US3396302A - Electronic tube with evaporation-proof cathode and electromagnetic electrostatic andheated grids controls - Google Patents

Description

Aug. 6, 1968 H. GREBER 3,396,302

ELECTRONIC TUBE WITH EVAPORATION-PROOF CATHODE AND ELECTROMAGNETIC ELECTROSTATIC AND HEATED GRIDS CONTROLS Filed Aug. 5, 1966 nce: 26

0 000090.. 6' 'ZI'QIIQOIIOIIZ INVENTOR.

United States Patent 3,396,302 ELECTRGNIC TUBE WITH EVAPQRATEGN-PRGGF CATHEDDE ANfi ELECTROEEAGNETEC ELEC- TRQSTATIE AND HEATED GRIDS CGNTRBLS Henry Greher, 225 W. 80th St., Apt. 8D, New York, NSY. 1%24 Filed Aug. 5, 1 366, Ser. No. 579,699 1 Claim. (Cl. 313--3ilii} ABSTRACT OF THE DHSCLUSURE This invention relates to an electronic tube whose cathode is protected against evaporation by that it consists at least of two parts emitting particles toward each other. The current of this electronic tube can be controlled by means of three grids: first, an electrostatic grid deviating, by electrostatic repulsion, the electron beam from the anode, second, an electromagnetic grid consisting of a coil acting as a blowout coil preventing the electron beam from reaching the anode, third, a heated electronemitting grid, whose electrons collide with those of the controlled electron beam. The anode consists of sawtooth shaped straps, or wave shaped wires connected between two circular conductors, so that when the controlled electron beam is deviated a smaller part of it is intercepted by the anode.

The purpose of this invention is to provide an electronic tube with a cathode which is protected against evaporation, so that it can emit a large thermionic current. A further purpOse of this invention is to provide this electronic tube with three dilferent controls, an electromagnetically acting grid, an insulated grid acting electrostatically, and a heated grid that acts through emission of thermionic current. Two of these functions can be combined in one grid. For example a heated grid can act electromagnetically, as a blowout coil, and it can also act through its emission of thermionic current, at the same time. An insulated grid can act electrostatically, by repulsing electrons emanated from the cathode, and at the same time, if it is passed by a current, it can also act as a blowout coil. It is conceivable that a specially arranged grid, for example a partly insulated grid, could carry out all three functions simultaneously.

It is generally known, that the ,main disadvantages of gas filled tubes, and especially of the thyratron, is that once the flow of the current between cathode and anode is started, it cannot be controlled by means of conventional grids. It is a further purpose of this invention to overcome these disadvantages of gas filled electronic tubes. Another disadvantage of these tubes is that they can conduct only comparatively small currents. Therefore, they are unsuitable for electric power applications in which large currents are used. It is a still further purpose of this invention to overcome this disadvantage of the gas filled electronic tubes, too.

The means to achieve all these purposes are: (l) A cathode, that consists of a metallic heating element in form of a strap. One side of this strap is covered with heat-resistant ceramic material. The strap is so arranged that its non-covered parts face each other. This arrangement serves for the purpose that metallic particles emitted from one noncovered part of the cathode land on another of its non-covered parts. As a result of this, the thickness of the strap remains unchanged. (2) An anode consisting of a cage-like structure, in which straight, or slightly waved wires, or straight tapes, or tapes with slight sawtooth shaped cutouts, with the wires as well as the tapes being parallel to the cathode, are fastened at their ends to two circular wires. (3) A grid made in form of a wire helix, as usual, except that both ends of the helix are brought outside the tube. This helix serves as a blowout coil. (4) Another grid, which is also given the shape of a helix, as usual, except that the wire used for this grid is insulated, in contrast to that used for ordinary grids. (5) A third grid that is also helically shaped, but it is made of heating Wire with both of its ends brought out side the tube, for connection to a source of heating current.

The nature of these means and their further design details are described in the following specification, and shown in the accompanying drawing. In this drawing, FIG- URE l is a schematic cross section of the tube according to this invention. All five elements enumerated above are shown and connected in this diagrammatic cross section. FIGURE 2 shows a part of the heating element of this tube, and FIGURE 3 shows two such elements facing each other with their heating straps. The structure of the anode is presented in the perspective view of FIGURE 4. A cross section of another embodiment of the cathode according to this invention is drawn in FIGURE 5. A cross section of still another embodiment of such cathode is presented in FIGURE 6. A further cathode according to this invention is shown in the perspective view of FIG- URE 7. FIGURE 8 shows a cross sectional view of a potlike cathode, and two such cathodes facing each other are presented in cross section in FIGURE 9. FIGURE 10 shows a cross section of a gas discharge tube incorporating elements of this invention. All figures are shown diagramatically.

In detailed review of this drawing, it can be seen in FIGURE 1, showing a diagramatic cross section of the electronic tube according to this invention, that envelope 1 contains cathode 2, which consists of a metallic strap bent in the form of a helix. The external side of the heating strap is covered with heat resistant ceramic material. The ends of the cathode 2 are brought out by ,means of conductors 3 and 4 to the terminals of battery 5. Battery 5 serves for heating the cathode 2. Envelope 1 contains also the cage-shaped anode. In the cross sectional diagram of FIGURE 1 the two horizontal wires 6 and 7, are shown connected to the circular wires 8 and 9. The anode is connected, by means of conductor it) to the plus terminal of battery ill. The negative terminal of this battery is connected, through wire 3, to cathode 2. Battery 11 serves to supply the potential difference between cathode 2 and the cage-shaped anode, 6, 7, 8, 9. Envelope 1 contains also the three enumerated grids. The nearest to the cathode is grid 1.2. Grid 12. is helical. Since FIGURE 1 is a diagramatic cross section of this electronic tube, the convolutions of helix 12 appear in this figure as little circles 12. Grid 12 is made of heating wire, which is supplied with energy, through conductors l3 and M, from a source of potential 15, shown diagrammatically. The next grid, further away from cathode 2 is grid 16, which consist of an insulated wire wound into a helix. The ends of this helix 16, are brought out, by means of conductors 17 and 13 to a source of potential 1%, also shown diagrammatically. The third grid 2% is also helical, and serves as a blowout coil. it can be made of a bare or of an insulated conductor. Grid 2% is connected, by means of conductors 21 and 22 to the diagrammatically shown source of potential 23.

In FIGURE 2 is shown the perspective view of end of cathode 2 shown in the preceding figure. It can be seen that the cathode consists of a heating strap 24, which is fastened to the ceramic layer 27, by means of little hooks Z5, 26, bent to it into corresponding endopenings in the ceramic layer 27.

As shown in the perspective view of FIGURE 3, two such combination straps can be used, one above the other. It can be seen that the heating straps 28 and 29 face each other, while their ceramic cover layers and 31 are turned away from each other. The hooks fastening heating straps 28 to cover 31 are designated with the numeral 32. Similarly, the hooks fastening heating strap 29 to its ceramic cover 36 are designated with the numeral 33.

The anode is shown diagrammatically in the perspective view of FIGURE 4. The two circularly bent wires 35 and 36 are connected with a plurality of horizontal wires, all designated with the number 36. Wires 36 are bent in the shape of a sine wave. In order to show also other possible design variations, also strap 37 connecting the circular wires 34 and 35 is presented. It can be seen the stnap 37 is provided with sawtooth-like cutouts 38. Similarly strap 39 is provided with another shape of cutouts 4%. Wires 41 and 42 serve for connection of the anode into its cirsuit. In the majority of cases only one lead wire 41 or 42 is necessary.

In the cross sectional view shown in FIGURE 5, it can be seen that cathode strap 44 can assume the form of a spiral, and so can its ceramic cover 45. Gap 47 serves for the exit of electrons. Metallic particles emitted from one part of heating strap 44 fall on another part of it. Only an insignificant part of them can escape through gap 47.

FIGURE 6 shows another cross sectional view of a cathode of a diiferent design. In this cathode, heating straps 48, 49, 50, 51, 52, and 53 are facing each other. They are covered with the ceramic covers 54, 55, 56, 57, 58, 59. The electrons can escape from the cathode toward the anode through the gaps -69, 61, 62, 63, 64, and 65.

In the perspective view of FIGURE 7, the metallic heating element 66 is tubular. It is surrounded with the ceramic tube 67. The lead wires to, and from the cathode are designated with the numerals 68, and 69.

FIGURE 8 is the cross sectional view of a cathode consisting of a pot-like ceramic housing 79, containing the circular heating element 71, connected with its lead wires 72, and 73 to a source of electric energy. If only one such heating element is used, it is not protected against evaporation. If two such elements are used, as shown in the cross sectional view of FIGURE 9, the metallic particles evaporated from heating element 74, for example, fall upon heating element 75, and vice versa, so that none of them becomes actually thinner. Gap 73 serves for the escape of electrons. Ceramic covers 76 and 77 protect the heating elements 74 and 75 respectively. The lead wires to and from heating element 7 are designated with 79, 80. The lead wires for heating element 75 are designated with 81, 82.

In the cross sectional view of a gas discharge lamp shown in FIGURE 10, it can be seen that envelope 83 contains the heating electrode 84, connected with the blowout coil 85 in series. The lead wires to this electrode and its blowout coil are designated with 85 and 87. Similarly, the juxtaposed heating electrode 88 is connected in series with its blowout coil 89. Both are connected to the lead-in wires 94 and 91.

The mode of operation of this electronic tube can be best described by breaking it down into the modes of operation of its components. The cathode consists of a heating element in form of a strap covered on one of its sides with a heat resistant layer. This layer can be made either of a ceramic material, or of graphite, particularly of pyrolitic graphite, or of asbestos, or of enamel. The heating strap is wound into a helix or bent into a tube, or spiral in such a way that the parts of the strap non-covered with the heat resistant layer face each other. Thereby, the metallic particles emitted by one part fall upon the juxtaposed part of the same strap, and vice versa. In effect, the thickness of the strap remains almost constant. This arrangement of the heating strap or straps permits to achieve a much higher thermionic current from this cathode than can be achieved from other cathodes of customary designs.

The grid that is nearest to the cathode, also acts on the principle of thermionic emission. It is made of a heating wire wound to form a helix. When heated, this grid emits electrons into the space around it. These electrons constitute a space charge which prevents, to some extent, the emission of electrons by the main cathode. By heating the electron-emitting grid to ditferent degrees, it can be used as a means to control the emission of thermionic current by the main cathode. The second grid further away from the cathode acts on the principle of electrostatic repulsion between charges of the same sign. This grid is made of an insulated wire wound into a helix. Only one end of this helix can be connected to a source of variable potential. The more negatively this grid is charged, the more it interferes with the emission of thermionic current by the main cathode. Consequently, this grid can be used as an effective means to control the emission of the cathode. The third grid, still further away from the cathode, and the nearest to the anode, operates on the principle of a blowout coil. It consists of a bare or insulated conductor wound to form a helix. When this helix, whose both ends are brought outside the tube, is flowing a current, it produces a magnetic flux parallel to the axis of this helix. Since the thermionic current emitted by the cathode of the tube is perpendicular to this magnetic flux, it is deviated in the direction of the circumference of the helix. An ordinary anode, which has the form of a cylinder would not be afiected by this deviation. The anode of the here described electronic tube, however, is of difierent design than customary. It consists of conductors parallel to the axis of the blowout helix. These parallel conductors are connected with one of their ends to one circular, collecting wire, and with their opposite ends to another circular wire. In result of this arrangement, the anode assumes the shape of a cage. The said parallel wires receive the thermionic current emitted by the cathode. The current received by them, however, is effected by the value of the magnetic flux produced by the blowout grid. The more intensive this magnetic flux, the more it deviates the current from the parallel wires of the anode, so, that some part of this thermionic current misses the parallel wires of the anode. To optimize this effect, the parallel wires of the anode are given the sine wave form. The greater the deviation of the thermionic current, the less surface of the anode wires it finds to intercept it. The same effect can also be achieved by other similar means. So, for example the parallel anode wires can be replaced with straps whose edges are cut out in form of sawteeth. The greater the current in the blowout helix, the more intensive the magnetic flux produced by it, the more deviated is the thermionic current approaching the anode straps. The more deviated the thermionic current is, the smaller is the surface of the sawteeth cutouts to receive it.

As mentioned, these difierently acting grids do not have to be used separately, they can be combined. Therefore, both ends of each grid are brought outside the tube. It is also possible to use the cathode itself, if it has the form of a helix, as in FIGURE 1 of the drawing, as a blowout grid.

The described electronic tube can be used for an infinite number of purposes, for detection, low and high frequency amplification, and generation of electric waves as an oscillator. It is particularly suitable for thyratrons, which cannot be controlled with customary grids. Since this electronic tube is capable of conducting large currents, an important group of its applications is an AC and DC circuit breakers. It can also be applied as lightning arrester. In this case the protected conductor is connected to the anode, and the cathode is connected to ground. At lightning surge voltage the thyratron conducts, and the follow up current is interrupted by the combined action of the grids. Also a mercury rectifier anode can be provided with the here described grids. These grids can be used to control the current through the rectifier. This control can be, for example, applied to limit the short circuit current through the rectifier. These grids can also be applied to smooth the wave form of the current, without the use of capacitors and reactors,

usually installed for this purpose. Since the blowout grid can be installed outside the electronic tube, it can be used for measuring large, including extra high voltage currents, and also for relaying purposes. The tube is also suitable to control the current in series circuits, such as used for illumination by means of gas discharge lamps connected in series.

One of the most important applications of this electronic tube is for control of the current in gas discharge lamps. This application is illustrated in FIGURE of the drawing. If at least one of the heated electrodes is provided with a blowout grid according to this invention, the current through the lamp can be kept below a preset maximal value, without the use of the customary ballasts. Since the ballasts are a source of losses, the economy of illumination by means of gas discharge tubes, including the popular fluorescent tubes, could 'be significantly increased. Interestingly, the same blowout grid, if bypassed by an adjustable resistor, installed outside of the tube, could be used for control of the light output, and for dimming of a gas discharge lamp.

As can be seen from the preceding, an infinite number of variations, modifications and changes of this invention, by different combinations of its elements can be made, without departure from its spirit, as defined by this specification and the following claim.

I claim:

1. An electronic tube consisting of a cathode having a heating strap whose one side is covered with a layer of heat resistant material, said strap being arranged in such a way that non-covered parts of it face each other, so that metallic particles emitted by one part land on the juxtaposed part and vice versa, of a first grid consisting of a heating wire wound to form a helix surrounding said cathode, with said first grid emitting electrons when a current from a potential source is passed through it, said electrons form a space charge partly preventing the cathode from emitting its thermonic current, of a second grid consisting of an insulating conductor wound to form a helix surrounding said cathode, which conductor when charged negatively from an outside source of potential suppresses the emission of electrons by said cathode, of a third grid consisting of a conductor wound to form a helix surrounding said cathode, which helix when a current passes through it produces a magnetic flux deviating the thermionic current from reaching the parallel wires of the anode, with an anode consisting of a plurality of conductors all essentially parallel to the axes of said first, second and third grids, said anode conductors are connected electrically in parallel, said anode conductors being also parallel to the axis of the magnetic flux produced by said third grid.

References Cited UNITED STATES PATENTS 743,237 11/1903 Bremer 315-347 X 749,793 1/ 1904 Hewitt 315-347 2,013,094 9/1935 Frantz 313 X 2,261,607 11/ 1941 Summers 313300 2,612,613 9/1952 Steiner 313167 X 2,947,902 8/1960 Post 313155 X JAMES W. LAWRENCE, Primary Examiner.

R. JUDD, Assistant Examiner.

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