EP0218561A2

EP0218561A2 - Deflection unit with ferromagnetic supports to be magnetized in relation to the coupling with the kinescope, and use procedure thereof

Info

Publication number: EP0218561A2
Application number: EP86830286A
Authority: EP
Inventors: Alfredo Fazzini; Romano Bonifazi; Rocco Panico; Massimo Madiai
Original assignee: Plessey SpA Dite Ste
Current assignee: Plessey SpA Dite Ste
Priority date: 1985-10-08
Filing date: 1986-10-07
Publication date: 1987-04-15
Also published as: EP0218561A3; IT8509497A0; IT1201361B; JPS62115631A

Abstract

A deflection yoke for TV monitors and the like, with ferromagnetic supports intended to correct distortions in the images obtained from the kinescope (C) to be coupled or being coupled with the yoke, comprising a magnetizable support (18) disposed around the yoke past the deflection zone, in the broader part of the yoke, whose local magnetizations are provided for correcting the distortions, in particular for the geometry correction.

Description

The deflection unit or deflection yoke is mounted on the neck of the kinoscope and has the function of deflecting the electronic beam emitted by the gun so as to carry out the scanning of the inner part of the screen which is covered with phosphorus.
Typically, the deflection unit or yoke is made up of two pairs of coils which generate a system of orthogonal magnetic fields capable of deflecting the elctronic beam into the directions x, y, the axis z being that of the kinoscope. These coils are kept in the correct position by a plastic support and are combined to two half-rings of ferrite. In the scanning system, the vertical coils are commonly named as the ones working at a lower frequency and deflecting with y axis and horizontal coils are named the other ones. The horizontal coils are almost always of saddle shape, while the vertical ones may be saddle or half toroidal shaped, that is, each one being wound on a half core and connected to each other in order to emit opposite fluxes. Usually, the inner profile of the ferrite is a revolution profile, and sometimes exhibits pole shoes; in this case the windings are placed in the slots and the whole is called a "stator" deflection unit.
The electronic beam - more or less off-centered owing to the construction tolerances of the kinoscope - is brought into alignment with the axis on the screen by acting on the electronic beam prior to the deflection through a pair of centering rings being diametrally magnetized. By rotating such magnets mutually and reversely to each other there is obtained a vector sum of the two magnetic fields and a change in the resulting field and thus the radial displacement, while by rotating the two rings together such displacement can be angularly oriented. Because of the construction tolerances of the yoke and of the kinoscope as well as of their coupling, geometrical distortions are generated (both systematic and casual) of the displayed image, and an intervention is necessary after the deflection. At present this is achieved by using a crown of small magnets (dipoles) individually adjustable for an almost local and selective correction of the image contour. These dipoles are generally mounted on radial, inclined or axial appendixes of the plastic support. The operation is to be carried out manually and results difficult and laborious.
The invention overcomes these difficulties.
Substantially, a yoke or deflection unit for television monitors and the like - with ferromagnetic supports intended to correct distortions, in the images obtained from the kinoscope to be coupled or being coupled with the yoke - comprises a magnetizable support arranged around the yoke past the deflection zone, in the broader part of the yoke, the local magnetizations of which are provided for the distortions correction and the geometry correction.
Said magnetizable support may be, in practice, developed as an annular continuous support provided with means for its fixed angular positioning. The magnetizable support is advantageously defined by surfaces having truncated cone development, but it may also have a cylindrical development, and mostly a constant thickness.
The yoke may also comprise a magnetizable support arranged to surrond the kinescope neck, this support being able in turn to acquire local magnetizations in order to exert an influence upon the beam prior to the deflection.
The invention has also the object to provide the removal or the reduction of the distortions in a yoke-kinescope group through the use of a yoke or a deflection unit as above defined.Starting with a yoke having the or each support demagnetized, local magnetizations are imposed on said support or on said supports to achieve the desired influence upon the image to be obtained. The magnetization is carried out either on the kinoscope to be steadily associated with the yoke and by direct control of the generated image, or on a sample kinescope. Alternatively, the magnetization may be even carried out on the yoke according to a predetermined program.
In any case, the magnetization of a magnetizable support may be simultaneously carried out in all the points provided therein or in sequence.
The invention will be better understood by following the description and the attached drawing, which shows a practical non limitative exemplification of the same invention. In the drawing:

Figs. 1, 2 and 3 show an axial view and two sections taken on the broken lines II-II and III-III of Fig. 1, to illustrate a deflection yoke according to the invention;
Figs. 4 and 5 show, an axial view and a section taken on the line V-V respectively of Fig. 4 of a plastoferrite ring located before the deflection zone.

According to what is illustrated in the attached drawing, numeral 1 indicates the plastic structure for supporting the yoke members; this structure is axially opened and is shaped to accomodate the kinescope C, of which Cl indicates the neck going through the narrowest part of the yoke. Numeral 3 indicates the two half rings made of ferrite, on which the vertical half- toroidal coils, indicated by 5, are wound; numeral 7 indicates the windings of the horizontal saddle-like coils. Numeral 9 indicates the member for the fixing of the yoke on the neck C1 of the kinescope; numeral 10 indicates the contacts group and numeral 12 indicates the clip means for blocking the ferrites. Traditionally, an auxiliary annular element 14 made of synthetic, mostly thermoplastic resin, is fitted on the broader part of the support 1 to hold a series of radial inclined appendixes 16 which are usually provided for receiving small magnets M intended for the manual correction of the distortions, mostly of the geometrical distortions, of the yoke by the above mentioned operations; at present this fitted auxiliary element 14 is provided for moulding requirements.
According to the invention, between the broader terminal part of the plastic support 1 and the element 14 fitted thereon, a plastoferrite ring 18 is engaged developing with a truncated cone shape to fit the profile of the kinescope C, to which it results substantially equidistant around the junction of the neck Cl; the ring 18 remains thereby engaged between the body 1 and the ring 14. The ring 18 is able to be locally magnetized with the criteria stated above and more specifically illustrated below.
The yoke according to the invention may also be provided - in place of the two adjustment rings apt to exert an influence prior to the deflection - with a second demagnetizable ring 20, shown in particular in Figs. 4 and 5, made of plastoferrite or other, which has the same purpose being traditionally attributed to the two angularly adjustable rings.
The ring 18 (and when it is present, also the ring 20) is magnetized by discrete magnetization means able to generate local magnetizations along the ring in order to achieve the geometrical correction. The magnetizations are performed simultaneously or in sequence. In particular the sum of the internal magnetization is zero. The or each ring is engaged to the structure 1 so as to prevent relative angular displacements.
The magnetization process may be carried out during the coupling of the yoke with the kinescope by a suitable magnetization equipment. The group of the yoke and the kinescope is then blocked and stabilized to obtain the yoke-kinescope unit to be marketed.
According to another procedure, the magnetization is generated of a plurality of yokes fitted on a reference kinescope, that is, a sample kinescope, so that the yokes will serve for the batch of kinescopes with which they are to be coupled and of which the reference kinescope represents a typical sample. This procedure allows the magnetization process to be accelerated, obviously to the detriment of the accuracy, but allowing a determined tolerance in the realization of the individual yoke-kinescope units.
A further magnetization process consists in performing the magnetization of the magnetic support fitted on the yoke, according to a predetermined scheme and without the mounting on the kinescope to be combined with the yoke or on the reference kinescope; in this way, there are obtained yokes that may result compensated for systematic errors in a batch of yokes.
In those cases in which the yoke is not coupled with a specific kinescope, the resulting product is the precorrected yoke and the mounting will take place at random on kinescopes similar to the reference one respectively to the kinescope according to which the systematic errors to be corrected by the magnetizations have been pre-established. Yokes of this type can be coupled with like kinescopes by intervening afterwards for the centering by means of traditional centering rings mounted on the yoke and providing a possible compensation of residual geometry errors by resorting to the small magnets M mounted on the appendixes 16, through an operation which is extremely easier than the one traditionally provided for the total correction as indicated at the beginning.
When the procedure includes the pre-magnetization of a magnetic support mounted on the yoke, independently of the presence of a kinescope on which the yoke has been fitted, a magnetization may be also provided from the inside rather than from the outside, that is, by transparency, as instead is necessary when the magnetization of the ring 18 (and correspondingly of the possibly present ring 20) is operated in the presence of a kinescope on which the yoke has been actually fitted.
The yokes may be of the saddle-tore type as shown in the drawing, or of the saddle-saddle type or of the stator type.
The invention applies to both single-colored and multi-colored kinescopes, for example, of light valve type.
The magnetization equipment may be realized to generate induction pulses by means of coils or other, while in case of standardized magnetization on the yoke, independently of the coupling with the kinescope, the equipment may be made up with static fields formed by magnets provided for generating a uniform magnetization and thereby equal for all the magnetic supports of the treated yokes; subsequently - after the coupling to its own kinescope - the yoke may be corrected by the small magnets M or similar.
The magnetic supports 18 and 20 may have an annular truncated cone development, as shown in Figs. 4 and 5 for the support 20, and may be made of plastoferrite or other suitable ferromagnetic material. The shape of the magnetic supports may be also different from the one having truncated cone development, for example, they may be realized in a cylindrical configuration. It is not excluded that a magnetic support can be also realized in more sectional portions so as to carry out a support being on an average continuous, or discontinuous, to a limited degree, around the yoke.
In any case the magnetic supports will be, provided with means for a steady angular engagement in addition to their axial retaining engagement over the yoke unit; to this purpose, a reference indentation and a catch may be provided, cooperating in the coupling between the ferromagnetic support and the plastic support structure 1 or the like.
It is understood that the drawing shows an exemplification of the invention given only as a practical demonstration of the invention, as this may vary in the forms and dispositions without nevertheless coming out from the scope of the idea on which the invention itself is based.

Claims

1. A deflection yoke or unit for television sets or the like, with ferromagnetic supports intended to correct the distortions in the images obtained from the kinescope to be coupled or being coupled to the yoke, characterized in that it comprises a magnetizable support (18) located around the yoke past the deflection zone, in the broader part of the yoke, the local magnetizations of which are provided for the correction of the distortions, especially for the geometry corrections.

2. Deflection yoke according to the preceding claim, characterized in that the magnetizable support (18) is developed as an annular continuous support with means for fixed angular positioning.

3. Deflection yoke according to claims 1 and 2, characterized in that the magnetizable support (18) is defined by surfaces having truncated cone development.

4. Deflection yoke according to claim 3, characterized in that the magnetizable support (18) has a constant thickness.

5. Deflection yoke according to at least one of the preceding claims, characterized in that it comprises in addition a magnetizable support (20) located to surround the kinescope neck (C1) and able as well to acquire local magnetizations in order to affect the beam prior to the deflection.

6. A procedure for the removal or the reduction of the distortions in a yoke-kinescope group with the use of a yoke according to the preceding claims, characterized in that starting with a yoke having the or each support (18,20) demagnetized, local magnetizations are imposed on said support (18) or said supports (18,20) to achieve the desired influence on the image to be obtained.

7. Procedure according to claim 6, characterized in that the magnetization is carried out on the kinescope destined to be steadily associated with the yoke and by direct control of the generated image.

8. Procedure according to claim 6, characterized in that the magnetization is carried out on a sample kinescope.

9. Procedure according to claim 6, characterized in that the magnetization is carried out on the yoke according to a predetermined program, especially for correcting systematic errors.

10. Procedure according to claim 6, characterized in that the magnetization is simultaneously carried out in all the areas.

11. Procedure according to claim 6, characterized in that the magnetization is carried out in sequuence on the various areas.

12. Procedure according to claim 6, characterized in that the sum of the internal magnetizations is zero.