Television degaussing system with saddle-type coils adjacent CRT cone

Claim 2

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along and from the large to the small end of said conical tube portion, side conductor groups being connected by End turns respectively at the large and small ends of said conical tube portion; and means connecting said coils to said source of alternating current in a manner to produce an alternating magnetic field within said picture tube.

Claim 3

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along and from the large to the small end of said conical tube portion, side conductor groups being connected by End turns respectively at the large and small ends of said conical tube portion; and means connecting said coils to said source of alternating current in a manner to produce an alternating magnetic field within said picture tube.

Claim 4

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along and from the large to the small end of said conical tube portion, side conductor groups being connected by End turns respectively at the large and small ends of said conical tube portion; and means connecting said coils to said source of alternating current in a manner to produce an alternating magnetic field within said picture tube.

Claim 5

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along said conical tube portion with each of said side conductor groups of one coil adjacent and substantially parallel to a side conductor group of the other coil, each of said coils also having a forward group of end turns connecting the forward ends of said side conductor groups and partially encircling one side of said tube adjacent the large end of said conical portion and a rear group of end turns connecting the rear ends of said side conductor groups and partially encircling one side of said tube adjacent the small end of said conical tube portion; and means connecting said coils to one another and to said source of alternating current in a manner to produce an alternating magnetic field in the vicinity of the viewing screen structure of said tube.

Claim 6

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along said conical tube portion with each of said side conductor groups of one coil adjacent and substantially parallel to a side conductor group of the other coil, each of said coils also having a forward group of end turns connecting the forward ends of said side conductor groups and partially encircling one side of said tube adjacent the large end of said conical portion and a rear group of end turns connecting the rear ends of said side conductor groups and partially encircling one side of said tube adjacent the small end of said conical tube portion; and means connecting said coils to one another and to said source of alternating current in a manner to produce an alternating magnetic field in the vicinity of the viewing screen structure of said tube.

Claim 7

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along said conical tube portion with each of said side conductor groups of one coil adjacent and substantially parallel to a side conductor group of the other coil, each of said coils also having a forward group of end turns connecting the forward ends of said side conductor groups and partially encircling one side of said tube adjacent the large end of said conical portion and a rear group of end turns connecting the rear ends of said side conductor groups and partially encircling one side of said tube adjacent the small end of said conical tube portion; means connecting said coils to one another and to said source of alternating current in a manner to produce an alternating magnetic field within said conical tube portion and in the vicinity of the viewing screen structure of said tube; and a generally planar annular member of magnetic material mounted between said forward and rear groups of end turns perpendicular to the axis of said tube and surrounding said conical tube portion to serve as a relatively low reluctance return path for magnetic flux produced by said coils.

Claim 8

Degaussing apparatus for a television picture tube adapted to be energized periodically by alternating current of a magnitude which initially is appreciable and which diminishes effectively to zero comprising in combination: a pair of saddle type coils mounted respectively on opposite sides of the conical portion of said tube, each of said coils having two side conductor groups extending generally longitudinally of said tube along said conical tube portion with each of said side conductor groups of one coil adjacent and substantially parallel to a side conductor group of the other coil, each of said coils also having a forward group of end turns connecting the forward ends of said side conductor groups and partially encircling one side of said tube adjacent the large end of said conical portion and a rear group of end turns connecting the rear ends of said side conductor groups and partially encircling one side of said tube adjacent the small end of said conical tube portion; means connecting said coils to one another and to said source of alternating current in a manner to produce an alternating magnetic field within said conical tube portion and in the vicinity of the viewing screen structure of said tube; and a generally planar annular member of magnetic material mounted between said forward and rear groups of end turns perpendicular to the axis of said tube and surrounding said conical tube portion to serve as a relatively low reluctance return path for magnetic flux produced by said coils.

Claim 9

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a coil structure mounted in such relation to said picture tube as to produce when energized a magnetic field within said tube extending transversely to the longitudinal axis of said tube; a power supply for said receiver including rectifier means for converting alternating current into direct current; means including a transformer for impressing alternating current upon said power supply; a first circuit including said transformer, said power supply and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coil structure across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch wHich when closed impresses alternating current upon said transformer, thereby impressing alternating current of appreciable initial magnitude upon said coil structure due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor.

Claim 10

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a coil structure mounted in such relation to said picture tube as to produce when energized a magnetic field within said tube extending transversely to the longitudinal axis of said tube; a power supply for said receiver including rectifier means for converting alternating current into direct current; means including a transformer for impressing alternating current upon said power supply; a first circuit including said transformer, said power supply and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coil structure across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch wHich when closed impresses alternating current upon said transformer, thereby impressing alternating current of appreciable initial magnitude upon said coil structure due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor.

Claim 11

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a power supply for said receiver including rectifier means for converting alternating current into direct current; means including a transformer for impressing alternating current upon said power supply; a first circuit including said transformer, said power supply and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said transformer, thereby impressing alternating current of appreciable initial magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor.

Claim 12

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a power supply for said receiver including rectifier means for converting alternating current into direct current; means including a transformer for impressing alternating current upon said power supply; a first circuit including said transformer, said power supply and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said transformer, thereby impressing alternating current of appreciable initial magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor.

Claim 13

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a generally planar annular member of magnetic material mounted intermediate the ends of said coils perpendicular to the axis of said picture tube and surrounding said conical tube section to serve as a return path for magnetic flux produced by said coils; a power supply for said receiver including rectifier means for converting alternating current into direct current; means including a transformer for impressing alternating current upon said power supply; a first circuit including said transformer, said power supply and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said transformer, thereby impressing alternating current of appreciable initial magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor.

Claim 14

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a generally planar annular member of magnetic material mounted intermediate the ends of said coils perpendicular to the axis of said picture tube and surrounding said conical tube section to serve as a return path for magnetic flux produced by said coils; a power supply for said receiver including rectifier means for converting alternating current into direct current; means including a transformer for impressing alternating current upon said power supply; a first circuit including said transformer, said power supply and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said transformer, thereby impressing alternating current of appreciable initial magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor.

Claim 15

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a generally planar annular member of magnetic material mounted intermediate the ends of said coils perpendicular to the axis of said picture tube and surrounding said conical tube section to serve as a return path for magnetic flux produced by said coils; a powEr supply for said receiver including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; means including a transformer having a primary winding and a secondary winding for impressing alternating current upon said power supply; a first circuit connecting said transformer secondary winding with said power supply and including a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said transformer primary winding, thereby impressing an initial surge of alternating current of appreciable magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor, said initial surge of alternating current being caused at least in part by the relatively high charging current for said capacitive filtering means.

Claim 16

In a television receiver embodying a picture tube, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a generally planar annular member of magnetic material mounted intermediate the ends of said coils perpendicular to the axis of said picture tube and surrounding said conical tube section to serve as a return path for magnetic flux produced by said coils; a powEr supply for said receiver including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; means including a transformer having a primary winding and a secondary winding for impressing alternating current upon said power supply; a first circuit connecting said transformer secondary winding with said power supply and including a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said transformer primary winding, thereby impressing an initial surge of alternating current of appreciable magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor, said initial surge of alternating current being caused at least in part by the relatively high charging current for said capacitive filtering means.

Claim 17

In a television receiver embodying a picture tube and a plurality of signal processing electron tubes, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a generally planar annular member of magnetic material mounted intermediate the ends of said coils perpendicular to the axis of said picture tube and surrounding said conical tube section to serve as a return path for magnetic flux produced by said coils; a power supply for said receiver including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; means including a transformer having a primary winding, a secondary winding for impressing alternating current upon said power supply and at least one tertiary winding for energizing the heater elements of said electron tubes; a first circuit including said transformer primary winding and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said first circuit, thereby impressing an initial surge of alternating current of appreciable magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor, said initial surge of alternating current being caused in part by the relatively high current drawn from said tertiary transformer winding by the cold heaters of said electron tubes and in part by the relatively high charging current for said capacitive filtering means.

Claim 18

In a television receiver embodying a picture tube and a plurality of signal processing electron tubes, degaussing apparatus for said picture tube comprising in combination: a pair of saddle type coils mounted on opposite sides of and extending along the major portion of the conical section of said picture tube; a generally planar annular member of magnetic material mounted intermediate the ends of said coils perpendicular to the axis of said picture tube and surrounding said conical tube section to serve as a return path for magnetic flux produced by said coils; a power supply for said receiver including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; means including a transformer having a primary winding, a secondary winding for impressing alternating current upon said power supply and at least one tertiary winding for energizing the heater elements of said electron tubes; a first circuit including said transformer primary winding and a thermistor having a relatively high resistance and large voltage drop thereacross when cool and a relatively low resistance and small voltage drop thereacross when hot; a second circuit connecting said coils across said thermistor and including a varistor having a relatively low resistance when subjected to high voltage and a relatively high resistance when subjected to low voltage; and means including a switch which when closed impresses alternating current upon said first circuit, thereby impressing an initial surge of alternating current of appreciable magnitude upon said coils due to the relatively large voltage drop across said thermistor with resultant low resistance of said varistor and which diminishes effectively to zero due to the decrease in voltage drop across said thermistor and the consequent high resistance of said varistor, said initial surge of alternating current being caused in part by the relatively high current drawn from said tertiary transformer winding by the cold heaters of said electron tubes and in part by the relatively high charging current for said capacitive filtering means.

Claim 19

Degaussing apparatus for a television picture tube adapted to be energized by alternating current of a magnitude which initially is appreciable and which diminishes effectively to a small value, comprising in combination: a coil structure mounted in such relation to said picture tube as to produce when energized a magnetic field within said tube; a power supply for said receiver Including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; a source of alternating current; circuit means connected between said source of alternating current and said power supply to impress alternating current upon said power supply; said circuit means including current diverting means coupled to said coil structure, said current diverting means passing from an initial state obtaining at the initiation of said impressing of alternating current upon said power supply to an altered state subsequent to said initiation, said current diverting means (1) in said initial state, permitting alternating current to flow through said coil structure initially as a surge of appreciable magnitude which diminishes as a function of the charging of said capacitive means, and (2) in said altered state, diverting said alternating current from said coil structure, whereby to subsequently cause alternating current of no more than said small value to flow through said coil structure.

Claim 20

Degaussing apparatus for a television picture tube adapted to be energized by alternating current of a magnitude which initially is appreciable and which diminishes effectively to a small value, comprising in combination: a coil structure mounted in such relation to said picture tube as to produce when energized a magnetic field within said tube; a power supply for said receiver Including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; a source of alternating current; circuit means connected between said source of alternating current and said power supply to impress alternating current upon said power supply; said circuit means including current diverting means coupled to said coil structure, said current diverting means passing from an initial state obtaining at the initiation of said impressing of alternating current upon said power supply to an altered state subsequent to said initiation, said current diverting means (1) in said initial state, permitting alternating current to flow through said coil structure initially as a surge of appreciable magnitude which diminishes as a function of the charging of said capacitive means, and (2) in said altered state, diverting said alternating current from said coil structure, whereby to subsequently cause alternating current of no more than said small value to flow through said coil structure.

Claim 21

Degaussing apparatus for a television picture tube adapted to be energized by alternating current of a magnitude which initially is appreciable and which diminishes effectively to a small value, comprising in combination: a power supply for said receiver including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; a source of alternating current; circuit means connected between said source of alternating current and said power supply and operative to impress said alternating current upon said power supply, thereby producing an initial surge of alternating current of appreciable magnitude through said circuit means; said initial surge of alternating current being caused at least in part by the relatively high charging current for said capacitive filtering means; said circuit means including a coil structure connected in a first current path between said source of alternating current and said power supply so as to be traversed by said initial surge of alternating current and mounted in such relation to said picture tube as to produce a magnetic field within said tube when subjected to said surge of alternating current; said circuit means also including disabling means operative subsequent to said initial surge of alternating current for reducing the alternating current through said coil structure to said small value, said disabling means providing a second current path between said source and said power supply and diverting said alternating current from said first current path to said second current path subsequent to said initial surge.

Claim 22

Degaussing apparatus for a television picture tube adapted to be energized by alternating current of a magnitude which initially is appreciable and which diminishes effectively to a small value, comprising in combination: a power supply for said receiver including rectifier means for converting alternating current into direct current and capacitive means for filtering said direct current; a source of alternating current; circuit means connected between said source of alternating current and said power supply and operative to impress said alternating current upon said power supply, thereby producing an initial surge of alternating current of appreciable magnitude through said circuit means; said initial surge of alternating current being caused at least in part by the relatively high charging current for said capacitive filtering means; said circuit means including a coil structure connected in a first current path between said source of alternating current and said power supply so as to be traversed by said initial surge of alternating current and mounted in such relation to said picture tube as to produce a magnetic field within said tube when subjected to said surge of alternating current; said circuit means also including disabling means operative subsequent to said initial surge of alternating current for reducing the alternating current through said coil structure to said small value, said disabling means providing a second current path between said source and said power supply and diverting said alternating current from said first current path to said second current path subsequent to said initial surge.

Claim 23

Degaussing apparatus as defined in claim 10, wherein: said circuit means also includes a switch effective when closed to render said circuit means operative.

Claim 24

Degaussing apparatus as defined in claim 10, wherein: said disabling means includes a heat responsive element.

Claim 25

In a color television receiver, a color picture tube having a display face with a plurality of different phosphors distributed across the display face, said phosphors in the plurality being effective to luminesce with visible light of particular colors when bombarded by electrons; electron means for scanning the display face with electrons to excite the phosphor into luminescing with the particular colors; a mask disposed in said tube between the face and said electron means, said mask being positioned to shield the different phosphors in the plurality from electrons representing different colors; at least a pair of coils positioned adjacent the mask at spaced positions and extending in a direction transverse to the mask to produce a magnetic flux field in the mask without any dead spot at any position on the face of the color picture tube, and means coupled to the pair of coils for energizing the coils with a signal of decaying intensity to graduAlly reduce the intensity of the magnetic flux field in said mask and degauss the color picture tube.

Claim 26

In a color television receiver, a color picture tube having a display face with a plurality of different phosphors distributed across the display face, said phosphors in the plurality being effective to luminesce with visible light of particular colors when bombarded by electrons; electron means for scanning the display face with electrons to excite the phosphor into luminescing with the particular colors; a mask disposed in said tube between the face and said electron means, said mask being positioned to shield the different phosphors in the plurality from electrons representing different colors; at least a pair of coils positioned adjacent the mask at spaced positions and extending in a direction transverse to the mask to produce a magnetic flux field in the mask without any dead spot at any position on the face of the color picture tube, and means coupled to the pair of coils for energizing the coils with a signal of decaying intensity to graduAlly reduce the intensity of the magnetic flux field in said mask and degauss the color picture tube.

Claim 27

In a color television receiver, a color picture tube having a display face; groups of phosphors distributed across the face of said tube, the phosphors in each group being effective to luminesce with visible light of a particular color when bombarded by electrons; electron means effective to scan the display face with electrons and excite preselected phosphors in each group into luminescence in accordance with such scan; a mask disposed between the display face and electron means, said mark having a plurality of apertures aligned with the electron means and the phosphors in said groups to block preselected electrons from reaching the phosphors in all but one of said groups; at least a pair of coils mounted adjacent the mask at spaced positions relative to the mask and disposed in a direction transverse to the mask to produce a magnetic flux field in the mask without any dead spot at any position on the display face of the tube, and means operatively coupled to the pair of coils for applying a signal to the coils to gradually reduce the intensity of the magnetic flux field produced by said coils for a degaussing of the face of the color picture tube.

Claim 28

In a color television receiver, a color picture tube having a display face; groups of phosphors distributed across the face of said tube, the phosphors in each group being effective to luminesce with visible light of a particular color when bombarded by electrons; electron means effective to scan the display face with electrons and excite preselected phosphors in each group into luminescence in accordance with such scan; a mask disposed between the display face and electron means, said mark having a plurality of apertures aligned with the electron means and the phosphors in said groups to block preselected electrons from reaching the phosphors in all but one of said groups; at least a pair of coils mounted adjacent the mask at spaced positions relative to the mask and disposed in a direction transverse to the mask to produce a magnetic flux field in the mask without any dead spot at any position on the display face of the tube, and means operatively coupled to the pair of coils for applying a signal to the coils to gradually reduce the intensity of the magnetic flux field produced by said coils for a degaussing of the face of the color picture tube.

Claim 29

In a color television receiver, a color picture tube having a display face; groups of phosphors distributed across the face of said tube, the phosphors in each group being effective to luminesce with visible light of a particular color when bombarded by electrons; electron means effective to scan the display face with electrons and excite preselected phosphors in each group into luminescence in accordance with the incidence of such electrons on the phosphors; a mask disposed between the face and said electron means, said mask having a plurality of apertures aligned with the electron means and the phosphors in said groups to provide for preselected electrons to reach the phosphors in only one of said groups; at least a pair of coils mounted adjacent the mask in a direction transverse to the mask and disposed in spaced relationship to each other to produce a magnetic flux field extending into the mask without any dead spot at any position on the display face of the tube; and means interconnected with the pair of coils to circulate a decaying magnetic flux field of alternating characteristics through the mask for a degaussing of the display face of the color picture tube.

Claim 30

In a color television receiver, a color picture tube having a display face; groups of phosphors distributed across the face of said tube, the phosphors in each group being effective to luminesce with visible light of a particular color when bombarded by electrons; electron means effective to scan the display face with electrons and excite preselected phosphors in each group into luminescence in accordance with the incidence of such electrons on the phosphors; a mask disposed between the face and said electron means, said mask having a plurality of apertures aligned with the electron means and the phosphors in said groups to provide for preselected electrons to reach the phosphors in only one of said groups; at least a pair of coils mounted adjacent the mask in a direction transverse to the mask and disposed in spaced relationship to each other to produce a magnetic flux field extending into the mask without any dead spot at any position on the display face of the tube; and means interconnected with the pair of coils to circulate a decaying magnetic flux field of alternating characteristics through the mask for a degaussing of the display face of the color picture tube.

Claim 31

In a color television receiver, a color picture tube having a display face with clusters including a separate primary phosphor in each cluster for each primary color; a plurality of electron guns each being provided for a different one of the primary colors to scan said display face with electron beams, each gun being positioned to direct its beam of electrons onto the phosphor in each cluster having a particular primary color corresponding to the particular gun; a mask disposed between the face and said electron guns, said mask having a separate aperture for each cluster and positioned in alignment with the electron guns and the respective primary phosphors in the cluster; a pair of coils disposed in spaced relationship to each other and in transverse relationship to the mask to produce a magnetic flux field; means mounting said coils adjacent and transverse to the mask and in spaced relationship to each other to direct the flux field through the mask; current means connected in a circuit with the coils to circulate an alternating current through the coils for providing the magnetic flux field through the mask with alternating characteristics; resistance means connected in the circuit with the coils for controlling the magnitude of the current through the coils in accordance with the value of its resistance; actuatable switch means connected in the circuit with the current means and the coils upon the actuation of the switch means; and means couplEd to the resistance means and the switch means for providing for a progressive change in the value of the resistance means in a direction to progressively decrease the current through the coils upon the actuation of the switch means.

Claim 32

In a color television receiver, a color picture tube having a display face with clusters including a separate primary phosphor in each cluster for each primary color; a plurality of electron guns each being provided for a different one of the primary colors to scan said display face with electron beams, each gun being positioned to direct its beam of electrons onto the phosphor in each cluster having a particular primary color corresponding to the particular gun; a mask disposed between the face and said electron guns, said mask having a separate aperture for each cluster and positioned in alignment with the electron guns and the respective primary phosphors in the cluster; a pair of coils disposed in spaced relationship to each other and in transverse relationship to the mask to produce a magnetic flux field; means mounting said coils adjacent and transverse to the mask and in spaced relationship to each other to direct the flux field through the mask; current means connected in a circuit with the coils to circulate an alternating current through the coils for providing the magnetic flux field through the mask with alternating characteristics; resistance means connected in the circuit with the coils for controlling the magnitude of the current through the coils in accordance with the value of its resistance; actuatable switch means connected in the circuit with the current means and the coils upon the actuation of the switch means; and means couplEd to the resistance means and the switch means for providing for a progressive change in the value of the resistance means in a direction to progressively decrease the current through the coils upon the actuation of the switch means.