US2167379A

US2167379A - Cathode ray tube deflecting device

Info

Publication number: US2167379A
Application number: US66171A
Authority: US
Inventors: William A Tolson
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1936-02-28
Filing date: 1936-02-28
Publication date: 1939-07-25
Anticipated expiration: 1956-07-25
Also published as: GB495016A; IT349671A; FR816431A

Description

July 25, 1939. w A. TOLSON CATHODE RAY TUBE DEFLECTQING DEVICE Filed Feb. 28, 1936 Patented July 25, 1939 UNITED STATES PATENT. OFFICE OATHODE RAY TUBE DEFLEOTING DEVICE William A. Tolson, Westmont, N. J., assignor to Radio Corporation of America, a corporation,

of Delaware Application February 28, 1936, Serial No. 86,171

11 Claims. (01. 250-157) 3. There must be linear velocity of the scanhing spot on the fluorescent screen, that is, there must be freedom from distortion of the scanning pattern.

4. There must be a satisfactory ratio of scanning velocity to return line velocity.

5. There must be freedom from transients.

6. There must be freedom from interaction between the horizontal and vertical deflecting circuits, that is, freedom from "cross-talk.

Where the deflecting device is to be employed in television receivers, it is important that the production cost be low.

I have found that by properly designing defleeting coils, they may be made to meet the above requirements.

It is, accordingly, an object of my invention to provide improved deflecting coils for a cathode ray tube.

It is a further object of my invention to provide improved deflecting coils which meet the above-mentioned requirements.

It is a still further object of my invention to provide improved deflecting coils which are cheap to manufacture.

It is a still further object of my invention to provide an improved cathode ray deflecting device which is compact and rugged in constructlon.

In practicing a preferred embodiment of my invention I utilize a distributed winding of the general character described and claimed in Patent No. 2,155,514, issued April 25, 1%39, to W. A. Tolson and L. G. Maloff, and assigned to the Radio Corporation of America. However, instead of placing the winding in the slots of an iron core, I place the entire winding inside a steel sleeve or tube. Generaiy, both horizontal and vertical deflecting windings are placed in the steel tube, arranged concentrically and at right angles to each other, whereby an electrostatic shield may be placed between them if desired. This form of construction permits the realization of certain other inherent advantages which will be apparent from the following description.

Other objects, features, and advantages of my invention will appear from the following description taken in connection with the accompanying drawing in which Figure 1 is a full scale cross-sectional view of one embodiment of my invention, the section being taken along the line l-l in Figure 2;

2 is a view taken along the line 2-2 of 8- I Fig. 3 is a view which is referred to in explaining how a deflecting winding is manufactured;

Fig. 4 is a perspective view of the vertical defleeting coils used in the deflecting device shown in Figs; 1 and 2;

Fig. 5 is a perspective view of the completely assembled deflecting device; and

Fig. 6 is a diagram which is referred to in explaining my invention.

Referring to Figs. 1 and 2, the deflecting device includes two diametrically opposed vertical deflecting windings I and 2, each of which is constructed as shown in Fig. 4. Each winding consists of a plurality of concentrically wound coils, there being eight coils for each vertical winding, each coil preferably consisting of several turns. All the coils are wound in the same direction and connected in series. The two d flecting windings I and 2 may be connected in series or in parallel, as preferred, and in such direction that their fields are aiding in accords ance with usual practice. These connections are the same as those of the deflecting windings described in the above-mentioned Tolson and Maloff patent. It will be noted that the winding does not occupy all the available space, but instead, there is a space in the center of the winding in which several coils that could have been added have been omitted.

The method of making a deflecting winding will be better understood by referring to Fig. 3, only six coils being shown in this particular view. In making the winding, the inner coil is first wound around a form which may consist of four pegs inserted in holes in a board. The next coils are then wound around similar forms, each form being of increasingly greater dimensions. As previously stated, all coils are wound in the same direction. At this point in the winding manufacture, the winding is flat, as indicated,

by the plan view (a) and the end view (b).

The next step in themanufactureis to impregnate the winding and then remove it from the forms after the impregnating material has cooled and stiflened. The impregnated flat winding is next placed between curved blocks (not shown) and bent into the form indicated by the end view 0 (Fig. 3) to produce the finished preformed winding. If desired, the coils may be taped instead of impregnated to hold the turns in place.

Referring again to Figs. 1 and 2, it will be seen that the deflecting device includes three concentrically positioned cylindrical tubes 4, 6 and I, the two inner tubes 4 and 6 being of insulating material such as flbre, andthe outer tube or sleeve 1 being of magnetic material. In a preferred embodiment, the'sleeve I is a seamless steel tube.

The outer flbre tube 6 has two rectangular spacer rods 8 and 9 of insulating material mounted thereon in diametrically opposed relation. One end oi. the rod 8 extends slightly beyond the tube 6 for centering purposes, as will be explained hereinafter. In Fig. 2 the spacer rod 9 has been omitted in order to show the winding 2.

As shown in Fig. 1, the preformed vertical deflecting windings I and 2 are supported by the flbre tubeB and are located between this tube and the magnetic sleeve I. Proper spacing of the deflecting windings is maintained. by the spacer rods 8 and 9. In order to prevent short circuiting of the winding turns, the inner surface of the sleeve I is preferably covered with a sheet of insulating material ll.

The inner fibre tube 4 also supports two concentrically wound distributed windings l2 and i3 which preferably are manufactured in the same way as above described. Rectangular spacing rods 14 and I6 oi! insulating material are attached to the fibre tube 4 in diametrically opposed relation for keeping the horizontal deflecting windings l2 and i3 properly spaced. The

ends of these rods project beyond the tube 4 for centering purposes as hereinafter described. It will be noted that the horizontal deflecting windings are positioned at right angles to the vertical deflecting windings, whereby the two sets of windingsmay be employed for causing a cathode ray to scan a screen. 7

One of the advantages of my invention is that an electrostatic shield consisting of a sheet of conducting material, such as copper, may be placed between the vertical windings and the horizontal windings as indicated at H. In this way, undesired electrostatic coupling between the two sets of windings may be avoided. In certain-applications of the invention it has been found that the electrostatic coupling is so small that the electrostatic shield may be omitted.

Fibre washers l8 and I! at each end of the device protect the deflecting windings as shown in Figs. 2 and 5. The washer l8 supports the horizontal deflecting winding terminals 2| and the vertical deflecting winding terminals 22. This washer also has an opening 23 and two notches 24 therein which are utilized to center the two sets of deflecting windings. The previously mentioned projecting end of the spacer rod 8 extends through the opening 23 tom: the vertical deflecting windings in position with respect to the washer l8.

The projecting ends of the spacer rods I4 and I6 extend through the notches 24 to fix the horizontal deflecting windings in position with respect to the washer l8 and at right angles to the vertical deflecting windings. At each end of the assembled device the fibre washer is held in position by means of lugs 26 extending from Y the magnetic sleeve I, these lugs. being bent over after the several component parts have been assembled.

In addition to the advantages of cheapness of manufacture and ruggedness oi the completed unit, my deflecting device has other important advantages over other deflecting devices, one of' these other advantages being that it reduces deshown in Fig. 6, the several figures indicate the relative strength or this magnetic fleld at the several points where the figures are located. This particular fleldpattern was obtained with distributed horizontal windings similar to the ones illustrated, but having the inner coil omitted. In other words, it is the field pattern for a pair of horizontal deflecting windings,.each winding con.- sisting of five coils. The two inner coils had fourteen turns each and the three outer coils had twenty turns each.

The specific unit illustrated in Figs. 1 and 2 provides a deflecting fleld which is uniform enough for present television receivers. In this particular unit all coils of the horizontal deflecting windings have the same number of turns and the sameis true of the vertical deflectin windings.

The number of turnsused in the deflecting windings depends upon various factors. It is generally desirable to supply the deflecting windings with deflecting current through a trans former so that a fewer number of turns may be used than would be required if the windings were driven directly from the output tube. By'using a transformer and a smaller number of winding turns, the distributed capacity of the winding is reduced, whereby it is easier to obtain a satisfactory ratio of scanning velocity to return line velocity. A further advantage in the use of a low-impedance winding driven through a stepdown transformer lies in the fact that electrostatic coupling between horizontal and vertical deflecting windings is reduced as a result of the lower potential applied across the windings.

In order to get sufflcientinductance in the vertical deflecting windings to make possible the production of a good saw-tooth wave, they usually have a considerably larger number of turns than the horizontal deflecting windings. It will be understood that by the term vertical deflecting windings applicant means the deflecting windings which have the lower frequency deflecting wave applied thereto. The magnetic sleeve I acts to increase the inductance of the vertical deflecting windings more than is practical merely by increasing the number of turns. Since this magnetic sleeve is much closer to the vertical deflecting windings than to the horizontal deflecting windings, it has a comparatively small eiiect on the horizontal windings. However, it does increase the inductance of the horizontal deflecting windings a certain amount and p it also provides a certain amount of iron loss in areas-r9 l of 100 (200 turns for the pair of windings) and each vertical deflecting winding has a total number of turns of 5600. The vertical deflecting coils are supplied with deflecting current impulses at the rate of 60 per second through an auto-transformer having a step down ratio of 3:2, the output tube being of the 56 type. The horizontal deflecting windings are supplied with deflecting current impulses at the rate of 10,290 per second through a step-down transformer having a turns ratio of 6:1, the output tube being of the 42" type.

In this receiver the ratio of scanning time to return line time in the horizontal direction is approximately 13:1, these ratios being. of course, for saw-tooth scanning. In the vertical direction this ratio is approximately 43:1.

In the television receiver referred to, it was found that the high frequency iron losses in the horizontal deflecting circuit due to the step-down transformer and to the magnetic sleeve eliminated all transient effects from the horizontal deflection. It had been found that if the horizontal deflecting coils were driven directly from the output tube without any iron in the circuit, a high frequency transient was produced on the horizontal saw-tooth and that this transient was not affected in any way by the use of resistance damping across the deflecting coils.

It will be understood that the assembled defleeting device shown in Fig. 5 is slipped over the neck of the cathode ray tube and held in position, by any suitable means, for deflecting the cathode ray. The deflecting device, preferably, is used with a cathode ray tube of the type having electrostatic focusing for the cathode ray.

In the claims the term distributed winding means a winding of the well known distributed type commonly used in motors and generators and illustrated on pages 33 and 34 of Principles of Alternating Current Machinery by R. R. Lawrence, published by McGraw-Hill Book 00., New York, 1921, 2nd edition. In the claims the term concentrically wound distributed winding means a winding of the type which is sometimes referred to as a spiral winding and which is illustrated on page 33 of the above-mentioned Lawrence publication and in Fig. 3 of the aboveidentified Tolson and Maloif patent.

From the foregoing description it will be understood that various other modifications may be made in my invention without departing from the spirit and scope thereof and I desire, therefore, that only such limitations shall be imposed thereon as are necessitated by the prior art and are set forth in the appended claims.

I claim as my invention:

1. An electro=rnagnetic deflecting device for a cathode ray tube, said device comprising a pair or" concentrically wound distributed windings which are diametrically opposed and which are curved to conform to a cylindrical surface, and

, a second pair of concentrically wound distributed windings which are diametrically opposed and which are curved to conform to a cylindrical surface of smaller diameter than said first surface, said second pair of windings being located inside said first pair of windings and substantially at right angles thereto, said two pairs of windings being concentrically positioned with respect to each other, and a sleeve of magnetic material surrounding said first pair of windings.

2. An electro-magnetic deflecting device for a. cathode ray tube, said device comprising a pair of concentrically wound distributed windings which are diametrically opposed and which are curved to conform to a cylindrical surface, and a second pair of concentrically wound distributed windings which are diametrically opposed'and which are curved to conform tda cylindrical surface of smaller diameter than said first surface, said second pair of windings being located inside said first pair of windings and substantially at right angles thereto, said two pairs of windings being concentrically positioned with respect to each other, and an electrostatic shield located between said two pairs of windings.

3. In combination, a cathode ray tube, an electro-magnetic deflecting device for said cathode ray tube, said device comprising a pair of distributed windings which are diametrically opposed and which are curved to conform to a cylindrical surface, and a sleeve of magnetic material surrounding said windings.

4. In ocmbination, a cathode ray tube, an electro-magnetic deflecting device for said cathode ray tube, said device comprising a pair of concentrically wound distributed windings which are diametrically opposed and which are curved to conform to a cylindrical surface, and a sleeve of magnetic material surrounding said windings.

5. An electro-magnetic deflecting device for a cathode ray tube, said device comprising a pair of distributed windings each of which is so curved that it occupies approximately 180 degrees, and each of which consists of a plurality of coils nested one within the other, and a sleeve of magnetic material surrounding said windings.

6. The invention according to claim 5 characterized in that there is a space in the center of each winding large enough to'accommodate a plurality of coils in which coils have been omitted.

7. An electr c-magnetic deflecting device for a cathode ray tube, said device comprising a pair of distributed windings 'each of which is curved to conform to a. cylindrical surface, and a sleeve of magnetic material surrounding said windings, said windings being so distributed that they produce a substantially uniform magnetic field in a plane substantially at right angles to the longitudinal axis of said cylindrical surface and in a region surrounded by said windings.

8. The invention according to claim 7 characterized in that each of said windings consists of a plurality of coils concentrically positioned with respect to each other, each of said coils consisting of a plurality of turns.

9. An electro-magnetic deflecting device for a cathode-ray tube, said device comprising a cylindrical sleeve of magnetic material, a rigid cylindrical tube of insulating material positioned concentrically inside said sleeve, a pair of preformed distributed windings located between said sleeve and said cylindrical tube and positioned in diametrically opposed relation, a second rigid cy-= lindrical tube of insulating material positioned concentrically inside said first cylindrical tube, and a second pair of preformed distributed windings located between said two cylindrical tubes in diametrically opposed relation and substantially at right angles to said first pair of coils.

iii. [an electro-magnetic deflecting device for a cathode-ray tube, said device comprising a cylindrical tube of insulating material, a pair of distributed windings which are positioned on said cylindrical tube in diametrically opposed relation and which are curved to conform to said cylindrical tube, a layer or insulating material surrounding said windings, a second pair of distributed windings which are diametrically opposed 11. The invention according to claim 10 chatand which are curved to conform substantially to acterized in that there is a layer of conducting the outer surface of said first windings, said secmaterial between said two pairs of windings and pair oi. windings being positioned substanwhich functions as an electrostatic shield.

tialiy at right angles to the first pair or windings 5 and being supported on said layer of insulating WILLIAM A. TOLSON. material.