US3824515A - Screening cage - Google Patents

Screening cage Download PDF

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Publication number
US3824515A
US3824515A US00252938A US25293872A US3824515A US 3824515 A US3824515 A US 3824515A US 00252938 A US00252938 A US 00252938A US 25293872 A US25293872 A US 25293872A US 3824515 A US3824515 A US 3824515A
Authority
US
United States
Prior art keywords
cage
wires
ground
electron beam
deflection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00252938A
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English (en)
Inventor
B Holman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL7002232A priority Critical patent/NL7002232A/xx
Priority to DE2104221A priority patent/DE2104221C3/de
Priority to FR7105548A priority patent/FR2078768A5/fr
Priority to GB21812/71A priority patent/GB1280289A/en
Application filed by Individual filed Critical Individual
Priority to US00252938A priority patent/US3824515A/en
Application granted granted Critical
Publication of US3824515A publication Critical patent/US3824515A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/867—Means associated with the outside of the vessel for shielding, e.g. magnetic shields
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H01F27/36—Electric or magnetic shields or screens
    • H01F27/363—Electric or magnetic shields or screens made of electrically conductive material

Definitions

  • This invention relates t'o'a device for electric screening, which does not disturb magnetic fields and which comprises a cylindrical cage composed mainly of electrically conductive material.
  • This kind of screening may be used in the deflection units of camera tubes between the line deflection coil and other parts such as the frame deflection coil and the target plate. It is important in this case that the electric screening should be effective at frequencies up to a few M Hz without disturbing the magnetic field of the line deflection coil. It is known to use for this purpose a thin metal screen within the deflection coil, for example, copper foil. In order to avoid eddy currents voids have to be provided therein. This is harmful to the screening effect and the manufacture is expensive. It is, moreover, difficult to secure connecting wires in a reliable manner to this thin metal foil for the requiredground-connection of the screen.
  • a screening device comprising a helically wound wire connected to ground only at one end for avoiding magnetic short-circuit does not exhibit the said disadvantage, but this solution is only appropriate for low frequencies, for example, for screened supply transformers.
  • a screening cage of this kind is only effective near the ground-connected end because, due to the inductance of the turns, the other end is not grounded for high frequencies.
  • a reduction of the inductance by spacing the turns further apart has the disadvantage that the openings between the turns become larger,
  • An object of the invention is to provide a structure which is free of the aforesaid disadvantages.
  • this is achieved by forming the cage from at least two multifilarly, helically wound wires, one end of each wire being connected to ground and the grounded ends of each pair of adjacent wires being located at opposite ends of the cylinder.
  • This structure has an appearance similar to the bifilar coil shown in US. Pat. No. 2,026,308, FIG. 2, which coil serves, however, as a primary winding of a highfrequency transformer so that the resemblance only lies in the form and is not related to the function.
  • FIGS. 1 and 2 in which two embodiments are shown in axial sectional views;
  • FIG. 3 shows a screening coil in accordance with the invention disposed between deflection coils and about a camera tube.
  • the screening cage of FIG. 1 comprises two insulated wires 3 and 5, bifilarly wound to form a closed cylindrical sheath.
  • the wire 5 is indicated in the Figure by a marking line for the sake of clarity.
  • the end 7 is free and the end 9 may be directly connected to ground.
  • the end 13 of the wire 5 is free and the end 15' is directly connected to ground, which is represented by the symbol. 17.
  • the advantages over a foil as a screening means are that no eddy currents can pass through the closed cylindrical wall, the structure is automatically provided with connecting wires for ground connection, and it is cheap.
  • the advantages over a single, helically wound wire are that theturns of the wires 3 and 5, considered separately, are not in contact with each other so that the inductance is lower, while the openings in one helix are filled in by the turns of the other helix.
  • each wire is grounded via the capacitance relative to the grounded end of the other wire for high frequencies so that the influence of the inductance is further reduced.
  • FIG. 2 shows one embodiment of a cage 21 formed by four insulated wires 23, 25, 27 and 29, which are marked differently in the Figure for the sake of clarity. It will be seen from FIG. 2 that the ground-connected ends of each pair of adjacent wires are located at opposite ends of the cylinder. The wires 23 and 27 are connected to the ground point 31 and the wires 25 and 29 are connected to the ground point 33.
  • the advantage of this embodiment over that of FIG. 1 resides in the fact that the turns of the separate wires are spaced further apart so that the inductance is even further reduced. I
  • FIG. 3 shows the screening coil 1 disposed between .vertical deflection coil 40 and horizontal deflection coil 42. All of the coils 1, 40 and 42 are about a camera tube 44.
  • a deflection unit for an electron beam device comprising, a line deflection coil and a frame deflection coil mounted on said electron beam means, and at least one device for electric screening which does not disturb magnetic fields and which comprises a hollow cylindrical cage composed mainly of electrically conductive material mounted on said electron beam device, said cage comprising at least two wires helically wound in a multifilar fashion with one end of each wire connected to ground and the ground-connected ends of each pair of adjacent wires being located at opposite ends of the cylindrical cage.
  • a deflection unit as claimed in claim 1 wherein one of the wire ends to be connected to ground is extended at one end of the cylinder and is passed back to the other end where all ends in common are connected to ground.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Details Of Television Scanning (AREA)
  • Coils Or Transformers For Communication (AREA)
US00252938A 1970-02-18 1972-05-12 Screening cage Expired - Lifetime US3824515A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
NL7002232A NL7002232A (fr) 1970-02-18 1970-02-18
DE2104221A DE2104221C3 (de) 1970-02-18 1971-01-29 Ablenkeinheit für eine Elektronenstrahlröhre mit einer Zeilenablenkspule
FR7105548A FR2078768A5 (fr) 1970-02-18 1971-02-18
GB21812/71A GB1280289A (en) 1970-02-18 1971-04-19 Screening cage for a deflection coil
US00252938A US3824515A (en) 1970-02-18 1972-05-12 Screening cage

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL7002232A NL7002232A (fr) 1970-02-18 1970-02-18
US11045771A 1971-01-28 1971-01-28
US00252938A US3824515A (en) 1970-02-18 1972-05-12 Screening cage

Publications (1)

Publication Number Publication Date
US3824515A true US3824515A (en) 1974-07-16

Family

ID=27351544

Family Applications (1)

Application Number Title Priority Date Filing Date
US00252938A Expired - Lifetime US3824515A (en) 1970-02-18 1972-05-12 Screening cage

Country Status (5)

Country Link
US (1) US3824515A (fr)
DE (1) DE2104221C3 (fr)
FR (1) FR2078768A5 (fr)
GB (1) GB1280289A (fr)
NL (1) NL7002232A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4152745A (en) * 1977-04-11 1979-05-01 Eul Edward A Magnetic shield device
US4392083A (en) * 1981-11-20 1983-07-05 Teletype Corporation Radiation shield for a cathode ray tube
US4709220A (en) * 1985-09-13 1987-11-24 Mitsubishi Denki Kabushiki Kaisha Radiation suppression device
US4767969A (en) * 1987-05-26 1988-08-30 Honeywell, Inc. RF emission shield for CRT displays
US4806894A (en) * 1986-12-09 1989-02-21 Mitsubishi Denki Kabushiki Kaisha Apparatus for cancelling leakage magnetic field
US6297583B1 (en) * 1998-10-08 2001-10-02 Federal-Mogul World Wide, Inc. Gas discharge lamp assembly with improved r.f. shielding

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1416635B1 (fr) * 2002-11-01 2012-12-12 Omron Corporation Dispositif capteur

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2217409A (en) * 1937-04-26 1940-10-08 Rca Corp Cathode ray control apparatus
US2754415A (en) * 1950-10-09 1956-07-10 Du Mont Allen B Lab Inc Receiver antenna coupling circuit for balanced or unbalanced input
DE1095313B (de) * 1957-01-04 1960-12-22 Fernseh Gmbh Ablenkspulenanordnung fuer Fernsehaufnahmeroehren vom Vidikontyp
US3158774A (en) * 1962-06-08 1964-11-24 Joel F Fleming Image orthicon focusing coil and field flaring ring

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2217409A (en) * 1937-04-26 1940-10-08 Rca Corp Cathode ray control apparatus
US2754415A (en) * 1950-10-09 1956-07-10 Du Mont Allen B Lab Inc Receiver antenna coupling circuit for balanced or unbalanced input
DE1095313B (de) * 1957-01-04 1960-12-22 Fernseh Gmbh Ablenkspulenanordnung fuer Fernsehaufnahmeroehren vom Vidikontyp
US3158774A (en) * 1962-06-08 1964-11-24 Joel F Fleming Image orthicon focusing coil and field flaring ring

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4152745A (en) * 1977-04-11 1979-05-01 Eul Edward A Magnetic shield device
US4392083A (en) * 1981-11-20 1983-07-05 Teletype Corporation Radiation shield for a cathode ray tube
US4709220A (en) * 1985-09-13 1987-11-24 Mitsubishi Denki Kabushiki Kaisha Radiation suppression device
US4806894A (en) * 1986-12-09 1989-02-21 Mitsubishi Denki Kabushiki Kaisha Apparatus for cancelling leakage magnetic field
US4767969A (en) * 1987-05-26 1988-08-30 Honeywell, Inc. RF emission shield for CRT displays
US6297583B1 (en) * 1998-10-08 2001-10-02 Federal-Mogul World Wide, Inc. Gas discharge lamp assembly with improved r.f. shielding

Also Published As

Publication number Publication date
DE2104221C3 (de) 1980-07-17
DE2104221A1 (de) 1971-08-26
NL7002232A (fr) 1971-08-20
DE2104221B2 (fr) 1979-08-30
GB1280289A (en) 1972-07-05
FR2078768A5 (fr) 1971-11-05

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