US2188579A - Cathode ray tube, more particularly for television purposes - Google Patents

Description

Jan. 30, 1940. $HLE$|NGER 2,188,579

CATHODE RAY TUBE, MORE PARTICULARLY FOR TELEVISION PURiOSES Filed May 19, 1934 2 Sheets-Sheet 1 Uni/enter:

Mas/M Jan. 30; 1940. 2,188,579

CATHODE RAY TUBE, MORE PARTICULARLY FOR TELEVISION PURPOSES K. SCHLESINGER Filed May 19, 1934 2 Sheets-Sheet 2 Urn/en fo 2'.-

6 2 P 6 -l WA n 0 m a C/ m E ii 7 H 3 Patented Jan. 30, 1940 UNITED STATES PATENT omcsff Q CATHODE RAY TUBE, MORE PARTICULARLY FOR TELEVISION PURPOSES Kurt Schlesinger, Germany, aslignor, by memo assignments, to Loewe Radio, Inc., a corporation of New York Application May 19, 1

In Germany 934, Serial No. 720,477 M8! 2', 1933 8 Claims. (Cl. 250-157) trol outputs are required, so that the coils cannot be replaced, or only with extreme dimculty, by permanent magnets, evenin those cases in which only a constant deflection oi the ray is called for.

Combination of the magnetic action with an electrostatic action on the ray is incapable of being performed in the majority of cases.

To avoid certain of the disadvantages referred to it has already been proposed to arrange the magnet coils within the Braun tube. This proposal, however, is extremely difficult to fulfil in practice owing to the-difiiculties associated with the outgassing, and moreover causes an increase in the fields oi dispersion. Y I

The object of the invention is aBraun tube which avoids the disadvantages referred to, permits of operation without fields of dispersion and with comparatively low outputs, and allows oi anydesired combination of the magnetic and electrostatic action on theray. According to the invention, field generators (magnet coils or permanent magnets) are combined, 'outsideoi the tube but asclose as possible to the walls 01' the tube, with pole shoes within the tube vacuum, which shoes likewise extend as close as possible up to the wall.

For deflecting devices the pole shoes may be constructed in the form of a slotted plate, the slot (air gap) of which is situated in the desired direction of diversion. M I

This most simple form of embodiment may be employed according to the invention for example for producing a constant preliminary deflection of the ray before its entry into the deflecting systemsuch as necessary when using static deflecting means for producing images devoid of an ion 50 cross.

For producing a constant deflection of this kind it is convenient in accordance with the invention to ,employ a permanent magnet.

This magnet may be conveniently constructed,

u for example, as a double magnet composed oi two half-rings furnished with a gap and surrounding the neck of the tube, and made to be rotatable to permit of adjustment of the deflecting device.

In order at the same timeior purposes of adjustment-also to be able to vary the strength 01 the magnetic deflection, there is iumished between the two half-ring magnets, in accordance with the invention. a magnetic shunt, the strength of which is adjustable and regulates the strength of the main field. This regulating device according to the invention--which in its most simple form consists of an adjustable wiper of term-magnetic material. which enables different points of the two magnets to be connected together-may be employed quite generally for adjusting the strength of field of permanent magnets.

For producing. fields free of interference there may be employed in accordance with the invention double-ring arrangements, the rings oi. which are connected with each other magnetically outside of the tube, and are acted upon in such iashion that the one ring acts as north pole and the other as south pole. Since the field lines in this arrangement are disposed solely in the space between the two annular plates, this arrangement according to the invention does not "reveal any lens, which may be employed, for example, as

concentration lens in Braun tubes for television purposes.

In accordance with the invention, the pole-shoe plates may at the same time also assume an additional electrostatic function which is independent of their function proper, for example may be connected with a suitable potential and employed as anode of the system, control orconcentration element or the like.

Instead of producing the entire plate 01' ferromagnetic material, it is also possible in accordance with the invention toemploy a plate 01' non-magnetic material (for example copper), and to furnish this on the one or on both sides with coatings of a suitable ierro-magnetic material (for example, permalloy or steel), which in the particular instance concerned possess the most suitable iorm,ior the pole-shoes.

This form of embodiment also has the additional advantage that the non-magnetic supporting plate does not require to be slotted over its entire width, and it is sufficient to make the transverse slot merely of the width necessary for the desired deflection.

It is, however, also possible according to the invention to produce the pole-shoes in the form of a plate of ferro-magnetic material with throughgoing slot, and to fill out the slot-so far as the same is not required as aperture for the cathode ray-with a non-magnetic but electrically conductive material, for example copper, and

in this manner to supplement the slotted plate electrostatically to form, for example, a cylinder (perforated disc).

In numerous cases it is desirable to furnish 6 more particularly the side of the pole-shoe electrodes directed away from the cathode with a special, say, mould-like form, as in this manner the concentration effect for example may be additionally amplified.

In order to be able to manage with a control output as small as possible, the magnetic arrangement in accordance with the invention is located-as far as p0ssible-at those points of the tube at which the cathode ray, corresponding with the drop in potential, possesses the least speed.

As will readily be apparent, the arrangement according to the invention permits of a large number of very difierent combinations of magnetic and electrostatic action on the ray, preferably by the use of the same electrodes, of which merely the following shall be mentioned by way of example:

1. Electrostatic (space charge) control and magnetic concentration.

2. Static anode effect and magnetic deflection.

,3. Static concentration and magnetic deflection.

4. Static control, magnetic concentration and magnetic deflection.

The use of the magnetic concentration enables the high-tension anode to be provided after the deflecting system, and the deflection to be performed in the space in which the ray possesses a low speed.

As already set forth, the invention is in no way limited to the stated combinations.

Some possible forms of embodiment of the inventlon are illustrated by way of example in the drawings, in which Fig. 1 shows a Braun tube, in which the arrangement according to the invention produces a constant preliminary deflection of the ray (geometric bias), and at the same time is employed as anode of the system.

Fig. 2 shows the same arrangement in section, whilst Fig. 3 illustrates a form of embodiment of the magnetic shunt according to the invention.

An element according to the invention, in which the pole-shoes are secured to a non-magnetic but electrically conductive base, is shown in section in Fig. 4a, and in plan elevation in Fig. 4b.

A modification in which the two massive pole plates are filled out by filling the ends of the gap with non-magnetic metal, is shown in section in Fig. 5a, and in plan elevation in Fig. 5b.

In Fig. 6 there is indicated diagrammatically a Braun tube with electrostatic control and magnetic concentration, whilst in ment in which both the vertical and the horizontal scanning deflections are effected on the cathode ray in the same cross-section of the tube, one of the said two deflections being produced by electro-magnetic, the other one by an electro-static influence acting on the ray.

In Figs. 1 and 2, l is the two-part permanent magnet, which surrounds the neck of the tube 2 with the least possible spacing and preferably is arranged to be rotatable, 3 and 4 are the poleshoes according to the invention having the slot 9 disposed at an angle of 45 to the deflecting plates 5 and 6, or I and 8. To the plates 5 and I there is conducted the deflecting potential from the generators I I and I2, and the constant negative bias necessary for the return of the ray from the potential source l0. The pole- shoes 3 and 4 and also the plates 6 and 8 are earthed. The pole-shoe plate may accordingly be quite readily employed itself as anode of the system.

As shown in Fig. 3, there may be provided at the magnet l--l a magnetic shunt, which comprises the loops I3 and i4 and the connecting piece I 5 consisting of ferro-magnetic material, and which does not affect the main field when the loops l3 and I4 connect points of equal magnetic potential, but more or less weakens the main field in all other positions of the loops.

As indicated in Figs. 4a and 4b, the pole- shoes 3 and 4 may be mounted on a plate i6 composed of non-magnetic but electrically conductive material.

According to Figs. 5a and 5b, the gap between the pole- shoes 3 and 4 may be filled out with a strip I! of non-magnetic metal (for example copper), and in this manner supplemented to form an element acting electrostatically as a plate (cylinder).

In the arrangement according to Fig. 6 the bundle of electrons produced by the cathode I8 is concentrated by the field between the pole plates l9 and which field is produced by a also by a permanent magnet. The alternating potential controlling the intensity of the ray is cathode l8 and the front field plate IS. The plate 20, if desired, may be furnished with a potential which is positive in relation to I 8, as the magnetic concentration is so. intense that the variation in the static field does not produce any kind of appreciable interference.

A form of embodiment of a-complete tube according to the invention is illustrated diagrammatically in Fig. 7.

In the same I8 is the cathode, l9-20 the magnetic concentration arrangement, 24 and 25 are the magnetic deflecting elements, 2i, 22, 23 screening means, which are furnished with a constant positive potential and ensure that the ray does not undergo any variation in speed upon its passage through the deflecting systems,- 26 is the (high-tension) anode of the system and 30 the bottom of the tube preferably covered at its inside with a fluorescent layer.

The intensity control potential indicated by the generator 29 may be applied direct between the cathode l8 and the plate l9, which if desired may be furnished with a negative bias. The deflecting elements 24 and 25 maybe constructed in accordance with Figs. 4a, b or 511, b. The element 24, if desired, may be furnished with a negamagnet coil 3| arranged outside of the tube, or

- located between the equipotential surface of the tive potential, and then acts as after-concentration device.

fundamentally by varying the potential at the anode 26, as a variation in potential at this point.

of the system does not aifect either the concentration or the deflection of the ray.

In an arrangement according to Fig. 8 the elements 33 and 34 act at the same time as poleshoes of an electro-magnet 32, excited by a deflecting voltage generator 35, and as deflectingelectrodes supplied with deflecting voltages from another generator 38. Thus both the vertical and the horizontal deflections are effected on the cathode ray in the same cross-section of the tube. The arrangement according to the invention is quite readily capable of use both for gas-filled as well as high vacuum tubes. It is particularly convenient, however, to employ the same in conjunction with residual-gas tubes, i. e., tubes in which the gas filling discloses a pressure of approximately l0- -10- mm.

I claim:

l. A Braun tube including an evacuated envelope, means for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen, and pole shoes mounted entirely within said envelope to extend substantially in a cross-section of said envelope from a close vicinity of the wall of said envelope to a close vicinity of said ray; means for producing a magnetic field mounted outside said envelope and arranged in operative relationship to said pole shoes but mechanically separated therefrom by the wall of said envelope.

2. A Braun tube including an evacuated envelope, means for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen, and pole shoes mounted entirely within said envelope to extend substantially in across section of said envelope from a close vicinity of the wall of said envelope .to a close vicinity of said ray; means producing a magnetic field mounted outside said envelope and arranged in operative relationship to said pole shoes but mechanically separated therefrom by the wall of said envelope; and means for connecting said pole shoes with a potential source.

3. A Braun tube including an evacuated envelope, means for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen and pole shoes ,mounted entirely within said envelope on a common base consisting of a non-magnetic but.electrically conductive material having a circular cross-section substantially coinciding with a cross-section of said envelope from a close vicinity of the wall of said envelope to a close vicinity of said ray, means for producing a magnetic'field mounted outside said envelope and arranged in operative relationship to said pole shoes but mechanically separated therefrom by the wall of said envelope, and means for connecting said pole shoes with a potential source.

4. A Braun tube including an evacuated envelope, means for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen and pole shoes mounted entirely within said envelope to extend substantially in a cross section of said envelope from a close vicinity oi the wall of said envelope to a-close vicinity of said ray, the gaps between said pole shoes being filled up with a non-magnetic electrically conductive material for combining said pole shoes mechanicallyto form an electrically conductive unit of circular cross-section, means for producing a magnetic field mounted outside said envelope and arranged in operative relationship to said pole shoes but mechanically separated therefrom by the wall of said envelope, and means for connecting said pole shoes with a potential source.

5. A Braun tube including an evacuated envelope, means for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen, and two pairs of pole shoes mounted near each other and entirely inside said envelope to extend each substantially in a cross section of said envelope from a close vicinity of the wall of said envelope to a close vicinity of said ray; means mounted outside said envelope for causing the formation of a concentrating fleld between said two pairs of pole shoes, said last mentioned means being mechanically separated from said pole shoes by the wall of said envelope. I

6. A Braun tube including an evacuated envelope, means for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen and pole shoes mounted entirely within said envelope to extend substantially in a cross section of said envelope from a close vicinity of the wall of said envelope to a close vicinity of said ray, the gaps between saidpole shoes being filled up with a non-magnetic electrically conductive material for combining said pole shoes mechanically to form an electrically conductive unit of circular cross-section, means for producing a magnetic field mounted outside said envelope and arranged in operative relationship to said pole shoes but mechan-' ically separated therefrom by the wall of said envelope, said last mentioned means includingtwo half-ring-shaped magnets and a magnetic shunt comprising two loops; each of said loops surrounding one of said magnets, and a piece of ferro-magnetic material connecting said loops with one another, and means for connecting said pole shoes with a potential source.

7. A Braun tube including an evacuated envelope, a cathode, means including said cathode for producing a cathode ray directed substantially along the axis of said envelope, a picture receiving screen, and two pairs of pole shoes mounted near each other and entirely inside said envelope to extend each substantially in a cross section of said envelope from a close vicinity of the wall of said envelope to a close vicinity of said ray; means mounted outside said envelope for velope, a picture receiving screen, means for producing a cathode beam and for directing this beam substantially along the axis of the Braun tube onto said picture receiving screen, and a 10 one, said elements being thus adapted to deflect said cathode beam in a plane perpendicular to that in which it would move in approaching any of said elements; means for producing a magnetic field mounted outside said envelope and arranged in operative relationship to said elements but mechanically separated therefrom by the wall of said envelope; and means for connecting said elements with a potential source.

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