CN1488158A - Plastic tensioned mask assembly - Google Patents

Abstract

A color picture tube has a compliant tension mask frame assembly mounted within said tube. The tension mask frame assembly includes a peripheral frame including opposing side support frame members is attached to the peripheral frame at a single location and the mask is attached to longitudinal edges of the intermediate members. Further included are clips that serve as guides for holding the intermediate members. Further included are clips that serve as guides for holding the intermediate members to the frame while permitting expansion of the frame relative to the intermediate members and permitting compliance.

Description

Plastic tensioned mask assembly

technical field

This invention relates to a color picture tube having a tensioned shadow mask, and more particularly to a tensioned shadow mask assembly having means for connecting the tensioned shadow mask to a support frame for improved moldability.

Background technique

A color picture tube includes an electron gun for generating and aiming three electron beams at the phosphor screen of the picture tube. The phosphor screen is located on the inner surface of the kinescope faceplate and is made of an array of phosphor elements that emit three different colors. A color selection electrode, which may be a shadow mask or a focusing mask, is interposed between the electron gun and the phosphor screen to allow each electron beam to strike only the phosphor elements associated with that electron beam. The shadow mask is a thin sheet of metal, such as steel, and is typically configured parallel to the inner surface of the kinescope faceplate.

One form of color picture tube has a tensioned shadow mask to which two parallel support frame members are attached under tension and mounted within the faceplate screen of the picture tube. This tension contributes to vibration control or microphonic control of the shadow mask during tube operation. In the manufacture of a CRT (cathode ray tube), a shadow mask and a frame pass through a furnace and are heated to a high temperature, thereby causing expansion of the frame and the shadow mask. During this heating cycle, the mask and frame material weakens and deforms beyond its plastic limit. When the mask and frame are subsequently cooled, the tension on the mask decreases in approximately the ratio of the total plastic deformation to the original plasticity. Traditional frame designs have high central plasticity but low edge plasticity. This low edge plasticity provides little margin for tension control at the edge of the mask. The plastic form of the conventional frame results in deformation of the mask which can wrinkle the mask. In order to maintain tension on the mask in a conventional tensioned mask frame, the mask must be attached to a relatively heavy support frame. It has been suggested that lighter frames could be used in tensioned mask tubes if the required tension on the mask was reduced. One way to reduce the required tension on the mask is to use a material with a low coefficient of thermal expansion for the mask. However, shadow masks made of this material require a support frame of material having a similar coefficient of thermal expansion to prevent thermal expansion mismatches during the thermal processing required for kinescope manufacture. Because metallic materials with low coefficients of thermal expansion are relatively expensive, it is relatively costly to manufacture shadow masks and frames from the same or similar low coefficients of expansion materials. It is therefore desirable to use a combination of a tensioned mask with a low coefficient of expansion and a support frame with a higher coefficient of expansion, and to provide the benefits that exist when there is a significant thermal expansion mismatch between the tensioned mask and its support frame. The solution to the problem. It would also be desirable to provide a method of modifying the plastic form of the mask frame to control the tension lost on the mask through heat treatment and to prevent wrinkling of the mask.

Contents of the invention

SUMMARY OF THE INVENTION The present invention provides an improvement in color picture tubes having a plastic tensioned mask frame assembly mounted within the picture tube. A tensioned mask frame assembly includes an edge frame having opposed edge support frame members and a pair of parallel intermediate pieces. Each middle piece is connected to a side member at a single location between the ends of the middle piece. The shadow mask is held in tension by an intermediate piece which provides means for achieving higher edge plasticity relative to plasticity in the center of the frame. Such a plastic form makes it possible to avoid wrinkling without losing an unacceptable amount of tension.

The present invention further provides devices using materials with different coefficients of thermal expansion. In this case, the material of the middle piece may be similar to that of the shadow mask having a first coefficient of thermal expansion, and the edge frame may be made of a material having a second coefficient of thermal expansion. For example, the tensioner mask and intermediate piece may be made of Invar or a similar material having a lower coefficient of thermal expansion relative to the coefficient of thermal expansion of the material used to form the edge frame. In another embodiment, said edge frame comprises clamping members acting as guides to hold the intermediate piece on the frame while allowing expansion of said frame relative to the intermediate piece and preventing any undesired deformation of the intermediate piece.

Description of drawings

in:

Fig. 1 is a partial side view on an axial section of a color picture tube implementing the present invention;

Figure 2 is a perspective view of a tensioned shadow mask assembly;

Fig. 3 is a top view of the mask frame assembly with the tensioned mask removed to clearly illustrate the plasticity of the intermediate member;

Figure 4 is a graph showing the illustrative plastic distribution according to the present invention;

Fig. 5 is a top view of another embodiment of the present invention;

Fig. 6 represents the embodiment figure along 1-1 line among Fig. 5;

Fig. 7 represents the embodiment figure along 2-2 line among Fig. 5;

Detailed ways

FIG. 1 shows a color picture tube 10 having a glass envelope 11 comprising a rectangular panel screen 12 and a tubular neck 14 connected by a cone 15 . Cone 15 has an inner conductive coating (not shown) extending from anode button 16 to screen 12 and tubular neck 14 . Screen 12 includes a substantially cylindrical face plate 18 and peripheral flanges or side walls 20 and is sealed to cone 15 by glass frit 17 . A three-color phosphor screen 22 is carried by the inner surface of the panel 18 . The phosphor screen 22 is a line screen in which phosphor lines are arranged in three-dot phosphor groups, and each three-dot phosphor group includes phosphor lines of each of three colors. The tensioned mask frame assembly 24 is removably mounted in a predetermined spaced relation to the phosphor screen 22 . An electron gun 26, shown schematically in dashed lines in FIG. 1, is mounted inside the center of the neck 14 to generate and pass a train of three electron beams, a central beam and two side or outer beams, along the tensioned shadow mask. The converging paths of frame assembly 24 are aligned with phosphor screen 22 .

Picture tube 10 is designed for use with an external magnetic deflection coil such as coil 30 shown near the cone-neck junction. When energized, the coil 30 subjects the three electron beams to a magnetic field which causes the beams to scan horizontally and vertically in a rectangular raster extending across the phosphor screen 22 .

As shown in FIG. 2, the tensioned mask frame assembly 24 includes an edge frame 28 comprising two opposing long side support frame members 32 and 34 and two opposing short side support frame members 36 and 38. The two long sides of the frame support frame members 32 and 34 parallel to the central long axis X of the picture tube; the two short sides 36 and 38 are parallel to the central short axis Y of the picture tube. The tensioned mask frame assembly 24 further includes a perforated mask plate 27 and a pair of opposing intermediate members 40 . The intermediate member 40 varies in height longitudinally from the center of each segment to the ends of each segment to obtain optimum curvature and tension plasticity across the entire mask.

Each intermediate piece 40 extends the length of the long side support frame members 32 and 34 . The middle piece 40 is welded to the edge frame 28 only at a single location 50 where the long sides support the frame members 32 and 34 . The tensioned shadow mask 27 is welded along the longitudinal upper end edges of the two parallel intermediate pieces 40 . The intermediate member 40 may be made of a material having a coefficient of thermal expansion similar to that of the shadow mask 27 . Temperature variations therefore have little effect on the position of the shadow mask 27 relative to the intermediate member 40 .

FIG. 3 is an illustration showing the plastic deformation of an intermediate member 40 supporting a tensioned shadow mask (not shown) by dotted lines. The connection point shown at central location 50 (as 501) is at the location where the long side support frame members 32 and 34 deform under the tension load of the shadow mask (not shown).

Fig. 4 is a plasticity graph showing the relationship between the plastic form of the conventional mask frame assembly and the plasticity associated with the new mask frame assembly of the present invention. More specifically, the graph shown in FIG. 4 illustrates the plastic behavior of the intermediate member 40 of the present invention at ends 52 and 54 (shown in FIG. 2 ). The connection of the middle piece 40 at only one point allows the deflection of the ends 52 and 54 independently of the outer edges of the edge frame 28 . In particular, the intermediate member 40 provides enhanced plasticity at the edge of the tensioned mask since the ends of the intermediate member 40 are not connected to the edge frame 28 .

In yet another embodiment shown in FIGS. 5-7, the intermediate member 40 has a generally T-shaped cross-section, and the two ends 52 and 54 are held by two clamping members 56 and 58, respectively, which also There is an upwardly open slot 60 and a longitudinally extending notch 62 . The intermediate member 40 includes guide members 64 and 66 provided in the above-mentioned groove portion 60 and notch 62 . The T-shaped intermediate member is longitudinally spaced relative to the clamping members 56 and 58 to define internal cavities 68 and 70 in which the inner guide members 64 and 66 of the intermediate member 40 are vertically slidably supported , so as to act as a guide for holding the middle piece 40, so that when the middle piece 40 moves longitudinally, it prevents the rotation relative to the edge frame 28 near the end caused by the expansion of the middle piece 40 during the operation of the kinescope. Clamping members 56 and 58 may be formed by cutouts extending from edge 28 or may be separate pieces secured to the frame.

An advantage of the present invention is that the tensioned mask frame assembly provides plasticity at the edge of the mask. This enhanced edge plasticity and improved plasticity distribution allows the frame to reliably control tension and prevent wrinkling in the shadow mask, thus improving efficiency in the manufacturing process. Furthermore, the present invention provides for the use of materials with significantly different coefficients of thermal expansion for the mask and frame.

There are many other possible embodiments within the scope and spirit of the invention. For example, although the long side and short side support frame members are shown as hollow square tubes, other preferred configurations such as having L-shaped, C-shaped or rectangular cross-sections are possible for these parts. It is therefore intended that the foregoing description be regarded as illustrative rather than restrictive, the scope of the invention being given by the appended claims along with their full scope of equivalents.

Claims (5)

1, a kind of color picture tube with plasticity tension type mask frame assembly, this assembly is installed in the described picture tube, and it comprises:

Edge frame with middleware of relative limit scaffold parts and pair of parallel, the single position of each middleware between the end of this middleware links to each other with this framework; With

Be connected to the shadow mask on this middleware, this shadow mask is maintained between this middleware under tensioning state thus.

2, color picture tube as claimed in claim 1 is characterized in that, this edge frame also comprises the minor face scaffold parts that two relative long leg spares are relative with two, and wherein above-mentioned middleware is connected in two relative limit parts at least one.

3, color picture tube as claimed in claim 1 is characterized in that, it also comprises near the clamping element that is positioned at the above-mentioned middleware end.

4, color picture tube as claimed in claim 1 is characterized in that, above-mentioned shadow mask and above-mentioned middleware are made by the material with first thermal coefficient of expansion, and above-mentioned edge frame is made by the material with second thermal coefficient of expansion.

5, color picture tube as claimed in claim 4 is characterized in that, above-mentioned first thermal coefficient of expansion is lower than above-mentioned second thermal coefficient of expansion relatively.

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