US2219107A - Electron discharge device - Google Patents

Description

Oct. 22, 1940. o. s. LANGMUER 2,219,107

I ELECTRON DISCHARGE DEVICE Filed Aug. 29, 1959 INVENTOR. 04 W0 8. LANGMU/R ATTORNEY.

Patented Oct. 22, 1940 PATENT OFFICE ELECTRON DISCHARGE DEVICE David B. Langmuir, Engiewood, N. 1., assignor to Radio Corporation of America, a corporation of Delaware Application August 29, 1939, Serial No. 292,398

5 Claims.

My inventiorrrelates to electron discharge devices, particularly to seals and lead-ins for such devices.

The required large number of lead-in con- 5 ductors in many commercial tubes seriously com- In some plicates the manufacture of the tubes. cathode ray tubes, for example, the number of focusing and accelerating electrodes is limited by the number of Wires that can be sealed into the i stem at the end of the tube. Wires are difficult to seal into the side wall of a tube, and the presence of even the ends of the wires on the interior of the envelope distorts the focusing field of the ring-shaped electrodes.

it! An object of my invention is an electron discharge device into which any desired number of lead-ins may be easily sealed.

A more specific object of my invention is a tube of the cathode ray type in which a plurality of go coaxial ring-shaped electrodes with lead-in conductors may be easily made and in which the fields of the electrodes are undistorted.

The characteristic features of my invention are defined in the appended claims and a preferred 25 embodiment is described in the following specification and shown in the accompanying drawing in which Figure l is a sectioned view of a cathode ray tube embodying my invention and Figure 2 is a detailed transverse sectional view of a 30 lead-in conductor of Figure 1 constructed according to my invention.

The cathode ray tube chosen for illustrating the characteristic features of my invention and shown in Figure 1 comprises an envelope l with an elongated tubular portion joined at one end to a viewing plate 2 internally coated with an electron responsive luminescent material 3 and closed at the other end with a conventional re-entrant stem carrying an electron gun 4. A beam of 4 electrons emitted from the inner end of the gun is directed toward the screen, the electrons being accelerated and focused to a sharply pointed beam by the coaxial ring-shaped electrodes 5. The focusing electrodes 5 may conveniently be 45 rings of metal deposited as thin films upon the inner wall of the envelope. Direct current positive potentials may be applied to the ring electrodes to cause the beam of electrons emanating from the end of the electron gun to sharply 50 focus upon the screen.

The usual type of lead-in conductor for each ring electrode 5 comprises either a separate wire sealed through the cylindrical side wall of the envelope and soldered or otherwise ioined at its my inner end to the film electrode, or a wire ex tending to the electrode from the press at the end of the envelope. The wire in either arrangement electrically disturbs the smooth continuity of the inner surface of the cylindrical electrode and distorts the electrostatic field with 5 a resulting defocusing of the beam. Lead-in conductors for the electrodes, according to my invention, leave the fields of the inner surfaces of the ring electrodes cylindrical in shape and the fields undisturbed.

The lead-in conductors, according to my invention, are made by perforating the envelope and by making one hole in the envelope opposite each focusing electrode. The holes may conveniently be made by heating a tungsten wire white hot and pushing the end of the wire through the glass. The surface of the glass in the holes and on the inside and outside of the envelope is then coated with a thin layer of metal so that a continuous film of metal not only forms the electrode but also extends along and is hermetically sealed to the walls of the hole and continues to the outside where it forms an outside contact. Any metal which will form an adherent conductive film on the glass and also a hermetical seal to the glass may be used, although I prefer to use and have obtained good results with the adherent conductive metal coating produced with a platinizlng solution such as that commercially known as Liquid Bright Platinum No. 05. The entire inner surface of the envelope, between the ends of the focusing region, may be coated with the metal film and the separate sections of the film electrically separated by removing the film as with a lathe tool. Alternatively, of course, the as separate ring-shaped deposits may be separately applied with suitable spraying and masking means. A narrow strip 6 of the metal film on the exterior of the envelope is extended some distance from the hole on the outside of the envelope to form an exposed area of film to which external contact may be made. Each metal-lined hole is then closed with a plug such as a bead of glass, which will hermetically seal to the metal film. The envelope is heated nearly to the softening point but not to its deformation temperature, and the end of a piece of caneglass, preferably of the composition of the envelope, heated until it is soft enough to form a workable globule on the end of the rod, is pushed down so over and puddled in the hole in the hot envelope to fill and seal the hole, and the rod of cane glass pulled away. I have found that in this way I can hermetically seal the metal film on the walls of the hole to the glass plug andalso to the 66 envelope. As the envelope is below its deformation temperature the shape 01' the hole in the envelope is not changed during the puddling of the glass head in the metal lined hole. Solder with the proper coeilicient of thermal expansion could, alternatively, be employed to close the leadin holes. After the holes have been closed the tube may be exhausted and sealed oil in the usual manner. Electrical connection is easily made to each of the focusing electrodes with spring contactors 7 bearing on the exterior metal film at each hole.

Since the lead-in conductor does not extend inwardly beyond the inner surface of the envelope the electrostatic fleld produced by the electrodes is concentric with the axis of the envelope and the electron beam, and there is no distortion in the field or in the beam. Since the outer diameter of the envelope is not increased, a close fitting deflection coil may he slipped over the envelope. The exterior metal film for each lead-in may conveniently be extended toward the ends of the envelope to a point beyond the end of the coil.

By my invention it is easy and inexpensive to make an electron discharge device with a great number of lead-in conductors. Cathode ray tubes for example may have a plurality of coaxial an- ,nular electrodes very closely spaced and in which the fields of the electrodes are undistorted, yet with ample spacing between lead-in conductors which extend through the wall and may be staggered around the circumference of the envelope.

The lead-in conductors are of minimum length,

which is the thickness of the envelope wall, and are therefore of great utility in very high frequency apparatus.

I claim:

1. An electron discharge device comprising a so glass envelope, a plurality of electrodes in said envelope, a lead-in conductor for each electrode, each electrode comprising a metal coating on the interior wall of said envelope, a. hole in the envelope wall opposite each coating, and each conductor comprising an annular him of metal on the wall oi said hole and on the exterior wall of said envelope integral with the coating of one of said electrodes, and a bead of glass sealed gastight in each hole.

2. An electron discharge device comprising an envelope of insulating material, a plurality 01 small spaced holes in the wall of the envelope, a plurality of electrodes in the envelope, a short lead-in conductor for each electrode comprising 10 an adherent coating of metal on the interior and exterior walls of the envelope electrically communicating with a metal coating on the sides of the hole, and a plug sealed gas-tight in each of said holes.

3. An electron discharge device comprising a cylindrical envelope of insulating material, a plurality of spaced holes in the cylindrical wall of the envelope, a metal coating on the sides of each hole, each coating extending inwardly and outwardly along the inside and outside walls of the envelope, and a plug sealed gas-tight in each of said holes.

4. The method of sealing in a plurality of short lead-in conductors in the side wall of a cylindrical envelope, comprising forming a plurality of spaced holes through the wall of the envelope, depositing an adherent coating of metal on the interior and exterior surfaces of the envelope and on the sides of said holes, then heating a mass of sealing material and depositing the heated mass in gas-tight union with the coated sides of said holes.

5. The method of sealing a short lead-in conductor in the wall of an envelope, comprising forming a hole through the wall of the envelope, depositing an adherent metal coating on the interior and exterior surfaces of the envelope and on the sides of said hole, the metal coating on the interior and exterior surfaces and in the hole being deposited so that the coatings are conductively connected to form a lead-in conductor, then hermetically sealing said hole.

DAVID B. LANGMUIR.

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