US3054923A

US3054923A - Electron discharge tube

Info

Publication number: US3054923A
Application number: US794603A
Authority: US
Inventors: Bayard R Corson
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1959-02-20
Filing date: 1959-02-20
Publication date: 1962-09-18
Anticipated expiration: 1979-09-18

Description

Sept. 18, 1962 B. R. CORSON ELECTRON DISCHARGE TUBE.

Filed Feb. 20, 1959 INVENTOR Bayard R. Corson ezia/ mwrar 2 4 E 8% 4 o I [3 Illa l w IIL F S w a w s 03 E N m m 22 n w United grates Patent @fihce 3,954,923 Patented Sept. 1%, 1962 N.J., assignor to Westing- East Pittsburgh, Pa., a cor- This invention relates to an electron discharge tube and more particularly to an improved electrode assembly.

One particular application of this invention is in a damper diode. A damper diode is a high perveance diode used in the horizontal deflection circuit of television receivers. In this application, the tube is required to carry a relatively high current in the forward direc tion and to hold off a relatively high voltage in the reverse direction.

One of the problems encountered with damper diodes is the tendency of the tubes to arc internally when the high inverse voltage is applied. The most common type of arc originates at the anode and terminates at the cathode, and its path is parallel to and between the lam-inations of a mica spacer member used to support the anode and cathode within the tube envelope.

Previous attempts have been made to eliminate the tendency of damper diodes to arc by two general methods used separately or in combination. One method utilizes slots cut in the mica spacer between apertures provided for the cathode support rods and the apertures provided for the anode support rods. These slots lengthen the arc path and diminish the cross section of the leakage path. In another method, the mica spacers are coated with an oxide or hydroxide of magnesium or aluminum either alone or in combination.

The previous attempts to eliminate the arcing tendency in a damper diode have been only partially successful. Hence, it is a general object of this invention to provide an improved high voltage tube.

It is another object of this invention to provide a damper diode which will operate at high inverse voltage Without arcing.

It is a further object of this invention to provide improved means for supporting and positioning an electrode assembly within the envelope of an electron tube.

It is an additional object of this invention to provide an electrode support means that will prevent arcing at high inverse Voltages.

It is an auxiliary object of this invention to provide anode support means which prevent the anode from contacting the cathode support means.

These and other objects of this invention will be apparent from the following description taken in accordance FIGURE 1 shows an electron tube embodying this invention with the envelope and portions of the electrodes cut away to show the details of the electrodes;

FIG. 2 is a top view of the electron tube shown in FIG. 1 with the top of the envelope and the getter holder cut away;

FIG. 3 is an expanded view of a portion of the tube shown in FIG. 1 showing the assembly of the spacer members; and

FIG. 4 is a cross-sectional view of the top of FIG. 1 along lines IV IV showing the space relation and shape of the electrodes.

A study of the arcing problem Within a damper diode tube was conducted, and it was observed that the arcing usually takes place between the laminations of the mica spacer from anode to cathode. It was discovered that when there are two metallic elements, one of which is in contact with mica, there is a polarity eiiect. This polarity elfect is thought to be due to conducting or semiconducting impurities such as metals and lower oxides of metals in the material used to cement the mica sheets together.

It is probable that these impurities form a discontinuous film which does not degrade the insulating properties at low voltage but which does degrade the insulating properties at high voltages resulting in breakdown. It has also been found that, due to this polarity effect, when the metallic element in contact with the mica spacer is at a negative potential with respect to the other metallic element, breakdown will occur at a much lower voltage than when the metallic element in contact with the mica spacer is at a positive potential with respect to the other metallic element.

The arcing problem with the damper diode lies in the inverse region where the anode is thousands of volts negative with respect to the cathode. This invention provides a structure in which the anode is supported by insulative means other than the mica spacer member used to support the cathode and in which the anode does not contact the mica spacer member.

Although this invention is broadly applicable to all high voltage tubes, it has been illustrated and described in conjunction with a damper diode tube.

FIG. 1 shows a damper diode tube 10 in which the invention has been incorporated and which includes an evacuated envelope it of suitable material such as glass and an electrode assembly positioned within the envelope The envelope 11 is comprised of an elongated tubular body portion 28 closed at one end and closed at the opposite end by a stem comprising a glass disc 31 to which is attached a base portion 12. The electrode assembly includes an anode 13, a cathode 14 and a cathode heater 15. In the embodiment shown, the cathode 14 comprises a tubular member of an electrically conductive material, such as nickel, having a suitable electron emissive coating on its outer surface. The heater 15 is supported within the hollow part of the cathode i4 and is insulated therefrom by a spiral shield member 16. The heater provides the necessary heat to cause electrons to be emitted from the electron emissive coating. The spiral shield member 16 comprises an electrically conductive electrodes are connected to supporting and connecting wires 3% which extend through the glass disc 31 and some of which are connected to external contact pins 17 which extend through the base 12. In the embodiment shown, anode 13 comprises a central elongated cylindrical portion 25 and planar wing-like portions 26 extending from opposite sides of the cylindrical portion 25. A cylindrical opening is provided in each of the Wing portions 26.

The electrodes l3, l4, 15 are combined into the electrode assembly by the use of

spacing members

19, 20, and support

members

21, 23.

One of the spacing members member 19. This apertured member can be made of any down in the same manner as the mica, but at a somewhat higher voltage gradient. The insulating members 19 are provided with an interior aperture to provide clearance for the top ends of the cathode-heater assembly, and to provide an opening for the cathode, shield, and heater Although the insulating apertured members 19 are illustrated as being ring-shaped, it is apparent that the members can have any suitable shape.

The other spacing member is a fiat insulating disc-like member 20 of a material such as mica. This disc member 20 has a plurality of apertures in its interior and a plurality of projections 27 on its periphery. Four apertures are provided for the support members and a central aperture is provided to support one end of the cathode. The apertures for the main support members 23 are of substantially larger diameter than the support wire diameter to insure that the disc member 20 does not contact the main support wires 23. In the embodiment shown, the central aperture is substantially the same size as the cathode l4 and is used to support the cathode in properly spaced relation to the anode and to the envelope 1].. The apertures for the auxiliary support members 21 are substantially the same diameter as the diameter of the auxiliary support wires 21 and must be accurately located with respect to the central aperture since these apertures determine the interelectrode spacing and the concentricity of the electrodes in the completed tube.

In the preferred embodiment of the invention, the rigid

metallic support members

21, 23 are molded into the apertured insulating members 19 by the application of heat and pressure to form an integral subassembly. During this operation, the relative position of the

support members

21, 23 must be closely controlled since the positioning of these support members controls the interelectrode spacing and the concentricity of the electrodes in the completed tube.

A flat disc member 20 is added to this subassembly by passing one end of the auxiliary support members 21 into the apertures provided in the disc member 20, moving the disc member 20 in contact with the apertured member 19 and locking the disc member 20 in this position by means of eyelets 22 that are attached to the ends of the auxiliary support members 21 by any suitable means such as welding. The disc member 20 may also be locked into position by bending the auxiliary support members 21, or by other suitable means.

The ends of the main support members 23 which extend above the disc member 20 are inserted into the end of the cylindrical openings in the wing portions 26 of the anode 13 nearest the base 12 and secured to the anode 13 by any suitable means; for example, Welding. In a similar manner, the subassembly to which a disc member 20 has been added is attached to the end of the anode remote from the base after the ends of the cathode-heater assembly have been positioned within the central aperture of disc members 20. The cathode is thereby supported within the hollow cylindrical portion 25 of the anode and in coaxial relation with the anode by and between the disc members 20. The other end of the main support members which are attached to the base end of the anode are attached to the supporting and connecting wires. The free end of the main support wires 23 attached to the other end of the anode 13 may be used to support other components such as a getter 18.

In the embodiment shown, when the tube is assembled the disc-shaped members may additionally serve "as spacer members to position the electrode assembly within the envelope. The outside diameter of the projections 27 is slightly larger than the inside diameter of the envelope 11 so the projections 27 are slightly deformed when the electrode assembly is placed within the envelope.

The electrodes could also be combined into the electrode assembly by using the individual spacing and

support components

19, 20, 21, 23 rather than by using these members after they have been combined into a subassembly. The anode 13 is supported at the base end by two rigid metallic support members which enter the cylindrical opening of the wing portions 26 of the anode and which are secured to the anode by any suitable means; for example, Welding. The anode 13 is supported at the other end by two rigid metallic support members 23 which enter the cylindrical opening of the wing portions 26 of the anode and which are secured to the anode in the same manner as the members at the base end.

The free ends of the main support rods 23 that have been attached to the anode are passed through apertures provided in both the disc shaped members 20 and the apertures insulating members 19 for the main support members 23. Auxiliary support rods 21 are passed through apertures provided in the apertured insulating members 19. The

support members

21, 23 may be rigidly attached to the apertured insulating members by any suitable means such as a ceramic cement, silicate base materials, for example, sodium silicate or potassium silicate admixed with kaolin, such as now sold under the trademark of Sauereisen are suitable cements. The auxiliary support members 21 are passed through apertures provided in the disc members 26. The disc members 20arc locked adjacent to the insulating members by eyelets 22 that are attached to the auxiliary support members by any suitable means such as welding. The free ends of the support members attached to the base end of the anode are attached to supporting and connecting wires 30'. The ends of the main support wires which extend above the insulating member 19 remote from the base 12 may be used to support other components, such as a getter 18.

By application of suitable potentials to the electrodes, the operation of a tube using this invention is similar to the operation of a conventional damper diode tube. A damper diode using this invention will operate without mica arcing beyond 12,000 volts inverse voltage, whereas a conventional damper diode often arcs at inverse voltage of the order of 5000 volts or less.

While the present invention has been shown in one form only, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modificataions without departing from the spirit and scope thereof.

I claim as my invention:

1. An electron discharge device comprising an envelope having an electrode structure therein, means for supporting and positioning said electrode structure in said envelope, said support means comprising a plurality of main support members and auxiliary support members, said electrode structure comprising a hollow cylindrical anode having opposite laterally extending portions and an elongated cylindrical cathode, said main support members being attached to said laterally extending portions of said anode to support said anode within said envelope, a pair of annular insulative members of glass attached to said main support members, a pair of planar disc-like members of mica attached to said annular insulative members by said auxiliary support members, said cathode supported by said planar disc-like members within the hollow cylindrical portion of said anode and substantially coaxial therewith, said planar disc-like members positioned transversely to said cathode within said envelope and contacting the inner wall of said envelope.

2. An electron discharge device comprising an envelope having electrode structure therein, means for supporting and positioning said electrode structure within said envelope, said electrode structure comprising an anode and a cathode, said anode having a hollow elon gated cylindrical portion and planar wing portions extending outwardly from opposite sides of said cylindrical portion, said cathode comprising an elongated cylindrical member having securing means at one end, said support means comprising a plurality of support members some of which are attached to the base portion of said envelope, a pair of spaced annular glass members attached to and being pierced by a plurality of said support members, said planar wing portions of said anode being attached to said support members between said pair of annular glass members, a pair of thin fiat disc-like members attached to said annular glass members by others of said support members, each of said thin fiat disc-like members having a plurality of projections on its periphery and a plurality of apertures in its interior portion, said cathode supported by and between said thin fiat disc-like members within the hollow cylindrical portion of said anode and substantially coaxial thereto, said positioning means comprising said thin flat disc-like members positioned transversely to said cathode, said projections on the periphery of said thin flat disc-like members resiliently contacting said envelope.

3. An electron discharge tube comprising an envelope having electrode structure sealed therein, said envelope comprising a base portion, a central hollow cylindrical portion, and an axis, means for supporting and positioning said electrode structure within the envelope in spaced insulated relation, said electrode structure comprising an anode and a cathode, said anode having a central hollow cylindrical portion and planar wing portions on opposite sides of said cylindrical portion, said cathode comprising an elongated cylindrical member, said support means comprising main support members and auxiliary support members, a pair of glass rings pierced by and supported from said main support members, said anode Wing portions attached to said main support members to support said anode between said glass rings, a pair of fiat mica discs attached to said glass rings by said auxiliary support members, said flat mica discs having a plurality of projections on their periphery and a plurality of interior apertures, said interior apertures comprising a central aperture for supporting one end of said cathode, clearance apertures for said main support members having a substantially larger diameter than the diameter of said main support member, said cathode being supported between said flat mica discs by securing an end in each of the flat mica discs, said cathode being supported within the hollow cylindrical portion of said anode and coaxial therewith, said electrode structure positioned in said envelope and coaxial thereto by said flat mica discs, said flat mica discs being positioned transversely to said cathode and contacting said central portion of said envelope.

4. An electron device comprising an envelope including a tubular Wall portion and having an electrode assembly positioned within said tubular Wall portion, said electrode assembly comprising an elongated cathode and anode, a planar disc member of mica for positioning said electrode assembly within said envelope, said disc member transverse to the longitudinal axis of said envelope with its outer periphery in contact with said wall portion at a plurality of points, said disc having a first aperture, said cathode positioned within said first aperture to position said cathode with respect to said envelope Wall, an annular insulating member of different material than said disc attached to said disc member and to said anode for positioning said anode with respect to said cathode.

References Cited in the file of this patent UNITED STATES PATENTS 2,052,882 Krahl Sept. 1, 1936 2,057,115 Rothe Oct. 13, 1936 2,058,921 Steimel Oct. 27, 1936 2,118,002 Bennett May 17, 1938 2,350,003 West May 30, 1944 2,429,954 Corson Oct. 28, 1947 2,760,100 Klopping Aug. 21, 1956