US2570606A - Damper bar for filamentary cathodes - Google Patents

Description

1 Oct. 9, 1951 SIMPSON 2,570,606

DAMPER BAR FOR FILAMENTARY CATHODES Filed May 12, 1949 INVENTOR ATTO EY Patented Oct. 9, 1951 DAMPER FOR FI LAMENTARY CATHODES Kenneth H. SimpsonpMaplewood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May "12, 1949, Serial No. 92,788

1 My invention relates to electron dischargedevices having filamentary cathodes and more particularly to a damping means for such cathodes to prevent vibration thereof.

Some electron discharge devices. employ two spaced parallel insulating plates, usually of mica, for suitably spacing a concentric array of electrodes. Where a filamentary cathode is ineluded in the device it is usually threaded through apertures in the plates and engaged at one or both ends thereof by suitable tensioning means for maintaining the cathode or filament taut between the plates. To prevent vi- 5 Claims. (01. 313269) bration of the taut filament various expedients have been proposed including mica strips and insulated metallic damper bars for engaging a portion of the filament intermediate the plates.

Such expedients, however, have not proven completely satisfactory. For example, some electrode mounting procedures require that the electrodes other than the cathode .be first assembled in a mount together with the cathode damping means. In such instances the subsequent mounting of the cathode in the mount becomes difiicult due to the necessity of observing care that the cathode filament is threaded properly with respect to the damping means. Usually the damping means is designed to engage the cathode by a critical side or portion thereof and to assure such engagement recourse sometimes has been made to special vibrating jigs for guiding the filament in a predetermined path between the insulating plates referred to for proper orientation of the filament with respect to the damping means. The necessity for the high degree of care and special jigs'that has characterized prior practices in mounting filamentary cathodes in assemblies that include damping means, adds to the cost of manufacture by slowing down the cathode mounting operation and increasing the expense of equipment.

While this difliculty has heretofore been recognized and attempts to overcome it have been made, such attempts have not provenfully acceptable. Thus, one proposal involves the use of a wire hook having insulation thereon for engaging the filament by either one of opposite sides of a hook. This arrangement permits greater freedom in threading the filament in the mount since care need not be exercised to position the filament to a particular side of the damper hook. However, an objectionable feature of this proposal resides in th'ejneed for a relatively large structure for the damper hook,

since it includes angularly disposed portions re quiring a wider area for accommodation than is sometimes provided by the electrode adjacent the cathode. For example, when a wound control grid is employed the distance between opposite portions of the turns thereof maybe less than the lateral extent of the damper hook between these portions. Since the greater portion of the damper hook is usually provided with a relatively thick coating of insulation to insulate it from the cathode this proposal restricts the spacing between adjacent turns of the grid to a magnitude greater than the thickness of the coated hook. This type of damping means cannot therefore be used in instances where the control grid is closely wound or where it is of relatively small overall size such as in miniature electron discharge devices.

Another objection to this and' other types of damping means of the prior art is that the form of the damping means must be very carefully made and the mounting of the damping means must be accomplished in a very critical manner to assure proper engagement therewith by the filament.

Accordingly, it is the object of the present invention to provide an improved damping means for filamentary cathodes.

A further object is to provide an improved damper bar for properly engaging a filamentary cathode in any one of several positions in which the cathode may be threaded in a mount. f

Another object is to provide a straight damper bar for a filamentary cathode that is suitable for relatively cramped space conditions in 'a mount.

A further object is to provide a straight damper bar that is properly mounted in an electrode assembly with a relatively small degree of care.

Another object is to reduce the cost of manufacture of electron discharge devices having filamentary cathodes by providing an'improved straight damper bar that is easily and quickly mounted in the assembly of the device and that permits a rapid and accurate mounting of-the cathode in the device.

Further objects and advantages of the invention will become apparent as the present description proceeds.

Referring to the drawing for a better under standing of the invention;

Figure 1 is an elevation partly in section of an electron discharge device employing the im proved damper bar of the invention;

Figure 2 is a transverse section along 2-2 of Figure 1;

Figure 3 is a longitudinal section along 3-3 of Figure 2; and

Figure 4 is a modification of the manner in which my novel damper bar may be mounted.

Referring now in more detail to the drawing, there is shown in Figure 1 thereof a miniature type of electron discharge device including an envelope l closed at one end by a fiat stem H and having an electrode mount comprising anode I2, grid 53 supported on grid side rods I4, I5 and a filamentary cathode [6. The electrodes referred to are mounted between insulating spacer plates H, l8 and are connected to suitable lead-ins 19. The filamentary cathode IB is tcnsioned by a spring member 20, sup: ported on rod 2!, which is fixed to spacer I! by eyelet 22. The spacers ll, 18 are provided with suitable apertures for receiving the side rods i4, i5 and for threading the filament l6 therethrough. The side rod and filament apertures referred to are preferably disposed in a plane normal to said spacers for appropriate disposition of the filamentary cathode with respect to the grid.

According to the invention, means are provided for damping vibrations that otherwise might occur in the portion of the filamentary cathode it that extends between the spacers ll, i8. In one embodiment of the invention as shown in Figures 1, 2 and 3 the damping means comprises a straight damper bar 23 having a coating of insulation 24 intermediate two bare end portions thereof.

The damper bar is preferably disposed between grid side rods l4, 15 in such a manner that one bare end portion engages one side of side rod l4 and the other bare end portion of the damper bar engages the opposite side of rod 15. The damper bar 23 may be fixed to one or both of side rods l4, [5 as by welding shown at 25 and 26 in Figure 2.

This manner of mounting of the damper bar according to the invention causes the intermediate insulated portion thereof to symmetrically cross the axis of suspension of the filamentary cathode [6 as shown in Figure 3. Thus, at the point where the damper bar crosses said axis an equilateral extent of said bar occurs on opposite sides of the axis referred to. This has two advantages. It permits the mounting of the damper bar on the side rods with a minimum of care. Thus, proper positioning of the damper bar is assured by merely causing its bare end portions to engage opposite sides of the grid side rods l4, l5 and fixing one or both end portions to the side rods. This reduces the demand for skill on the part of the operator and speeds up the mounting operation, resulting in substantial economies in manufacture.

A-nother advantage of this arrangement is that the filamentary cathode I6 is properly engaged by either of two opposite sides of the damper bar. There is therefore no need to employ expensive jigs and resort to the tedious and comparatively slow operation of threading the cathode so as to lie to one particular side .of the damper bar. This reduces the operation of mounting the cathode to such simple terms that all the operator needs to positively provide for is the threading of the cathode through the two registering apertures provided for in the spacers -11, l8. This contributes to a further reduction in the cost of making an electron discharge device wherein a filamentary cathode is desirably .damped.

It will be noted that the straight damper bar' 23 with its insulation 24 requires a space between the side rods l4, 15 that is characterized by a relatively small lateral extent. This feature renders the damper bar of the invention particu larly suited for devices of the miniature type where the space defined by control grid [3 is relatively small. In addition, the damper bar 23 is comprised of a wire or rod having a relatively small cross section at its end portions so that it is suitable for use with relatively closely wound grids without interfering with any grid turns.

A modification of the invention is shown in Figure 4 which involves a diiferent mounting of the damper bar 23 on the grid side rods [4, I5 than that shown in the figures heretofore discussed. In this instance the damper bar 23 is mounted to engage analogous sides of the side rods i4, i5. This disposes the greater portion of the insulated intermediate portion 24 of the damper bar to one side of the axis of suspension of the filamentary cathode 16. In some types of miniature electron discharge devices this manner of mounting of the damper bar results in a relatively close spacing between one side of the damper bar and one side of grid [3. This spacing may be so close as to prevent threading of the filamentary cathode l6 therethrough. This has the advantageous consequence of permitting the cathode to be threaded only in a path that is adjacent the opposite side of the damper bar which side is spaced farther from grid [3 than the first mentioned side. the structure of this modification inherently limits the position of the cathode to one particular side of the damper bar contributes to ease, rapidity and accuracy of the cathode mounting operation which add to economical manufacture of an electron discharge device in which it is used.

It will be noted that the magnitude of deflection of the filamentary cathode 16 from its axis of suspension in the two embodiments described is different. Thus, when the damper bar engages one of opposite sides of the grid side rods as shown in Figure 2, a greater lateral deflection of the cathode occurs than where the damper bar is connected to corresponding sides of the side rods as shown in Figure 4. In some larger types of tubes opposite portions of the grid are spaced by a relatively large magnitude that would not permit the relatively close spacing between the insulated portion of the damper bar and the grid as shown in Figure 4. In such case the cathode would find a path on either side of the damper bar. However, the engagement of the cathode by one side of the damper bar would result in a greater magnitude of deflection than would occur if the opposite side of the damper bar engages the filament. This latter condition is undesirable since it might cause differences in the characteristics between several tubes of the same type. Consequently, in such instances, the diagonal mounting of the damper bar on the side rods as shown in Fig. 2 would be necessary. The greater deflection that this would impart to the cathode is not objectionable in tubes of relatively large size since the deflection would be I small in relation to the size of the tube.

However, in some small size tubes the deflection afiorded by the arrangement of Fig. 2 might be excessive. In such cases the arrangement shown The fact that l in Fig. 2 which provides for a smaller deflection of the cathode is preferred. As indicated before herein, the mounting of the damper bar as shown in Fig. 4 in addition to reducing the degree of deflection of the cathode as required in a small tube, also utilizes to advantage the small size of the tube including the relatively close spacing of opposite sides of the grid I3 for restricting the threading of the cathode to a path that is adjacent one particular side of the damper bar.

The damper bar of the invention and its manner of mounting are therefore advantageous in large and small size electron discharge devices, and lend themselves to particular utility in each of these types of devices. The damper bar is quickly, easily and accurately mounted in a device and permits in turn quick, easy and accurate mounting of the cathode in the device, resulting in appreciable economies in manufacture.

Various additional embodiments of my invention may present themselves to persons skilled in the art without departing from the spirit of the invention and I desire to include such embodiments within the scope of the appended claims.

I claim:

1. An electron discharge device having a filamentary cathode, a grid having transverse wires and side rods supporting said wires, two spacer plates having apertures for receiving said side rods and said cathode, said apertures in said two plates being disposed in a common plane, and a straight damper bar engaging said side rods between two of said transverse wires and intermediate said spacer plates, said damper bar having an intermediate portion coated with insulating material and bare end portions, said intermediate portion extending across the axis of the apertures for said cathode for engaging said cathode and deflecting the same in a plane normal to said common plane for improved operation of said device, one of said bare end portions being fixed to one of said side rods.

2. An electron discharge device having a filamentary cathode, a grid comprising a plurality of turns of wire forming a tubular structure, grid side rods lying in a common plane including the axis of said structure and engaging opposite sides of said tubular structure for supporting said turns of wire, whereby the maximum effective portion of said grid is disposed in a plane normal to said common plane, and a damper bar consisting of a straight wire having bare end portions engaging said side rods and having a coated portion for deflecting said cathode and restraining vibrations therein in said normal plane, whereby said cathode is fixed against relative movement with respect to said maximum effective portion of said grid.

3. An electron discharge device having a fllamentary cathode extending along the axis of said electron discharge device, a grid surrounding said cathode and having oppositely disposed side rods extending parallel to the axis of said electron discharge device, a plurality of turns of conductors supported on said side rods, a damper bar consisting of a straight conductor having bare end portions engaging said side rods and having a coated portion intermediate said ends, said coated portion engaging and deflecting said filamentary cathode intermediate its ends and away from the axis of said device and restraining vibrations therein in a direction normal to said axis whereby said filamentary cathode is fixed against relative movement normal with respect to the surface in which the conductors of said grid lie. E has 4. An electron discharge device having a filamentary cathode, a tubular electrode surrounding said filamentary cathode and having opposite portions of maximum effect on electrons emitted by said cathode, and a damper bar consisting of a straight wire having bare end portions engaging opposite portions of said tubular electrode intermediate said first named opposite portions, said damper bar having an insulating coating thereon intermediate its ends for engaging and deflecting said cathode, whereby said cathode is fixed against vibratory movements with respect to said first named opposite portions for improved operation of said device.

5. A sub-assembly for an electron discharge device comprising a control grid including a plurality of spaced turns of wire forming a tubular structure and grid side rods at opposite sides of said structure for supporting said turns of wire, and a straight damper bar consisting of a straight wire having bare ends engaging leading sides of said side rods during rotation of said grid in a predetermined direction and intermediate two F adjacent turns of said wire, whereby said damper bar is adapted to be mounted on said grid by automatic mechanized means and extends across the axis of said tubular structure, an intermediate portion of said damper bar having an insulating coating adapted to engage and deflect a filamentary cathode supported axially of said tubular structure, in the plane of maximum control by said grid for improved operation of said device.

KENNETH H. SIMPSON.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,572,726 Kelly Feb. 9, 1926 1,636,239 Metcalf July 19, 1926 1,886,991 Van Horne Nov. 8, 1932 1,930,563 Ponte Oct. 17, 1933 2,259,703 Miller Oct. 21, 1941 2,266,080 Rockwood Dec. 16, 1941 2,303,277 Ishler Nov. 24, 1942 2,303,278 Ishler Nov. 24, 1 942 2,350,003 West May 30, 1944 2,358,829 Rockwood Sept. 26, 1944 FOREIGN PATENTS Number Country Date 389,176 Great Britain Mar. 16, 1933 515,288 Great Britain Nov. 30, 1939

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