US3461337A

US3461337A - Electron discharge device filament structure

Info

Publication number: US3461337A
Application number: US479208A
Authority: US
Inventors: Kiyoshi Uchimaru; Tetsuo Tsuji
Original assignee: Nippon Electric Co Ltd
Current assignee: NEC Corp
Priority date: 1964-08-15
Filing date: 1965-08-12
Publication date: 1969-08-12
Anticipated expiration: 1986-08-12

Description

Aug. 12, 1969 Kwosm H M ET AL 3,461,337

ELECTRON DISCHARGE DEVICE FILAMENT STRUCTURE Filed Aug. 12, 1965 INVENTORS 0s/// flaw/M400 BY 757500 75m 3 ATTORNEYS United States Patent US. Cl. 313-278 6 Claims ABSTRACT OF THE DISCLOSURE A cage-like filament support structure in which the filament wires are provided with intermediate supports connected to a movable support member, said support member being freely slidable. on a centrally located fixed support in a direction generally parallel to said wires.

This invention relates to electron discharge device construction, and more particularly to heating filaments for such devices.

It is an object of this invention to provide an improved type of support for electron discharge device filaments whereby long length filaments are supported in a mor reliable and satisfactory manner.

Another object is to provide a filament support having a longer life than prior support arrangements.

All of the objects, features and advantages of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a diagrammatic side view of a heating filament assembly for use in an electron discharge device,

FIG. 2a is an enlarged vertical sectional view of an intermediate support and insulating structure for heating filaments according to one embodiment of the invention,

FIG. 2b is a perspective view of the binding wire supporting portion of said filaments,

FIGS. 3aand 3b are views similar to FIGS. 201 and 2b, but of the conventional intermediate support and insulating portion,

FIGS. 4 and 5 are views illustrating deformation of the binding wire and the heating filament incorporated in a conventional assembly, and

FIGS. 6a and 6b, and 7a and 7b are views corresponding to FIGS. 2a and 2b showing modifications of the latter embodiment of the invention.

In a cage-like assembly of heating filaments comprising a multiplicity of element wires 1 arranged as shown in FIG. 1, it has been necessary to provide a plurality of supports at intermediate positions along the length of the assembly, as well as a central pole, in order to prevent deformation, vibration, listing, and the like of the element wires, because of their length. With such an assembly of heating elements, the heating current usually flows along every other element wire arranged parallel to one another, so that the directions of the currents in adjoining wires are opposite to one another, as indicated by the arrows in FIG. 1. As a consequence, there is a drop of the heater voltage along the axial direction of the filaments. It has therefore been necessary to bind and support every other filament at the points of same potential with metallic wires or conductors 2, 2'. Thus, when two intermediate supports which are to support the points "Ice of difierent potential are to be fitted to a common central pole 5, the intermediate supports and the central pole 5 must be insulated from each other.

In a conventional structure as shown in FIGS. 3a and 3b, the intermediate supports comprise binding wires 2 of heat-resistant metal such as tungsten or molybdenum which directly support filaments 1, and binding wire holders 3 also of heat-resistant metal. The holders 3 are supported by heat-resistant insulators 4, of for example, talc, steatite, or alumina ceramic. These insulators 4 are fixed to a central pole 5, in such a manner that the filament wires 1 and binding wires 2 are slidable along the supporting points 7 upon thermal expansion on heating or contraction on cooling of the filaments. With such a structure however, if the filaments are heated to a high temperature, the binding wires 2 tend to become baked on the filaments 1, so that slidable movement between these wires 2 and the filaments 1 at the supporting points 7 cannot occur. Thus, whenever the filaments 1 are heated or cooled, the binding wires 2 are pulled up or down by the filaments 1 as indicated by the dashed lines in FIG. 30, until the wires 2 are ultimately broken. Another disadvantage is that, because the binding wires 2 are not wound completely around the filaments, deformation of the filament wires due to inward deflection of the filaments as indicated in FIG. 5 cannot be avoided.

The present invention eliminates all of the foregoing difl'iculties, and provides a cage-like assembly of heating filaments protected against deformation, since intermediate supports which hold the heating filaments in place are made freely slidable upon the expansion and contraction of the filaments in the longitudinal direction. In one embodiment of the invention, illustrated in FIGS. 2a and 2b, each binding wire 2 is wound securely around a filament 1, and each intermediate support comprising a binding wire 2 and a binding wire holder 3 is fixed to a heat-resistant insulator 4, which in turn is held for slidable movement on a central pole 5. Also provided are upper and lower limiters 6 each spaced from the insulator 4 a distance equivalent to or greater than the amount of expansion and contraction of the filament 1. By such construction all the intermediate supports and the insulators 4 of the assembly can slide upward or downward along the central pole, according to the expansion or contraction of the filaments 1 on heating or cooling, as the case may be. It will thus be appreciated that'the binding wires 2 in such an assembly will not be bent upward or downward, and any possibility of inward deformation of the filaments as shown in FIG. 5 is prevented. The intermediate supports may be fixed to the insulators 4 by inserting the supports from the upper and lower portions of the insulators 4 as shown in FIG. 2, or by laminating the insulators and the intermediate supports alternately and fixing the uppermost layer with a retainer 8 as shown in FIG. 6a, or by any other suitable method. What have thus far been described are merely preferred embodiments of the present invention, and it is of course to be understood that the invention is also applicable to an assembly wherein the binding wires are fitted directly to the insulators in a suitable m-anner, as illustrated in FIGS. 7a and 7b. It will further be understood that various different arrangements may be provided whereby the insulator 4 may moves relative to the pole 5 upon expansion and contraction of the filament wires.

While the foregoing description sets forth the principles of the invention in connection with specific apparatus, it is to be understood that the description is made only by way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A heating filament support structure for an electron discharge device characterized in that binding wires are provided which support the heating filaments and are fixed to a heat-resistant insulator through the medium of attachment of binding wire holders of heat-resistant metal,

said heat-resistant insulator being supported on a central pole in a given position thereon solely by reason of the attachment thereof to said filaments and unbiased in the longitudinal direction thereof, and said insulator also being freely slidable upward and downward on said central pole in accordance with expansion and contraction of the heating filaments in the longitudinal direction.

2. In combination,

an array of heating filament strands which change in length upon heating and cooling thereof,

a first support member positioned amidst said array,

a second member supported on said first member in a given position thereon solely by reason of the connection of said first and second means to said strands and unbiased in the longitudinal direction thereof,

first means connected to said strands intermediate the length thereof for restraining lateral movement of said strands,

second means connecting said first means to said second member,

said second member being freely slidable in a first direction generally parallel to said filament strands upon heating thereof, and said second member also being freely slidable in the direction opposite to said first direction upon cooling of said filament strands.

3. The invention described in claim 2 wherein said first means comprises wires wound around said strands.

4. The invention described in claim 2 wherein said first member comprises a cylindrical support positioned centrally in said array.

5. The invention described in claim 4 wherein said second member comprises an insulator having a central aperture, said insulator being slidably mounted on said cylindrical support with the latter passing through said aperture.

6. In an electron discharge device, the combination comprising a plurality of heating filament strands which change in length upon heating and cooling thereof, said filaments being positioned relative to one another to form a cage-like structure,

a fixed member disposed generally centrally within said structure and generally parallel to said strands,

a movable member having an aperture therein, said movable member being mounted on said fixed member with said latter member passing through said aperture to provide slidable movement of said movable member relative to said fixed member,

means connected to each of said filament strands intermediate the length thereof and to said movable member for restraining lateral movement of said strands.

said movable member being supported in a given position on said fixed member solely by reason of the connection of said means between said strands and said movable member,

said movable member being unbiased in the longitudinal direction of its movement on said fixed member,

said second member being freely movable in a first direction generally parallel to said filament strands upon heating thereof, and said second member being freely movable in the direction opposite to said first direction upon cooling of said filament strands.

References Cited UNITED STATES PATENTS 1,723,904 8/ 1929 White 313-276 1,819,146 8/1931 Bol 313-273 X 1,927,084 9/ 1933 Depew 313-278 2,344,552 3/1944 Knochel et a1. 313-278 2,385,435 9/1945 Werner et al 313-278 JOHN W. HUCKERT, Primary Examiner A. J. JAMES, Assistant Examiner US. Cl. X.R. 313-273, 276