US2451026A - Television system - Google Patents

Description

0a. 12, 1948. A, FR E D 2,451,026

TELEVISION SYSTEM Filed 001',- 2, 1945 3 Sheets-Sheet 1 3 a w 9 No R MN 3. 15 g M E58 Q J '83 5 N D h k N; 3 2 tQl O k h g V e 0 Pan 5e ourpur fuss INVENTOR +1 Q AL 65?? W fk/E/Vp ATTORNEY Oct. 12, 1948. A. w. FRIEND 2,451,026

TELEVISION SYSTEM Filed Oct. 2, 1945 3 Sheets-Sheet 2 INVENTOR AL 55?;- /4. Fem/v0.

ATTO RN EY Oct. 12, 1948. A. w. FRIEND 2,451,025

TELEVISION SYSTEM I I Filed Oct. 2, 1945 3 Sheets-Sheet 5 d ql a g I A INVENTOR ALBERT Wfk/E/VD ATTO RN EY Patented Get. 12, 1948 TELEVISION SYSTEM Albert W. Friend, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 2, 1945, Serial No. 619,869

I 12 Claims. 1

The present invention relates to cathode ray beam deflection circuits, especially as employed in television receiving systems of the type having a cathode ray image-reproducing or kinescope tube, and more particularly relates to means for regulating the size of the image raster scanned by the cathode ray beam of such a tube.

Television receiving systems utilizing the prin- -ciple of electromagnetic deflection of a cathode ray scanning beam normally include a power output tube which is adapted to deliver cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time, through a coupling transformer to a pair of cathode ray beam deflection coils encircling the neck of an image-reproducing cathode ray tube. Since the instantaneous angle of deflection of the cathode rayscanning beam is a function of the instantaneous strength of the magnetic deflecting field in the vicinity of the deflection coils, and since this deflecting field is, in turn, dependent upon the amplitude of the current flowing through the deflection coils at such time, it follows that a change in the peak amplitude of the current flowing through the deflection coils will produce a change in the size of the image raster scanned by the cathode ray beam.

Control over the peak amplitude of the deflecting current for the purpose of image size regulation is accomplished in some instances by means of a variable inductance shunted across several turns of the secondary windin of the coupling transformer. While such an expedient produces satisfactory results, it requires a tap on the transformer secondary. This is not only inconvenient from the standpoint of assembly, but, in addition, increases the cost of the equipment. Furthermore, the extra variable inductor adds to the over-all size and weight of the television apparatus.

According to a feature of the present invention, the necessity for employing a separate variable inductor for image size regulation is eliminated, and the design of the deflection transformer is modified so that the transformer itself may be utilized as a size control. In one preferred embodiment, this is achieved by forming in the transformer core an aperture which is adapted selectively to receive a slug of magnetizable material. This slug, by varying the permeability of the core as it enters the aperture, changes the over all impedance of the transformer. As a result, the peak amplitude of the cyclically varying current flowing through 2 the cathode ray beam deflection coils is altered, thus effecting a change in the size of the image raster scanned by the cathode ray beam.

One object of the present invention, therefore, is to provide an improved form of image size control for television receiving systems.

Another object of the invention is to provide means whereby the usual output or coupling transformer in television deflection circuits may be modified to act as an image size control device.

A still further object of the invention is to provide an image size control apparatus for television receivers which eliminates the necessity for employing a separate variable inductive member in conjunction with the coupling transformer.

Other objects and advantages will be apparent from the following description of preferred forms of the invention and from the drawings, in which:

Fig. 1 is a circuit diagram of a preferred embodiment of the present invention, showing the output transformer in section and the remaining circuit elements schematically;

Fig. 2 is a sectional View of a modification of the output transformer of Fig. 1;

Fig. 3 is a plan view, partly in section, of the output transformer of Fig. 2;

Fig. 4 is a sectional view of Fig. 3;

Fig. 5 is a plan view of a modification of the output transformer of Figs. 2, 3, and 4; and

Figs. 6 and '7 are sectional views of Fig. 5.

Referring first to Fig. 1, there is shown a cathode ray beam deflection circuit including a power output tube 50 having at least an anode, a cathode, and a control electrode. Power tube I0 is adapted to deliver, when voltage variations having a wave form such as indicated by reference character 12 are applied between the cathode and control electrode thereof, cyclically varying current to a pair of cathode ray beam deflection coils is through an output or coupling transformer 18. A portion of each cycle of the current output of power tube it? varies in a substantially linear manner with respect to time as indicated by the sawtooth current waveform it.

One end of the primary winding 26 of transformer I8 is connected b a lead 22 to the anode of power output tube H]. The other end of primary winding 28 is connected by a lead i i to the positive terminal of a battery or other source of potential 26, the negative terminal of battery 25 being joined to the cathode of power tube i9 as illustrated. .The primary winding 28 of transformer l8 thus forms part of the output, or anode cathode-circuit of the power tube 10.

A damper tube 28, in series with a parallel resistor-condenser combination 30, is connected across the secondary winding 32 of transformer 18. Damper tube 28, together with the resistorcondenser combination 30, prevents oscillations in the circuit by acting as a switch which closes at the end of the return, or snap-back, portion of each cycle of the sawtooth current wave Id. In other words, tube 28 becomes conductive at the beginning of each deflection cycle, The switching operation of tube 28 causes a current to flow therethrough which is of such wave form as to assist the power tube H) in producing the desired linear current flow through the deflection coils IS. The operation of such a damper tube is set forth in U. S. Patent No. 2,309,672 granted on February 2, 1943, to Otto H. Schade, and hence will not herein be described in detail.

The cathode ray beam deflection coils l6 preferably form part of a yoke assembly encircling the neck of an image-reproducing cathode ray tube or kinescope (not shown), and are connected across both the secondary winding 32 of transformer l8 and the series combination of damper tube 23 and R.-C. combination by a pair of leads 3 and 38.

Transformer 18 includes a core 38 composed of some suitable homogeneous magnetizable material, such as powdered iron, the core preferably being formed of two E-sections 4i] and 42, assembled as shown. In one of the legs 44 of the E-section 40 is formed an aperture 46 of substantially cylindrical outline. This aperture 46 is adapted to receive a substantially cylindrical slug 48 preferably, but not necessarily, homogeneous magnetizable material, such as powdered or comminuted iron, which forms the core 38.

The permeability of the core 38 is varied to vary the impedance of transformer 18 by changing the position of slug- 48 relative to the core leg 44. To permit a controlled movement of slug 48 relative to the core leg 44, a threaded screw 50 is embedded in, or otherwise securely affixed to, the upper end of the slug. This screw 50, which has a knurled head adapted for manual actuation, passes through a bushing 52 in a support 54. A look nut 56 maintains screw 50 and hence slug 48 in any selected position.

Upon selective manual actuation of screw 50, the slug 43 will be moved so as to have a greater or lesser proportion of its volume received within the aperture 46. Since aperture 46 constitutes, in effect, an air gap in the core section 40, such movement of slug 48 will vary the dimensions of this air gap, and, consequently, the magnetic flux density in the core 38. The result of such a change in flux density in the core 38 is to alter the over-all impedance of the transformer l8 and, hence, the size of the image raster scanned by the cathode ray beam.

Since screw 50 is securely afiixed to the upper end of slug 48, turning of the screw will also cause a rotary movement of the slug. However, since the slug is cylindrical in shape, and is composed of homogeneous material, such a rotary movement thereof will have no noticeable efiect on the electrical characteristics of the transformer 18.

Figs. 2, 3, and 4 illustrate a modification of the invention in which the two E-sections 40a and 42a, comprising the core 38 of transformer I8, are composed of a plurality of laminations rather than of homogeneous material as in Fig. 1. In Figs.

2, 3, and 4, the aperture 46a in the leg 44a of core section 40a is shown as substantially rectangular composed of the same 4 in outline, and the slug 48a (corresponding to the slug 48 of Fig. 1) is shown as substantially rectangular in shape and of such dimensions as to fit compactly in the aperture 46a.

The slug 48a is composed of a plurality of laminations in a manner similar to the core sections 49a and 42a, withthe laminations of the slug being respectively substantially coplanar with the laminations'of the core sections.

Movement of slug 48a. is controlled by a manually-actuatable screw 5!! as in Fig. 1. However, since the slug 48a is not capable of rotary movement in the aperture 460. in the manner that the slug 48 of Fig. 1 turns in the aperture 46, means are provided for permitting a rotation of screw 56 without requiring a rotary movement of slug 48a. These means include a rotary bearing 58 posi tioned in a cut-out portion in the upper end of slug 48a. The inner element of the rotary bearing 58 is secured to the screw 50, while the outer element of the bearing frictionally engages the wall of the cut-out portion of slug 48a in the manner best shown in Figs. 2 and 4.

Bearing 58 is held in place in the cut-out portion of slug 48a by means of a retaining strip 6!! overlyin the bearin in the manner best shown in Figs. 3 and 4. An opening in retaining strip 6!] permits passage therethrough of screw 50. A pair of further screws 82 rigidly secure retaining strip 66 to the slug 43a. By means of this construction, selective manual actuation of screw will cause slug 48a to be raised or lowered within the aperture 46a to vary the flux density in the core 33, but at the same time no rotary movement of slug 58a is necessary due to the presence of the bearing 58. Y

In Figs. 5, 6, and '7 there is shown a modification of the transformer l8 of Figs. 2, 3, and 4. While the laminated style of core construction for the E-sections 40a. and 42a, is retained, a portion of one outer leg of each such E-section is cut away in the manner best shown in Fig. 6. In the aperture 64 thus formed is positioned a rotatable core segment 68 composed of a plurality of substantially elliptical laminations, and so arranged that the laminations of the core segment 66 are respectively substantially co-planar with the laminations of the E-sections 40a and 42a (see Fig. 7)

A shaft 58 passes axially through the core segment (56. On one end of shaft 58 is a manuallyactuatable knob 70. Shaft 68 is supported by two bearings 1 2 and 14, respectively positioned in openings in two parallel supporting plates 16 and E8 each of which are rigidly secured to the E-sections 45a and 42a by means of bolts 80 and 82, respectively. The portion of shaft '68 adjacent knob '36 is threaded, and a lock nut 84 on the shaft permits the latter to be locked in any desired position.

As will be best appreciated from viewing Fig. 6, the aperture 64 constitutes an air gap in the core 38. Since each lamination of the rotatable core segment 66 is substantially elliptical in shape, rotation of the segment acts to vary the width of this air gap and, hence, the flux density in the core 3%. This results in a change in the over-all impedance of the transformer IS in the same manner as does an axial movement of the slug 48 or 48a in the modifications of Fig. 1 or Figs. 2 through 4, respectively. The end result in each of the modifications illustrated and described is to effect a change in the size of the image raster scanned by the cathode ray beam.

It will be understood that, if desired, any fraction of the total number of laminations in the modificationof the inventionillustrated in Figs. through '7 may beseparated-to'admit a rotatable core segment, rather than-havingthe entire core separated asin the example shown. Furthermore, the precise outlined the aperture-64,- or the shape of the rotatable coresegment 66 may readily be altered, the only; requirement being that a selective movement of the core segment act to change the width of the air gap between the E-sections and, therefore, the permeability of the core, Also, it will be readily apparent to those skilled inthe art-that numerous methods of rotating the core segment 66 other than by manual actuation of knob 70 may be utilized, if desired.

Having thus described. my invention, I claim:

1. Apparatus for regulating the size of the image raster scanned by a cathode ray beam in a television system of the type in which a power output tube is adapted to deliver cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time, through a'coupling-transformer to at least one cathode ray beam deflection coil, said coupling transformer being designed with a core having an aperture therein, said apparatus including a core segment normally lying at least partly within said aperture, and means for varying the position of said segment :relative to'saidcore and, hence, the .permeability of saidlcore, whereby the peak amplitude of the cyclically varying current flowing through said cathode ray beam deflection coil is altered to effect a change in the size of the image raster scanned by the cathode ray beam.

2. Apparatus according to claim 1, in which the aperture in said core is of substantially cylindrical outline, with said core segment being approximately cylindrical in shape and substantially coaxial with the wall of said aperture, and in which said means for varying the position of said segment relative to said core includes means for controllably moving said segment along the common axis of said segment and said aperture wall.

3. Apparatus according to claim 1, in which said core is composed of a substantially homogeneous material such as powdered iron and has an aperture therein of substantially cylindrical outline, said core segment also being composed of a substantially homogeneous material such as powdered iron, being approximately cylindrical in shape, and being substantially coaxial with the wall of said aperture, and in which said means for varying the position of said segment relative to said core includes means for controllably moving said segment along the common axis of said segment and said aperture wall.

4. Apparatus according. to claim 1, in which the aperture in said core is of substantially rectangular outline, with said core segment being approximately rectangular in shape, and in which said means for varying the position of said segment relative to said core comprises means for varying the proportion of said segment which lies within said aperture, said last-mentioned means including a manually-actuatable adjusting screw rotatably secured to said segment.

5. Apparatus according to claim 1, in which said core is composed of a plurality of laminations and has an aperture therein of substantially rectangular outline, in which said core segment is approximately rectangular in shape and is also composed of a plurality of laminations respectively substantially co-planar with the lamina- 6 tions ofisaid core, and .in :which said .meansior varying the position ,-of said segment relative :to said core comprises 'means: for: varying the proportion of said segment which lieswithinesaid aperture-said last-mentioned means including a manually-actuatable adjustingscrew rotatably secured .to said segment.

6: Apparatus accordinggto claim 1, in which said core is com-posed of a plurality-of laminations; with said-core segment being composed of plurality of laminations of approximately-ellipth; cal configuration lying; respectively substantially co-planar with the laminations-of said coreand substantial-1y wholly within-said aperture, and ingwhich- :said means. for-varying, the position of saidsegment relative z-tozsaid core comprises means forvrotating. said core segmentabout an axis approximately perpendicular. to the plane of said laminations;-

.7. Apparatus for regulatingthe sizeof'the image; raster scannedbya. cathode 'rayibeam in a television system .of zthe type in which a power output tube-is adapted to deliver cyclical-1y vary ing current, a, portion of eachcycleof which varies in aisubstantially linear mannerywith re.- spect totime, through a coupling transformerrto a pair :of cathode ray beam deflectioncoils, said coupling transformer being. designed; with 'a .core composed of magnetizable material andhaving an aperture therein, saidapparatus including a 'slug also composed: of magnetizablematerial; and adapted to be Wholly or partly received within said aperture, and means for varying the proportion of said slug which is received within said aperture and hence the permeability of said core, whereby the peak amplitude of the cyclically varying current flowing through said cathode ray beam deflection coils is altered to effect a change in the size of the image raster scanned bythe cathode ray beam.

- 8. The combination of claim '7, in which said means for varying the proportion of said slug which is received within said aperture includes a threaded screw one end of which is secured to said slug, a support having a threaded opening to receive said screw, and means for locking said screw in the threaded opening of said support to thereby maintain a selected proportion of said slug within said aperture.

9. Apparatus for regulating the size of the image raster scanned by a cathode ray beam in a television system of the type in which a power output tube is adapted to deliver cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time, through a coupling transformer to at least one cathode ray beam deflection coil, said coupling transformer being designed with a core having an aperture therein of substantially cylindrical outline, said apparatus including a cylindrical core segment having an outer diameter approximately equal to the inner diameter of the cylindrical aperture in said core, said core segment being adapted to be wholly or partly received in said aperture, and means for varying the axial position of said core segment in said aperture, and, hence, the permeability of said core, whereby the peak amplitude of the cyclically varying current flowing through said cathode ray beam deflection coil is altered to eiTect a change in the size of the image raster scanned by the cathode ray beam.

10. Apparatus for regulating the size of the image raster scanned by a cathode ray beam in a television system of the type in which a power output tube is adapted to deliver cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time, through a coupling transformer to at least one cathode ray beam deflection coil, said coupling transformer being designed with a laminated core having an aperture therein of substantially rectangular outline, said apparatus including a laminated core segment of approximately rectangular configuration and designed to fit securely but movably in said aperture, the laminations of said segment being respectively substantially coplanar with the laminations of said core, and means for moving said segment within said aperture, and, hence, for varying the permeability of said core, whereby the peak amplitude of the cyclically varying current flowing through said cathode ray beam deflection coil is altered to effect a change in the size of the image raster scanned by the cathode ray beam.

11. Apparatus for regulating the size of the image raster scanned by a cathode ray beam in a television system of the type in which a power output tube is adapted to deliver cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time, through a coupling transformer to at least one cathode ray beam deflection coil, said transformer being designed with a core having an aperture therein which is substantially rectangular in cross-sectional outline, a core segment which is substantially elliptical in cross section lying substantially wholly within said aperture, and means for selectively varying the position of said core segment within said aperture, and, hence, the permeability of said core, whereby the peak amplitude of the cyclically varying current flowing through said cathode ray beam deflection coil is altered to efiect a change in the size of the image raster scanned by the cathode ray beam.

12. Apparatus in accordance with claim 11, in which said means for selectively varying the position of said core segment within said aperture includes means for rotating said core segment about an axis approximately perpendicular to the plane of said elliptical cross-section.

ALBERT W. FRIEND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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