Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
2001-05-01
2003-07-22
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S402000, C313S405000, C313S406000, C313S407000
Reexamination Certificate
active
06597094
ABSTRACT:
The invention relates to a colour display tube comprising a display window with a circumferential upright edge and corner areas, a colour selection electrode comprising corner sections to which suspension means, comprising a resilient element having a flat portion incorporating an apertured part with an entrance opening, are coupled, which colour selection electrode is suspended in the corner areas from supporting elements each having a free end portion engaging the apertured part at at least three contact points, which are located on surfaces of engagement, the free end portion having a centre which substantially coincides with a plane through the flat portion, the apertured part being formed so that at least one of the contact points is situated outside the plane of the flat portion, on the side facing away from the free end portion.
The invention also relates to a corner section for use in a colour selection electrode of such a colour display tube and to a colour selection electrode provided with such a corner section.
A colour display tube as described in the opening paragraph is disclosed in U.S. Pat. No. 4,763,039. The colour display tube according to this specification is provided with a colour selection electrode, which is suspended in the corners of the display window. In this corner suspension system, the supporting elements, which are connected in the corners of the upright edge of the display window, are coupled to the suspension means of the colour selection electrode. The suspension means comprise a flat portion, the resilient element and a part with an aperture for receiving the spherically curved free end portion of the supporting elements. This aperture is provided with at least three contact points for engaging the free end portion, at least one contact point being situated outside the plane of the resilient element. Furthermore, the part containing the aperture is provided with a member that acts as a spring to lock the spherically curved free end portion in the aperture of the suspension means. Thus, the aperture and the free end portion act as a detent, locking the individual suspension means to the supporting elements.
The colour selection electrode has to be stabile positioned in the colour display tube to ensure that the picture displayed on the display window always shows the right colours. Instabilities in the position of the colour selection electrode lead to misregistrations of the electron beams impinging on the phosphors of different colours. This will cause discolorations of the picture, resulting in a deterioration of the picture quality.
The colour display tube disclosed in U.S. Pat. No. 4,763,039 has the disadvantage that it has a corner suspension system which requires large forces for clamping the suspension means on the supporting elements. This is necessary in order to fulfil a basic requirement, namely that the colour selection electrode must not become detached from the supporting elements in a finished colour display tube. However, in the production process the high clamping forces lead to loose particles in the colour display tube due to scratching of the spring element along the supporting elements. This high clamping force influences the positional stability of the colour selection electrode in the colour display tube in a negative way because the friction between the supporting elements and the suspension means is considerably increased.
It is an object of the invention to provide a colour display tube having a colour selection electrode with an improved suspension system as compared to the type described in the opening paragraph, which strongly reduces the registration errors on the display window and which leads to a cheaper production process of colour display tubes in the factories.
According to the present invention, this object is achieved by means of a colour display tube, which is characterized in that the surfaces of engagement of contact points that coincide with the plane through the flat portion are substantially perpendicular to said plane, and the surfaces of engagement of contact points that are situated outside said plane are substantially perpendicular to the connection between the contact points and the centre of the free end portion, which free end portion is allowed free passage through the entrance opening of the apertured part.
The invention is based on the insight that by having an entrance opening of the apertured part that is slightly larger than the diameter of the free end portion, the mounting of the colour selection electrode becomes quite easy. The colour selection electrode is positioned by pressing the suspension means on the supporting elements, thereby overcoming only the spring force of the resilient elements. The surface of engagement containing a contact point situated outside the plane through the flat portion makes sure the free end portion is positioned such that its centre substantially coincides with the flat portion. Mechanical shocks exerted on the colour display tube can cause a shift of the colour selection electrode with respect to the display window, but the positioning of the surfaces of engagement in combination with the preload of the spring force of the resilient elements ensures that the colour selection element will resume its original position. As a result, the colour display tube will not be sufficient to misregistrations, thereby improving the picture quality.
Furthermore, as this construction results in a very stable positioning of the colour selection electrode, it becomes superfluous to weld the suspension means to the supporting elements, as is done in currently produced colour display tubes. This makes it possible to reclaim the colour selection electrode if a colour display tube is rejected, and reuse it for the production of another colour display tube, leading to a significant saving in the production centre.
In a preferred embodiment the apertured part is formed so that the coupling between the apertured part and the free end portion is self-locking for forces applied in the direction of the flat portion.
Mechanical shocks exerted on the colour display tube lead to a force in the suspension element that is directed in the flat portion containing the resilient element. In order to prevent that the colour selection electrode becomes detached from the supporting elements, it is important that a self-locking action exists in the direction of the flat portion. For that reason, the surfaces of engagement of the apertured part are arranged so that if a force is applied that is directed in the plane of the flat portion, a shift may occur between the suspension means and the supporting element, but when this force disappears the original position is resumed. In the direction perpendicular to the flat portion, a self-locking action is unwanted, because this makes handling in the production process more difficult. During the manufacture of a colour display tube, the display window is provided—by a photochemical exposure process—with a screen comprising, for instance, a black matrix layer and phosphors of three colours. For the exposure of each of them the colour selection electrode has to be inserted and extracted from the display window. This is most easily done when, in the direction perpendicular to the flat portion, these are no obstructions between the suspension means and the free end portion.
In a further embodiment, a friction force arises between the surfaces of engagement of the contact points that are situated outside the plane of the flat portion and the free end portion when a force is applied in the direction of the flat portion.
When a force is applied in the direction of the plane of the flat portion, the surfaces of engagement having their contact points situated in this plane will have no friction force between them and the free end portions, because the applied force is perpendicular to these surfaces of engagement. However, the surfaces of engagement having their contact points outside the plane of the flat portion are not perpendicular to the applied force,
Bergmans Hendrik Pancratius Maria
Hendriks Arnoldus Antonius Maria
Jacobs Hernes
Meissner Jörg
Post Jan Harmannus
Koninklijke Philips Electronics , N.V.
Patel Nimeshkumar D.
Perry Anthony
LandOfFree
Color display tube with improved suspension of the color... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color display tube with improved suspension of the color..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color display tube with improved suspension of the color... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3080044