said last named means including beam deflecting means, a source of potential, a stylus and a resistance area whereby the potential applied to the deflecting means and accordingly the deflection of the cathode ray beam may be controlled in accordance with the position of the stylus on the resistance area, and means for preventing the development of the beam of electrons when the stylus is removed from the resistance area comprising a relay responsive to the current present in the stylus circuit.

2. A telautograph comprising a cathode ray tube including means for producing a beam of electrons of small cross-sectional area, means responsive to the presence of the produced cathode ray beam, and means for deflecting the cathode ray beam in substantially mutually perpendicular directions, said means including beam deflecting plates, a source of potential, a stylus, and a resistance area whereby the potential applied to the deflecting plates and accordingly the deflection of the cathode ray beam and its position on the beam responsive means may be determined by the position of the stylus on the resistance area, means for normally biasing the cathode ray beam to beam cut-off and means including a relay for permitting the production of a cathode ray beam whereby the beam may be produced only when the stylus is in contact with the resistance area.