US3558961A

US3558961A - Getter mounting assembly with elongated springlike support having u-shaped channel portion

Info

Publication number: US3558961A
Application number: US776864A
Authority: US
Inventors: Edward M Palsha
Original assignee: Union Carbide Corp
Current assignee: SAES Getters SpA
Priority date: 1968-11-19
Filing date: 1968-11-19
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

An improved getter assembly for mounting a getter container in an electron tube at the end of a flat springlike support arm wherein the getter container has a mounting tab and the end of the support arm is a U-shaped channel portion formed by bending opposite side portions of the strip upwards to form the legs of the channel with the mounting tab of the getter container lying in said channel and connected to the underlying end of the metallic strip.

Description

United States Patent Edward M. Palsha Lakewood, Ohio Nov. 19, l 968 Jan. 26, 1971 Union Carbide Corporation New York, N.Y.

a corporation of New York Inventor Appl. N 0. Filed Patented Assignee GETTER MOUNTING ASSEMBLY WITH ELONGATED SPRINGLIKE SUPPORT HAVING U- SHAPED CHANNEL PORTION 7 Claims, 4 Drawing Figs.

U.S. Cl 313/174, 206/04, 313/180 Int. Cl H0lj 19/70 Field of Search 313/174, 180; 206/04; 316/14, 25

[56] References Cited UNITED STATES PATENTS 3,385,420 5/1968 Della Porta 206/0.4 3,390,758 7/1968 Reash et al. 206/04 Primary Examiner-John Kominski Assistant Examiner-Palmer C. Demeo Attorneys-Paul A. Rose, Thomas I. OBrien, Harrie M.

Humphreys and Leo A. Plum ABSTRACT: An improved getter assembly for mounting a getter container in an electron tube at the end of a flat springlike support arm wherein the getter container has amounting tab and the end of the support arm is a U-shaped channel portion formed by bending opposite side portions of the strip upwards to form the legs of the channel with the mounting tab of the getter container lying in said channel and connected to the underlying end of the metallic strip.

pArsmwmzsmn 3558.961

INVENTOR. EDWARD M. PALSHA W A PM ATTORNEY GETTER MOUNTING ASSEMBLY WITH ELONGATED SPRINGLIKE SUPPORT HAVING U-SHAPED CHANNEL PORTION This invention relates to an improved arrangement for mounting a getter in an electron tube, particularly a television picture tube, against awall thereof in a proper position for effective flashing and without danger of interference by the getter with the operation of the electronic system in the tube.

The use of getter materials in the manufacture of electronic tubes is well known. Getter materials, for example endothermic bariurn-aluminum alloys, are pressed into suitable containers and mounted in the interior of the glass electron tube. After the tube is partially evacuated by means of a vacuum pump and sealed, the getter material is flashed to evaporate the barium, generally by induction heating of the metallic getter container. The barium vapor reacts with the residual gases in the tube and removes them as a solid condensate on the walls of the tube. The resulting barium film continues to adsorb any further liberated gases throughout the life of the tube and thus provides the high vacuum needed for operation of an electron tube.

A typical getter container used in electron tubes, particularly television picture tubes, comprises an annular, U-shaped channel. The television picture tube in which the getter container is mounted generally comprises a neck portion in which are located the electron gun or guns and auxiliary equipment; an enlarged bulb portion which terminates in a generally flat viewing screen; and a funnel-shapedportion joining the neck and bulb portions. A central tube axis extends symmetrically through these parts of the tube, as shown in FIG. 1. Whereas in the past the ring-shaped getter container was mounted in the neck portion of the tube positioned on the electron gun, it is now a desired practice to mount the getter in or near the funnel portion of the tube. This is accomplished by mounting the getter container at the end of a flat springlike metallic strip support arm or antenna, the other end of which is fixed to a wall of the electron gun in the neck portion of the tube. The spring is biased to force the getter container against the wall of the tube in the funnel portion.

The getter material in the container is flashed by positioning an R-F heating coil proximate the exterior wall of the tube in the vicinity of the getter container. The R-F field induces a current flow in the metallic getter container, heating the container and its contents to a high enough temperature to flash or evaporate the contained barium. The flashing of an exothermic getter material, which contains nickel in addition to the barium-aluminum alloy, involves heating of the container to about 1300 C. to vaporize the barium. As a result of this heating, the unvaporized residue and the channel ring container and its support arm are themselves heated to a high temperature. This heating results in the melting or sintering of the residue, either the aluminum powder in an endothermic getter, the barium-aluminum-nickel powder in the case of the exothermic getter, or whatever unflashed getter material is present. The container itself, generally stainless steel, is heated to a temperature near its melting point. If the getter container is improperly positioned relative to the heating coil, the stainless steel getter container may melt or the getter residue may melt and flow out of the container. It is therefore important to have the getter container accurately positioned during heating of the getter material so that no such failures occur.

It has also been found that the severe heating of the getter support arm during the flashing operation can cause the support arm to soften and bend, causing the getter container to move away from the wall of the tube and out of its proper position relative to the induction coil outside the tube. The duration of the heating cycle needed to evaporate all of the barium can vary from to or 30 seconds, depending on the type of getter involved; and any interruption of this heating cycle, as will occur if the getter container moves away from the wall of the tube, will result in an incomplete flashing of the barium and the attainment of a lesser degree of vacuum in the tube.

Additionally, any change in alignment of the getter container to its heating coil can cause excessive localized heating of the container or its contents causing failure of the device. A further hazard of such bending of the getter support arm is that the getter container could be moved away from the wall of the tube towards the center of the funnel portion where the getter container would intercept the electron beam path and cause a shadow on the tube screen. Such occurrences as those outlined above can require an expensive reworking of the tube, i.e., its disassembly and refitting.

It is the primary object of this invention therefore to provide improved means for mounting a getter container in an electron tube, particularly a television picture tube, whereby the getter container is properly positioned therein and permanently held in such a position during and after flashing of the getter material.

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

According to the present invention, an improved getter assembly is providedfor mounting a getter container in an electron tube in an abuttingrelationship to a wall of the tube, said assembly comprising a getter container having at least one receptacle for holding getter material and having a mounting tab on said container extending past an edge of the container, and a getter support comprising an elongated springlike flat metallic strip having at one end thereof a U-shaped channel portion formed by bending opposite side portions of the strip upwards to form the legs of the channel with the mounting tab of the getter container lying in said channel and connected to the underlying end of the metallic strip.

In the drawings:

FIG. 1 is a partial schematic view of the neck and funnel portions ofa television picture tube, in cross section, including a getter assembly of the present invention mounted in the antenna position and showing the positioning of the heating coil;

FIG. 2 is a perspective, exploded view in enlarged scale showing the getter container and its mounting tab and the channel-shaped portion of the support arm;

FIG. 3 is a side view of the getter assembly;

FIG. 4 is a plan view of the getter assembly.

Referring to FIG. 1 there is shown a portion 10 of a typical glass television picture tube. Such a tube may be viewed as having three main parts: a neck portion 11; a funnel portion 12; and the bulb or main tube, only a portion 13 of which is shown. The central axis 6 of the tube extends through these parts. It is of course understood that the division of a tube into such parts is arbitrary and it is not meant here that the getter assembly of this invention can only be used in a funnel portion of a tube. Under suitable circumstances the getter assembly of this invention could be mounted nearer to the gun in the neck of the tube or further into the bulb of the tube as desired. Additionally, it is to be understood that the getter assembly of this invention can be used in other types of electron tubes than the television picture tube described herein and can also be used in other types of evacuated vessels.

More specifically, an electron gun 14 (or guns in the case of a color tube) is shown positioned in the neck of the tube. An antenna spring or support arm 15 is shown fixed at one end 16 to the sidewall of the gun and having mounted on its opposite end 17 a getter container 18. The support arm 15 is a piece of thin, flexible, flat metal strip, such as for example stainless steel or a nickel-base alloy, biased to urge the getter container 18 against the wall 19 of the tube and out of the path of the electron beam, which is represented by the lines 20. The getter container is supported in a position out of direct contact with the glass wall of the tube by a support member such as 21, otherwise the glass wall might crack if it were contacted directly by the hot getter container.

An R-F induction heating coil 22 is shown positioned near the outer wall of the funnel portion of the tube. The coil and getter container must bearranged symmetrically so that the heating currents induced in the getter container are uniform and symmetrical. This requires that the getter container be properly positioned inside the tube and that it keep this position during the whole of the heating cycle. The flux lines generated by the energized coil loop through the center of the coil and extend into the tube interior where they are intercepted by the metallic getter container as well as by the end portion 17 of the metallic support arm 15. In the prior art practice, the flat end portion of a flat support arm is connected to a flat mounting tab on the getter. The wide flat end portion of such a support arm thus projects a large area in a plane normal to the direction of the flux lines, and in intercepting these flux lines, is subjected to a high heating current. If this heating is so high as to soften the end portion of the support arm, then the biasing effect of the spring 15, which is outside the field of the coil and which has not been so heated or softened, acts to bend the end portion of the arm towards the tube wall. The getter container being still attached to the bending end portion of the support arm, can be pivoted around its base member 21 and tilted up and away from the tube wall. The symmetry of the coil getter container arrangement is thus disturbed and the heating of the getter container becomes nonuniform. Additionally, the far end of the getter container may be tilted up into the path of the electron beam. In those cases where the getter container is mounted at the top 23 of the tube wall, in the so-called 12 oclock position when looking into the viewing screen (as opposed to the mounting of the getter container in the 6 o'clock position as shown in the drawing) similar problems occur. In such a case the effects of gravity may cause the getter container and softened support arm to sag even further into the path of the electron beam.

These problems are eliminated by use of the arrangement of this invention. As seen in the drawings, the getter container 18 has a mounting tab 24 which extends past an edge, the wall 25, of the getter container. The support arm has its end portion 17 formed into a U-shaped channel by bending opposite side portions of the metal strip upwards to form the

legs

26 and 27 of the channel. The floor 28 of the channel has a width sufficient to receive the mounting tab 24. The length of the channel, i.e., the distance down the longitudinal or long axis of the strip along which the side portions are bent upwards, should be at least as long as the length of the tab extending past the wall of the getter container and should be sufficiently long to extend outside the high flux density portions of the R-F field which could cause excessive heating and bending of the metallic strip. The channel shape of the end portion of the metallic strip support member protects this member from excessive heating as well as minimizing the tendency to bend in the following way: the

vertical legs

26 and 27 of the channel, being generally parallel to the lines of flux generated by the coil, do not intercept as many flux lines and are not heated to a high temperature; the channel floor portion 28, while normal to the flux lines, is of a narrower width than the original strip width with the result that this channel portion intercepts less flux and is not heated to as high a temperature as in the prior art situation where the full width of the strip 15 was arranged normal to the flux lines. The channel portion of the support arm is thus not heated to as high a temperature, meaning that the bending stress exerted on this end portion of the support arm is less. Additionally, since the U-shaped cross section of the channel portion has a greater section modulus, or resistance to flexure, than that of a flat strip, the resistance to bending of the channel portion is greater than in the case where the flat end of a support strip is connected to the mounting tab of the getter. There is thus less bending force generated when using the channel member on the end of the support arm since there is less heating of this member, and there is more resistance to bending because of the channel shape. The tendency for the support arm to bend and tilt the getter container out of its proper position is thus greatly minimized. As noted previously, the length of the support arm extremity which is formed into a channel shape is determined by the shape and strength of the R-F field since the channel configuration is needed only for that part of the support arm adjacent the getter container where the flux lines are most dense. The channel portion should not extend so far up the strip support arm as to interfere with the springlike action needed to bias the getter con tainer against the tube wall.

The getter container and support arm can be assembled by positioning the mounting tab 24 in the bottom of the channel with the vertical ends, 29 and 30, abutting the vertical wall 25 of the getter container. The mounting tab is then joined to the floor 28 of the channel, for example by one or more spot welds. The use of the channel arrangement makes it easier to properly align the getter container on the support arm since there is only one position, that of proper alignment, in which the channel will accept the mounting tab. In the prior art practice, it was necessary to carefully align the getter container on the end of the support arm.

The abutting relationship of the vertical end faces 29 and 30 of the channel legs against the container wall 25 assures proper alignment of the container and the support arm and also provides a rigid structure which will not allow relative movement of the two parts. If the sidewall 25 of the getter container is formed at an angle other than vertical, then the ends 29 and 30 of the support arm may be arranged at a complementary angle, or at whatever angle is needed to give a desired orientation of the getter container to the support arm.

The improved getter supporting arrangement of this invention may be used with various types of getter containers. As shown in the drawings, a typical getter container 18 is a circular ring-shaped structure having inner 31 and outer 25 opposing sidewalls and an annular floor member 32 joining these sidewalls to form an annular space into which getter material 33 can be packed. The mounting tab 24 can be an end portion of a flat mounting bar 34 which extends across a diameter of the ring container and which is joined to the underside of the floor member 32 as by spot welds at opposite points of the channel. The opposite end 35 of the mounting bar can extend past the wall of the container and be bent upwards to allow for easy insertion of the device into the tube. The mounting bar 34 is thus used as an alignment axis of the getter container so that when the mounting tab is inserted into the channel and the spot weld made, the longitudinal axis of the support arm will coincide with the alignment axis of the getter container. The assembly may be inserted in the tube with proper positioning of the getter container thus insured.

The getter container could have other shapes than that shown and need only be any type of receptacle for holding getter material having one or more openings for directing vaporized getter material into the tube interior and intended to be mounted at the end ofa springlike support arm.

The getter container may also have a base member for properly positioning the getter container off the wall of the tube so as not to cause excessive heating of the tube wall during flashing of the getter. Such base members may be ceramic insulating members attached to the underside of the getter container or the wire base member 21 shown in the drawings could be employed. This member 21 comprises a small cross section wire member 36 arranged transversely of the mounting bar 34 and connected at its midpoint to the underside of the mounting bar. The

end portions

37 and 38 of the wire member are each bent in a plane parallel to the axis of the mounting bar, first in a downward direction and then in an upward direction to form curved bases for supporting the getter container off the wall of the tube. The

curved bases

37 and 38 allow for low friction slideable insertion of the getter container into the tube interior. The improved arrangement of this invention whereby the getter container and support arm are properly aligned insures that the curved bases will be properly oriented, i.e., the planes of the curved bases are parallel to the mounting bar whose axis is an extension of the longitudinal axis of the support arm. If the getter assembly is inserted into the tube with the longitudinal axis of the support arm extending in the same direction as the central axis of the tube, then the getter container will be properly slid into its intended position. Additionally, since an exact and permanent alignment of the getter container and its base member with the support arm is obtained by means of the channel arrangement on the support arm, the getter container can be positioned accurately relative to the heating coil as well as in a proper position to direct its vaporized getter material in a desired direction into the tube interior. For the open-topped getter container described herein, the axis of the barium cloud produced will be perpendicular to the flat bottom member of the container, as shown by the arrow in FIG. 1. By suitable arrangement of the getter container, mounting tab and base member, and the channel portion of the support arm, the getter container can be positioned in the tube so as to direct its vaporized barium in other directions as desired.

lclaim:

1. An improved getter assembly formounting a getter container in the funnel portion of an electron tube abutting against a wall thereof for discharging active getter material into the interior of the tube when the getter container is heated by currents induced from an RF field created by a coil positioned outside the tube opposite the getter, said assembly comprising a getter container having at least one receptacle for holding getter material and having a mounting tab thereon extending past an edge of the container, and a getter support comprising an elongated springlike flat metallic strip adapted at one end thereof for resilient connection to the neck portion of the tube and having at the other end extending into the funnel portion of the tube a U-shaped channel portion formed by bending opposite side portions of the strip upwards to form the legs of the channel portion, with the mounting tab of the getter container lying in said channel and connected to the underlying end of the metallic strip, whereby when a heating coil is energized to create a R-F field which intercepts and heats both the getter container and the U-shaped channel portion of the getter support, the U-shaped portion having a greater section modulus than the flat strip portion of the support will resist bending due to the heating and will maintain the getter container in an abutting position against the wall of the tube during the entire heating cycle.

2. The assembly of claim 1 in which the getter container has at least one sidewall member and a floor member connected to said wall and having getter material pressed into the space formed by said sidewall and floor member.

3. The assembly of claim 1 in whichthe getter container comprises inner and outer vertical sidewalls and an annular floor member connecting said sidewalls to form an annular space into which getter material is pressed.

4. The assembly of claim 3 in which the getter container additionally comprises a flat mounting bar extending across the bottom of the getter container and joined at opposite points on the underside of the floor member, with one end of the mounting bar extending past the outer wall of the getter container to form the mounting tab.

5. The assembly of claim 4 in which the end faces of the legs of the channel portion of the getter support abut the outer wall of the getter container forming a rigid structure.

6. The assembly of claim 4 in which a base member depends downwardly from the getter container for contacting the wall of an electron tube and supporting the getter container off said wall.

7. The assembly of claim 4 in which a wire support depends downwardly from the getter container, the ends of the wire support each being bent in a plane-parallel to the axis of the mounting bar, first downwardly and then upwardly to form two spaced apart curved bases for contacting the wall of an electron tube and holding the getter container off said wall.

Claims

1. An improved getter assembly for mounting a getter container in the funnel portion of an electron tube abutting against a wall thereof for discharging active getter material into the interior of the tube when the getter container is heated by currents induced from an RF field created by a coil positioned outside the tube opposite the getter, said assembly comprising a getter container having at least one receptacle for holding getter material and having a mounting tab thereon extending past an edge of the container, and a getter support comprising an elongated springlike flat metallic strip adapted at one end thereof for resilient connection to the neck portion of the tube and having at the other end extending into the funnel porTion of the tube a U-shaped channel portion formed by bending opposite side portions of the strip upwards to form the legs of the channel portion, with the mounting tab of the getter container lying in said channel and connected to the underlying end of the metallic strip, whereby when a heating coil is energized to create a R-F field which intercepts and heats both the getter container and the U-shaped channel portion of the getter support, the U-shaped portion having a greater section modulus than the flat strip portion of the support will resist bending due to the heating and will maintain the getter container in an abutting position against the wall of the tube during the entire heating cycle.

3. The assembly of claim 1 in which the getter container comprises inner and outer vertical sidewalls and an annular floor member connecting said sidewalls to form an annular space into which getter material is pressed.

7. The assembly of claim 4 in which a wire support depends downwardly from the getter container, the ends of the wire support each being bent in a plane parallel to the axis of the mounting bar, first downwardly and then upwardly to form two spaced apart curved bases for contacting the wall of an electron tube and holding the getter container off said wall.