US2737617A - Devices for focussing an electron beam - Google Patents

Devices for focussing an electron beam Download PDF

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Publication number
US2737617A
US2737617A US260702A US26070251A US2737617A US 2737617 A US2737617 A US 2737617A US 260702 A US260702 A US 260702A US 26070251 A US26070251 A US 26070251A US 2737617 A US2737617 A US 2737617A
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United States
Prior art keywords
focussing
plate
sleeve
electron beam
magnetic
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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
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US260702A
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English (en)
Inventor
Montgomery William Alan
Morgan Arnold Dudley
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International Standard Electric Corp
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International Standard Electric Corp
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Publication date
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Publication of US2737617A publication Critical patent/US2737617A/en
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    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/54—Arrangements for centring ray or beam

Definitions

  • the present invention relates to focussing and centering arrangements for the electron beams of cathode ray tubes utilising magnetic focussing by means of a permanent magnet or an electromagnet.
  • the usual arrangement for magnetically focussing an electron beam in a cathode ray tube comprising a magnet assembly positioned about the neck of the tube in a mounting arrangement which provides means for tilting the assembly in order to adjust the magnetic axis for centering the electron beam spot upon the cathode ray tube screen.
  • the focussing and centering arrangements for the electron beam of a cathode ray tube comprise means for producing a magnetic beam focussing field between a pair of annularv pole pieces and means for adjusting the eccentricity of one pole piece with respect to the other.
  • embodiments of the invention provide a focussing and centering arrangement for the electron beam of a cathode ray tube comprising a cylindrical sleeve of magnetic material to be placed around the longitudinal axis of the said beam, a plate of magnetic material spaced from the end of the said sleeve substantially at right angles to the longitudinal axis thereof, and having a central circular aperture surrounding said axis, magnetic means for producing a beam focussing magnetic field in the space between the said end of the sleeve and the said plate and means for adjusting the eccentricity of the central aperture of the said plate with respect to the longitudinal axis of the said sleeve to provide any required steady deflection for centering the electron beam.
  • Fig. 1 shows in part section a view of a focussing and centering arrangement according to the present invention
  • Fig. 2 shows, in part section and in part diagrammatically a front view of the arrangement of Fig. 1 with the centrally apertured plate in one extreme position with respect to the said sleeve, and
  • Fig. 3 shows a view similar to that of Fig. 2 but with the apertured plate in another extreme position.
  • 1 represents the magnetic core (the said sleeve) of an electromagnetic focussing unit 2 in concentric relation to the neck portion 3 of a cathode ray tube (not fully shown).
  • the focussing unit comprises a coil 4 wound on a bobbin 5, which fits over the cylindrical magnetic sleeve 1. Except for a said air gap at one end the coil 4 is completely enclosed magnetically by the sleeve 1, a cup-shaped shroud 6, which 2,737,617 Patented Mar. 6, 1956 may be of drawn steel, an end plate 7 of magnetic material and the aforementioned apertured plate (indicated at 8).
  • the sleeve 1 is provided at one end with a shoulder 9 which fits inside a central hole in the base of shroud 6, the end of the sleeve being swaged over the metal of the shroud.
  • the end cap 7 is secured to a mounting bracket 10 and after insertion of the coil 4, the shroud 6 is secured to the end cap 7 in any convenient manner which will ensure good magnetic contact between them.
  • the mounting bracket 10 is fixed to the chassis of the cathode ray tube unit in such manner that the axial position of focussing unit 2 may be adjusted with respect to the tube 3.
  • the end cap 7 does not completely cover the end of the coil 4; the closure is completed by the centrally apertured plate 8, which we call a shift plate, held in sliding contract over the base of the end cap 7.
  • This shift plate forms one pole of the focussing magnet the end of the seeve 1 the other.
  • the shift plate 8 is dished, so that the more central portion lies in the same plane as the base of the end cap.
  • the passage of current through the coil 4 sets up a predominantly axial magnetic field in the space between the adjacent end of sleeve 1 and the inner circumference of the shift plate 8. If the sleeve 1 and the aperture in the shift plate 8 are coaxial, the radial components of the magnetic field are symmetrical about the axis and the focussing arrangement merely provides a magnetic lens for focussing the electron beam to form a spot upon the cathode ray tube screen. In order that the electron optical magnification may be a maximum, the focussing arrangement should be mounted with the shift plate facing the cathode ray tube screen.
  • the shift plate 8 be mounted so as to be eccentric with respect to the axis of the sleeve 1, a resultant radial component of the magnetic field will exist in the air gap and will cause deflection of the electron beam; thus by adjustment of the shift plate in its own plane, the electron beam can readily be centered on the tube screen in spite of eccentricity of mounting of the tube and sleeve 1 or of the electron gun within the tube. A small movement of the shift plate 8 in its own plane is sufiicient to shift the electron beam over a relatively large distance.
  • an angle bar 12 of metal (say aluminum in the present embodiment) is riveted to the end cap 7 by rivets 13 and 14 so as to press against the shift plate.
  • a spring clip can be added, if necessary, say to the bottom of the end cap 7, to act as an additional retainer for the shift plate 8.
  • the bar 12 may be replaced by a plurality of such spring clips.
  • a clamping stirrup 15 for supporting the neck 3 of the cathode ray tube may conveniently be secured to the bar.
  • each of the links 16 and 17 is a. U-shaped metal. plate, of aluminium, say, having near the curved endthereof a; circular aperture. (118 and19 respectively).
  • Two raised lugs 23, one. of. which is shown in Fig 1 and both. of which are indicated diagrammatically in Fig. 2, are provided on. the front surface of the end; cap 7 for mounting.
  • Each spindle carries a control knob in the: form of. a thumb wheel 26, as shown in Fig: 1.
  • Each thumb wheel. is. retained against the front surface of its respective link by means. of spring loading, indicated at 27 in. Fig. 1, betweenthe rear end of thespindle and the lug 23, thus introducing. sufiicient friction between the. respective. links and 1-7 and the end cap 7 to keep the shift plate: 8 in any desired position once the thumb. wheels.
  • the magnet coil 4 was. designed to provide 500 ampere turns and a gapv of i'nch was provided. between. the end of the sleeve 1. and the rear of the shift plate 9.
  • the magnetic lens. gave a magnificationof 6.3.. Under these conditions it. was found. that a. movement. of i%g; inch of the shift plate produced onthe cathode ray tube screen a corresponding spot deflection of il /a inch.
  • a focussing and centering arrangement for the electron beam of a cathode ray tube comprising a cylindrical sleeve of magnetic material, a cup-shaped shroud of magnetic material fixed atone end of said sleeve and extending substantially parallel with said sleeve and beyond an end thereof to provide an annular cup-shaped opening, a, magnetic coil positioned over said sleeve within. said cup-shaped opening, a closure member. of magnetic material extending from said shroud atv and opening radially inwardly toward the axis of said sleeve to leave. a' predetermined circular opening, a plate of magnetic material mounted.

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  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • Transforming Electric Information Into Light Information (AREA)
  • Details Of Television Scanning (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
US260702A 1950-12-15 1951-12-08 Devices for focussing an electron beam Expired - Lifetime US2737617A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB308664X 1950-12-15

Publications (1)

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US2737617A true US2737617A (en) 1956-03-06

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US260702A Expired - Lifetime US2737617A (en) 1950-12-15 1951-12-08 Devices for focussing an electron beam

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US (1) US2737617A (fr)
CH (1) CH308664A (fr)
GB (1) GB694517A (fr)
NL (1) NL165991B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3247411A (en) * 1962-07-09 1966-04-19 Rca Corp Post-deflection color purity correcting magnet system for a color tv cathode ray tube
US3629751A (en) * 1969-04-16 1971-12-21 Warwick Electronics Inc Deflection yoke mounting

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109720897B (zh) * 2018-12-07 2020-07-31 台州市大安塑料模具股份有限公司 一种防水果压伤下料装置

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2416687A (en) * 1944-03-30 1947-03-04 Bell Telephone Labor Inc Magnetic focussing device
US2418487A (en) * 1944-03-31 1947-04-08 Bell Telephone Labor Inc Cathode ray magnetic focusing device
US2501516A (en) * 1947-12-31 1950-03-21 Gen Electric Deflecting and focusing device for cathode-ray apparatus
US2533688A (en) * 1950-01-31 1950-12-12 Quam Nichols Company Focusing device
US2533689A (en) * 1950-06-28 1950-12-12 Quam Nichols Company Magnetic focusing device
US2568668A (en) * 1950-08-18 1951-09-18 Best Mfg Co Inc Cathode-ray tube focusing device of the permanent magnet type
US2579941A (en) * 1949-07-06 1951-12-25 Ferguson Radio Corp Cathode-ray tube
US2580606A (en) * 1951-03-21 1952-01-01 Best Mfg Company Inc Cathode-ray tube focusing device
US2581657A (en) * 1950-07-26 1952-01-08 Myron R Heppner Focusing and centering device for cathode-ray tubes
US2591820A (en) * 1948-02-07 1952-04-08 Pye Ltd Suspension mounting for the focussing device of cathode-ray tubes
US2592185A (en) * 1950-12-09 1952-04-08 Quam Nichols Company Focusing device
US2635204A (en) * 1950-10-04 1953-04-14 Zenith Radio Corp Cathode-ray tube beam-centering device

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2416687A (en) * 1944-03-30 1947-03-04 Bell Telephone Labor Inc Magnetic focussing device
US2418487A (en) * 1944-03-31 1947-04-08 Bell Telephone Labor Inc Cathode ray magnetic focusing device
US2501516A (en) * 1947-12-31 1950-03-21 Gen Electric Deflecting and focusing device for cathode-ray apparatus
US2591820A (en) * 1948-02-07 1952-04-08 Pye Ltd Suspension mounting for the focussing device of cathode-ray tubes
US2579941A (en) * 1949-07-06 1951-12-25 Ferguson Radio Corp Cathode-ray tube
US2533688A (en) * 1950-01-31 1950-12-12 Quam Nichols Company Focusing device
US2533689A (en) * 1950-06-28 1950-12-12 Quam Nichols Company Magnetic focusing device
US2581657A (en) * 1950-07-26 1952-01-08 Myron R Heppner Focusing and centering device for cathode-ray tubes
US2568668A (en) * 1950-08-18 1951-09-18 Best Mfg Co Inc Cathode-ray tube focusing device of the permanent magnet type
US2635204A (en) * 1950-10-04 1953-04-14 Zenith Radio Corp Cathode-ray tube beam-centering device
US2592185A (en) * 1950-12-09 1952-04-08 Quam Nichols Company Focusing device
US2580606A (en) * 1951-03-21 1952-01-01 Best Mfg Company Inc Cathode-ray tube focusing device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3247411A (en) * 1962-07-09 1966-04-19 Rca Corp Post-deflection color purity correcting magnet system for a color tv cathode ray tube
US3629751A (en) * 1969-04-16 1971-12-21 Warwick Electronics Inc Deflection yoke mounting

Also Published As

Publication number Publication date
CH308664A (fr) 1955-07-31
NL165991B (nl)
GB694517A (en) 1953-07-22

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