US2269115A - Cathode-ray tube - Google Patents

Description

Jan. 6, 1942. s. J. KOCH CATHODE-RAY TUBE Filed Nov. 12, 1940 5 Sheets-Sheet l INVENTOR (qyd 06A Jan. 6, 1942. J, KOCH CATHODE-RAY TUBE Filed Nov'. 12, 1940 3 Sheets-Sheet 2 Jan. 6, 1942. 5, J CH 2,269,115

CATHODE-RAY TUBE Filed Nov. 12, 1940 3 Sheets-Sheet 3 SECOND ACCELERATINQ ELECTRODE +Sooov.

FOCUS\NG awe-meme +\5oov.

FlRST AcceLeRA-rmq ELECTRODE +snoov.

. INVENTOR g0 Sfqzzgy 06% MODULATWG ELECTRODE CATHODE'.

Patented Jan. 6, 1942 CATHODE-RAY TUBE Stanley J. Koch, Newark, N. J., asslgnor to Allen B. Du Mont Laboratories, Inc., Passaic, N. .L, a corporation of Delaware Application November 12, 1940, Serial No. 365,216

7 Claims.

My invention relates to improvements in cathode-ray tubes of the general type more particularly adapted for television reception, and such as is disclosed in Patent No. 2,186,635 issued Janu- Heretofore, the importance of electrode position, and size, shape and spacing of the same,

have been overlooked in cathode-ray tubes of the prior, general type referred to. As a result, the

ary 9, 1940 to Allen B. Du Mont and Alfred J. uses to which such tubes can be put, and the Hinck, Jr., and Patent No. 2,225,099, issued Detheoretical advantages to be enjoyed with cercember 17, 1940, to Peter S. Christaldi. tain types of operation, are sharply curtailed.

As a result of development of the so-called Inorder to gain high intensity, while maintain- Braun tube for television reception, it has been in high-deflection sensitivity, it is desirable to definitely determined that certain values, 10 make as large as possible the ratio of post-acwhether they be of operating potentials on cerceleration to pre-acceleration potential. It has tain electrodes, or of dimensions in the tube been found that unless certain designs are apstructure itself, must be properly correlated in plied, defocusing of the fluorescent spot occurs, order to obtain the desired operating action. For distorting fields are set up, and it may be imexample, it is known that by increasing the op- 1 possible to utilize more than thirty percent of the erating potential on an accelerating anode of a efiective fluorescent screen area. conventional cathode-ray tube, the intensity or With the foregoing in mind, it is one of the brightness of the trace or picture is increased. A objects of my invention to provide an improved point or potential range is finally reached, howconstruction of cathode-ray tube of the charever, whereat the sensitivity of deflection is reacter referred to in which the operating potenduced a prohibitive amount, so thatit is not tials, and dimensions in the tube structure itself, practical to further increase the brightness of the are such that a picture of the desired brightness picture by this method alone. Another diificulty on the fluorescent screen can be obtained without has been found to reside in the matter of mainnecessarily or unduly interfering with the focus taining the scanning electron ray at a good focus or the sensitivity of deflection. on the fluorescent screen. That is, in making Another object of my invention resides in the certain changes or variations in some of the opprovision of an improved construction of cathodeerating potentials or in the structure of the tube ray tube of the character referred to, which has itself to correct for or improve upon certain opadvantages over those proposed heretofore in the crating conditions, the result has been to impair, 'way of a brighter or more intense picture on the at the same time, the operating action in other fluorescent screen for similar operating condiways, such as by causing some form of distortion tions, higher picture detail, greater uniformity of of the pattern or by causing some degree of dethe pattern, greater simplicity of construction focusing of the electron ray on the fluorescent and of assembly in manufacturing, and more screen. Alon with this development work, the favorable disposition of the various parts and subject of electron optics has been given conleads with respect to each other to withstand the siderable attention, in an attempt to formulate high difierences of potential within the tube. some working basis or formulae for use in the Another object of my invention resides in the most efiicient design of cathode-ray tubes for provision of a simplified construction for a cathtelevision reception. In putting this theoretical 40 ode-ray tube in which there is post-deflection information to practice, however, it has been found that there are still limitations in the way of an occurring decrease in efiiciency of operationof the tube in one important sense if certain acceleration of the electron beam or ray, and which overcomes the disadvantages and th limitations of the various designs proposed heretofore. are maids to cause an Increase m 43 Other objects and advantages will hereinafter ciency of operation of the tube in another sense. appear Many different types of cathode-ray tubes have been constructed in which there is postdefiection acceleration of the electron beam. In most of these various constructions, however, an elaborate system of electrodes has been necessary which makes these tubes impractical. A simplified construction or system, employing a single electrode in the form of a ring disposed in proximity to the fluorescent screen, is disclosed in the Patent 2,186,635 referred to above. This novel construction makes feasible commercial production of cathode-ray tubes having the desired operating characteristics referred to.

For the purpose of illustrating my invention, an embodiment thereof isshown in the drawings, wherein Figure 1 is an enlarged, fragmentary view taken from Fig. 10, and being partly broken away, partly in elevation, and partly in section, the section being taken on the line ll in Fig. 2;

Fig. la is a detail, fragmentary view, partly in section and illustrative of a novel step in the assembly of my improved cathode-ray tube, in some cases;

. Fig. 2 is a view looking toward the right in Fig. 1, the electron gun being shown in elevation and '66, 8-3 and -3 in Flam-1 and 2; and

each being a true projection taken vertically from Fig. 1, but on the enlarged scale;

Fig. 4a is an enlarged, fragmentary, sectional:

view showing a detail of my improved construc-- tion, the section being taken in th plane 4-4 in Fig. 1;

horizontal N Fig. 10 is a longitudinal, sectional viewer a complete cathode-ray tube constructed and operating in accordance with my invention, the electron gun'and associated parts being shown 8 18-11" vation; and

Fig. 11 is an enlarged view taken from and showing more clearly the electrodes comprisfing the electron gun. g

The drawings show a cathode-ray tube having a gun construction similar to that described inthe patents mentioned above. For convenience of comparison, the various parts have been designated by the same reference characters as the corresponding and respective parts in these prior disclosures. r I

With reference particularly to Figs. 1, 2, 10 and 11, my improved cathode-ray tube comprises a tube l0 having a bulbous portion II on the end wall of which is a fluorescent screen 9. In the neck portion l2 of the tube is the gun for developing the ray of electrons directed at and focused on the screen.

The gun is supported from the stem I5 which is sealed to the open end of the neck i2, and comprises a cathode IS, a modulating electrode 20 in which the cathode I6 is disposed, a first acceleratingelectrode 22, and a mica disc 24. f

The gun comprises further a focusing electrade 29, 29a and a second accelerating electrode 30 provided with the apertured discs 30a and 30b. Deflecting plates 33 are supported by the wires 3311/3312. 33c and 33d, and a second set of deflecting plates 36 is supported by the wires 36a,

36b, 36c and 36d.

The first or preaccelerating electrode 22 above the modulating electrode 20 is operated at the same voltage asthe second accelerating electrode 30. For this purpose, a connection 42 is made from the electrode 30 to the electrode 20. By applying a high voltage to the electrode *22; a brighter spot is obtained, and there is less tendency to defocus during modulation.

In my improved construction, there is a relatively large distance A from the tip 41 of the gun to the adjacent edges 48 of the second set of deflecting plates 36. The relation exists approximately, where A is measured in inches, C is the diameter in inches of the fluorescent screen, and B is the distance in inches from the screen to the adjacent edges 49 of the first set of deflecting plates 33. Satisfactory results have been obtained by making A equal to .4 inch with C and B both 14 inches. In the constructions used heretofore, the distance A is much less. By making the distance A greater, and using the relation above expressed, defocusing of the spot during deflection is eliminated. The

reason for this is that in my improved construction no appreciable bending or deflection of the beam or ray within the gun structure takes place.

Heretofore it has been generally supposed that no motion or deflection of the ray occurs below the deflecting plates. Actually, this is not true, and the motion of the ray in the gun during defiection has been the cause of poor focusing in the prior constructions.

Important and novel characteristics of my improved tube reside in the provision of the electrodes 58 and. 59, which may be in the form of silver coatings on the inside surface of the tube l0, and in the dimensions and relations hereinafter specified. By this means, it is possible with my'improved tube to obtain a very intense trace or picture by using an extremely high final accelerating voltage, but without, at the same time,

reducing the deflection sensitivity by about 50%,

when the final accelerating voltage is doubled, for example, as would be the case in the various television'receiver tubes used heretofore, The reason for this is that in my improved tube the deflection sensitivity is not an inverse function of final accelerating voltage or potential, as is the case in tubes of the prior art.

' .In a practical construction of my improved .tube, the outside diameter of the neck portion I 2 was made 2% inches, the distance between the edges 58a and 59b of the ring electrode" was made two inches, the distance between the edges 59a and "(1 was made 1 /2 inches, and the distance between the edges 58d and 580 was made one inch.

, In the case of my improved tube, a potential of say 10,000 volts can be applied to the top electrode 58, 5,000 volts to the electrode 30, and a picture intensity corresponding to 10,000 volts will be obtained accordingly, but instead of cutting down the deflection sensitivity byabout 50% as heretofore, it is only reduced by approximately 18% in my tube.

In the sizes of tubes commonly referred to as a 20 inch" tube, and a "14 inch" tube, respectively, the following dimensions, relations and values have been found to give very satisfactory results.

In either case, Y may be made equal to Z.

In either case, with E from 2 to 4 inches, Z may be made from inch to 1 inches.

The following voltages, measured with respect to cathode, have been found to give satisfactory results for the 14-inch tube.

Cathode (16) -40 volts Preaccelerator (22) +5000 volts First anode (29, 29a) +1500 volts Second anode (30) +5000 volts Deflection plates +5000 voltsirespective signal voltages Electrode 58 +l0,000 volts Electrode 59 +5000 volts The ed e 58a of the electrode 58 may be disposed a distance of about an inch from the edge 9a of the screen 9.

It is possible with my improved tube, embodyv ing the structural features and using the relations and values given above, to employ an extremely high accelerating voltage in order to get a very intense trace or picture, and still deflect the ray to cause the same to scan substantially the entire area of the screen 9, since the deflection sensitivity is only reduced by approximately 18%. as against about 50% reduction in the cathode-ray tubes of the prior art, should the final accelerating voltage be doubled.

It has been found that when the distance from the edges 49 to the edge 59a of electrode 59 is too great, electrostatic fields are set up such that the useful area of screen 9 is reduced as a strong function of the ratio of potentials on electrodes 58 and 59. In addition to the reduction of possible, effective screen area, a radial distortion is introduced, and the outer ends of normally straight lines off the axis are caused to return toward or through the axis of the tube.

On the other hand, when the distance from 49 to 59a is too small, the electrostatic lines of force that would normally terminate in 59 to produce a spherical field within the intervening space, terminate instead on the deflection plates 33 and, to some extent, on the deflection plates 36. As a result, the accelerating field in that space is no longer spherical and produces a distortion of the fluorescent spot. Thus a normally round spot would become elliptical with its major axis parallel to the edges 49.

The electrode 58 may be a coating of colloidal graphite known as Aquadag" and a terminal coating 58b of silver which contacts or overlaps the Aquadag coating at 580. The electrode 59 is a silver coating.

Spot-welded to the electrode 30 is a metal disc 3! provided with the circular openings shown in Figs. 3 and 4, and with a mica-disc insert 32. The disc 6| acts as a conducting shield for 001- lecting stray electrons which otherwise would form or set up a halo on the screen 9 in the absence or presence of signal voltage. Such a halo, when signal is present, would reduce contrast. The diameter of the shield 6! .is relatively large, so that its edge is in close proximity to the wall of the neck of the tube.

A whisker 6 la spot-Welded to the shield and spring-biased outwardly to cause engagement of its free end with the electrode 59 provides connection between the latter and the shield.

The adjacent ends of ceramic rods I, 2, 3 and 4 abut the mica disc 32, and are secured to electrode30 by the straps 30c, 30d, 30c and 3M.

The part 29a of the focusing electrode is secured to the ceramic rods by the straps 29b and 29c (Fig. 6).

The part 29 of the focusing electrode is secured to the ceramic rods by the straps 29d and 29e.

The electrode 22 is secured to theceramic rods by the straps 22a.

The electrode 20 is secured to the ceramic rods by the straps 20a, 20b and the complementary pieces 200.

The cathode I 6 is supported by a short piece of wire Ilia spot-welded to one of the straps l6b secured to the ceramic rods.

. The cathode-heater is supported by having its terminals I6e spot-welded to the short pieces [5 of wire which are spot-welded to the respective terminal wires l6 and I6" extending through the press.

With regard to the supporting wires 33a, 33b,

33c and 33d for the deflecting plates 33, the wires welded to the wire 36a.

33a and 330 terminate at the mica disc 32, but the wires 33b and 33d continue through the mica disc 24 to the respective terminal wires 33!) and 3311' which extend through the press.

With regard to the supporting wires 36a, 36b,

36c and 36d for the deflecting plates 36, the wires 36b and 36d terminate at the mica disc 32, but the wire 36a continues to and terminates at the mica disc 24, and the wire 360 extends through disc 24 and is spot-welded to the terminal wire 36c extending through the press.

An important feature of my improved tube resides in the means for making connection to the intensifier electrode 58. This comprises a coaxial cable made up of a wire 58f extending through a glass tube 589 which is bent as shown, and is provided with an outercoating 58h. of silver. As shown in Fig. 10, one end of the wire 58f makes contact with the silver coating 58!). The other end of the wire 58) is spot-welded to a short piece of wire 58k Fig. 8 which is spotwelded to one end of an L-shape piece 581'. The other end of the piece 587' is spot-welded to the terminal wire 58 which extends through the press. The tube 589 extends loosely through the shield GI and the mica discs 32 and 24, and the silver coating 58h makes electrical contact with the shield 6|. When inserting the entire press assembly into the tube blank, the bent glass tube 58g is placed in the position shown in Figs. .1 and 2, so that it clears. The tube 589 is then rotated through degrees and moved axially so that its bifurcated end portion 581' straddles and interlocks with one leg of the L-shape piece 587, as shown in Fig. 1a and as indicated by dash-line in Fig. 8. When the gun and press assembly are fully inserted into the neck of the tube, therefore, the tube 589 is in the position shown in Fig. 10 and the free end of the wire 58 engages the silver coating 58b.

One end of the connection 42 is spot-welded to the shield 6|, and the other end extends through disc 24 and is spot-welded to the wire 22b. One end of the wire 22b is spot-welded to the straps 22a, and the other end is spot-welded to the terminal wire 22' extending through the press.

Connection with the electrode 20 is made by a piece of. wire 20d spot-welded to the straps 20a and to the terminal wire 20 extending through the press.

Connection with the cathode I6 is made through a piece of wire l6c spot-welded to the straps I61) and to the terminal wire I6.

'One end of a connecting wire 36m is spot- The wire 36:): passes through the disc 24 and is spot-welded to the terminal wire 36a.

A connecting wire 29d is spot-Welded to the straps 29c and 29d. The wire 29d passes through the disc 24 and is spot-welded to the terminal wire 29'.

From the foregoing it will be seen that connection to the intensifier electrode 58 is made by the terminal 58'. Connection to electrode 59, shield BI, and electrodes 30 and 22 is made by the terminal wire 22'. Connection to electrode 20 is made by the terminal wire 20'. Connection to the cathode l6 and one side of the cathodeheater is made by the terminal wire i6, and connection to the other side of the cathode-heater is made by the terminal wire it". Connection to electrode 29, 29a is made by the terminal wire 29'. Connection to the plates 33 is made by the terminal wires 33b and 33d. Connection to the plates 36 is made by the terminal wires 36a and 380'.

By making connection with the intensifier electrode 58 through the press, by means of the coaxial cable, the old tip or protrusion on the bulb for this purpose is eliminated. Also. all hightension leads are automatically connected when the bulb is plugged into the socket therefor.

Another important detail of my improved construction resides in the means for assembling and securing together the deflecting plates and the respective supporting wires therefor. For example, and with reference particularly to Figs. 1, 2 and 3, the ends of the wires 36a and 38b for supporting the associated deflection plate are placed against this plate, and upon these ends is placed the strap 38c of sheet metal and having the stamped-out portions shown, to receive these ends. The securing strap lies flush against the deflection plate, and is spot-welded thereto and to the ends of the supporting wires. As shown, the ends of the supporting wires are sandwiched between the deflection plate and the strap 36c, and by reason of the stamped-out portions of the latter, the strap functions as a gauge for quickly and conveniently spacing and positioning the ends of the supporting wires properly and ensuring correct alignment of the parts and uniformity of construction. As shown in the drawings, the other deflection plates and the respective supporting wires therefor are secured together by similar straps, in the same way. Reenforcing pieces, such as 33', join the pairs of adjacent supporting wires for the deflecting plates.

With reference to Figs. 4a. and 4b, the wire 36c passes through a grommet 32a having the portions 32c riveted over onto the mica disc 32, and the portions 32c spot-welded to the wire 360. The distance from the grommet to the edge 32b provides suflicient insulation between the shield .6i and wire 360. Similar grommets are used for the other wires which pass through or terminate at the mica discs 32 and 24.

It will be understood that various modifications within the conception of those skilled in the art, are possible without departing from the spirit of my invention or the scope of the claims.

I claim as my invention:

1. In a cathode-ray tube, a tube having a screen at the end wall thereof, said tube at the end thereof opposite said screen being provided with a press, a gun supported by said press and disposed in said tube for developing a ray of electrons directed at and focused on said screen, deflecting means for said ray of electrons in said tube, an electrode extending along said tube and beyond said deflecting means in the direction toward said screen, a second electrode disposed between said first-named electrode and said screen for minimizing defocusing of the ray-spot on said screen and for minimizing reduction of deflection sensitivity, said second-named elect r ode being adapted to operate at a potential higher than the potential of operation of said first-named electrode, and connection means comprising a conductor extending through an elongated insulator having conducting material on the outside thereof, said conductor engaging said second-named electrode and extending along said tube within the same and through said press to provide exteriorly of said tube at said press a terminal for application of potential to said second-named electrode.

2. In a cathode-ray tube, a tube having a screen at the end wall thereof, a gun disposed in said tube for developing a ray of electrons directed at and focused on said screen, a press supporting said gun, means for deflecting said ray to cause the same to scan said screen. an electrode extending along said tube and beyond said deflecting means in the direction toward said screen, a second electrode disposed between said screen and said first-named electrode, said second electrode being adapted to operate at a potential positive with respect to the potential of operation of said first-named electrode, the diameter of said tube at a plane in proximity to said screen being substantially greater than the maximum effective diameter of said screen, and connecting means comprising a conductor extending through an elongated insulator having conducting material on the outside thereof, said conductor extending from said second electrode and along said tube within the same and through said press to provide exteriorly of said tube at said press a terminal for application of potential to said second-named electrode.

3. In a cathode-ray tube, a tube having a screen at the end wall thereof, said tube at the end thereof opposite to said screen being provided with a press, a gun supported by said press and disposed in said tube for developing a ray of electrons directed at and focused on said screen, means for deflecting said my to cause the same to scan said screen, an electrode extending along said tube and beyond said deflecting means in the direction toward said screen, a second electrode disposed between said first-named elec trode and said screen for minimizing defocusing of the ray-spot on said screen and for minimizing reduction of deflection sensitivity, said second-named electrode being adapted to operate at a potential higher than the potential of operation of said first-named electrode, and coaxialcable means engaging said second-named electrode and extending along said tube within the same and through said press to provide exteriorly of said tube at said press a terminal for application of potential to said second-named electrode.

4. In a cathode-ray tube, a tube provided with screen structure and with a gun for developing a ray of electrons directed at said screen structure, a pair of plates for deflecting said ray, at least one of said plates being supported by wires whose ends are disposed against one side of said plate at an edge thereof and are perpendicular to said edge, and a strap disposed against said ends and flush against said plate at said edge thereof and secured to said plat and said ends,

said strap being pressed out to receive and accommodate said ends whereby said strap initially can function as a gauge to space and position said ends with respect to said plate prior to the securing of said parts together.

5. In a cathode-ray tube, a layer of conducting material on the inside of said tube between the gun and screen of said tube, means for supporting an electron gun in said tube, and an elongated insulator carrying an electrical conductor to contact with said layer of conducting material, said insulator and conductor being bent and revoluble with respect to said tube to provide contact of said conductor with said layer of insulating material.

6. In a cathode-ray tube, a layer of conducting material on the inside of said tube between the gun and screen of said tube, means for supporting an electron gun in said tube. an electrical conductor to contact with said layer, an insulating supporting member for said conductor, and a conducting electrical shield on a portion of said member to prevent the electric field 0! said conductor from distorting the electron beam between the gun and the screen.

7. In a cathode-ray tube, a layer of conducting material on the inside of said tube between the gun and screen of said tube, means for sup- 10 porting an electron gun in said tube. an electrical conductor to contact with said layer, an insu-' lating supporting member for said conductor, and a conducting electrical shield on a portion of said member to prevent the electric field of said conductor from distorting theelectron beam between the gun and the screen, said member being bent and revoluble and means to locate and secure said member in its operating position. STANLEY J. KOCH.

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