Electric lamp and discharge devices – Cathode ray tube – Beam deflecting means
Reexamination Certificate
2001-05-30
2004-06-01
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Beam deflecting means
C313S412000, C313S428000
Reexamination Certificate
active
06744192
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multipole unit for a color picture tube of the type including a support tube, a retaining ring, and at least one magnetic ring.
2. Description of the Related Art
Color picture tubes for color television sets and color monitors are provided with a multipole unit by means of which static convergence adjustment is carried out. Convergence adjustment guarantees that the three color separation images which are produced in a color picture tube appear on the front screen with raster superposition, i.e. that the three electron beams of the electron gun impinge on respective neighbouring, associated phosphor dots over the whole screen area. This will only be the case if the electron beams cross in a common shadow mask opening of the shadow mask provided on the inner side of the front screen in the picture tube. In the case of static convergence adjustment minor deviations of the electron beams are corrected with the aid of so-called multipole fields. These multipole fields are produced by permanent-magnetic rings consisting of a slightly permeable material so that the deflection field will not be influenced.
Hitherto known multipole units consist of a support tube, a threaded ring which can be screwed onto the support tube, and a plurality of (permanent-) magnetic rings. The magnetic rings are arranged between the threaded ring and a flange on the opposite end of the support tube. For static convergence adjustment of a color picture tube, the magnetic rings can be rotated on the support tube. When the adjustment has been finished, the magnetic rings are fixed at the position in question by fully tightening the threaded ring. The static convergence adjustment for the color picture tube will be preserved permanently in this way.
In order to permit adjustment with the aid of the magnetic rings before said rings are fixed completely, said magnetic rings must be rotatably supported on the support tube without rotating on their own. They must always be held at their respective position in this adjustment phase. As soon as all the magnetic rings have been brought to their final position, the threaded ring is tightened firmly so as to fix the magnetic rings completely.
In the adjustment phase, the magnetic rings are held in a clamped condition. For this purpose, an additional spring ring is normally used between the magnetic rings. By means of a force acting in the axial direction, this spring ring clamps the magnetic rings between the threaded ring and the flange in the adjustment phase. The spring ring is provided with axially effective spring elements for this purpose.
Such a conventional structural design is disadvantageous insofar as an additional spring ring is required.
OBJECTS AND SUMMARY OF THE INVENTION
It is the object of the present invention to provide an improved multipole unit having a simplified structural design.
This object is achieved by providing a multipole unit for a color picture tube comprising a support tube, a retaining ring and at least one magnetic ring. The magnetic ring is attachable to the support tube and a spring element is provided between the retaining ring and a stop on the outer circumference of the support tube. The spring element acts in axial direction and is integrated in the stop or the retaining ring.
According to the present invention, a spring element is integrated in the retaining ring or in the flange of the support tube. A separate spring ring is therefore no longer necessary.
The structural design of the multipole unit according to the present invention has been simplified substantially in comparison with conventional multipole units, since the production as well as the mounting of an additional spring ring can be dispensed with.
Further advantageous embodiments of the present invention are disclosed below and in the claims.
REFERENCES:
patent: 4050042 (1977-09-01), Anthony
patent: 4065737 (1977-12-01), Anthony
patent: 4728854 (1988-03-01), Fendley
patent: 4898746 (1990-02-01), Opresko
patent: 5955830 (1999-09-01), Uyama
patent: 0 643 413 (1995-03-01), None
patent: 2224869 (1974-10-01), None
patent: 02 199749 (1990-08-01), None
patent: 10 188846 (1998-07-01), None
Boyle Fredrickson Newholm Stein & Gratz S.C.
Matsushita Display Devices (Europe) GmbH
Patel Vip
Zimmerman Glenn
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