KR19990037516A - Evaporative getter device using current transformer - Google Patents

Abstract

The evaporative getter device is arranged on top of the free surface of the ring-shaped container 6 and the getter G which contains the evaporative getter material G, and along the small base 7a of the evaporative getter device G to the container 6. A centrally coupled truncated conical current transformer (7). The current transformer 7 has an edge 7b along its upper edge, which edge is parallel to the axis of the device and combines with an activated magnetic field to produce a local heating which prevents the condensation of barium vapor. In addition, the small base 7a of the current transformer 7 has a diameter smaller than the inner diameter of the sheet of ring evaporative getter material G.

Description

Evaporative getter device using current transformer

The present invention relates to a getter device, and more particularly to an evaporative getter device provided with an improved deflector.

Getter materials are known to be used in all applications where vacuum maintenance is required for a long time. In particular, Cathode-Ray Tubes (CRTs) used in TV-sets and monitors tend to solidify gas traces that may remain in the CRT after venting and sealing, or result in venting of constituent materials. Getter material.

The getter material used in this application is almost generally metallic barium deposited in the form of a thin layer on the inner wall of the CRT. For this purpose,

A device consisting of an open top metal container, known in the art such as an evaporative getter, is used, in which there are barium and aluminum compounds (BaAl ₄ ) and nickel powder (Ni).

Once the CRT is evacuated and sealed, the device arranged therein is induction heated by a coil arranged in a position corresponding to the position where the device outside the tube is located. Magnetic induction causes the metal container to heat up to the packing powder contained within the container. When the temperature of the powder reaches a value of about 800 ° C., a violent exothermic reaction raises the powder temperature to about 1200 ° C., at which temperature causes evaporation of barium deposited on the CRT wall to form a metal thin film. .

However, it is desirable to prevent barium from depositing on the mask and from depositing the phosphor on the screen inner surface. In practice, this causes a reduction in screen brightness because electrons must pass through the barium thin film before they hit phosphorus. As the thickness of the thin film increases, the electron decreases.

In order for the barium evaporation to be directed towards the conical surface of the tube, known devices are provided with a current collector arranged above the free surface of the getter. This current transformer consists of an inclined metal surface arranged on top of the getter material container and spaced far from it to allow discharge of the barium vapor. Various embodiments of this type of device are disclosed in the applicant's patent US 3719433.

The main problem with this known device is that some of the evaporated barium condenses on the current transformer during the evaporation of barium. In particular, barium accumulation on the top of the current transformer occurs at its upper edge and appears to a minimum at the junction region between the current transformer and the jitter vessel. The practical effect is that the formation of such barium deposition over a large area often causes two kinds of disadvantages.

The first obvious disadvantage is the reduction in the amount of barium deposited substantially on the tube wall. This reduces the effect of the overall gettering action produced by the device.

A second disadvantage to be considered is that separation of debris from barium deposition is possible during subsequent working steps or even during CRT use. In practice, it occurs that the barium grains away from the current transformer finish on top of the inner mask of the electron gun and / or screen. In the first case they cause an arc or short circuit, while in the second case they interfere with the excitation of the phosphor they are covering, resulting in a dark area on the screen. In both cases, the full functionality of the CRT is clearly compromised.

It is an object of the present invention to provide an apparatus which overcomes the above mentioned disadvantages.

1 schematically shows a possible position for mounting the device inside the CRT.

2 shows a plan view of a first embodiment of the apparatus.

3 shows an enlarged cross-sectional view along the T-T line of FIG. 2.

4 shows a schematic perspective view of a second embodiment of the device.

* Description of the symbols for the main parts of the drawings *

2: electron gun 4: positive button

6: mask 7: current transformer

G: getter

The object is to have a cylindrical edge parallel to the axis of the device at least 0.8 mm high.

Achieved by an evaporative getter device comprising a current transformer provided along its upper edge. Further useful features for the improved device of the invention are described in the dependent claims.

The main advantage of the getter device according to the invention is to prevent the deposition of barium vapor along the upper edge of the current transformer. This is achieved due to the effective coupling between the magnetic field activating the device and the axial edge of the current transformer. Such coupling causes significant heating to the current transformer edge, thus preventing the condensation of barium vapor. This lack of deposition eliminates the risk of malfunctions described above.

The above and other advantages and features of the device according to the present invention will become apparent to those skilled in the art from the following detailed description of two embodiments of the present invention, with reference to the accompanying drawings.

The schematic diagram of FIG. 1 shows three mountable positions of the device within a CRT. A commonly used position is the "antenna" position A in which the device 1 is mounted on the electron gun 2 via the shaft. Otherwise the free end of the shaft can be fixed to the positive button 4 (position B) or the inner mask 6 (position C).

Referring to FIGS. 2 and 3, it is shown that the apparatus 1 comprises a vessel 6 for the current transformer 7 and the evaporative getter material G arranged on the free surface of the getter G.

The container 6 is ring-shaped and is cast from a circular sheet, preferably made of AISI 304 steel, to obtain the outer wall 6a, the bottom wall 6b and the central rise. The central rise forms a central plane 6d which is used for joining the inner part 6c to the seat of the getter G and the current transformer 7.

The current transformer 7 is truncated conical with a small base 7a in contact with the plane 6d of the vessel and having a diameter smaller than that plane. The large base is open and has a cylindrical edge 7b along the edge. The conical lateral surface 7c is flat but curved to have a slightly convex shape towards the container 6. In this case, the bending radius of the surface 7c should be at least 1.5 times the radius of the current transformer 7, preferably 2 to 5 times the radius value. The figure shows a current transformer having a larger diameter than the vessel 6 but the ratio between the diameter of the large base of the current transformer and the diameter of the vessel ranges from about 0.8 to 1.2. A ratio of 0.8 or less results in a current transformer surface that cannot effectively prevent the deposition of barium vapor on the screen, while the increased area does not gain improvement in its function and increases weight and volume. The edge 7b is at least 0.8 mm high; It can be seen that the low height of the cylindrical edge cannot form an effective coupling with the magnetic field, so that heating of the current transformer truncated conical surface will not be sufficient to prevent barium condensation problems. Instead the maximum height of the edge is limited by practical reasons; For example, an excessive height of 3 mm or more does not achieve a functional improvement and only increases the weight of the structure, preferably the height of the edge 7b is in the range of about 1 to 2.5 mm.

As mentioned above, the edge 7b substantially parallel to the device side allows for strong heating of the upper edge of the conical surface 7c of the current transformer 7, in which a considerable barium deposition in a device of the type known in the current transformer is known. Is formed. In addition, the fact that the small base 7a has a smaller diameter than the central plane 6d in which the small base is located allows to remove the second area for barium deposition as well. In fact, the corner between the base 7a of the current transformer and the joining plane 6d lies in the "shaded area" of the center of the device, where barium vapor is not passed because it is deflected outwardly by the surface 7c.

The effectiveness of the above described solution is evident in the comparative tests performed by the applicant for the prior art device and the device provided with the improved current transformer of the present invention. In this test, barium deposition is formed in more than half of the above case when using the conventional apparatus, while no formation for such deposition occurs when using the apparatus according to the present invention.

Finally, FIG. 4 shows a second embodiment different from the previous one in the presence of the screen 8, which partially closed the discharge space of the barium vapor. An advantage to this partial closure is that it limits or prevents barium deposition in the region of the electron gun 2 that generates a pseudo current that interferes with the correct operation of the CRT. The device thus uses a screen 8 facing the gun 2 inside the CRT, i.e. a screen 8 close to the support shaft 3 in the case of antenna mounting A or in two other cases (position B And on the side facing C).

The screen 8 can be provided by cutting, pressing and bending a single metal sheet, integrating with a large diameter part between the vessel 6 and the current transformer 7. (This last case is shown in FIG. 4. Otherwise, the screen 8 may be a detachable member welded to the current transformer 7 and / or the vessel 6. Its large or small extension along the outer periphery of the device clearly depends on the desired extension of the shield of the gun 2.

In accordance with the present invention, the described and illustrated embodiments are capable of many variations. In particular, the area of the current transformer is variable within the above-mentioned range, and the connection between the current transformer 7 and the vessel 6 may be obtained using other methods. For example, a central hole may be provided with a suitably sized axial cylindrical edge provided in the base of the current transformer 7 which is provided in the plane 6d and inserted therein, which thus provides its small base 7a. Open and thus form a funnel.

According to the present invention, by forming an effective coupling between the magnetic field and the axial edge of the current transformer and the magnetic field activating the device, the coupling will cause significant heating to the current transformer edge to prevent condensation of barium vapor on the current transformer. Can be.

Claims (10)

Ring-shaped vessel 6 with an open top and containing evaporative getter material and a truncated current transformer arranged on the free surface of the getter G and centrally coupled to the vessel 6 along its small base 7a An evaporative getter device comprising (7), The current collector (7) is characterized in that it has an edge (7b) along its upper edge parallel to the axis of the device and having a height of about 0.8mm. 2. The getter device according to claim 1, wherein the height of the edge (7b) is in the range of 1 to 2.5 mm. 3. The getter device according to claim 1 or 2, characterized in that the small base (7a) of the current transformer (7) has a diameter smaller than the inner diameter of the ring-shaped sheet of evaporative getter material (G). 4. The getter device according to claim 1, wherein the ratio between the diameter of the large base of the current transformer and the outer diameter of the vessel is in the range 0.8 to 1.2. 5. The getter device according to claim 1, wherein the lateral surface (7c) of the current transformer (7) is flat. The lateral surface of the current transformer (7) is curved to have a convex shape facing the container (6), the convex shape of the current transformer (7). A getter device, characterized in that it has a bending radius that is at least 1.5 times the radius of the large base of. 7. The getter device according to claim 6, wherein the bending radius of the curved lateral surface (7c) is in the range of 2 to 5 times the radius value of the large base of the current transformer (7). The device according to any one of the preceding claims, further comprising a screen (8) integral with the vessel (6) and / or the current transformer (7) along its periphery and parallel to the axis of the device. Getter device, characterized in that. 9. The getter device according to claim 8, wherein the screen is provided integrally with a part having a large diameter between the vessel (6) and the current transformer by cutting, pressing and bending a single metal sheet. 9. The getter device according to claim 8, wherein the screen (8) is a detachable member welded to the device.