US2692355A - Cathode-ray tube deflection yoke - Google Patents

Description

Oct. 19, 1954 R. F. SICKLES ET AL 2,692,355

CATHODE-RAY TUBE DEFLEICTION YOKE Filed June 29 1951 2 Sheets-Sheet l INVENTORS 20/?44 /-T 5/6164 Oct. 19, 1954 R. F. SICKLES ET AL CATHODEl-RAY TUBE DEFLECTION YOKE Filed June 29, 1951 2 Sheets-Sheet 2 s g F D/zaw" A 4Q9V F Y g F I -%Z; g

01/ A Y g 92 INVENTORS.

Patented Oct. 19, 1954 CATHODE-RAY TUBE DEFLECTION YOKE Royal F. Sickles, Longmeadow, Walters, Springfield, Mass.,

and William F. assignors to General Instrument Corporation, Elizabeth, N. J., a corporation of New Jersey Application June 29, 1951, Serial No. 234,322

2 Claims.

The present invention relates to the construction of a cathode ray tube deflection yoke, and in particular to the construction of an insulating form on which the coils of the deflection yoke may be mounted.

In a cathode ray tube, either of the instrument type or the type used for television purposes, means must be provided for deflecting the stream of electrons passing through the tube in order to control the image produced by the tube. The most customary method of controlling the stream of electrons is to provide means, usually of electromagnetic type, for deflecting that stream horizontally and vertically according to signals received by or produced in the apparatus with which the tube is employed.

In by far the greatest number of cases the deflection of the stream of electrons in a cathode ray tube is accomplished by two pairs of coils positioned at an appropriate point along the neck of the tube, one pair of coils controlling vertical deflection of the electron stream and the other pair of coils controlling horizontal deflection thereof. Since each pair of coils thus acts in a direction at right angles to the other pair of coils, the coils must be appropriately oriented at right angles to one another around the neck of the cathode ray tube.

Since the signals sent to one set of coils may differ radically from the signals sent to the other set of coils, and since relatively high voltages on the order of 4000 volts are often involved, it is apparent that insulation must be provided between the coil pairs, and that said insulation not only must be capable of withstanding the high voltage differences involved without breakdown, but also must not interfere with the accurate alignment of the coils with respect to one another.

Because of the geometry of the cathode ray tube, and in order to produce certain more or less essential effects, deflection yokes for this purpose customarily assume a conventional shape, which may well be described as a rectangular ring curved into semi-cylindrical form so as partially to encompass the neck of the cathode ray tube and with the top and bottom portions of the coil bent with respect to the sides thereof so as to flare outwardly therefrom almost at a right angle. One pair of coils is arranged inside the other pair of coils so as to define coaxial cylinders surrounding the cylindrical tube neck, the radius of curvature of the inner pair thus being smaller than that of the outer pair, the side portions of each of the coils are oriented parallel to the axis of the neck of the tube, and each pair of coils is disposed in quadrature relationship to the other set of coils, that is to say, the coils of each pair are diametrically opposite one another and each coil is oriented 90 degrees about the axis of the tube with respect to each coil of the other pair.

Reference has already been made to the necessity for providing insulation between the coils of different pairs because of the high potential difference which might exist between them during their operation. It has not usually been necessary in the past to provide insulation between coils of the same pair, even though particular turns of those coils may be extremely close to one another. However, it is becoming more and more frequent, particularly for certain systems of color television, to wind and connect the coils of a given pair in such a way that a high potential difference might exist between adjacent turns of such coils. Since each coil of a given pair is substantially semicylindrical in overall area, it will be apparent that the outer windings of the two coils of a given pair will be very closely spaced with respect to one another and in some instances might even abut one another, and if any appreciable potential difference should exist between such turns adequate insulation must be provided or a breakdown will result. The coils are formed of many turns of relatively fine wire the insulation on which is comparatively thin and is capable of withstanding only the potential difference between adjacent turns of the same coil, which potential difference may be only a few volts, but is clearly incapable of withstanding potential differences on the order of several thousand volts, such as might occur between turns of different coils of the same pair. I-Ience some extra insulation must be provided between such adjacent turns of coils of the same pair.

In the past deflection coils of this type have been manufactured with multiple layers of thin, flat sheets of insulating material, usually of synthetic composition, interposed between the two pairs of coils. Since these sheets were flat and flexible, since they had to be interposed not only between the longitudinally extending sides of the coils of different pairs, but also between their outwardly flaring ends, and since several thicknesses of these sheets were required in order to provide the necessary insulation, many problems, both electrical and fabricational, were presented. Because of the nature and shape of the insulating material, Wrinkles or folds were inevitably produced when the sheets of insulating material were caused to conform to the configuration of the coils, and in some areas of the sheets stretching occurred. After the sheets of insulating material had been caused to conform to the outer configuration of the inner pair of coils, the outer pair of coils were placed in position therearound, and were pressed down against the insulating material.

From an electrical point of view, this type of structure had numerous disadvantages. The unavoidable wrinkles and folds in the insulating sheets, by increasing the thickness of the material where they occur, limited the maximum overall thickness of the material which could be employed between the coils, it being borne in mind that the outer pair of coils must be as close as possible to the neck of the tube in order to have the desired deflection effect on the stream of electrons. Hence the amount of insulation which could be provided between the coils of different pairs was definitely minimized for a given spacing of the outer pair of coils from the neck of the tube. This, of course, limited the magnitude of the voltage which could be safely applied to the windings without voltage breakdown. Moreover, the wrinkles and folds created air pockets in the insulation material where high voltage corona could occur, with consequent deterioration of the insulating material leading to ultimate breakdown. In addition, in those areas where the insulating material was stretched the thickness of the material was reduced, thus producing areas of decreased insulating effect and further enhancing the possibility of breakdown.

From a fabricational point of view, the manufacture of each yoke presented an individual problem requiring great care and attention on the part of the personnel involved. Sheets had to be handled individually, care had to be taken that wrinkles and folds were kept to a minimum and that stretching of the insulating sheets was kept within bounds, and despite exercise of the greatest care and skill, no one deflection yoke was exactly like another.

When the individual coils of a pair were to be wound and connected in such a manner that insulation was necessary between adjacent turns of such coils, separate insulating strips had to be interposed between the adjacent turns and secured in some appropriate manner in the yoke. This, too, was a hand operation requiring individual care on the part of the operator.

In addition, and independently of the provision and arrangement of the insulation between coils, the assembler had to see to it that the coils were accurately aligned, the coils of a given pair being diametrically opposite one another and coils of different pairs being in quadrature relation one to the other.

It is a prime objective of the present invention to provide a deflection yoke construction which avoids the disadvantages inherent in the structures heretofore commercially used for this purpose, as outlined above. In particular, the yoke structure of the present invention is designed to more effectively utilize the space available between the inner and outer pairs of coils for insulating purposes, to more accurately orient the coils of both pairs around the axis of the oathode ray tube, to make for greater uniformity in manufacture, to reatly facilitate assembly of the yoke structure, and to greatly decrease the likelihood of breakdown of the insulating material.

To this end a segmental molded plastic insulator is provided which is preformed substantially to the shape which it must ultimately assume. As a result this new molded insulator can be approximately three times thicker than the former fiat sheet type insulator because of the absence of wrinkles or folds. Whatever the spacing allowed for insulation between inner and outer pairs of coils, the entire space can be utilized with a maximum uniform thickness of molded insulating material. Since there are no folds in the insulator to give rise to pressure points, there is a more even distribution of pressure throughout the entire insulator, thus providing for higher efficiency of the insulation qualities of the insulator. Moreover, the insulator can be subjected to higher potentials without breakdown not only because of the uniformly greater thickness of insulating material when compared With the prior art, but also because of the absence of air pockets, thus minimizing the possibility of destructive corona effects.

As an additional feature, the molded plastic insulator is provided with integral insulating and locating fins, the fins being so positioned with respect to the segments of the insulator as to provide insulation between adjacent portions of coils of the same pair and at the same time to provide for orientation of the coils with respect to one another so that they are in nearly perfect quadrature relation.

The construction of the individual segments of the plastic insulator is such as to facilitate assembly. In the form here specifically disclosed the insulating and locating flns are provided at the ends of each of the segments, those fins abutting when the segments are assembled. Thus the parts of the segments which abut one another are substantially thicker than the remainder of the segments, and in this way accurate assembly or" the segments without overlapping is provided for.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to the construction of a cathode ray tube deflection yoke and the insulating form embodied therein, as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in which:

Fig. 1 is a side elevational view of a deflection yoke of the present invention shown in place on a cathode ray tube;

Fig. 2 is a side elevational view, on an enlarged scale, of a portion of that yoke showing the deflection coils and the insulating form on which they are mounted;

Fig. 3 is an exploded view of the components of Fig. 2, illustrating one manner in which the unit of Fig. 2 may be assembled;

Fig. 4 is an end elevational view of one of the segments of the insulating form of Fig. 2;

Fig. 5 is a top cross sectional view, taken along the line of 5-5 of Fig. 4, of one of the segments of the insulating form, the other and mating insulating form segment being shown in assembled position in broken lines;

Fig. 6 is a cross sectional view of the unit of Fig. 2, taken along the line 5-5 of Fig. 2;

Fig. 7 is a cross sectional view of the entire deflection yoke, taken along the line of 7-! of Fig. 1; and

Figs. 8, 9, 10 and 11 are schematic wiring diagrams illustrating different ways in which the coils of a given pair may be wound and connected and showing the necessity in some cases for insulation between coils of the same pair.

Customarily one pair of coils is employed for controlling deflection of the electron beam in a given direction and the other controlling deflection thereof pendicular thereto. These directions are generally termed horizontal and vertical. Whether one pair of coils or the other controls deflection in a given dierction is a matter of choice and engineering design. Therefore, in the description to follow, one pair of coils will be termed the inner pair and the other pair of coils will be termed the outer pair, the terms inner and "outer referring to the relationship of the coil pairs to the axis of the neck 2 of the cathode ray tube 4 with which the yoke is associated. While each pair of coils normally controls deflection in a direction perpendicular to that controlled by the other pair of coils, each pair of coils thus being positioned around the axis of the tube neck 2 in quadrature relation, it may be desired, in certain special applications, to vary the angular relationship between the coils from that which they normally assume. While the invention will be here described in terms of the normal coil orientation, it should be understood that variations may be made therein, as dictates of electrical design may determine, without modifying the invention other than by requiring the use of locating and insulating elements somewhat differently positioned on the insulating form than is here specifically disclosed.

The yoke includes a pair of inner coils 6, 6' and a pair of outer coils 8, 8. Each coil has parallel side portions I and end portions I2 flaring outwardly from the side portions ID at an appropriate angle substantially at right angles thereto, the upper and lower surfaces of the end portions I2 having different inclinations, all as is well known in the art. The side portions I o of the outer coils 6, 6' are shorter than the corresponding side portions III of the outer coils 8 and 8', the end portions ii of the outer coils 8 and 8 approach perpendicularity with respect to the side portions I 0 of those coils more closely than do the end portions I2 of the inner coils 6 and 6 with respect to their side portions Ill, and the radius of curvature of the outer coils 8, 8' is greater than that of the inner coils 6, 6', all to the end that, as is customary in the art, the outer coils 8, 8' snugly fit around the inner coils 6, 6' and the two coils of a given pair will substantially completely surround the tube neck 2 except for a slight peripheral gap therebetween and except for the central opening I4 in each of the coils. Hence, with respect to the axis of the tube neck 2, the coils 6 and 6 may be considered as peripherially adjacent one another, the coils 8 and 8 may be similarly considered with respect to one another, and each of the coils 6 and 6' may be considered as radially adjacent to each of the coils 8 and 8'.

Insulation between the deflection coils is provided by a pair of identical segments I 6, I6 of shaped insulating material. From an economic point of view, both with respect to cost of raw materials and cost of shaping, some synthetic plastic material having appropriate insulating properties, such as one of the vinyl resins, is preferred, but any insulating material could be employed. While a molded segment is here specifically employed, molding is preferred because of the facility with which synthetic plastic insulating material of the type described may be shaped by that method. It will be understood that any other mode of shaping which seems appropriate might also be employed. The important factor is that the segments I6 and I6 are shaped in set is employed for in a direction peradvance to conform to the space between the inner coils 6, 6' and the outer coils 8, 8.

Each of the segments I6, I6 includes a curved wall I8 substantially semi-cylindrical in shape and having a radius of curvature intermediate between that of the inner coils 6, 6 and the outer coils -8, 8'. Consequently the wall I8 can be readily interposed between radially adjacent coils in the deflection yoke without distortion and without requiring the exercise of care or skill in fitting segment I6 in place. At the top and bottom of the wall I8 outwardly flarin top and bottom portions 20, 22 are provided of substantially the same thickness as the wall I8 and angularly extending out therefrom in a direction such as to interpose between the outwardly flaring end portions I2 of the radially adjacent deflection coils.

Although each of the coils of a given pair is substantially similar, both in shape and in dimensions, they are not precision-made objects, and hence must be expected to vary somewhat from the norm in ordinary manufacturing practice. As a result, it is most desirable that the insulating form segments I6 be somewhat flexible in order that they can accommodate themselves to these manufacturing variations. The use of synthetic plastic such as one of the vinyl types is there fore particularly strongly indicated, since such a resin, when molded, and with the thicknesses usually here involved, such as between and a; of an inch, is sufficiently flexible to permit its efficient use.

In order to position the coils around the axis of the tube neck 2, and further in order to provide insulation between adjacent turns of peripherially adjacent coils, the segments I6, I6 are provided with fins projecting inwardly and outwardly from the wall I8 a distance substantially equal to the thickness of the coils. In the form here specifically disclosed, each of the segments IE, I5 is provided With a fin 24 extending inwardly therefrom midway between its ends, and is provided with outwardly extending fins 26, 26 at each end thereof, each of the fins 24, 26 and 26 extending substantially the full length of the wall I8. Since only two segments I6, I6 are employed, each segment thus defining half of the entire insulating form, this arrangement and location of fins, all integral with the segments I6, I6 and hence accurately positioned with respect thereto, will provide for correspondingly accurate location of the coils around the tube neck 2 and will also provide for insulation between adjacent turns of every peripherially adjacent coil. (When only location, and not insulation, is a factor, the fins 24, 26 and 26 need not extend the full length of the Walls I8.) Thus, as may best be seen from Fig. 3, the segments I6 and I 5' are assembled so that the fins 26 and 25 of one segment I6 abut the fins 26 and 25 of the other segment I 6. In this position (see Figs. 2 and 6) the walls I8 of the segments I6, I6 define a cylinder of solid insulation material interposed between the inner coils 6, 6' and the outer coils 8, 8' radially adjacent thereto. The inwardly projecting fins 24 extend between adjacent turns of the peripherially adjacent inner coils 6 and 6', thus not only insulating those coils from one another but also ensuring that they are positioned diametrically opposite one another. The fins 26 and 26 of the segments I5, I6 abut one another and define composite fins of double thickness each interposed between adjacent windings of the peripherially outer coils 8, 8'. This not only provides insulation between those coils '7 but also ensures that those coils are located diametrically opposite one another and are also located in quadrature relation with respect to the inner coils 6, 6.

A further function of the fins 26, 25' positioned at the ends of the wall l8 of the segments It, IE3, is to ensure proper assembly of those segments and to prevent unwanted overlapping thereof. The walls l8 are comparatively thin and might, if subjected to careless handling, overlap at one end and leave a gap at the other end, thus producing a deflection yoke assembly which would break down almost immediately upon use. The abutting fins 20, 2t and 26, 28 at the ends of the segments l6 and it, because of the increased area of abutting surfaces which are presented thereby, make it well nigh impossible for any such overlapping to take place without preventing subsequent assembly of the unit.

The remainder of the deflection yoke may take a more or less conventional form insofar as the invention is concerned. A strip 28 of cellophane or other insulating material may be wound about the outer surfaces of the outer coils 9 and 8, magnetizable segments 30 may be placed in position therearound, and a clamping and mounting ring 32 may be placed thereover and tightened by means of screw 34. Fiber insulating plates 35 and 38 may also be mounted on the assembly, terminal lugs at being fastened to the disk 38 to facilitate electrical connection to the coils.

The entire unit is adapted to be placed around the neck 2 of a cathode ray tube 4 and to be slid along that neck to an appropriate position, usually right up against the flaring forward portion of the tube 4 (see Fig. 1). The inner surfaces of the outwardly flaring end portions 42 of the inner coils 6, 6' are usually oriented so as to mate with the flaring portion of the tube 4, and thus fix the position of the deflection coil yoke. In orderto assist in this, the inwardly extending fins 24 are provided with correspondingly tapered end edges 2 at the top ends thereof.

Assembly of the deflection yoke of the present invention is simplicity itself, and may best be described with reference to Fig. 3. The segment i6 is grasped and the two inner coils 6 and 6 are positioned therein so that each abuts the inward- 1y extending fin 24. The segment is is then placed on top of the thus defined sub-assembly so that its inwardly extending fin 24 is positioned between the coils ii and 6. The two segments are manually pressed together until their respective fins 28 and 20' abut or substantially so. Each of the outer coils 8 and 8 is then placed in position so that their side portions it abut the outwardly extending fins 26 and 2% of the segments it, It, and the entire assembly is then compacted. Usually manual pressure is sufiicient for this purpose. The other elements of the yoke are then placed in position in conventional. manner.

Figs. 8, 9, and 11 illustrate various ways in which coils of a given pair might be wound and connected. In Figs. 8 and 9 the two coils are wound in the same direction, Whereas in Figs. 10 and 11 one of the two coils is wound in reverse direction. The start and finish of each coil is represented by the letters S and F, the convention being adopted that the inner turns of the coil represent its start and the outer turns its finish. Thus it is the outer or finishing turns of each peripherially adjacent coil which are adapted to be adjacent one another. In the winding arrangements of Figs. 8 and 11 the potential difference between adjacent turns of peripherially adjacentcoils is no greater than the potential difference between the turns of a given coil. This represents the standard situation and does not require separate insulation between adjacent turns of peripherially adjacent coils. However, in the winding of Fig. 9 the entire potential difference Of 4000 volts is applied between the adjacent finishing turns, and in the winding of Fig. 10 half of the applied maximum voltage of 4000 volts is efiective therebetween. With these manners of winding and connection, breakdown is sure to occur unless some provision is made for insulation between peripherially adjacent coils.

The advantages of the mode of construction herein set forth will in the main be fully obvious from the above description. The space between the coils is fully filled by insulating material of uniform thickness which is subjected to substantially uniform stress. Maximum insulation is thus provided for given coil dimensions, thin sections are eliminated, and air pockets where corona discharge might accumulate are not formed. Since each insulating form is exactly like the other, each yoke will be substantially similar electrically to another. Assembly of the yokes is substantially foolproof; if a coil or an insulating segment is improperly aligned or misplaced, the subsequent assembly steps will be prevented. No particular care is involved; no individual fitting or manipulating must be resorted to. The productivity of a given worker is greatly increased, the number of rejects is significantly decreased, and the amount of skill and training required on the part of the employee is minimized. Moreover the coils are accurately oriented with respect to one another, the coils of individual pairs being positioned diametrically opposite one another and the coils of different pairs being positioned in quadrature relationship to one another, and insulation is provided between adjacent turns to peripherially adjacent coils, all without requiring the exercise of any appreciable attention or care on the part of the person performing the assembly operation.

While the present invention has been here disclosed in but a single embodiment, it will be apparent that many variations may be made therein without departing from the spirit of the invention, as defined in the following claims. Thus, merely by Way of example, more than two segments might be employed, the segments might be of unequal size, the fins might be differently positioned with respect to the individual segments and might project from diiierent sides thereof, a different number of coils might be employed, and the coils might have specifically difierent shapes and orientations, all of which factors could, according to the present invention, be taken into account through the exercise of ordinary skill.

We claim:

1. In a cathode ray tube deflection yoke comprising an insulating form, a pair of horizontal deflection coils, and a pair of vertical deflection coils; the improvement which comprises said insulating form comprising a pair of mating shaped pieces of molded flexible insulating material, each of said pieces comprising a semi-cylindrical wall, a longitudinal fin propecting from said wall on one side thereof midway between its ends, and a pair of longitudinal fins projecting from the other side of said wall at opposite ends thereof, each of said fins having an appreciable height on the order of magnitude of the thickness of a deflection coil, said wall having integral top and bottom extensions flaring outwardly at an obtuse angle therefrom, said pieces being adapted to be fitted against one another with the pair of fins of one piece abutting the pair of fins of the other piece so that the walls define a cylinder with diametrically opposed pairs of fins on opposite sides thereof, each fin being disposed 90 degrees about the axis of said cylinder with respect to adjacent fins, said pair of horizontal deflection coils being mounted on one side of said wall with the diametrically opposed pair of fins on that side of said wall being interposed between and in engagement with adjacent edges of said horizontal deflection coils, and said pair of vertical deflection coils being mounted on the other side of said wall with the diametrically opposed pair of fins on said other side of said wall being interposed between and in engagement with adjacent edges of said vertical deflection coils.

2. In a cathode ray tube deflection yoke comprising an insulating form, a pair of horizontal deflection coils, and a pair of vertical deflection coils; the improvement which comprises said insulating form comprising a pair of mating shaped pieces of molded flexible insulating material, each of said pieces comprising a semi-cylindrical wall, a longitudinal fin projecting from said wall on one side thereof midway between its ends, and a pair of longitudinal fins projecting from the other side of said wall at opposite ends thereof, each of said fins having an appreciable height on the order of magnitude of the thickness of a defiection coil, said wall having integral top and bottom extensions flaring outwardly at an obtuse angle therefrom, said pieces being adapted to be fitted against one another with the pair of fins of one piece abutting the pair of fins of the other piece so that the walls define a cylinder with diametrically opposed pairs of fins on opposite sides thereof, each fin being disposed degrees about the axis of said cylinder with respect to adjacent fins, those fins projecting from the inside of said walls extending lengthwise of said form to the flaring top extension thereof and having a correspondingly tapered top edge, said pair of horizontal deflection coils being mounted on one side of said wall with the diametrically opposed pair of fins on that side of said wall being interposed between and in engagement with adjacent edges of said horizontal deflection coils, and said pair of vertical deflection coils being mounted on the other side of said wall with the diametrically opposed pair of fins on said other side of said wall being interposed between and in engagement with adjacent edges of said vertical deflection coils.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,167,379 Tolson July 25, 1939 2,207,777 Blain July 16, 1940 2,229,977 Kenyon Jan. 28, 1941 2,395,736 Grundmann Feb. 26, 1946 2,428,947 Torsch Oct. 14, 1947 2,443,025 DeTar June 8, 1948 2,562,394 Schlesinger July 31, 1951 2,562,395 Schlesinger July 31, 1951 2,563,116 Hultgren Aug. 7, 1951 2,565,331 Torsch Aug. 21, 1951

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