US2229977A - Electron beam deflecting means - Google Patents

Description

Jan. 28, 1941. F, R @NYON 2,229,977

ELECTRON BEAM DEFLECTING MEANS Filed March 16, 1959 2 Sheets-Sheet 1 FRAME- SIGNALP GENERATOR OJ LINE EAGNAL. GENERATOR INVENTOR. Franklin 8? Ufcngon ATTORNEYS Jan. 28, 1941. KENYON 2,229,977

ELECTRON BEAM DEFLECTING MEANS Filed March 16, 1939 2 Sheets-Sheet 2 INVENTOR. franklin S? Jfe rayon ATTORNEYS Patented Jan. 28, 1941 r 2,229,977

UNITED STATES PATENT OFFICE ELECTRON BEAM DEFLECTING MEANS Franklin P. Kenyon, New York, N. Y.

Application March 16, 1939, Serial No. 262,078

7 Claims, (01. 250-457) My invention relates to cathode-ray tube beam inductance, which provides an eflicient transdefleoting arrangements nd mor particular y mission for the complex saw-tooth Wave harrelates to novel electromagnetic beam deflecting monic frequencies of the high frequency coil means for such tubes. scanning arrangement. Furthermore, a small The invention is useful for cathode-ray be effective axial length of the high frequency coil appliwtions in general. However, the present system is efiective in producing th requisite disclosure is made With Sp fi application to beam deflection sensitivity. The elimination of television scanning systems, without intending the prior common .magnetic yoke for t d to limit the scope thereof. The invention relates flectjng 0011 sets permits decoupling of these In to electromagnetic means TO]: deflecting a cathsections and substantially reduces any interferode-ray beam along two coordinate planes, gene308. ff t between them erally mutually perpendicular. In television the The i ar high frequency coil set i l Cathode-1 3 beam is deflected at line frequency to trically magnetic-ally and mechanically balanced traverse a Squar? rectangular field- On the to substantially minimize intercoupling with the Screen all definlte number of frames per low frequency or other circuit. This coil set is Saw-tooth Wave forms are generally used closely mechanically related and arranged with for F P lower frequency as Well as for the iron core low frequency coil set to constitute the higher, or line, frequency. The fundamental a ccmpact mutually independent magnetic line frequency is generally of the order of 13,000 fleeting system In the preferred embodiment cycles" ailment action the sawtooth the effective portion of the high frequency coils 20 Wave, form 1t 15 necessary to mould? g is juxtaposed with the effective pole faces of the memos, up to cycles or more m the lme low frequency coil system as will be hereinafter defiectmg sectmn' described in more detail.

w A l gj igig g i gg gg f i g iigg zgg zi Resultant features of the arrangement of the present invention are the substantial eliminaray beam deflecting sysbem which Is highly emtion of pincushion effect on the cathode ray cient and operable over a wider frequency range tube screen in the simultaneous deflection of n1 ,la *1 10 e o r and W m mm y W I V Rages than pno the beam with the low and high frequency 0011 structures. The arrangement of the magnetic t d th ti f b dfif deflecting system is to entail a minimum induct- 2 1; 5 :2 an e e lmma on O 6am Ocusmg ance and intercoupling between the sets of de- It n 1 t f t fleeting coils for effective utilization of all the acwr j an 0 366 o presen upper harmonics of the Sam/400th Signal Wave vention to provide a novel magnetic deflecting form. The framing or low frequency magnetic Sysbem for beam of P l tube' portidn of the System is provided with a lamb Another obyect of the 1nvent1on 1S- to provlde hated iron magnetic path for high defieotional dual magnet-1c defiectmg system emclenjoly Opel" sensitivity. Large pole faces, equal to the diamable Over a Wide frequency band extendmg from low frequencies up to radio frequencies.

eter of the neck of the cathode-ray tube, are pygvided fo u if r defle ti n fi ld to Stlll another obJect of the present invention 40 stantially minimize defocusing and pincushion proud? a {nagnetlc deflectlng System yefiectg mg an eii1c1ent 1ron core low frequency path in An important feature of my present invention Combination With highly efficient 81 C h g is the provision of a highly efficient air core magfrequency p neti system for th i or high frequency A further obJect of the present invention 1s fleeting section. I have found that a serious deprovld-e a novel dual margnetlfl n 45 feet with prior magnetic deflecting systems ret y mutually 091 3 d sides in the provision of an iron core in the effecpendent and With Substantially negligible tive magnetic construction of the high frequency lletic intercoupling bet e he two ections. section, In accordance with my present, inven- Still a further object Of the present invention tion, I eliminate iron in the magnetic path of is to provide anovel compact highly efficient cath- 50 this section to substantially increase the deflecode ray beam magnetic fl c i g system simultional eificiency of the coils. Power loss in the taneously perable in twodirections with a wide iron at the high frequencies becomes serious, and frequency range of Operationelimination of this iron path results in many ad- These and further objects of the present invantages. A resultant advantage is a decreased vention will become apparent in the following 55 description taken in connection with the drawings, in which:

Figure 1 is a perspective illustration of the magnetic deflecting system arranged on a cathode ray tube.

Figure 2 is an elevational view of the magnetic deflecting device with a cover removed.

Figure 3 is a horizontal cross-sectional view through the deflecting device taken along the line 3-3 of Figure 2.

Figure 4 is a vertical cross-sectional view through the magnetic deflecting device taken along the line 44 of Figure 3.

Figure 5 is an enlarged perspective illustration of the high frequency deflecting coil section of the device.

Figure 6 is a diagrammatic representation of the magnetic lines of force emanating from the deflecting sections of the magnetic device of the invention.

The magnetic deflecting device generally indicated by III is shown in operative correlation upon the neck I2 of a cathode ray tube I I. Cathode ray tube II is of the conventional type having an electron gun which generates the electron beam I4 impinging upon the fluorescent screen l5 at the opposite end of the tube. Sources of potential (not shown) are applied to the tube in the conventional manner.

In television systems, the cathode ray beam I4 is deflected in a. regular manner to traverse a rectangular region such as It on the fluorescent screen I5. The number of frames or complete traversals for the image I6 is termed the framing frequency and corresponds to the number of images projected per second. The number of lines constituting each frame I6 determines the line frequency. The fundamental line frequency in present systems ranges in the order of 13,000 cycles per second.

As is well known in the art, saw tooth wave forms for the framing and line signals are used to obtain the uniform rectangular pattern. As indicated schematically at IT, the frame signal generator is connected by leads I8 to posts I9 of the deflecting device for the low frequency or framing magnetic section thereof.

The higher line signal frequency generator is indicated at 2B and is connected by leads 2| to posts 22 of the device. The simultaneous action of the framing and line signal generators through the corresponding magnetic portions of the deflecting device I!) motivates electron beam I4 in a manner to produce the rectangular image I6 as will be understood by those skilled in the art.

The magnetic deflection device of my present invention is a compact unit relatively inexpensive to manufacture. The width of the unit along the neck I2 of the cathode ray tube is made relatively short without sacrificing defiectional sensitivity of the system. I incorporate the frame or low frequency magnetic section together with the line or frequency section while maintaining both sections highly efficient and without electrical or magnetic interference between them.

The low frequency section comprises an iron magnetic core path to produce a uniform transverse field across the cathode ray tube. The high frequency section is arranged to have a substantially all air magnetic path for maximum efficiency and minimum inductance. The saw-tooth wave form of generators I1 and 20 are accordingly faithfully imparted upon both magnetic sections for producing the proper uniform magnetic fields within the cathode ray tube for obtaining the rectangular deflection pattern Hi. The correlation of both magnetic systems is such as to materially diminish the possibilities of defocusing or pincushion effects in the cathode ray tube operation.

Figures 2, 3 and 4 are respectively elevational and sectional views through a preferred form of the magnetic deflecting device In. The physical embodiment is essentially a transformer unit having an additional air core magnetic coil section for the high frequency deflections. As seen in the drawings, unit I0 is constructed within a non-magnetic shell 25 fitted on both ends by composition or Bakelite cover plates 26 and 21. The low frequency or framing section of the device comprises the laminated magnetic iron section 28 and two symmetrically disposed windings 30 on opposite legs of the magnetic structure. Core 28 may be constructed of silicon steel stampings having a thickness of the order of .014 inch.

The assembly of laminations 28 is similar to that of a transformer, and in a preferred embodiment is a closed. core unit having a central spacing or opening to accommodate the neck I2 of the cathode ray tube.

Vertical angle irons 3I-3I are welded or otherwise secured along the rear edges of casing 25 and are arranged for securing laminations 28 by bolts 32. Horizontal cross-bars 3333 are arranged at the front side of the laminated structure for clamping the laminations into a rigid structure in cooperation with bolts 32. The low frequency coils 30 are prewound and inserted upon the outer legs of the core structure in a manner similar to the assembly of transformers.

A plurality of tap leads 35 are made in each of the coils 30 for individual connection to the terminal posts I9 of the unit. By suitable interconnection of frame signal generator leads I8 with posts I9, 2. wide range of impedance matching between the low frequency magnetic system and generator is feasible.

Low frequency coils 3B are connected for producing a common additive magnetic flux extending between pole faces 36, 36. Fiber spacers 31 are inserted between the sides of coils 30 and the inner core regions to prevent movement of the coils upon the core. The vertical height of pole faces 36 is preferably made at least equal to the diameter of the cathode ray tube neck I2 which fits into the cylindrical central fiber tube 38 of the device. The frame signal currents flowing through coils 30 which generates a magnetic field across pole face 36, 36. The magnetic field is substantially uniform in intensity throughout the region corresponding to the movement of the cathode ray beam therewithin, as will be explained in further detail in connection with Figure 6. The horizontal disposition of the magnetic field causes the electron beam to sweep vertically up and back in accordance with the framing frequency.

An important feature of my present invention resides in the provision of a substantially air cored coil system for the high frequency of line signal deflections. The high frequency coils are shown at 4!]. They are constructed by originally winding the coils in a rectangular form with a rather flat hank. Coils 40 are curved about tube 38 to substantially of it. The longitudinal section of coils 40 are parallel to the axis of the cathode ray tube and are arranged symmetrically with respect to the low frequency coil system 30. The arcuate ends of coils 43 are twisted around for a complete 360 turn to substantially eliminate defocusing effects of these turns as will be described hereinafter.

A physical advantage of the twisting of the arcuate portions of coils 4B is that the coils are fitted between pole faces 36 with a squeeze fit and folded over edges prevent axial dislodgernent of the walls as will be further shown.

The current fiow through the curved sections of coils 40 which lie in two planes perpendicular to the axis of the tube is such that their magnetic effects normally cancel. However, the folding over of these portions further reduces efiective action of these coil sections upon the cathode ray beam. The magnetic fields about these portions lie outside of the path of movement of the electron beam in the neck of the tube, practically eliminating defocusing and pincushion effects by the magnetic system. Both coils 40 of this section are electrically connected to produce a common magnetic deflecting field within the cathode ray tube. The coils 40 are shown connected in series by leads 4!, 4| connected to terminal posts 22, and bridging lead. 42 between the coils.

Figure 5 is an enlarged perspective view of the high frequency coil section 4040 with the coacting low frequency magnetic pole faces 36-36, shown in dotted. The coils 40 are originally wound flat with many layers to keep its distributed capacity relatively small. Each coil section 40 is then bent around the central tube to subtend about 180 thereof. The longitudinal legs 45 of coils 49 accordingly are arcuate and lie flat against the central tube 38. The windings of legs 40 are all parallel to the tube and produce a magnetic field within the cylindrical neck [2 of the cathode ray tube, in a vertical direction, for the orientation of the coils as shown in Figure 5. The arrows at sections of coils 49 generally indicate the efi'ective direction of current flow therethrough to produce the desired magnetic effects.

The transverse legs 45 of the coils are arcuate about the central tube. It will be noted that the current flow through the turns of coil sections 46 is such as to mutually cancel magnetic effects between them. However, an important added precaution for insuring elimination of defocusing and pincushion effects by these coil sections is provided as follows:

The originally flat transverse coil sections 45 are rolled back on themselves for one complete revolution of 860. The bank of turns is tied by threads 4'! to keep them together as a unitary structure. The folding over of the transverse turns 45 reduces the path for the leakage flux so that the non-linear field therefrom is concentrated in an area closer'to the coil itself. This area is substantially removed from the path traversed by the electron beam in the central cylindrical portion.

The folding over of transverse turns 46 produces bulged portions 50 where they meet the flat smooth longitudinal leg portions 45. The length of legs 45 is made equal to the width of the pole faces 36. It will be understood, however, that the length of the legs 45 may be varied depending upon the degree of desired sensitivity of the high frequency deflecting coils. Thus, for example, for greater sensitivity of the high frequency coils, the length of the legs 45 would be greater than the pole faces and for lesser sensitivity would be shorter. The transverse legs 46 accordingly constitute ridges for the coil units 40. the coils 40 are juxtaposed against the faces of poles 3B. The outside diameter of the coil assembly 40, 40 is made equal to the distance between the pole faces 3636. A closely integrated structure accordingly results. The coils assembly is fitted between the pole faces 36 and maintained in rigid position by the close fitting nature of the assembly.

The structure is economical to construct and relatively simple to manufacture in mass production. The complete device is relatively small in bulk and light in weight. The magnetic efficiency of the system is very high and extends from the very low frequencies required for framing to the very high frequencies including the upper harmonics of the television line signal waves. The iron path is for the low frequency section and imparts a very good beam deflection sensitivity for this section with a relatively short longitudinal dimension. Thus the length of pole faces 36 parallel to the tube axis may be of the order of one inch. With nominal signal intensity of energization from the framing frequency generator H, such construction has been found to produce very satisfactory results.

The high frequency coil section 48, 459 has its effective magnetic action along the fiat longitudinal leg portions 45 which are juxtaposed against the pole faces 36. Legs 45 are as close to the electron beam position as is feasible. The effective air core opening in the central section of coils 40 is designed to give a uniform flux pattern inside the portion of the tube over which the beam traverses. This opening can be found by calculation or experimentation in accordance with well defined procedure known in the art.

The effective air core path for the magnetic system of the high frequency coil section 40, in conjunction with its relatively short over all length, (less than two inches) results in a highly efficient magnetic action therefor with low losses and low inductance when compared with prior equivalent structures. I have found that this coil section effectively functions with frequencies extending up into the radio frequency spectrum. This simplified design is accordingly capable of handling very high line frequencies of the sharp saw tooth Wave form required for television use. Its construction is also capable of other applications than television particularly where the required frequency band is very wide.

I have further discovered that by constructing the casing 25 of a non-magnetic material that I prevent thereby any magnetic losses that may otherwise occur by reason of a tendency of the magnetic lines of force flowing in a by-pass around such a magnetic casing.

Figure 6 is an enlarged cross-sectional view transverse to the axis of neck 62 of the cathode ray tube with the adjacent sections of the magnetic deflecting device positioned thereon. On Figure 6 is schematically drawn magnetic lines of force emanating from the two magnetic sections of the device to illustrate how they cooperate to act upon the cathode ray beam within the tube for producing the rectangular television scanning pattern l6 referred to hereinabove with a minimum of beam defocusing and pin cushion effects. The rectangle shown with dashed lines centrally within the neck 12 of the cathode ray tube represents the boundaries of the movement of the cathode ray beam of the tube during The central fiat section 45 of 1 the production of the rectangular image I6 upon fluorescent screen l5 shown in Figure 1. For negligible defocusing action and little pincushion effect it is essential that the magnetic fields extending within the region 60 be of uniform intensity and parallel with respect to the size of the boundaries thereof. As seen, the horizontal dash-dot lines extending between pole faces 36 constitute the resultant magnetic action of the low frequency coil system 3il3ll operating upon the closed core 28.

The pole faces 36 are extended and in a practical case are made about equal to the diameter of the neck II! of the cathode ray tube. The magnetic lines extending intermediate of the outer edges of the pole faces 36 are truly horizontal and of uniform intensity. The outer magnetic lines 8| between pole faces 36 are curved as will be evident to those skilled in the art. However, the essential portion of the magnetic path, namely that lying within boundary 60, is truly horizontal and of uniform intensity as required.

The horizontal legs 45 of coil section 40-40 produces magnetic lines adjacent thereto and curved thereabout, gradually merging to form a common vertical magnetic array 9| intermediate thereof. Current flowing through the right and left leg portions are similar, producing the additive magnetic effect centrally of the tube. The disposition of the magnetic fields 9| within the rectangular region 90 is truly vertical in the illustrated example and of uniform intensity. Any unevenness or curving of the magnetic lines occurs outside of this boundary and is immaterial since it does not affect the operation of the beam deflection system.

It is thus seen that in the described example the compact magnetic system produces twosets of fields mutually perpendicular and uniform throughout the central beam deflection region 60. It is to be understood that the orientation of coil set 40, 40 with respect to pole faces 36, 36 may differ from that shown to constitute a dual magnetic deflection system not mutually perpendicular in action. It is to be understood that the magnetic deflection device of the present invention is applicable to other uses than television. Thus it may be applied to deflecting a cathode ray tube beam in radio direction finders or blind landing systems, laboratory oscillograph applications, etc. The two respective deflection circuits are electrically, mechanically and magnetically balanced to greatly minimize the effects of intercoupling between the high and low frequency circuits. The balanced nature of the coil systems materially decreases the possibility of interference from extraneous electrical action.

Although I have illustrated a particular embodiment of the invention, it is to be understood that modifications which fall within the broader spirit and scope of the invention are feasible, and accordingly, I do not intend to be limited except as set forth in the following claims.

I claim:

1. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a closed laminated core structure having centrally opposed flat pole faces at least as wide as the neck of the cathode ray tube and of the order of one inch in thickness; a pair of windings individually and symmetrically wound on said core structure, said windings being interconnected to constitute with said core structure the lower frequency beam deflection section of the device with relatively small inductance; a pair of aircored layer flat-wound coils bent around to subtend substantially 360 degrees of arc with side portions parallel to the longitudinal axis of the device, the arced sections of said coils being twisted about themselves for a complete revolution of substantially 360 degrees to localize magnetic flux thereabout and to prevent beam defocussing thereby.

2. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a closed laminated core structure having opposed flat pole faces at least as wide as the neck of the cathode ray tube and of the order of one inch in thickness; winding on said core structure, said winding constituting with said core structure the lower frequency beam deflection section of the device with relatively small inductance; a pair of air-cored layer fiat-wound coils bent around to subtend substantially 360 degrees of arc with side portions parallel to the longitudinal axis of the device, the arced sections of said coils being twisted about themselves for a complete revolution of substantially 360 degrees to localize magnetic flux thereabout and to prevent beam defocusing thereby, and

being symmetrically disposed to minimize intercoupling effects therefor, the air-core section of said coils lying outside the region of said iron pole faces to minimize inductance and losses for the coils for efficient utilization of a relatively wide frequency band by the coils for uniform deflection of the beam thereby.

3. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a laminated core structure having opposed pole faces; a winding on said core structure; said winding constituting with said core structure the lower frequency beam deflection section of the device; a hollow cylinder fitted between said pole faces; a pair of air-cored flat-wound coils bent around said cylinder to subtend substantially 360 degrees of arc thereabout with side portions parallel to the longitudinal aXis of the device, the arced sections of said coils being twisted about themselves for a complete revolution of substantially 360 degrees to localize magnetic flux thereabout, the flat longitudinal side portions of said coils being juxtaposed between said cylinder and pole faces with the twisted over sections of the coils extending adjacent the outer sides of said pole faces to constitute a mutually supporting and mechanically stable structure for the device.

4. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a laminated core structure having opposed pole faces; a pair of windings individually and symmetrically wound on opposite legs of said core structure, said windings being interconnected to constitute with said core structure the lower frequency beam deflection section of the device with relatively small inductance; a hollow cylinder fitted between said pole faces; a pair of air-cored flat-wound coils bent around said cylinder to subtend substantially 360 degrees of arc thereabout with side portions parallel to the longitudinal axis of the device, the arced sections of said coils being twisted about themselves for a complete revolution of substantially 360 degrees to localize magnetic flux thereabout and to prevent beam defocusing thereby and being symmetrically disposed to minimize intercoupling effects therefor, the flat longitudinal side portions of said coils being juxtaposed between said cylinder and pole faces with the twisted over sections of the coils extending adjacent the outer sides of said pole faces to constitute a mutually supporting and mechanically stable structure for the device, the air-core section of said coils lying outside the region of said iron pole faces to minimize inductance and losses for the coils and permit eificient utilization of a relatively wide frequency band by the coils for uniform deflection of the beam thereby.

5. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a closed laminated core structure having centrally opposed flat pole faces at least as wide as the neck of the cathode ray tube and of the order of one inch in thickness; a pair of windings individually and symmetrically wound on opposite legs of said core structure, said windings being interconnected to constitute with said core structure the lower frequency beam deflection section of the device with relatively small inductance; a pair of air-cored layer flat-wound coils bent around to subtend substantially 360 degrees of arc with side portions parallel to the longitudinal axis of the device, the arced sections of said coils being twisted about themselves for a complete revolution of substantially 360 degrees to localize magnetic flux thereabout and to prevent beam defocusing thereby, and being symmetrically disposed to minimize intercoupling effects therefor, the air-core section of said coils lying outside the region of said iron pole faces to minimize inductance and losses for the coils for efficient utilization of a relatively wide frequency band by the coils for uniform deflection of the beam thereby.

6. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a laminated core structure having centrally opposed pole faces; a pair of windings individually wound on opposite legs of said core structure; said windings being interconnected to constitute with said core structure the lower frequency beam deflection section of the device; a hollow cylinder fitted between said pole face; a pair of air-cored fiat-wound coils bent around said cylinder to subtend substantially 360 degrees of arc thereabout with side portions parallel to the longitudinal axis of the device, the arced sections of said coils being twisted about themselves for a complete revolution of substantially 360 degrees to localize magnetic flux thereabout, the flat longitudinal side portions of said coils being juxtaposed between said cylinder and pole faces with the twisted over sections of the coils extending adjacent the outer sides of said pole faces to constitute a mutually supporting and mechanically stable structure for the device.

7. A device for magnetically deflecting the electron beam of a cathode ray tube comprising a closed laminated core structure having centrally opposed flat pole faces at least as wide as the neck of the cathode ray tube and of the order of one inch in thickness; a pair of windings individually and symmetrically wound on opposite legs of said core structure, said windings being interconnected to constitute with said core structure the lower frequency beam deflection section of the device with relatively small inductance; a hollow cylinder fitted between said pole faces; a pair of air-cored coils bent around said cylinder to subtend substantially 360 degrees of arc thereabout with side portions parallel to the longitudinal axis of the device, the arced sections of said coils being twisted about themselves for a complete revolution to localize magnetic flux thereabout, and the flat longitudinal side portions of said coils being juxtaposed between said cylinder and pole faces with the twisted over sections of the coils extending adjacent the outer sides of said pole faces to constitute a mechanically stable structure for the device, the air-core section of said coils lying outside the region of said iron pole faces to minimize inductance and losses for the coils and permit efficient utilization of a relatively wide frequency band by the coils for uniform deflection of the beam thereby.

FRANKLIN P. KENYON.

Images