US 3917968 A
An electron source is provided by thermionic filaments in the form of elongated strips or wires, such filaments being mounted within a casing. A deflector electrode is formed on a wall of the casing behind the filaments and director electrodes placed forward of the filaments in the direction in which the electron flow is desired. The various electrodes are positioned relative to the filaments and have potentials applied thereto such that uniform distribution of electrons is provided over a predetermined area over which electron flow is desired. The filaments are resiliently supported in the casing so that they are appropriately tensioned to avoid sag when they are heated, and are able to withstand shock and vibration.
Description (OCR text may contain errors)
United States Patent 1 1 Di Benedetto et al.
[451 Nov. 4, 1975 1 AREA FLOOD GUN  Assignee: Texas Instruments Incorporated,
 Filed: Feb. 22, 1974  Appl. No.: 444,798
Stapleton et a1. 313/278 Adams, Jr 313/278 Primal ExaminerSaxfield Chatmon, Jr. Attorney, Agent, or Firml-larold Levine; James T. Comfort; Richard L. Donaldson  ABSTRACT An electron source is provided by thermionic filaments in the form of elongated strips or wires, such filaments being mounted within a casing. A deflector electrode is formed on a wall of the casing behind the filaments and director electrodes placed forward of the filaments in the direction in which the electron flow is desired. The various electrodes are positioned relative to the filaments and have potentials applied thereto such that uniform distribution of electrons is provided over a predetermined area over which electron flow is desired. The filaments are resiliently supported in the casing so that they are appropriately tensioned to avoid sag when they are heated, and are able to withstand shock and vibration.
2 Claims, 5 Drawing Figures US. Patent Nov. 4, 1975 mdE AREA FLOOD GUN This invention relates to electron guns, and more particularly to such a gun capable of distributing electrons emitted from a thermionic filament over a predetermined area.
In US. Pat. No. 3,769,540, issued on Oct. 30, 1973, an area electron flood gun is described which utilizes a plurality of strip filaments in conjunction with appropriately positioned deflector and director electrodes to generate electrons which are uniformly distributed over a predetermined area. In the illustrative embodiment of the invention shown in said patent, the filaments are mounted within a deflector electrode in the form of a flat dish, this deflector electrode being a separate member which is mounted within a casing. in the device shown in the patent, the filaments are suspended between opposite wall portions of the dish electrode by means of filament leads which provide a small amount of spring tensioning therefor.
It has been found that while an assembly of this type operates satisfactorily under conditions involving little shock or vibration, it is unable to withstand high shock and vibration conditions such as, for example, encountered in military aircraft. A highly ruggedized design has been used to overcome this difficulty. This design, while highly successful in withstanding vibration and shock tests, was found to be much heavier and more expensive to manufacture than to be desired. Further, it was found difficult to de-gas the device due to the need for welding of parts and the use of nuts and bolts in its construction which tended to trap gas. Further, it was found difficult to maintain the distance between the filament and the deflector electrode constant with the heating of the filaments.
The present invention provides an improvement over the device of the aforementioned patent as well as prior attempts at a ruggedized design, in affording an area cathode in which the structural members of the deflector electrode are eliminated by forming this electrode on a wall of the casing.
Further, a novel spring tensioning device is embodied in the filament support which is of simple design, yet highly effective in maintaining the filaments uniformly spaced from the deflector electrode during heating, at the same time affording a proper resilient support for enabling the filaments to withstand shock and vibration. This end result is achieved in the device of the present invention with structure which is of simple and economical design and has a minimum weight.
Referring now to the drawings, FIG. 1 is a cross-sectional view of one embodiment of the invention;
FIG. 2 is a view illustrating the spring tensioning mechanism of the embodiment of FIG. 1;
FIG. 3 is a cross sectional view taken along the plane indicated by 3-3 in FIG. 2;
FIG. 4 is a cross-sectional view showing an alternative embodiment ofa spring tensioning mechanism that may be utilized in the device of the invention; and
FIG. 5 is a cross sectional view taken along the plane indicated by 5-5 in FIG. 4.
Briefly described, the device of the invention is as follows: A deflector electrode is formed by depositing a thin metallic film on the inner wall of the casing housing the electron gun, which is opposite to the wall of such casing towards which the electrons are to be directed (for example, the wall on which the display is generated). Thermionic filaments for generating the 2 electrons are mounted in spaced relationship to the deposited deflector electrode by means of resilient support mounts in the form of spring members which tension the ends of the filaments.
Referring now to FIGS. 1-3, one embodiment of the invention is illustrated. Deposited on a wall of casing 11 is a thin metallic film 12 which may, for example, be of aluminum deposited by conventional vacuum deposition techniques. Deposited layer 12 forms a deflector electrode and extends over the area through which the electron flow is desired, as described in the aforementioned US. Pat. No. 3,769,540. Spaced from electrode 12 are a plurality of thermionic strip or wire filaments l4. Positioned between the filaments and electron target 15, which may comprise a phosphor layer, are a plurality of control plates and deflector electrodes 17, as described in US. Pat. No. 3,769,540. The construction and operation of the control plates, deflector electrodes and target form no part of the present invention and therefore will not be discussed further herein. This invention is rather concerned with the structure for the deflector electrode 12 and the means for supporting filaments l4.
Filaments 14 are each attached at one end thereof, e.g., by welding, to metallic strip 18 which is attached to posts 20 mounted on a wall of casing 11. Casing 11 may be fabricated of glass or ceramic material. The other ends of the filaments are fixedly attached, as by welding, to metallic strip member 25 which is welded to pins 27, the pins being fused to casing ll. Fixedly attached to strip 25 as by welding are a plurality of spring members 30. Also attached to strip member 25 is a rod 32. Spring members 30 are fabricated of a highly resilient material. such as Inconel 750, and have bent over end portions 30a which are joined to U-shaped portions 30b at the opposite ends thereof by a linear portion 300. The filaments 14 are spaced from deflector electrode 12 by means of rod 32 over which they pass, and are resiliently held in this position by virtue of the abutment of end portion 30a of the spring members thereagainst. it thus can be seen that the filaments are resiliently tensioned to maintain the desired spacing from electrode 12 and at the same time are cushioned against shock and vibration by virtue of the spring action of the spring members.
Referring now to FIGS. 4 and 5, an alternative embodiment for the spring members is illustrated. This second embodiment has the advantage in that it requires less space laterally for its implementation. In this embodiment, the rod 32 is eliminated and spring 30 is formed from a pair of generally vertically extending leaf portions 30a and 30b. Leaf portion 30a is attached to support strip 25 which is mounted on casing 11. Leaf spring portion 300 has a plurality of vertical slots 300 formed therein and the filaments 14 are placed within one of these slots and fixedly attached to the spring at this point by suitable means such as welding. The springs are appropriately tensioned to provide the desired resilient support for filaments 14.
While the device of the invention has been described and illustrated in detail, it is to be clearly understood that this is intended by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the following claims.
l. in an electron flood gun for providing a uniform flow of electrons over a predetermined area, said gun 3 comprising elongated filament means for generating electrons. flat deflector electrode means encompassing substantially said predetermined area and proximate to said filament means in a first direction therefrom and flat director electrode means parallel to said deflector electrode means and proximate to said filament means in a direction therefrom opposite to said first direction and towards which the flow of electrons is desired, and a casing, said gun being mounted within said casing, the improvement including:
said deflector electrode means being formed on one of the walls of said casing, and means for resiliently supporting the filament means in spaced relationship from the deflector electrode means in a plane parallel to said deflector electrode means, said resilient means comprising a spring 4 member resiliently tensioning one end of each of said filament means,
said spring members each comprising a bent over portion at one end thereof and further including a rod member fixedly mounted adjacent to said spring members, the filament means being passed over said rod member and resiliently urged against said rod member by the bent over end portions of the spring members.
2. The device of claim I wherein said spring members each include a U-shaped portion at the ends thereof opposite said one end, said U-shaped portions being fixedly attached to the casing and a linear portion inter connecting said U-shaped portions and said bent over portions.
a e a a