US2452620A - Electrode support in television tubes - Google Patents

Description

Nov. 2, 1948. PQK. .WEIMER ELECTRODE SUPPORT IN- TELEVISION TUBES Filed Nov. 14, 1946 Snnentor 1 ff Wiifii" Patented Nov. 2, i948 umrso STAT OFFICE ELECTRODE SUPPORT IN TELEVISION TUBES Delaware Application November 14, 1946, Serial No. 709,734

6 Claims. i

This invention relates to television tubes of the image orthicon type and more especially to means for mounting the plurality of electrodes together.

In prior art tubes it has been the practice to mount the gun on the glass base flange of the tube envelope and to plate an anode on the inside wall of the tube Which has been called the wall coating. Also the electrodes in the image end of the tube have been mounted on the flange joining the main body of the envelope with the enlarged head containing the image part oi the tube as shown and described in my co-pending application filed September 16, 19%, Serial No. 554,494, new U. S. Patent No. 2,433,941, issued January 6, 1948. While the construction shown in that application is very satisfactory once the tube is completed, it is not so desirable from the standpoint of manufacture because the electrodes are grouped into two separate units that are separately mounted and adjusted in the tube envelope.

It is an object of this invention to mount all the electrodes, except the photocathode, of the television tube together so that they may all be adjusted in relation to each other on the bench while outside the envelope.

Another object is to provide a construction that reduces distortion of the image produced by the photocathode.

Another object of the invention is to substitute a metal cylinder for the usual wall coating and to mount it on insulation tubes enclosing wires sealed in the base of the tube envelope.

Other objects will appear in the following description reference bein had to the drawing in which:

Fig. l of the drawing is a longitudinal section through a television pick-up tube containing the invention, parts being broken away to shorten the length of the figure as well as to better illustrate the construction of the parts; and

Fig. 2 is an elevation of the base flange on which the electrodes are mounted.

The tube comprises a gun having a cathode I, grid 2 and first anode 3 the end surface 6 of which constitutes the first dynode of the multiplier. A cylinder surrounds the region immediately in front of the first dynode to direct the secondary electrons emitted thereby into the second stage of the multiplier and because of this function it has been called the persuader electrode.

' The second, third and fourth stages, 6, 'l, 8 and 9 of the multiplier surround the gun but are spaced therefrom. These have a plurality of blades somewhat like an electric fan and have been called pin wheels. The secondary electrons from the first dynode strike the blades of the second dynode and the secondary electrons bombarded therefrom are drawn into the third stage, the secondary electrons of which pass through the meshes of the collector screen it). to bombard secondary electrons from the fourth dynode which may be a disc. These are attracted to and collected by the screen collector Ill which is connected to the output terminal. The detail constructions of the multiplier and collector stages are not claimed herein and hence they are not shown, but reference is made to my said co-pending application for a full disclosure thereof.

The parts of the gun may be mounted in any way, but preferably they are assembled and mounted in a base member H as disclosed in the application of Stanley Forgue, filed January 28, 1946, Serial No. 643,925, now United States Patent 2341315, issued May 11, 1948, and reference is made thereto for details of the construction.

In the image end of the assembly I position an accelerating anode cylinder !2 comprised of three short metal cylinders increasing in diameter toward the photocathode. A target :3 of very thin glass is stretched across and secured to the end of cylinder l2 facing the gun. This thin glass target is sufiiciently conductive to enable the electrons landin from the beam to pass through and discharge the charge image on the opposite side produced by the photoelectrons but suinciently no-nductive to prevent material spreading of the electrons or charges lengthwise of the film. The details of construction and operation of this glass target are described fully in the application of Albert Rose filed November 28, 1945, Serial No. 631,441. A fine mesh screen It is placed close to the glass film to collect secondary electrons produced by the photoelectrons emanating from the photocathode it on the end of the tube envelope 16 when a light image is focused thereon. This photocathode is a transparent film of silver or other suitable metal which'is I caesiated to activate it as is well known in the art. To produce a more uniform direction of the electrostatic field over the entire photocath'ode, I extend a fine mesh screen over the end of this electrode adjacent thereto. This screen is electrically connected to the electrode so as to receive its potential. The uniform electrostatic field produced by the screen reduces spiraling of the photoelectrons and this reduces distortion of the charge image on the photocathode side of the target l3. A strip ll of silver or other metal is coated on the inside wall of the tube and is conductively joined to the photocathode. The fronthalf of the tube envelope I6 does not appear in the section of Fig. 1 but this strip is shown in dotted lines in correct position so as to make clear the. way the potential is applied to the photocathode.

Instead Of using the wall coating on the tube envelope as shown in my said application, I employ an anode cylinder ill of ametal of highresistivity, such as Nichrome, of 5 mil thickness, Across the end of the cylinder 18 adjacent the target is placed a fine meshscreenlll which may be electrically connected thereto 50 as to receive its potential therefrom. The screen provides a decelerating and reaccelerating field. in front of. the target that is perpendicular thereto and reduces the size of the scanned area of thefi'rsfl dynode 4 by the return beam as disclosed in my application filed February 7, 1946; Serial. No; 6%;076.

. For mounting the electrodes together, except the photocathode I5, I employ four ceramic rods Zl, 22, 23 and 24 containingv metal wires that are welded or otherwise connected to wires 2|, 22', 23' and 24' sealed into the glass flange 25 (Fig. 2). These rods are fastened to. the base member I l inwhich the gun is mounted by clamps 26.- and rods 2|, 22 and 24 are similarly fastened to the rims of the multiplier and collector stages 6,,1', 8, 9 and Ill. The clamps are thin strips of metal extending around the rods and the ends are; welded to the cylinders and rims. The ceramic rods are also similarly clamped to the persuader 5, anode cylinder [8 and image cylinder anode I2 so that all these parts are mounted on. these ceramic rods.

The wire inside ceramic rod 23-has a spring clip or. snubber 21 that contacts, when the units are. assembled in the envelope, with the metal coating strip I! so that the photocathode may receive its proper potential which is several hundred voltsnegative to screen M. The cylinder l2 and screen l4 receive potential through wire 28 joined to the wire'in ceramic rod 22.

The wire in ceramic rod 24 is connected to one.

end of a tungsten wire. ring 29 carrying at uniform. points around the circumference several silverbeads two of which are visible in Fig. 1 at 29'- The, other end of the ring 29 is joined to the. cylinder l2 n the side hidden in the figure. Wire 28-is connected. to the anode I2 at a. point not shown on the drawing. When a suitable voltage is applied across the wires in the rods. 22, 24 the tungsten wire heats up and vaporizes; part of the silver beads and the vapor is deposited on the end of the envelope l 6 to form the photos cathode I in a well known way. v

The spring clip 2] together with spring clips 30, 3|, and 32 (Fig. 2) bear against the inside surface of the envelope and act as snubbers to align and support the assembled parts in the; tube envelope.

It will be seen that with my improvement all.

of the parts except the photocathode are:

mounted together on the rods outside the en.-- velope-and can be readily adjusted and spaced;

When the assembly is completed it is'slid-into theenvelope l6 and the glass fiange'25 is then sealedthereto by applicationof heat in a known manner. The flange supports and centers the assembly at the gun end of the envelope and thesnubbers support and center. it near the other end: so that correct alignment is readily mainL-- talned. Caesium vapor may be introduced through a tubulation to activate the photocathode in a known way. The tube is evacuated through the tubulation and it is then sealed off at the tip 33.

Insulated conductors 34 are connected to the multiplier electrodes, persuader 5E and; cylinder anode l8 and the ends are sealed in the base flange for application of suitable potentials. The potential leads to the cathode, grid and first anode: are. notshown.

By my improved mounting truer alignment can be obtained with mandrels than was possible in the prior art construction such as shown in my said' application. Ser. No. 554,494, filed September 16, 1944, where correctness of alignment depends in; part; on glass blowers skill. The mounting of the target and the screens is greatly simplified as these may be secured in place outside the envelope. The-thin glass target is cut from the film surface of a glass bubble and hencerequires careful handling. It ispreferableto-attach it to the anode cylinder [2; The four supporting rods 21, 22, 23 and 24 are therefore placedoneonly one half of the circumferenceas shown by Fig. 2, so that the delicate glass target can'readily be inserted in place from the'opposite side. All of the conductors are'brought out at oneend of the envelope which permits one to" eliminate the enlarged head containing the image section and the contacts at the fiangeconnecting' thetwo sections together as illustrated in my said application. Hence the glass blowing'operation is much simplifiedl The plating'operatloni is 315011111011 simplified by theeliminationof'the" wall coating and the substitution of the anode cylinder therefor. By'eliminating the enlarged head of the envelope the deflecting coils (not. shown) may be adjusted for'best landing because the enlarged end does not limit the adjustment. Also a convenient space is left over. the image section for use of a bucking coil to cancel the. stray field of the deflection coils which cause cross talk in the electron image.

I-have found that with a 5 mil Nichrome anode cylinder for replacing the'wall coating the currents induced therein by the deflection coils are insulficient toafiect the scanning powerrequired but this thickness should not be. materially exceeded.

Whilecertain specific embodimentshave been. illustrated and described,.it1 will be understood" that variouschanges and modifications may be made therein without departing from the spirit and scope of l the invention;

What I claim as new is:

1. A- television tube comprising an envelope containing'a. cathode ray beam gun, a mount for said'gun at one end'of the envelope, a photoc'athodeat the opposite end of the envelope, a. target between the gun and the photocathode, a cylinder anode adapted to accelerate the photoelectrons from thephotocathode to said target, a finemesh screen across the cylinder anode ad- 'jacent one side of the target for collecting second ary 'electrons emitted by the target, a=second'cylinder anode of high resistance between the target an'dthe'gun, a fine mesh screen across tlie second mentioned. cylinder anode adjacent the other sideof. the target, insulation rods securedto-the gun end ofsaid envelope supporting said mount-and said cylinder anodes.

2;..A television tube comprising an. envelope containing 'acathode; ray beam. gun, amount for:

cathode at the opposite end of the envelope, 9. target between the gun and the photocathode, a cylinder anode adapted to accelerate the photoelectrons from the photocathode to said target, a fine mesh screen across the cylinder anode adjacent one side of the target for collecting secondary electrons emitted by the target, a second cylinder anode of high resistance between the target and the gun, a fine mesh screen across the second mentioned cylinder anode adjacent the other side of the target, insulation rods secured to the gun end of said envelope supporting said mount and said cylinder anodes, and a metal strip on said envelope connected to the photocathode, one of said rods having a conductor engaging said metal strip.

3. A television tube comprising an envelope containing a cathode ray beam gun at one end of said envelope, a photocathode at the other end of said envelope, a cylinder anode adjacent the photocathode having a fine mesh metal screen across its end facing said photocathode, a thin glass target across the opposite end of saidcylinder anode, and a fine mesh screen adjacentthe photocathode side of said target for collecting secondary electrons emitted thereby.

4. A television tube comprising an envelope containing a cathode ray beam gun, a mount for said gun at one end of said envelope, a photocathode at the opposite end of the envelope, a glass target, a cylinder anode adjacent the photocathode for accelerating the photoelectrons toward said glass target, a fine mesh metal screen adjacent the target on the photocathode side, a fine mesh metal screen at the end of the cylinder anode adjacent the photocathode, said glass target and the first mentioned fine mesh screen being mounted across the other end of the cylinder anode, and a second cylindrical anode between the gun and the glass target.

5. A television tube comprising an envelope containing a cathode beam gun, a mount for said gun at one end of the envelope, a photocathode at the opposite end of the envelope, a thin glass target, an accelerating cylinder anode adjacent the photocathode, a fine mesh metal screen spaced from the target on the photocathode side, said glass target and fine mesh screen being mounted across the end of the cylinder anode remote from the photocathode, a cylindrical anode between the gun and the glass target, a fine mesh metal screen mounted across the end of the second mentioned cylindrical anode adjacent the glass target, a plurality of ceramic tubes, conductors in said tubes sealed to the gun end of said envelope, means for supporting the gun mount and said cylinder "anodes on said ceramic tubes, and spring snubbers on one of said cylinder anodes adapted to space said ceramic tubes from said envelope.

6. A television tube comprising an envelope containing a cathode beam gun, a mount for said gun at one end of said envelope, a photocathode at the opposite end of the envelope, a thin glass target, an accelerating cylinder anode adjacent the photocathode, a fine mesh metal screen spaced from the target on the photocathode side, said glass target and fine mesh screen being mounted across the end of the cylinder anode remote from the photocathode, a cylindrical anode between the gun and the glass target, a fine mesh metal screen mounted across the end of the second mentioned cylindrical anode adjacent the glass target, a plurality of ceramic tubes, conductors in said tubes sealed to the gun end of said envelope, means for supporting the gun mount and said cylinder anodes on said ceramic tubes, and spring snubbers on one of said cylinder anodes adapted to space said ceramic tubes from said envelope, said ceramic tubes being located on one-half the circumference of the cylinder anodes to permit insertion of the glass target from the other side.

PAUL K. WEIMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,183,309 Flechsig et al Dec. 12, 1939 2,250,927 Davisson July 29, 1941

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