KR20010092695A - Cathode ray tube having a frame/mask assembly - Google Patents

Abstract

PURPOSE: A cathode ray tube is provided to obtain a low cost and low weight frame/mask assembly and use a mask manufactured by low thermal expansion coefficient material. CONSTITUTION: A cathode ray tube comprises a color selecting mask(2), that is manufactured by a lower thermal expansion coefficient material, and supported as extended by a frame. The frame is manufactured by a higher thermal expansion coefficient material. Two metal insert formed by material having similar thermal expansion coefficient as the mask(2) are arranged along two sides(4) of the frame. The inserts are fixed at a center part(7) for the opposite side of the frame. The mask(2) is welded to the inserts. During high temperature manufacture process for the cathode ray tube, mechanical problem due to difference between material of the mask(2) and the frame is avoided.

Description

Cathode ray tube with frame / mask assembly {CATHODE RAY TUBE HAVING A FRAME / MASK ASSEMBLY}

The present invention relates to a frame / color selection mask system disposed inside a glass envelope of a color cathode ray tube, more particularly the cathode ray tube. The present invention seeks its use in certain types of cathode ray tubes with color selection masks, in particular the invention applies to cathode ray tubes in which the mask is kept in tension by a frame to which it is fixed.

Conventional cathode ray tubes have a color selection mask disposed at an exact distance from the inside of the glass faceplate on which an array of red, green and blue light emitters is attached. Under the influence of three electron beams, each corresponding to a particular primary color, the array of light emitters causes the image to be reproduced on the screen, and the mask allows each particular beam to illuminate only light emitters of the corresponding color.

The color selection mask must be placed in the correct position within the cathode ray tube and maintained in that position during operation of the cathode ray tube. This holding function is performed by a generally very rigid rectangular metal frame in which the mask is typically welded. The frame / mask assembly is mounted to the faceplate of the cathode ray tube by elastic suspending means having at least three metal portions welded to the frame, the metal portion being coupled to one of a spring stud and a metal stud integral with the glass faceplate. It has an end formed. Suspension means in which two are arranged is commonly used at the center portion of the frame side or at the corner portion thereof.

In the cathode ray tube, the current trend is to make the faceplate more flat and to pursue a faceplate that is completely flat. Fabrication of cathode ray tubes with such faceplates requires the use of flat masks that remain in tension in at least one direction. Such a structure is described, for example, in US Pat. No. 4,827,179.

The color selection mask consists of a metal foil of very small thickness and is held in tension throughout the frame with very high mechanical strength to maintain the tension of the mask during operation of the cathode ray tube.

Since the mask blocks more than half of the electrons emitted by the electron gun of the cathode ray tube during operation of the cathode ray tube, the temperature of the mask increases rapidly, causing expansion at least in a predetermined area of the mask, and as a result, the tension and flatness of the mask Decrease occurs. As such, the image reproduced on the screen decolorizes because the mask is no longer flat and the point of impact of the three electron beams against the screen of the cathode ray tube no longer corresponds to the specific hoc lines of the luminescent material. Done.

As a first solution to solve this problem, a mask made of a material having a very low coefficient of thermal expansion, for example, Invar having a coefficient of thermal expansion of approximately 1.25 10 ⁻⁶ / ° C., is used. In this case, the mask expands very little during operation of the cathode ray tube, so that its flatness can be guaranteed. Thus, without fear of sagging during operation of the cathode ray tube, it is possible to ensure flatness using a relatively low tension of the mask, for example about 5 kg / mm ² , whereby the metal support frame is associated with the low tension applied. Mechanical strength.

A second solution is to use a standard steel mask with a coefficient of thermal expansion as high as about 1.5 10 ⁻⁵ / ° C., which is kept flat with as much tension as possible up to ten times the tension applied to the Invar mask. This requires the use of a holding frame with significant mechanical strength, which is obtained by using a large amount of material. Thus, this solution shows the disadvantage of high cost and high weight of the material.

However, the solution using a mask made of a material having a low coefficient of thermal expansion also has a number of disadvantages.

If the frame is not made of a material with a similar coefficient of thermal expansion as the mask, then the tensile mask cannot be welded directly to the frame which holds the mask in tension, in particular not made of standard steel. This is because, during the cathode ray tube manufacturing process step, the frame / mask assembly is raised to a temperature above 400 ° C., at this temperature, local damage to the welding occurs due to the expansion difference of the materials where the mask is welded to the frame, Any deformation occurs locally to the tension of the mask and these deformations cause defects in the color of the image reproduced on the screen of the cathode ray tube.

Thus, this solution requires the use of masks and frames made of similar and small thermal expansion coefficients, eg Invar. However, this type of material is about three times more expensive than standard steel, which significantly increases the price of the frame, and thus the cost of the cathode ray tube fabricated.

There is a need for the use of masks made of materials with low coefficients of thermal expansion with respect to frames made of conventional steel so that low cost and low weight frame / mask assemblies can be obtained.

1 is an isometric view of a frame / mask assembly according to the state of the art.

2 is a quarter cross-sectional perspective view of a frame / mask assembly in accordance with one embodiment of the present invention.

3 shows a metal insert acting as an interface between the frame and the mask.

4 through 6 are cross sectional views through frame / mask assemblies illustrating various embodiments of the present invention.

<Description of Symbols for Major Parts of Drawings>

1: frame 2: mask

4: side 5: suspension

10: Insert

15, 24: horizontal flange 14, 25: vertical flange

To this end, the frame / mask assembly according to the invention comprises a color selection mask and an almost rectangular metal frame which supports the mask and holds the mask in tension in at least one direction, the mask having a coefficient of thermal expansion of the frame. It is made of a material smaller than the coefficient of thermal expansion of the material constituting the part. Two metal inserts extend along two or more opposite sides of the frame and are secured to the opposite side, the metal insert being made of a material whose coefficient of thermal expansion is similar to that of the mask, the mask being, for example, 2 It is fixed to the frame by welding two metal inserts.

The invention will be better understood with reference to the following description and drawings.

1 shows a frame / mask assembly according to the state of the art as described in patent GB 2308223. The directions of X, Y, and Z represent the horizontal axis and the vertical axis and the major axis of the cathode ray tube perpendicular to the surface of the display screen, respectively. The rectangular frame 1 as a whole consists of two horizontal long sides and two vertical short sides. The frame 1 holds the color selection mask 2 in a tensioned state along at least one direction parallel to its short side. The suspension 5 cooperates with the metal studs that are inserted into the skirt of the faceplate of the cathode ray tube so that the frame / mask assembly can be kept at an exact distance from the screen of the cathode ray tube.

The welding quality of the mask 2 along the edge of the frame side 4 is such that the tension of the mask is high, e.g. the tension is high at the center 7 of the long side and at the end 8 of the side 4; This is to ensure that it stays at its predetermined low value. The change in tension along the side 4 depends on the size of the frame and the geometry of the frame. For example, in the case of a 16/9 type cathode ray tube, the mask is considerably larger in length than the length of the vertical Y axis in terms of the horizontal X axis length, so that the center of the tension at the end 8 is greater than the mask of the 4/3 type cathode ray tube. The tension is maintained so that the ratio of tension in the) is large, which is to ensure that the surface of the mask is kept at a slight distance from the screen of the cathode ray tube without showing a tendency to settle in its center 7.

In order to avoid the problems associated with the thermal expansion of the mask during the manufacturing process step of the cathode ray tube and during normal operation of the cathode ray tube, manufacturers tend to use materials having a low coefficient of thermal expansion when manufacturing the mask. Invar, which consists of a steel-nickel alloy containing about 36% nickel, is the most widely used material in this field.

Moreover, the fact that so far uses a mask made of a material such as Invar also means that the constituent material of the frame needs to be a material having a low coefficient of thermal expansion. This is because it is very difficult to weld the Invar mask to a frame made of standard steel, and if the thermal expansion between the two materials is very different, the welding strength is impaired during the manufacturing step performed at 400 ° C. or higher, and eventually some may be broken. However, using a frame to avoid the disadvantages described earlier has the greatest disadvantage that the value is very expensive.

Figure 2 illustrates an embodiment of the present invention that does not exhibit this drawback.

In Figure 2, a quarter of the frame / mask assembly is shown in perspective and cross-sectional views. The short side 3 of the frame has an L-shaped cross section in which the vertical flange 25 extends toward the screen of the cathode ray tube and the horizontal flange 24 extends in a plane substantially parallel to the screen. Similarly, the long side 4 also has a horizontal flange 15 extending toward the screen of the cathode ray tube and a vertical flange 14 extending in a plane substantially parallel to the screen of the cathode ray tube. The frame is made of conventional steel. The mask 2 made of a material whose coefficient of thermal expansion is lower than the coefficient of thermal expansion of the frame is pulled in at least one direction, for example in the Y axis. The long side 4 of the frame shows a horizontal flange 15 having a horizontal edge 13 wider toward the inside of the frame and having a substantially rectangular shape. 3 and 4, for example, a concave cross section, in this case a substantially U-shaped metal insert 10, covers the part widened toward the inside of the frame of each edge 13 of the two flanges 15. The insert is fixed to the center 7 of each opposing side 4 by welding, or by riveting or bolting, the basic feature being that the length of the area joined to the side of the frame is dependent on the length of the side 4. It is small compared. At this time, the end 18 of the insert extending around the joining area is independent of the displacement, but this displacement is limited to the XY plane in this embodiment, and the opposing face of the edge 13 of the side 4 of this frame Due to the complementary shape of the insert 10, the edge 13 acts as a guide for the displacement of the insert. The insert is made of a material having a low coefficient of thermal expansion, preferably made of the same material as the material of the mask. The mask 2 is welded in tension to the outer edge 12 of the insert 10 along the vertical Y axis. The tension of the mask tends to displace each end 18 of one insert in the XY plane according to the equilibrium position depending on the mechanical bending resistance of the insert and the initial tension of the mask. During the various stages of cathode ray tube fabrication, the frame / mask assembly is elevated to high temperature, where the insert and mask are expanded in the same way because the insert and mask are made of a material that exhibits similar thermal reactions. Moreover, the insert 10 is independent of expansion on both sides of the joining region 7 irrespective of the side 4 of the frame, and this joining region must extend over a length smaller than the length of the side 4. It is preferred to extend over the length not exceeding 25% of the side 4 length. In this way, the expansion of the frame and the mask takes place independently of one another. In addition, the structure of the invention shown in FIGS. 2 and 3 and the cross section through a plane perpendicular to the surface of the mask in FIG. 4 show several advantages as follows.

-Apply the same force along the entire end of the mask to tension the mask and release the force applied to the mask after welding the horizontal end 6 of the mask to the insert. As described above, the ends of the inserts are bent to reach an equilibrium position where the tension of the mask is at its center near the joining region 7 and at a minimum near the vertical free end 16. If the distribution of tensile values along the weld edge is precomputed, the structure of the present invention makes it possible to have a manufacturing process that can be performed simply because the tension applied on the mask is constant along the entire weld edge.

Since the U-shaped cross section of the insert cooperates with the cross section facing the edge 13, it acts as a guide roll in the XY plane and due to the tension exerted on the end 18 of the insert by the mask, this end faces the surface of the mask. Rotation can be prevented through the deforming lever effect.

Thus, such a structure can be effectively used for a frame and mask structure in which the frame and the mask are made of the same material or a material having similar values of the coefficient of thermal expansion.

5 shows another embodiment in which the position of the insert 10 is different. The insert 10 also shows a concave interior surface, preferably having a U-shaped cross section. The insert is disposed on the edge 51 of the flange 15 such that its concave inner surface surrounds a portion of the edge facing the screen of the cathode ray tube. As in the previous embodiment, the insert 10 is secured to the flange 15 over an area of small length on both sides of the central portion 7 of the flange. The mask is welded to the insert in tension along its opposite end 6. In this manner, thermal expansion of the mask may occur regardless of thermal expansion of the frame.

In another embodiment of the invention shown in FIG. 6, the insert comprises a cross section 19 of a solid body and is disposed on the outer side of the flange 15 to protrude above the edge 51 of the flange 15. have. The insert 10 is fixed to the flange 15 at the center 7 and the pretensioned mask is welded to the part of the insert which projects above the edge 51. This embodiment has the advantage of being economical to implement a simple form of the profile of these parts so that the cost of flanges and inserts can be reduced.

The present invention is not limited to the described embodiments, for example, in the case where the mask is pulled in two directions, horizontal and vertical, an insert of the type described previously is applied to the horizontal side 4 of the frame between the flange and the mask of the frame. ) And the flange of the vertical side 3 may be disposed.

According to the present invention, it is possible to use a mask made of a material having a low coefficient of thermal expansion with respect to a frame made of conventional steel so that a low cost and low weight frame and mask assembly can be obtained.

Claims (10)

A color selection mask 2 and a substantially rectangular metal frame 1 supporting the mask and holding the mask in tension in at least one direction, the mask having thermal expansion of a material whose coefficient of thermal expansion constitutes a major part of the frame; In a cathode ray tube made of a material smaller than the coefficient, Two metal inserts extend along two or more opposite sides of the frame and are secured to the opposite side, the metal insert being made of a material whose coefficient of thermal expansion is similar to that of the mask, the mask being, for example, 2 A cathode ray tube, which is fixed to a frame by welding two metal inserts. 2. The two metal inserts (10) according to claim 1, characterized in that they are fixed to the opposite side (4) of the frame (1) in a limited area (7) of small length compared to the length of the opposite side (4). Cathode ray tube. The cathode ray tube according to claim 2, wherein the insert (10) is fixed to the opposite side at the central portion (7) of the opposite side (4) of the frame (1). The cathode ray tube according to any one of the preceding claims, characterized in that the frame (1) is made of steel and the insert (10) is made of invar. The cathode ray tube according to any one of the preceding claims, characterized in that the cross section of the insert (10) represents a concave inner surface. 6. A cathode ray tube according to claim 5, characterized in that the concave inner surface covers a part of the opposing side (4) of the frame (1). 7. Cathode ray tube according to claim 6, characterized in that the insert (10) is arranged on the inner surface of the two opposing sides (4) of the frame (1). 7. Cathode ray tube according to claim 6, characterized in that the insert (10) at least partially covers the edges of the two opposing sides (4) of the frame (1). 6. The cathode ray tube according to claim 1, wherein the insert is arranged on the outer surface of the opposite side of the frame. 4. The frame (1) according to any one of the preceding claims, wherein the mask (2) is welded to, for example, four metal inserts (10) fixed to each of the four sides (3,4) of the frame. Cathode ray tube, characterized in that fixed to.