US3381805A - Getter assembly having support of low thermal conductivity - Google Patents

Description

May '2, 1968 P. DELLA PORTA ET AL 3,381,805

GETTER ASSEMBLY HAVING SUPPORT OF LOW THERMAL CONDUCTIVITY Filed Dec. 30, 1966 2 Sheets-Sheet l FIGZQ FIGZb FIG. 3Q

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INVENTORS PAOLO dELLA PORTA CESARE PISANI MARIO ZUCCHINELL! 6 ATTORNEYS 7, 1968 p DELLA PQRTA ET AL. 3,381,805

GETTER ASSEMBLY HAVING SUPPORT OF LOW THERMAL CONDUCTIVITY Filed Dec. 30, 1966 2 Sheets-Sheet i:

INVENTORS FIGS PAOLO dELLA PORTA CESARE PISANI MARIO ZUCCHINELLI BY @W {4M ATTORNEYS 3,381,805 GETTER ASSEMBLY HAVING SUPPORT OF LOW THERMAL CONDUCTIVITY laolo deila Porta and Cesare Pisani, Milan, and Mario Zucchinelli, Trezzo, Italy, assignors to S.A.E.S. Getters S.p.A., Milan, Italy, a company of Italy Filed Dec. 30, 196I6,lSei5!. lgio 610966615 889/66 Claims riori a lication ta y, u y

p DZZ. 1, 1966, 30,615A/66 Claims. (Cl. 206-.4)

ABSTRACT OF THE DECLOSURE A getter assembly having a getter container and a support for the container wherein the support 18 made of a material of low thermal conductivity and of high resistance to heating by induction currents. These getter assemblies can be subjected to induction currents while resting on the wall of a vessel such as a glass television picture tube.

Disclosure The present invention deals with improvements in a getter assembly, in particular, but not exclusively, for those getters to be mounted in colour television picture tubes, where there is a tendency for getters to be mounted within the glass bulb of the tube and directly resting on the glass.

Getters are well known and widely employed in the manufacture of electron tubes, television picture tubes, high vacuum systems and the like. The most widely used forms of getters consist of an annular shaped container having a channel of U or L shaped cross section, wherein the gettering material is arranged as a compressed powder.

The gettering material may be of the evaporable type, such as barium, or may be of the nonevaporable type, such as zirconium or titanium and their alloys. The getter is made active by heating it up to 700-1200" C. for times from 10 to 20 seconds. In the case of the evaporable getters, the liberated barium vapours form a thin film on some parts of the tube, which film acts as a getter or chemical pump.

For many applications, as for instance for the getters to be mounted on th electron gun of a picture tube, the heating for activation represents no problem. There are, however, special applications, as for instance for colour picture tubes, in which the getter is mounted so that it rests on the internal surface of that part of the tube having the shape of a wide cone. In this and in other similar cases, the glass upon which the getter rests is sensitiv to strong and localized temperature gradients. It is, therefore, necessary to avoid the heating to a high temperature for relatively long periods of time of any body resting on or near to the glass so as to avoid its breakage.

Furthermore, the heating of the glass would cause the emission of gas from its surface and this gas could darnage the cathode if it were not adsorbed with great rapidity by the gettr. These gases would cause, in turn, as a consequence of chemical reactions with the gettering film and with other metallic parts of the tube, the production of other gases which would damage the cathode and which are hardly adsorbed by the getter, such as methane or higher hydrocarbons.

It is evident that it is very important to hold the glass surface of the tube as cold as possible.

In the known methods of mounting such getters, long metallic feet are used for supporting the getters, so that transmission of heat by conduction is limited by the length of the supporting foot, while heat transmission by radiation is not avoided. The temperatures, which have been States Patent Otlice 3,381,805 Patented May 7, 1968 measured at the ends of the supporting feet which rest on the glass, reach values from 500 to 700 C. It may be pointed out that this high temperature is also caused by direct heating of the feet due to pick up of the high frequency currents flowing in the coils on the other side of the glass and which serve to heat the getter to evaporation.

The improvements according to this invention concern a getter assembly, in particular for getters to be mounted in colour television picture tubes, and the main object of said improvements is to provide a getter assembly, in which heating of the glass by the getter is greatly reduced, so as to avoid any danger of overheating and breaking of said glass.

Besides said main object, the improvements have other objects which are that the support of the getter has also the function of gas adsorbent, and that of a screen for the barium vapours, so as to avoid the deposition of vapours on parts of the tube near or under the getter in noticeable quantities.

The improvements according to this invention are all realized by using a support for the etter container which is made of an insulating material, such as ceramic material. A support made of ceramic materials is not heated by the induced high frequency currents used for heating the getter and it also does not transmit heat easily. It has in fact been found that the maximum temperature reached by the ceramic materials where they contact the glass of the tube is well below 200 C.

it has been found that silicates are efiicient adsorbers for methane and other hydrocarbons, that is to say for those gases which are less efiiciently sorbed by the getters or chemical pumps, and which are most dangerous for the good working of the cathode. Said gases are formed mainly by the metallic residue left from the evaporation of the barium, by the gases developed in the system which come into contact with this residue as well as by the same gases which come into contact with the barium film. This formation is due to catalytic reactions.

The ceramic insulating support according to this invention is generally made of silicates or silica (such as sillimanite, steatite, and the like) and, since it is an integral part of the getter assembly, it has the above mentioned functions and therefore acts as a chemical pump for hydrocarbons in the gaseous phase.

Another advantage of the support according to this invention consists in the fact that such a support, made of ceramic material, can be made in such dimensions and shapes so as to effectively act as a. screen which avoids barium being deposited as a thick layer on parts immediately below the getter. Such a screening action cannot be obtained by means of the known metallic screens, because these screens would be heated by the high frequency currents used to heat the getter. This heating should be and is avoided by using a screening support made of ceramic mate-rial according to the present invention. There are two main reasons why the formation of the thick barium layer should be avoided by using the ceramic screen. One of these reasons is that such a layer would pick up an appreciable quantity of high frequency currents and therefore be overheated and cause damage (cracking) of the glass of the tube. Another reason is that when a tube must be reexposed to air, for repair or re-calib-ration, the oxidation of the barium film (having, for example, thicknesses up to 0.1 mm.) would create porous layers which can easily break down to loose powders which are extremely dangerous for tube functioning.

The assembling of the improved ceramic support with the getter container can be carried out either by clamping or encasing with or without riveting, by means or" metallic tongues, or by welding or sintering according to techniques which are well known for mounting electron guns or tubes.

A particular problem of the getters which are discussed 'hereabove is that to obtain an assembly between the getter container and the support made of insulating material, by means of a coupling element between said container and said support, in such a way that a compact and a stable unit is obtained, and that at the same time the heat transmission to the support is reduced to a minimum. The solution of this problem is not easy, considering that the coupling element is a metallic plate having a thickness of about 0.1-O.2 mm. The problem is to firmly couple the container to the support by means of such a thin plate, whereby, however, the contact between the said plate and the said support is limited to a very small part of the total surface of the insulating support.

According to a particular feature of this invention the coupling element is shaped so as to have small protruding cones or collars, which permits bringing the two partssupport and coupling plateto the smallest possible distance between them to obtain a compact and stable assembly, and at the same time to have a minimum contact surface between them, so that the heat transmission from the coupling plate to the support, during heating of the getter, is also reduced to a minimum.

It has been found that with such a coupling plate, accordin to the invention, by which the support is clamped to the getter, not only the support remains relatively cold, but as a further consequence the heating time of the getter is reduced by about 20% with respect to an assembly in which the contact surface between the coupling plate and the support is a considerable part, for instance one fifth, of the total surface of the support.

Furthermore and particularly for getters to be mounted in the so called antenna position, i.e. for getters resting on the wide glass cone of the kinescope, care must be taken on shaping the ceramic support. This support must slide upon the surface of the kinescope without causing any abrasion when the getter is introduced and fixed in the kinescope. Such an abrasion would cause the presence of particles and powders coming either from the covering graphite) of the glass of the kinescope, or from the ceramic support, and said abrasion could also cause damaging of the covering of the glass. To avoid such an abrasion, the ceramic support according to this invention has rounded borders so that it can slide upon the covered glass surface of the kinescope without causing any abrasion.

The enclosed drawings show, by way of example, some embodiments of the improved getter assembly according to this invention.

FIGURES la to 4a are the sectional views of four embodiments of the improved getter assembly;

FIGURES 111 to 4b are the corresponding top views of the embodiments shown by FIGURES la to 4a;

FIGURE 5 is the top view of a fifth embodiment of the improved getter assembly according to this invention;

FIGURES 6 is the sectional View along line AA of FIGURE 5;

FIGURE 7 is the sectional view along line B-B of FIGURE 5;

FIGURE 7a shows a detail at point 11 of FIGURE 7.

In all figures, 1 indicates the gettering material which is compressed in an L-shaped annular container, 2 indicates the coupling element, and 3 indicates the ceramic support. Reference 4 indicates the fixing tongues, which can be spot welded on the coupling plate 2, as shown by FIG- URES 1 to 4, or which can be a part of said coupling late 2, as shown by FIGURES 5 to 7.

The ceramic support 3 shown by FIGURES la-lb has the form of a washer with a central hole and the coupling element 2 has also the form of a washer, the outer border of which. is raised and is soldered onto the getter container and the inner border of which is bent down into the hole of the support 3, so as to clamp the two parts 2 and 3 together.

The ceramic support 3 shown by FIGURES 2a-2b has the form of a disk with a central cylindrical raising with an annular groove, onto which. the coupling element 2 is inserted, having the form of a washer.

FIGURES 3a-3b show again a ceramic support 3 like that of FIGURES la-ib, but the coupling element 2 is here a small washer having three radial arms, which are spot welded onto the getter container.

FIGURES 4a-4b show a disk shaped ceramic support and a coupling element 2, which consists of a single elastic arm.

The ceramic suppont shown by FIGURES 5 to 7 is a disk having a raised and rounded outer border 3'. The coupling plate is a metallic disk having also a raised outer border, which is spot welded. onto the getter container. From said outer border, four tongues 6 extend radially outwards, which tongues are bent down around the rounded Outer border 3 of the support, so as to clamp this support onto the coupling plate 3. A further tongue 4 projects radially outwards from the coupling plate 2 and serves to fix the getter assembly in the kinescope. The coupling plate 2 has a central opening, the border 7 of which is bent down as shown clearly by FIGURE 70, so as to form a circular collar. In the surface of plate 2, which is parallel with the support 3, some protruding points 5 are provided. The edge of border 7 and the protruding points 5 are spacing elements, by which the plate 2 is spaced at a little distance from the support 3. Due to these spacing elements, the plate 2 and the support 3 can be arranged very close together and a very compact and mechanically stable unit is obtained, and at the same time the contact between the plate and the support is reduced to a minimim.

The embodiments shown by the annexed drawings are given by way of examples only, and it is clear that other embodiments are possible without departing from the scope of the invention as claimed in the following claims.

What we claim is:

1. A getter assembly, adapted to be subjected to induction currents while said assembly is within an evacuated vessel and resting on the wall of the vessel without transferring a damaging amount of heat to said wall of said vessel, comprising a getter container, 2. getter material in said getter container, a support and a coupling element joining said container and said support, wherein the support is made of a material of low thermal conductivity and of high resistance to heating by induction currents.

2. A getter assembly according to claim 1, in which the support has the form of a disk which is substantially laterally coextensive with the getter container.

3. A getter assembly according to claim 1, in which the support is clamped to the coupling element by means of bent parts of the coupling element, said bent parts terminating above the plane of the lower surface of the support.

4. A getter assembly according to claim 1, in which the coupling element has a plurality of small protruding points by which the coupling element rests against the support.

5. A getter assembly according to claim 1, in which the coupling element has linear spacing means, by which the coupling element rests against the support.

6. A getter assembly adapted to be subjected to induction currents while said assembly is within an evacuated vessel and resting on the wall of the vessel, said getter assembly comprising:

(A) a getter container heatable by induction currents,

(B) a getter material in said getter container,

(C) a coupling element attached to and extending below said getter container, and

(D) a support attached to said coupling element,

wherein said support is made of a material of low rents, the lower surface of said support being free of inductively heatable material, and

(D) means attaching said support to said container.

8. A getter assembly adapted to be subjected to induction currents while said assembly is within an evacuated vessel and resting on the wall of the vessel, said getter assembly comprising:

(A) a getter container heatable by induction currents,

(B) a getter material in said getter container,

(C) a support, the lower surface of which is adapted to contact the walls of the vessel, said support being made of a material of low thermal conductivity and of high resistance to heating by induction currents, the lower surface of said support being free of inductively heatable material, and

(D) a coupling element attached to said getter container at at least one point on said getter container, said coupling element passing under at least a portion of said support thereby holding said support under said getter container.

9. A getter assembly adapted to be subjected to induction currents while said assembly is within an evacuated vessel and resting on the wall of the vessel, said getter assembly comprising a getter material and a support attached to said getter material, said support having a lower surface which is adapted to contact the walls of the vessel, said support being made of a material of low thermal conductivity and of high resistance to heating by induction currents, the lower surface of said support being free of inductively heatable material.

10. The getter assembly of claim 7 wherein the support is made of a material which is substantially opaque to thermal radiation.

References Cited UNITED STATES PATENTS 1,146,298 7/1915 Ambruster 174--138 1,638,551 8/1927 Ronci 313-180 2,173,259 9/1939 Lederer 313l78 X 2,464,762 3/1949 Hilliard 313174 X 2,602,832 7/ 1952 Brennan 174-5054 X 1,628,045 5/ 1927 Hendry.

1,821,238 9/1931 -Rentsch'ler et a1.

2,072,342 8/ 1937 McMaste-r et a1.

2,275,864 3/ 1942 Record 3,144,569 23/1964 Coles.

3,197,546 7/ 1965 Hopper.

LARAMIE E. ASKIN, Primary Examiner.

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