US3327157A

US3327157A - Cathode unit for electric discharge tubes

Info

Publication number: US3327157A
Application number: US396882A
Authority: US
Inventors: Jurgens Wilhelmus Albert
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1963-09-20
Filing date: 1964-09-16
Publication date: 1967-06-20
Anticipated expiration: 1984-06-20
Also published as: CH425000A; NL298210A; ES304155A1; DE1234857B; AT250517B; NL142273B; GB1025168A; BE653296A

Description

June 1957 w. A. JURGENS CATEQDE UNIT FOR ELECTRIC DISCHARGE TUBES Filed Sept. 16, 1964 INVENTOR.

WILHELMUS A. JURGENS United States Patent 3,327,157 CATHODE UNIT FOR ELECTRIC DISCHARGE TUBES Wilhelmus Albert Jurgens, Emmasingel, Eindhoven, Netherlands, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Sept. 16, 1964, Ser. No. 396,882 Claims priority, application Netherlands, Sept. 20, 1963, 298,210 Claims. (Cl. 313278) My invention relates to a cathode for an electric discharge tu'be, and in particular to a directly heated cathode comprising a plurality of thin wires connected in parallel.

Known constructions of such cathodes comprising parallel thin wires utilize solid cylindrical supporting rods which, after being mounted in an electrode system, are pulled apart by spring action, resulting in the wire portions being tightened. The cylindrical supports are rods which, prior to incorporation of the cathode in an electrode system, are connected together solely by the wire portions of the cathode. However, such an assembly does not form a rigid unit which can readily be handled, while all of the wire portions must be connected to the supporting rods in order to avoid shifting thereof. Moreover, during mounting in an electrode system, complicated supports and guides for the supporting rods must be provided to prevent variation in the distance of the cathode from the other electrode.

This known construction of a cathode affords the important advantage, however, that the cylindrical supporting rods can adjust themselves so that all the wires of the cathode are tightened equally, irrespectively of small deviations resulting from not particularly accurate mountmg.

US. Patent 3,177,393 discloses a construction for a cathode unit in which the cathode wire is wound tightly over two U-shaped supports the supports being spaced apart by means of a supporting plate as long as the cathode is not mounted in an electrode system. After mounting, the U-shaped supports are pulled apart by spring action and can somewhat slide over the supporting plate so that the cathode wires invariably remain tightened. However, when inaccurately mounted in an electrode system, the U-shaped supports cannot, due to friction with the supporting plate, relatively adjust themselves sufiiciently to prevent the cathode wires from being tightened unevenly. However, this prior construction affords the advantage that the cathode forms a rigid unit which can easily be handled even prior to mounting. The wound cathode wire need only be connected at its ends to one of the supports.

The construction according to the present invention affords the advantages of the above-mentioned constructions without the disadvantages thereof. According to the invention, the cylindrical supporting bodies are hollow cylinders spaced apart by a body which is rod-shaped at least at its ends and passes through a central aperture provided in each cylindrical envelope.

Since the aperture in the cylindrical envelope is a little larger than the cross-section of the rod-shaped portion of this body, the cylindrical supports can adjust themselves with respect to the supporting rod and mutually, resulting in a uniform tension in the wire being obtained even if the mounting is not particularly accurate. Besides, the assembly comprising the cylinders and the body forms, after tightly winding the cathode wire on it, a rigid unit which can easily be handled. It is to be noted that the sectional area of the cylinders may have any arbitrary shape.

As a rule, metallic hollow cylinders will be used which are supported in an insulated manner by a ceramic rod.

However, it is also possible to use hollow cylinders internally covered with insulating material, together with a metallic body, or insulating cylinders on which a metallic strip may be provided for electrically connecting the wire portions of the cathode in parallel. If desired, the strip may be divided into various sections to enable certain groups or all of the parallel cathode wires to be connected in series for a higher heating voltage and a lower heating current to be used. As a further alternative, the body may be constituted by either two metal parts separated by an insulating body, or a plate, made of metal or of insulating material having rod-shaped portions which extend into the supporting cylinders.

The invention will now be described with reference to the accompanying drawing, in which:

FIGURE 1 shows a cathode unit after being mounted in a tube;

FIGURE 2 is a side view of the cathode unit of FIG- URE l, but prior to mounting in a tube;

FIGURES 3, 4 and 5 show portions of other em'bodiments according to the invention.

The cathode unit shown in FIGURES 1 and 2 comprises hollow supporting

cylinders

1 and 2 of metal, for example, of nickel. Each of the

cylinders

1 and 2 has a central aperture 12 through which extends an insulating rod 3, which bears against the inner sides of the

cylinders

1 and 2, thus spacing them apart. A cathode wire 4 covered with electron-emissive material 5 is wound over the

cylinders

1 and 2, the emissive layer 5 being scraped oil the portions of the wire 4 which bear on the

cylinders

1 and 2. The unit shown in FIGURE 2 forms a rigid assembly after the ends of the cathode wire are welded to the

cylinder

1 or 2.

The cylinder 2 is fixed in a mica plate 13 by means of clasps 6, 7 and 8, the cylinder 1 being secured to a spring 11 by means of

clasps

9 and 10. The spring provides for the wire portions of the cathode to remain tightened when the cathode wires expand upon heating.

Since the supporting rod 3 passes through the apertures 12 with some clearance, the cylinder 1 can slightly deviate sidewards and tilt about the supporting rod 3 so that, if the cylinder 2 is mounted inaccurately, the cylinder 1 can adjust itself so that all of the

wire portions

4, 5 are again tightened evenly.

In the embodiment shown in FIGURE 3, the cylinders 5 are of ceramic material, each having a metallic strip 16 formed or provided on it by chemical or mechanical means to enable the wire portions of the cathode to be electrically connected in parallel. If desired, the metal strip 16 may be subdivided on one or both cylinders so as to obtain series-connected groups of wire portions connected in parallel. As an alternative, all of the parallel wire portions may be electrically connected in series.

In the embodiment shown in FIGURE 4, the

metal cylinders

1 and 2 are spaced apart by

metal rods

17 and 18 which are connected together in an insulating manner with the aid of a glass or ceramic bead 19.

In the embodiment shown in FIGURE 5, the member is a metal plate 20 which spaces apart the

cylinders

1 and 2 by means of two ceramic rod-shaped parts 21.

The plate-shaped part 20 forms a separation between the two planes in which the cathode wires 4 are located and this is favorable for short waves since the electrons of the two planes in which the cathode wires are located are now separated, resulting in a specific, sharply-defined transit time of the electrons.

In conjunction with the embodiment of FIGURE 3 the parts 21 may likewise be of metal and integral with the plate 20, if desired. Since the plate 20 becomes fairly hot, it is possible to provide on it a metal having a gettering effect at a high temperature, for example, zirconium in the pulverulent state. If desired, a certain potential maybe appliedto the plate in order to improve its'shielding action or geetering action. As an alternative, the plate may be conductively connected to one of the supporting cylinders.

The present invention is not limited to the examples described.

What is claimed is:

1. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, and a body having a rod-shaped portion extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said apertures having a diameter larger than that of the rod.

2. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, and a body having a rod-shaped portion extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said apertures having a larger cross-section than that of said rod-shaped body.

3. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, and a rodshaped ceramic body extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said apertures having a larger cross-section than that of said rod-shaped body.

4. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, and a rod-shaped body extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said rod-shaped body comprising two metal portions connected together and insulated from each by the interposition of an insulating material, said apertures having a larger cross-section than that of said rod-shaped body.

5. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, and

'a body extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said body comprising a plate-shaped portion intermediate two rod-shaped portions each of which extend into one of said apertures, said apertures having a larger cross-section than that of said rod-shaped body.

6. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical insulating supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports,

each of said supports having a strip of conductive material for connecting said wires in parallel, and a body having rod-shaped portions extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said apertures having a larger cross-section than that of said body.

7. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, a body having rod-shaped portions extending between and through said apertures into each of said supports for spacing the supports a given distance apart, and means to connect said body in an electrically conductive manner to one of said cylindrical supports, said apertures having a larger cross-section than that of said body.

8. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, and a rod-shaped body covered at least in part with a getter material extending between and through said apertures into each of said supports for spacing the supports a given distance apart, said apertures having a larger crosssection than that of said body.

9. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical ceramic supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, each of said supportshaving metallized portions for connecting said wires electrically in parallel and a body having rod-shaped portions extending between and through said aperturesinto each of said supports for spacing the supports a given distance apart, said apertures having a larger cross-section than that of said body.

10. A directly heated cathode for an electric discharge tube comprising a pair of spaced hollow cylindrical supports having aligned apertures therein, a plurality of parallel thin wires wound over the two supports, a body having rod-shaped portions extending between and through said apertures into each of said supports for spacing the supports a given distance apart, and resilient means engaging said cylindrical supports for imparting tension to said wires mounted thereon, said apertures having a larger cross-section than that of said body.

References Cited UNITED STATES PATENTS 1,720,442 7/1929 Robinson 3 l3-278 1,980,937 11/1934 Dodge 3l3260- 2,656,477 10/1953 Herbold 313-346 FOREIGN PATENTS 249,768 5/ 1963 Australia.

JAMES D. KALLAM, Primary Examiner.

JOHN W. HUCKERT, Examiner.

A. 1; JAMES, Assistant Examiner.

Claims

1. A DIRECTLY HEATED CATHODE FOR AN ELECTRIC DISCHARGE TUBE COMPRISING A PAIR OF SPACED HOLLOW CYLINDRICAL SUPPORTS HAVING ALIGNED APERTURES THEREIN, A PLURALITY OF PARALLEL THIN WIRES WOUND OVER THE TWO SUPPORTS, AND A BODY HAVING A ROD-SHAPED PORTION EXTENDING BETWEEN AND THROUGH SAID APERTURES INTO EACH OF SAID SUPPORTS FOR SPACING THE SUPPORTS A GIVEN DISTANCE APART, SAID APERTURE HAVING A DIAMETER LARGER THAN THAT OF THE ROD.