US2900564A - Temperature compensated electromagnetic deflection yoke - Google Patents

Description

Aug. 18, 1959 w. H. BARKOW TEMPERATURE COMPENSATED ELECTROMAGNETIC DEFLECTION YOKE Filed Aug. 51. 1956 INVENTOR. W/LL/AM H. EAR/(0W mm M Arrow/E) United States Patent TEMPERATURE COMPENSATED ELEQTROMAG- NETIC DEFLECTION YOKE William H. Barkow, Pennsauken, N.J., ass'ignor to Radio Corporation of America, a corporation of Delaware Application August 31, 1956, Serial No. 607,307

8 Claims. (Cl. 315-27) The present invention relates to new and improved deflection yokes and, particularly, to electromagnetic deflection yokes including a temperature responsive element for compensating for variations in yoke resistance as a function of operating temperatures.

Deflection yokes of the type normally employed in television receivers conventionally comprise a first pair of coils energized at a high frequency for deflecting one or more electron beams of the receiver kinescope in one direction and a second pair of coils energized at a lower frequency and arranged at right angles to the first pair of coils for deflecting the one or more beams in a second direction perpendicular to the first direction. The first pair of coils (i.e., the horizontal deflection coils) presents a primarily inductive impedance to the high frequency energy applied thereto, while the second pair of coils (i.e., the vertical deflection coils) presents a primarily resistive impedance to the relatively low frequency energy applied thereto.

It has been known that, since television receivers have high operating temperatures, the resistance of the vertical deflection coils and, therefore, the amplitude of the vertical deflection are subject to variations as a function of operating temperature of the coils. This action is particularly noticeable and objectionable during the warmup period of the receiver which may run, for example, between 15 and 30 minutes, after which time the temperature become substantially steady, so that no further change in deflection amplitude occurs.

In view of the undesirability of deflection amplitude variation, there have been various proposals in the past for compensating for such temperature variations, including proposals of temperature-responsive impedance elements, for example, for varying the voltage applied to the deflection coils in such sense as to compensate for increasing deflection coil resistance with increased temperatures. It has been found, however, that the various prior art arrangements for such temperature compensation have been subject to the criticism that the temperature-responsive elements have ordinarily responded to ambient temperatures and have, therefore, been unable to track the actual temperature variations of the deflection coils.

It is, therefore, an object of the present invention to provide a new and improved electromagnetic deflection yoke including means for tracking temperature changes of the yoke and for compensating for variations in operation of the yoke occasioned by such temperature changes.

Another object of the present invention is that of providing an improved deflection yoke of the type in question, which yoke includes in its structure a temperatureresponsive element which is so connected in circuit with the yoke as to compensate for undesirable impedance variations as a function of temperature change.

In general, the present invention comprises a deflection yoke including horizontal and vertical deflection coils, the latter coils being arranged around the former but at right angles thereto, a core of magnetic material (e.g., ferrite or the like) of generally cylindrical form and located around the two pairs of coils in a conventional manner to provide a low reluctance return path for the flux produced by the coils, and a temperatureresponsive element having a temperature coeflicient of the opposite sense from that of the deflection coils, the temperature-responsive element being in heat transfer relation with the coils.

In accordance with one specific form of the invention, the vertical deflection coils are located outside of the horizontal deflection coils and directly in contact with the yoke core, the temperature-responsive impedance element being physically located between the end turns of the vertical coils and the end of the cylindrical yoke core. Since, in the conventional operation of such yokes, the vertical deflection coils and the core are nominally at the same potential, the temperature-responsive impedance element requires no insulation from either the coils or the core and is, therefore, capable of closely tracking temperature changes of the vertical deflection coils.

In accordance with a further aspect of the present invention, the usual terminal board forming part of the yoke and having terminal posts to which the connecting leads for the yoke are connected is located between the upturned end turns of the vertical deflection coils and the end of the yoke core. The terminal board is provided with an opening or pocket in the region between the coils and core, which pocket holds the temperatureresponsive element in physical contact with the vertical coil end turns and the core.

Additional objects and advantages of the present invention will become apparent to those skilled in the art from a study of the following detailed description of the accompanying drawing, in which:

Fig. l is a side-elevational view, partially in section, of a deflection yoke embodying one form of the present invention;

Fig. 2 is a front-elevational view of a terminal board according to the invention;

Fig. 3 is a fragmentary horizontal sectional view taken along the line 3-3 of Fig. 1;

Fig. 4 is a schematic circuit diagram illustrating the vertical deflection coil portion of the yoke of Fig. 1;

Fig. 5 illustrates another form of the invention; and

Fig. 6 is a view corresponding to that of Fig. 3 but illustrative of still another form of the invention.

Referring to the drawing and, particularly, to Fig. 1 thereof, the deflection yoke 10 comprises conventionally a pair of horizontal deflection coils l2 and 14 and a pair of vertical deflection coils 16, only one of which is visible in the side view of the drawing. An insulating liner 18 of suitable insulating material is located between the horizontal and vertical coils to insulate them from each other electrically. The coils may, as shown, have curved or flared configurations as indicated by the dotted lines 20 so that they conform closely to the flaring portion of the kinescope (not shown) with which they are associated. Surrounding the vertical coils, which are located around and in concentn'city with the horizontal deflection coils, is a multisection core 22 of ferrite or other material having high magnetic permeability, the several sections of the core being held in place around the coils by suitable means such as a metal clamp or strap 24 whose ends are secured by a bolt 26.

Further in accordance with conventional television deflection yoke design, the rear end turns 12 and 14' of the horizontal deflection coils are bent radially outwardly from the longitudinal or side conductors as are the rear end turns 16' of the vertical deflection coils. A terminal board 28, to be described in greater detail hereinafter, is located between the end turns 16' of the vertical deflection coils and the rear end of the core 22. That is, the terminal board 28 will be understood as being a generally disk-like structure having a central opening to accommodate the neck of the kinescope. The board 28 is, therefore, held in place by the vertical deflection coils and the core against axial movement. Mounted about the periphery of the terminal board 28 are terminal posts 30 to which the start and finish turns of the several coils comprising the yoke may be electrically connected for connection to the respective energy sources and other circuit elements such as damping resistors and/ or capacitors or the like.

As thus far described, the apparatus of Fig. 1 does not constitute a part of the present invention but is, rather, of a generally conventional design known to those skilled in the art. As may be seen in Fig. 1, however, the terminal board 28 is provided with an opening or pocket 32, shown more clearly in Fig. 2. The terminal board 28 may actually be in the form of 2 semi-circular members 28a and 28b which are provided with mating tongues and grooves 33 and 34, respectively, for facilitating as sembly of the terminal board about the coils. Each of the sections 28a and 28b of the board is further provided with a central recess such that, when the two sections are put together, a central opening 36 is defined to accommodate the neck of the kinescope. The recess may, further, be formed with the configuration shown, that is, with radially inwardly extending projections 38 which fit in the window openings of the vertical deflection coils, so that the terminal board is keyed to the vertical coils and is thereby restrained against rotational movement with respect to the coils.

The vertical deflection coils, which normally operate with current of the order of 60 c.p.s., may be considered as having a primarily resistive impedance (as opposed to the horizontal deflection coils which present a primarily inductive impedance to the approximately 15.75 kcs. energy applied to them). Further, the wire of which the vertical deflection coils are formed has a positive temperature coeflicient (i.e., the resistance of the wire is generally proportional to its temperature). Thus, the present invention provides a temperature-responsive resistive element 40 which is received in the pocket 32 in the terminal board 28. The element 40 has a negative temperature coefficient of such value as to compensate for the positive temperature coeflicient of the vertical deflection coils in a manner to be described in greater detail hereinafter.

As may be seen from the sectional view of Fig. 3, the temperature-responsive resistive element 40 is held in close physical contact with both the upturned end turns 16 of one of the vertical deflection coils 16 and the rear end 22' of the core 22. In this manner, the element 40 (which will hereinafter be referred to as a thermistor) is subject to the .'operating temperature of the vertical deflection coils 16 and the core 22, so that its temperature follows that of the coils and core.

One specific electrical form which the present invention may take is illustrated in Fig. 4 wherein reference numerals identical to those employed in the preceding figures indicate corresponding parts. The vertical deflection circuit of Fig. 4 conventionally comprises a deflection output amplifier 44 having a cathode 46, control electrode 48 and anode 50. Sawtooth deflection voltage waves 52 of vertical deflection rate are applied to the control electrode 48 of the amplifier 44 whose cathode 46 is connected to ground through a linearity control resistor 54 and whose anode 50 is connected through the primary winding 56 of a deflection output transformer to a source of positive operating voltage (+B) at a terminal 58. The deflection output transformer further includes a secondary winding 60 which is inductively coupled to the winding 56 and which is connected in series with the deflection coils 16. The thermistor 40 is also connected in series between the two coils 16, so that its re istap e is added to the resistance of the coils 16. The thermistor 40 may be formed of any suitable material having the desired negative temperature coeflicient and the value of the thermistor may 'be readily chosen to compensate for the resistance change of the coils 16. In one practical form of the invention, the deflection coils had a total nominal resistance of 13 ohms, while the associated thermistor had a nominal resistance at room temperature of 2.5 ohms, decreasing to 0.5 ohm at C. The thermistor in question was a product of the Keystone Carbon Company.

An additional advantage of locating the thermistor 40 electrically between the two coils 16 is that the thermistor itself, via its lead 62 (shown in Fig. 2), serves as an interconnecting jumper for the two coils 16, thereby obviating the need for a separate connecting jumper for the coils.

Insofar as the electrical operation of the thermistor is concerned, it will be understood that, since the thermistor is in direct physical contact with the vertical deflection coils and yoke core, its temperature will directly track the temperature of the vertical coils and its resistance will vary in such manner that the total resistance of the coils 16 and thermistor remains substantially constant despite increasing temperature of the coils during warm-up.

It will be understood that the thermistor 40 may be otherwise connected in circuit with the coils. Thus, for example, Fig. 5 illustrates an arrangement in which the thermistor 40 is connected in series with the coils 16 but at a point electrically located outside of the coils. Again, as in the case of Fig. 4, the resistance of the thermistor is effective in maintaining the total resistance substantially constant, such that vertical deflection amplitude remains unchanged despite temperature variations.

The physical form of the present invention described in connection with Figs. 1-3 is particularly advantageous in that the terminal board is located between the vertical coil end turns and the core and, therefore, serves to hold the thermistor in its proper physical location. Fig. 6 illustrates an arrangement which may be employed in the case of a yoke whose terminal board is not so located. In the structure of Fig. 6, the rear end of one of the core sections 22 is itself provided with a recess or pocket 22' for holding the thermistor 40 in direct physical contact and heat transfer relationship to the end turns 16' of the vertical deflection coil. The thermistor 40 therefore tracks the coils 16' and core 22 in temperature.

In both structures of yoke described, it will be understood that, since the vertical deflection coils are substantially at the same potential as the yoke core, no electrical insulation is required between the coils and core. Thus, the temperature insulation attendant upon the use of electrical insulating material is also precluded.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An electromagnetic deflection yoke which comprises: an electromagnetic coil formed of a conductor having a certain temperature coefiicient of resistancee such that its resistance varies as a function of its temperature; and a temperature-responsive impedance element in circuit with said coil and disposed in heat transfer relationship with said coil such that the net resistance of said coil and element remains substantially constant despite temperature variations of said coil.

2. An electromagnetic deflection yoke which comprises: an electromagnetic coil formed of a conductor having a certain temperature coeflicient of resistance such that its resistance varies as a function of its temperature; a temperature-responsive impedance element in circuit with said coil, said element having a temperature coeflicient of the opposite sense from said certain coeflicient; and means pp ng said element in heat transfer relationship with id @911.

3.' An electromagnetic deflection yoke which comprises: a pair of horizontal deflection coils arranged to conform to the neck of a cathode ray tube; a pair of vertical deflection coils disposed generally in concentricity with said horizontal coils, said coils having a certain temperature coefiicient of resistance; and a temperature-responsive impedance element in circuit with said vertical deflection coils, said element being disposed in heat transfer relationship with said vertical deflection coils and having a temperature coeflicient of opposite sense from said certain coeflicient.

4. An electromagnetic deflection yoke which comprises: an electromagnetic coil formed of a conductor having a certain temperature coefficient of resistance such that its resistance varies as a function of its temperature; a core of magnetic material disposed adjacent to said coil in heat transfer relation with said coil; and a temperatureresponsive impedance element in circuit with said coil and disposed between said coil and core in heat transfer relation with said coil and core, said temperature-responsive impedance element having a temperature coefficient of such sense that the net resistance of said coil and element remains substantially constant despite temperature variations of said coil.

5. The invention as defined by claim 4 including a disklike terminal board of insulating material having a terminal post to which said conductor is connected and being provided with a pocket-like opening, said board being located between said coil and core, said temperature-responsive element being disposed within said opening.

6. An electromagnetic deflection yoke as defined by claim 4 wherein said element has a negative temperature coefiicient of resistance and is connected in series with said coil.

7. An electromagnetic deflection yoke which comprises: a pair of horizontal deflection coils arranged to conform to the neck of a cathode ray tube; a pair of vertical deflection coils disposed around said horizontal deflection coils generally in concentricity therewith and having side conductors and upturned end turns extending radially outwardly from said side conductors, the conductors of said vertical deflection coil being subject to resistance change as a direct function of temperature variations; a core of magnetic material disposed around the side conductors of said vertical coils and extending to within a relatively short distance of said upturned end turns; a terminal board of electrical insulating material of disk-like shape and having a central opening located around the side conductors of said vertical deflection coils, said board being disposed snugly between said upturned end turns and the adjacent end of said core and having a pocket formed therein; a negative temperature coeflicient resistance element disposed in said pocket in heat transfer relation to said upturned end turns such that the temperature of said element tracks the temperature of said vertical coils; and means connecting said element in series with said vertical deflection coils.

8. An electromagnetic deflection yoke which comprises: a pair of horizontal deflection coils arranged to conform to the neck of a cathode ray tube; a pair of vertical deflection coils disposed around said horizontal deflection coils generally in concentricity therewith and having side conductors and upturned end turns extending radially outwardly from said side conductors, the conductors of said vertical deflection coil being subject to resistance change as a direct function of temperature variations; a core of magnetic material disposed around the side conductors of said vertical coils and extending to within a relatively short distance of said upturned end turns; a terminal board of electrical insulating material disposed snugly between said upturned end turns and the adjacent end of said core and having a pocket formed therein; a negative temperature coefficient resistance element disposed in said pocket in heat transfer relation to said upturned end turns such that the temperature of said element tracks the temperature of said vertical coils; and means connecting said element in series with said vertical deflection coils.

References Cited in the file of this patent UNITED STATES PATENTS

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