Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
1999-06-15
2001-02-13
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S402000
Reexamination Certificate
active
06188171
ABSTRACT:
This invention relates to a cathode-ray tube having an internal magnetic shield with at least one contact spring attached thereto.
BACKGROUND OF THE INVENTION
A color cathode-ray tube (CRT) typically has an internal magnetic shield located within a funnel thereof to reduce the influence of magnetic fields on electron beam trajectories. The shield is usually made of cold-rolled steel and fastened to a shadow mask frame. A flexible contact spring sometimes is attached to the shield or frame to make electrical contact with a conductive coating on the inner surface of the tube funnel. An early method of attaching a contact spring was by welding.
However, the welding method often resulted in undesirable loose particles in the tube.
There have been several improvements suggested to overcome the problem associated with welding contact springs to either a frame or an internal magnetic shield. For example, U.S. Pat. No. 4,310,779, issued to Penird et al., on Jan. 12, 1982, and U.S. Pat. No. 4,433,267, issued to Kuryla et al., on Feb. 21, 1984, disclose contact springs that include a wrap-around clip that snaps onto a flute formed at the rear end of a magnetic shield. U.S. Pat. No. 5,126,624, issued to Ji, on Jun. 30, 1992, discloses a contact spring that includes a triangular type head that fits within a hole in a shadow mask frame. U.S. Pat. No. 4,670,686, issued to Muenkel et al., on Jun. 2, 1987, discloses a spring with a leaf tab and stiffening structure that is inserted through two opposed slots in an internal magnetic shield. Each of the foregoing contact springs includes one or more disadvantages. The simpler ones may work loose or move around too much, and the more complex ones are costly to manufacture. Therefore, there is a need for a contact spring with a simple design, which will be easy to insert and will not move around.
An improved contact spring is disclosed in U.S. patent application Ser. No. 09/149,320, filed on Sep. 8, 1998, by A. W. Bucher now allowed. The Bucher application claims a contact spring that includes a clasp with a hook and latch that can be snapped onto a land of and internal shield. It has been found that there are conditions that may even cause the contact spring of Bucher to disengage from an internal shield. The present invention provides an improvement in the type of contact spring shown in the Bucher application that prevents such disengagement.
SUMMARY OF THE INVENTION
A cathode-ray tube has an internal magnetic shield and at least one contact spring attached to the shield. The shield includes a land with an outer edge and an inner edge. The spring includes two portions, an improved clasp portion attached to the shield at the land, and a contact leaf portion. The improved clasp portion includes a flat body with a reverse bend hook at a first end, and a latch and a catch at an end opposite to the first end. The hook engages the outer edge of the land, and the latch engages the inner edge of the land. The catch includes a bent end portion that forms an acute angle with the remainder of the catch. The bent end portion is positioned to engage the inner edge of the land if the spring is rotated about the hook. The leaf portion is connected to and extends from the latch.
REFERENCES:
patent: 4310779 (1982-01-01), Penird et al.
patent: 4433267 (1984-02-01), Kuryla et al.
patent: 4670686 (1987-06-01), Muenkel et al.
patent: 5126624 (1992-06-01), Ji
patent: 5561341 (1996-10-01), Won
patent: 6037709 (2000-03-01), Nagakawa et al.
Irlbeck Dennis H.
Patel Ashok
Tripoli Joseph S.
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