Thermal deformation member for electron tube and color picture t

Details Thermal deformation member for electron tube and color picture t Thermal deformation member for electron tube and color picture t

1998-02-19

2000-05-30

Patel, Nimeshkumar D.

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

313404, 313402, 313405, H01J 2980

Patent

active

060694378

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a thermal deformation member for an electron tube such as a color picture tube and the like and a color picture tube using thereof, and a thermal deformation member for an electric current control such as an overcurrent protection and the like and an overcurrent protection using thereof.


BACKGROUND ART

In a color picture tube using a shadow mask, the shadow mask, which has lots of fine holes transmitting an electron beam, is disposed in an opposite relation with respect to a phosphor layer formed inside a panel with a predetermined spacing. Surrounding an outer periphery of the shadow mask, a mask frame is fixed. A frame holder is disposed between the mask frame and the panel.
The electron beam that passes through the fine holes of the shadow mask is usually only about 20% of the total electron beam emitted from an electron gun. The remaining about 80% of the electron beam is absorbed by colliding with the shadow mask and the mask frame. When the shadow mask or the mask frame is thermally expanded by collision of the electron beam, the fine holes of the shadow mask and the dots formed in the phosphor layer are shifted in their relative positions to result in degradation of color purity.
Therefore, the shadow mask is generally formed of a low thermal expansion alloy such as an Fe--Ni based alloy and the like. Besides, the mask frame is conventionally formed of a generally used Fe based material from the view point of strength and the like. Therefore, in order to absorb thermal expansion of the mask frame, a spring material which is capable of deforming elastically is employed for a part of the frame holder.
In such a construction, since there is difference in the thermal expansions of the shadow mask and the mask frame when the electron beam is collided, absorption of the thermal expansion solely by the spring material is not enough to result in degradation of the color purity. Thus, a thermal deformation material which deforms in an opposite direction relative to the direction of thermal expansion of the mask frame is used for a part of the frame holder, aside from the spring material. For the thermal deformation member forming a part of such a frame holder, a so-called bimetal obtained by laminating a high thermal expansion member such as an Fe--Ni--Cr based alloy and a low thermal expansion member such as an Fe--Ni based alloy is conventionally used.
In addition, for over current protection, for example, use as a molded-case circuit-breaker and the like, a thermal deformation member is used to break overcurrent by opening a contact point. In the overcurrent protection, the thermal deformation member deforms due to its own Jule heat when the overcurrent flows. Otherwise, the overcurrent flows a resistor (heater) to induce a thermal deformation due to heating of the resistor. A circuit is broken due to deformation of the thermal deformation member. For the thermal deformation member for the over current protection, a 2-layered laminate material obtained by laminating a high thermal expansion member such as an Fe--Ni--Cr based alloy or an Fe--Ni--Mn based alloy and a low thermal expansion member such as an Fe--Ni based alloy, or an Fe--Ni--Co based alloy , or a 3 layered laminate material obtained by interposing Ni or a Cu--Zr alloy and the like as an intermedium is used.
In a bimetal using a high thermal expansion member such as an Fe--Ni--(Cr, Mn) based alloy and a low thermal expansion member such as an Fe--Ni based alloy, according to a required thermal deformation rate, a ratio between plate thicknesses of the high thermal expansion member and the low thermal expansion member is determined. Further, a total thickness of the laminate plate for securing material strength and long term reliability is determined. For example, for a bimetal for a color picture tube and the like, to make possible to secure the material strength and the long term reliability, a total plate thickness of 0.7 mm or more is required.
However, in the conventional bimetal, since

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