US3428168A - Getter construction - Google Patents

Description

Feb. 18, 1969 c. w. REASH 3,428,168

GETTER CONSTRUCTION Filed Feb. 2. 1967 Sheet 2 of 2 INVENTOR CLAIR W. REASH BY kw A ATTORNEY United States Patent 3,428,168 GETTER CONSTRUCTION Clair W. Reash, Fairview Park, Ohio, assignor to Union Carbide Corporation, a corporation of New York Filed Feb. 2, 1967, Ser. No. 613,539 US. Cl. 206-.4 12 Claims Int. Cl. H01j 19/70 ABSTRACT OF THE DISCLOSURE A wide channel ring getter having higher capacity of vaporizable getter material for use particularly in large color television picture tubes. A reinforcing means can be positioned in the channel to prevent cracking of the getter material during heating of the assembly flashing of the getter material.

Background 09 the invention This invention relates toan improved getter construction and more particularly to an improved channel ring getter for containing a higher capacity of getter material and for more effective flashing of such material.

The use of geter materials in the manufacture of electronic tubes is well known. A commonly used getter construction consists of a container, such as an annular U- shaped receptacle, with the getter material pressed into the container. This assembly is mounted in an electron tube, for example, a television picture tube. After the tube is evacuated, the residual gases left in the tube are removed by heating the getter container and material therein to a high temperature, suitably by induction heating, whereupon the getter material is flashed or vaporized. The vaporized getter material adsorbs or reacts with the residual gases and removes them as low vapor pressure solid condensates and continues to adsorb any further liberated gases throughout the life of the tube.

Usually the getter material principally comprises: a mixture or alloy of metals such as, for example, barium and aluminum. It is the barium component of this mixture which provides the reactive material. The clean up of residual gases in the larger sized television picture tubes, and particularly color tubes, requires a relatively large amount of active barium material. For example, color tubes having three electron guns and a metal shadow mask have been found to require a yield of 125 to 175 mg. of barium. Since the barium-aluminum powder mixture might have contained up to about 50% aluminum, the total amount of gettering powder mixture in the container before flashing could be from 250 to 350 mg. It has further been found desirable to employ exothermic gettering powders in color television picture tubes. An exothermic gettering powder can comprise: a bariumaluminum alloy or mixture plus about an equal weight of powdered nickel. The nickel reacts exothermically with the aluminum upon heating to supply additional heat for evaporating the barium. This self-generated heat lessens the getter flashing time and the nickel aluminum residue has been found to be more stable than the aluminum residue of the endothermic type getters.

A typical channel rinlg getter used in color television picture tubes thus may contain 250 mg. of a 50% barium-50% aluminum endothermic alloy. The yield of vaporized barium is normally 125 mg., i.e., 100% of the barium present in the powder alloy is vaporized. However, if an exothermic powder mixture of the same capacity is to be substituted, then it would be necessary to use at least 500 mg. of the exothermic 25% barium- 25% aluminum-50% nickel powder mixture, assuming "ice a yield can be obtained to supply the necessary mg. of barium. It has been found that serious yield problems exist when such large amounts of powder mixture are pressed into conventional getter containers such that 100% yields of effective barium vapor are not obtained in the normal flashing times.

Additionally it has been found that when such large volumes of getter material are flashed from getter containers, cracking of the material takes place with the ejection of solid particles into the tube enclosure. These ejected particles can cause short circuits and otherwise interfere with the operation of tube components.

It is the primary object of this invention therefore to provide an improved getter assembly.

It is another object of this invention to provide an improved getter assembly having a high capacity and freedom from cracking and ejection of solid particles.

Other aims and objects of this invention will be apparent from the following description, the appended claims and the attached drawings.

Summary of the invention According to the present invention, an improved channel ring getter is provided comprising a substantially U- shaped wide channel ring container having opposing side walls and a bottom wall connecting said side walls, and getter material packed therein to a depth of from 0.025 to 0.035 inch, and more specifically from 0.028 inch to 0.033 inch. A preferred thickness ordepth of packed getter material is about 0.030 inch. It has been found that when large amounts of getter material, for example, the 500 mg. exothermic mixture often needed for gettering color television picture tubes, are pressed into conventional channel ring getter containers, there is too great a thickness of tgettering material present and high yields of vaporized barium cannot be achieved in the normal heating times. For example, when. a 25 or 36 mm. diameter channel ring is used to hold this much material in the conventional 0.06 inch wide channel, the thickness of pressed powder is too great. Upon heating, the yield of vaporized barium is less than 100% for the normal 15 to 25 second flashing operation. The getter assembly must be heated for a longer than usual time to achieve higher yields of vaporized barium. Extended heating times are undesirable. However, when a wider channel, for example, 0.1 inch between side walls, is used to hold the pressed powder in the indicated ranges of powder thicknesses, the yield of vaporized barium is about 100% of the initial barium content of the powder mixture.

However, when a wider channel, for example, 0.1 inch is used to hold the pressed powder so that the depth of pressed powder is within the ranges specified herein, there is a tendency for the getter material to crack and for solid particles to be ejected.

In a preferred aspect of the invention, therefore, a getter material reinforcing member is at least partially buried in the packed getter material to ensure against cracking of said getter material during heating. This reinforcing member can be an insert such as a metallic wire ring having a diameter about midway between the diameter of the inner and outer walls of the channel. The ring is inserted in the channel and the powder pressed into the channel over the ring insert.

The drawings In the drawings:

FIGURE 1 is an enlarged plan view of a getter container with a ring-shaped wire reinforcing member disposed therein;

FIGURE 2 is a cross-sectional view taken along line 22 of FIGURE 1;

FIGURE 3 is an enlarged plan view of a getter container with an L-shaped reinforcing member disposed therein;

FIGURE 4 is a cross-sectional view taken along line 4-4 of FIGURE 3;

FIGURE 5 is a cross-sectional view of a getter container having a reinforcing member integrally formed with the getter container; and

FIGURE 6 is a cross-sectional view of a getter container similar to that shown in FIGURES 1 and 2, but with a flared side Wall for directing the flashed gases.

Preferred embodiments FIGURE 1 shows a channel ring getter 10 having side walls 11 and 12 joined by a bottom wall 13 defining a channel space 14. The width of the channel can be about 0.1 inch and the containers can hold about 500 mg. or more of pressed getter material 16. As previously stated the thickness of pressed getter material is maintained at about 0.030 inch. The diameters of the side walls and channel width are selected so that the thickness of pressed getter material is within the range of about 0.025 to about 0.035 inch, with a range of 0.028 to 0.033 being preferred. Thicknesses of getter material less than 0.025 inch are diflicult to press into the channel; and thicknesses of getter material over 0.035 inch do not upon flashing, give high yields of barium which this invention seeks to achieve.

The reinforcing member comprises a wire ring 17 of about 0.015 to 0.02 inch in cross-sectional diameter placed midway in the channel space 14. The ring 17 is shown at the bottom of the channel with the getter material 16 pressed into the channel over the ring. The ring could be elsewhere positioned in the bulk of the pressed getter material, for example, off the floor 13 of the channel if desired.

The reinforcing member can also have other shapes. For example, thin walled angular members having a configuration suited for insertion in the channel and having various types of cross sections are suitable. Flanges and other shapes having, preferably, a horizontal leg and a vertical leg can be used. The width of the horizontal leg can be one-half the width of the channel and the diameter of the circle formed by the vertical leg can be equal to the diameter of the mid point of the channel section. The member is then self-centering with the horizontal leg resting on the bottom of the channel with its edge abutting -a side wall of the container and with the other leg rising vertically at the center of the channel. The vertical leg need not rise above the level of the powder when pressed into the channel and, preferably, is buried beneath the surface of the pressed powder cake. Other shapes and types of insertable members can be used for reinforcing the gettering powder.

A flange-shaped form of insert member 18 is shown in FIGURES 3 and 4. This L-shaped member has a horizontal leg 19 and a vertical leg 20. The horizontal leg 19 can be of a width equal to one half the width of the channel space 14 so as to be self-centering. The width of the horizontal leg 19 is about 0.05 inch in this case. The horizontal leg can be formed on either side of the vertical leg and is shown here on the inside. The vertical leg has a height less than the level of the pressed getter material. These inserts can be dropped into the channel prior to filling with powder.

Such insertable reinforcing members generally need not be permanently joined to the container structure. It is not usually necessary to weld or otherwise join the insert member to the walls or floor of the channel, although this can be done if desired. The pressed gettering powder will generally hold the insert in place until heating. During and after flashing, the aluminum or aluminum-nickel residue will further hold the insert in place. The insert member can be connected to the channel member if desired, for example, to hold it in place while gettering powder is dispensed and stamped into the channel.

The reinforcing member can also be an integral part of the channel container. For example, a section of the channel floor can be crimped to form a thin-edged ridge rising above the floor of the channel. The ridge need not rise above the level of the pressed powder. FIGURE 5 shows a channel ring container 21, which is similar to those shown previously, but which has a reinforcing member 22 integrally formed in the channel floor 23. This member 22 is formed by crimping the floor portion to form a thin edged ridge as shown. The getter material 24 is packed down around the member 22 which will hold the powder residue in place during flashing.

Thereinforcing member can be of any type construction and shape provided it prevents the gettering material from cracking during heating and ejecting solid particles. While it is not intended to be bound to a particular mechanism by which cracking of the gettering material is prevented, it is believed that the reinforcing member serves to tie each segment of the annular body of gettering material to its neighboring segments, thereby preventing the movement, cracking or ejection of any individual segment. Additionally, the presence of the reinforcing member about midway between the side walls of the channel may also serve to provide support for the gettering material at that otherwise unsupported, intermediate point and thereby, in effect, reduce the unsupported Width of the getter material to about one half the actual distance between the channel walls.

The reinforcing member will generally have the same shape as the channel container, i.e., if the channel is ring-shaped then the reinforcing member will be circular. Other suitable forms of reinforcing members can be used for various shapes of containers.

Wide channel getter assemblies of the types described above were tested by flashing. The stainless steel channel ring containers had an overall diameter of about 27 mm. and the channel width was about 0.1 inch. The fill was about 500 mg. of the nickel-aluminum-barium exothermic material previously described. About 27 of these assemblies, which did not have any reinforcing members, were flashed by inductive heating under conditions similar to those experienced in a color television picture tube. The yield of flashed barium for a 20 second heating time was in all cases, i.e., a yield of mg. of barium. However, in all cases except one, there was cracking of the residue powder.

Getter containers similar to those used above were provided with a wire ring insert member of 0.015 to 0.020 inch wire diameter and the same amount of the above described exothmermic getter material packed into the channel space over the wire ring. Twenty of these assemblies were flashed with no cracking of the residue powder occurring in any case and no ejection of solids. The yield of vaporized barium was 100%, i.e., the full 125 mg. of barium.

Another group of similar getter containers were pro vided with stainless steel L-shaped inserts shown in FIG- URES 3 and 4 and described above. One hundred of these assemblies were flashed with no cracking of the residue powder or ejection of solid particles.

It is to be noted that while the invention here has been described in regard to ring shaped channels, it is not so limited and can be used in other shapes of containers. Additionally, the reinforcing members of this invention can be used in channel ring getter containers having flared side walls which give direction to the flow of vaporized material. Such containers generally have side walls parallel to each other and perpendicular to the floor of the channel in the area of powder fill with upper portions or one or both side walls flaring in or out at an angle to the vertical axis of the channel to direct the flow of vaporized material radially inward or outward. The reinforcing member would be placed in the lower portion of the channel occupied by the packed getter material. As an example, FIGURE 6 shows a channel ring container 25 having its inner wall 27 flaring outwardly so as to partially cover the getter material 27 which has a reinforcing member 28 therein. The term channel ring container as used herein is meant to include containers of other than ring shape, for example oval and other shapes whether or not the ends of the channel are joined together.

What is claimed is:

1. In a getter assembly provided with a substantially U-shaped channel ring container having opposing side walls and a flat bottom wall connecting said side walls and forming with said side walls an annular open-topped channel space, and getter material pressed into the bottom of said channel space formed by said side walls and the flat bottom wall, said getter material comprising at least 25 percent by weight barium as the active flashing getter material and the balance non-flashing material which forms a breakable residue in the channel space after the barium is flashed by heating the assembly, the improvement for preventing cracking of said getter material residue and the ejection of cracked particles from the container during heating comprising reinforcing means in said channel space at least partially buried in said pressed getter material for holding said residue together.

2. The getter assembly of claim 1 in which the getter material is pressed into said container to a depth of from 0.025 to 0.035 inch.

3. The getter assembly of claim 1 in which the reinforcing means is a metallic wire ring having a diameter about midway between the diameters of the inner and outer side walls of the channel.

4. The getter assembly of claim 1 in which the reinforcing means is a metallic, shaped ring member having one portion resting on the bottom wall of the channel and another portion rising vertically above the bottom wall of the channel.

5. The getter assembly of claim 1 in which the reinforcing means is an L-shaped flange having a horizontal leg with a width equal to about one-half of the channel width and having a vertical leg with a height less than the depth of the powder packed into the channel.

6. The getter assembly of claim 1 in which the reinforcing means is a member extending completely around the annular packed body of getter material and having the getter material adherently packed around said member whereby said member ties each portion of the annular body to adjacent portions and prevents relative movement thereof during heating to a flashing temperature.

7. The getter assembly of claim 1 in which the getter container and reinforcing means are constructed of stainless steel.

8. The getter assembly of claim 1 in which the upper portion of at least one of the side walls of the container is flared off at an angle to the vertical axis of the channel to direct the flow of vaporized material at the same angle.

9. The getter assembly of claim 1 in which the reinforcing means is an integral formed portion of the bottom wall of the channel, said formed portion rising above the surface of the bottom wall and partitioning at least a portion of the channel space into two compartments.

10. The getter assembly of claim 1 in which the formed partition extends to a point below the level of the packed powder.

11. In a getter assembly provided with a substantially U-shaped channel ring container having opposing side walls and a bottom wall connecting said side walls, an improvement for containing large amounts of getter material in said container and for flashing, upon heating of the container, the full amount of active getter material, said improvement comprising widely spaced apart side walls with about at least 500 mg. of exothermic, bariumcontaining getter material pressed into the annular space formed by said side walls and the bottom wall to a depth of from 0.025 to 0.035 inch, and reinforcing means in said annular space at least partially buried in said pressed getter material.

12. The getter assembly of claim 11 in which the width of the channel is at least 0.1 inch and the depth of the pressed getter material is about 0.030 inch.

References Cited UNITED STATES PATENTS 1,957,145 5/ 1934 Loewe 2060.4 X

2,060,861 11/1936 Glans 2060.4

3,225,910 12/1965 Della Porta 2060.4

3,023 ,8 83 3 1962 Meisen 2060.4

3,225,911 12/1965 Della Porta 206-0.4

2,824,640 2/ 1958 Della Porta 206--0.4

JOSEPH R. LECLAIR, Primary Examiner.

I. M. CASKIE, Assistant Examiner.

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