US1720442A - Vacuum electric-tube apparatus - Google Patents

Description

July 9, 1929.

E. Y. ROBINSON VACUUM ELECTRIC TUBE APPARATUS Filed June 1924 7 jab C1175? lhesflflfakizqali E Q Patented July 9, 1929 UNITED STATES PATENT OFFICE.

ERNEST YEOMAN ROBINSON, OF WITHINGTON, MANCHESTER, ENGLAND, ASSIGNOE TO ASSOCIATED ELECTRICAL INDUSTRIES, LIMITED, A BRITISH COMPANY.

VACUUM ELECTRIC-TUBE APPARATUS.

Application filed June 2, 1924, Serial No. 717,327, and in Great Britain June 19, 1923,

This invention relates to vacuum electric tube apparatus and especially to arrange ments :to-r supporting filamentary electron emitting cathodes. It is well known that for various reasons the filament is liable to move from the position in which it is located when the vacuum tube apparatus is manufactured. Such movement oitthe filament is especially undesirable in cases where there is a small gap or separation between the electrodes, as in those cases the filament or the like may move sutliciently to make contact with an electrode such as an anode which may be required, during the operation of the device, to be maintained at a potential which is widely different from that of the filament. The object of the present invention is to provide simple arrangements for supporting such filament-s, which will permit the gaps between the electrodes of the apparatus to be made short without the liability of the filaments moving relatively to the other electrodes and touching them.

According to this invention, the filament supported by one or more strip or blade like members in such manner that whilst the filament is continuously maintained under tension, it is constrained against movement in a lateral direction, that is to say, in the direction in which another electrode such. as an anode is located.

To enable the invention to be clearly understood, it will now be described with reference to the accompanying drawings, in which Figs. 1, 2 and 3 are diagrammatic views illustrating the principle of the invention carried out in three different ways,

Fig. t is a front elevation of a complete electrode structure embodying the inven tion;

Fig. 5 is a top plan view of the anode;

Fig 6. is a perspective view of one of the anode-supporting cross members;

Fig. 7 represents on an enlarged scale a section taken on the line 7-7 of Fig. 4 and looking toward the left;

Fig. 8 is an enlarged sectional view taken longitudinally through the free end oil one of the filament-supportingblades and the cooperating filament connecting strip; and

.Fig. 9 is an enlarged perspective view of the anchor frame for the filament-supporting blades.

In an arrangement commonly heretofore adopted for placing a single or a hairpin filament in tension, the filament is attached at one end to lead-in wire or wires or the like which arecomparatively rigid, and at the other end the filament is attached to a helical spring by means of a hook, the spring in turn being attached to a lead-in wire or other comparatively rigid support.

With that arrangement it will be appreciated that the filament is not in any way constrained, since in the first place the structure, especially in the. case of the hairpin filament, may be subjected to torsional strain, that is, it is capable of turning, but What is more important, especially in the case of a valve in which the inter-electrode gap is short, the filament is easily capable of moving laterally with respect to the otherv electrodes, due for example to electrostatic force, gravity or mechanical shock.

In another well known supporting and tensioning arrangement, the filament is attached at one end to a comparatively rigid lead-in wire whilst the other end is attached to the free end of a bow spring which is in turn attached to a comparatively rigid support or lead-in wire. With such arrangement the filament may be laterally deflected. Furthermore, the length of the filament changes when heated so that the position oi the spring is altered.

Other arrangements are known which have some or all the defects inherent in the prior arrangements just above described.

In Fig. 1 a cathode is shown consisting of two parallel filaments 1 which at one end are attached to rigid supports 2, such as leadin; wires, and are welded at their other ends to a spacing strip 3 of nickel which is fixed in any suitable manner to the free end of a strip member which is herein shown in the form. of a flexible blade 4, the other end of the blade being fixed to a rigid anchor or support 5., The blade 4 may be bent around the strip 3 as shown. The width of the blade ments due to expansion thereof under heat will not result in undesirable lateral deflection. The blade 4 may be elastic as well as flexible in which case it may constitute the tensioning means in substitution for the spring 6.- Thus in Fig. 2 the combined tensioning and registering devices therein illustrated comprise two substantially parallel elastic blades 9 and 10 connected together in bellows fashion attheir upper ends 11. The end 12 of the blade 9 is attached to the rigid support 13 whilst the free end 14 of the blade 10 has attached to it the filament 1.

The connection of the ends 11 of the blades is such that when a force in the direction of the arrow is applied to the free end 14 a partial 'contra-flexure occurs as shown by the dotted lines. It will be seen that inthis case the blades 9 and 10 must be elastic as well as flexible even if the elasticity is insufiicient to. provide the necessary tension for the filament.

The blades 9 and 10 may in effect be duplicated as shown in Fig. 3 in which the blade 10 is twice as long as the blades 9-and 15. Thefilament 1 is attached to the free end 14 of the blade 15 and the device may extend as shown by the dotted lines.

, Referring now to-Figs. 4 to 9 inclusive of the drawings, the electrode structure therein illustrated in Fig. 4 comprises a cathode consisting of two parallel filaments 1 and an anode 16 mounted on a'framework.

The framework comprises a pair of parallel and similar wires or rods 17 of nickel or molybdenum united at their ends by transverse members consisting of insulating -.rods18 preferably of pyrexglass into the ends of which rods are fused wires 19 which are welded. to the ends of the parallel wires 17 .f

The frame is supported on a re-entrant wtube 20, which may formcpart of the envelope of the device, by means of a clamp 21 havingoutwardly projecting webs 22 provided with perforations through which are; passed pieces of wire 23 the ends of which ,are twisted to drawthe clamp 21 tightly on to the re-entranttube 20. The clamp 21 has upstanding arms 21 to which are welded the side members 17 of the framework.

The anode, which is shown in top plan in Fig. 5, comprises a pair of similar plates 24,

each having two semicircular channels extending longitudinally therein, the plates be ing held together in any suitable manner so that two relatively cylindrical tunnels 26 are formed centrally within which the filament is disposed. The anode is supported upon and in electrical connection with the side members 17 of the framework by means of three cross plates 27, one of which is shown separately in perspective in Fig. 6. Each of the cross plates 27 comprises a rectangular strip of metal, for instance, malybdenum, having end perforations 28 through which the side members 17 on the supporting framework can be slidably passed. Each plate 27 also has an inner perforation 29 of double key-hole shape, conforming to the cross-sectional shape of and adapted to receive the anode 16. The cross plates 27 being positioned upon the side members 17 of the supporting framework, are secured thereon by pieces of binding wire such as indicated at 30 wound around the rods 17 on either side of the plates 27, the ends of each piece of wire being twisted together to obtain a secure grip. Other means of securing the plates 27 on to the rods 17 may obviously be employed, and obviously also the anode may assume other forms than that illustrated, the invention being concerned with particular means for registering a tensioned H filament with respect to another electrode.

The two filament-s 1 are secured at their lower ends to the upstanding portions 32 of a pair of clamps 33 consisting of strips of metal which embrace the lower insulating rod 18 and are clamped thereon by binding wires 35 or other suitable means, and lead in wires 38 for the filament heating current are welded to downwardly extending portions 34 of the clamps 33.

Secured around the upper insulating rod 18 is a clamp 39 which is shown clearly in section in Fig. 7, said clamp comprising two similar segmental portions held together at their lower ends by means of a rivet 4t) and holding between them an anchor or frame member 41 to be hereinafter described. The upper portions of the clamp 39 are secured by means of binding Wire 42 passing through perforations in the tops of the clamp members, so that the clamp 39 is securely held in position upon the upper insulating rod 18. The anchor or frame member 41 consists of metal and is bent fiatwise to the form of the letter L, as clearly shown separately in perspective in Fig. 9. The member 41 has a perforation 43 through which the rivet 40 is passed and is provided with a downwardly extending our 44 having a. perforation 45 therein adapted to receive one end of a helical spring 46 (shown in Fig. 4) for tensioning the filaments 1.

Upon the lower horizontal or laterally bent portion 47 of the anchor member 11 is welded and thus anchored one end of a blade ill) ltIO

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48 0t molybdenum to the opposite or free end of which blade is welded another molylr denum blade e l-9,21. nickel spacer 49 being preferably provided between the joined ends of these blades so that the latter are sulr stantially parallel with one another.

The tree end oil" the upper blade 49 is secured to a metal bar 50 to which the upper ends 01: the two filaments 1 are Welded. The bar 50 may be secured to the blade a9 by bending or folding the free end ot the latter to the shape shown at 51 in Fig. 8 so as to provide a channel to receive the lower portion of the bar 50 and providing claws 52 on the extremity of the blade which are bent over and engage the upper edge ot the bar 50 clearly shown. The bar 50 is provided with a perforation 53 through which passes the lower end of the spring 46.

The width of the blades 41-8 and 4:9 is rclatively much greater than the thickness thereoi, the operation ot these blades being similar to that described in connection with Figs. 1, 2 and 3, in registering the filaments 1 against lateralmovements with reference to the anode 16 in which they are located.

The structure illustrated in l 44; to 9 is for a diode of the type set torth in my prior Patent No. 1,677,850, granted July 17, 1928. The cathode is of a type providing aconcentrated source of electrons and the gap between the anode and cathode is small, and by reason of the short gap and the particular construction ol the anode, the inter-electrode space is small and the discharge is confined to this space by reason of the tact that the portions ot the filament which are adjacent the endsot the anode remain so cool that there is no appreciable electron emission from these parts.

The filaments l. at their upper ends are cooled by the bar 50 to which they are welded, whilst they are cooled at their lower ends by the upstanding portions 32 ot the clamping members 33.

Various modifications may be made in the construction and arrangement of the electrodes without departing from the scope of the invention. Furthermore, the invention is applicable to tubes having more than two electrodes, for example to tubes in which a grid is interposed between the cathode and the anode.

I claim as my invention 1. A vacuum tube electrode structure comprising an anode of rectilinear form having a longitudinal passage for a cathode, a straight. filament cathode therein having tensioning means connected to one end thereof, supporting means connected to said tensioning means at one end of the cathode, supporting means connected to and locating the other end of the cathode within th a anode, a yielding strip member cooperative at one part thereof with the portion of the cathode adjacent to its point of connection with said tensioning means and extending in a plane substantially perpendicular to the axis of the cathode, said member lowing a width substantially' greater than its thickness, and means connected, to another part of said strip member for supporting it.

2. A vacuum tube electrode structure comprising an anode of rectilinear form having a longitudinal passage for a cathode, a straight tensioned filament cathode located therein, an anchor member connected to and locating one end ot the cathode in the required position with respect to the anode, a blade member connected at one part thereof to the other end of the cathode and located in a plane substantially perpendicular to the axis ol the cathode said blade member having a width considerably greater than its thickness and an etlective length considerably greater than the changes in length of the ('fltllOllB, so as to be flexible only in the direction oi the cathode axis, and a rigid anchor member connected to another part of said blade member and locating the latter so that said other end of the cathode is held in the required position with respect to the anode.

3. A vacuum tube electrode structure comprising an anode of rectilinear :lorm having a longitudinal. passage for a cathode, a straight .tilament cathode located therein, an anchor member connected to and rigidly locating one end of the cathode in the required position with respect tothe anode, a thin metal blade men'lber connected at one part thereot to the other end oi? the cathode and locatedin a plane substantially perpenrilicula-r to the cathode axis, said blade member having a width considerably greater than its thickness and an effective length considerably greater than the changes in length of the cathode so as to be flexible only in the direction oi? the cathode axis, a rigid anchor member connected to another part of said blade member and locating the latter so that said other end of: the cathode is held in the required. position with respect to the anode, and a spring placing said cathode in tension.

4:. A vacuum tube electrode structure comprising an anode of rectilinear -form having a longitudinal passage for a cathode, a straight tensioned filament cathode located therein, an. anchor member connected to and locating one end of the cathode in the required position with respect to the anode, a cathode registering member comprising a plurality o'l substantially parallel. blades connecting with one another in bellows fashion, each blade having a Width and length considerably greater than its thickness so that the two tree ends of the several blades are flexible with respect to one another only in a direction perpendicular to the major surface of the blades, one of said free ends of said blades being secured to the other end of the cathode, and a rigid anchor member to which the other of saidvfree ends of said blades is secured for locating said other end of the cathode in the required position with respect to the anode.

5. A vacuum tube electrode structure comprising a rigid rectangular framework, an anode of rectilinear form secured to and within said framework and having a longitudinal passage for a cathode a straight tensioned filament cathode within said anode, having one end rigidly anchored to said framework in the required position with respect to the anode and insulated from the latter, ablade member connected at one part thereof to the other end of the cathode and located in a plane substantially perpendicular to the axis of the cathode, said blade member having a width considerably greater than its thickness andan effective length considerably greater than the changes in length of the cathode, so as to be flexible only in the direction of the cathode axis, and a rigid anchor member connected to another part of said blade member and also connected to said framework in insulated relation with the anode so that the end of the cathode connected to said blade member is located in the required position with respect to the anode and is insulated from the latter.

6. A vacuum tube electrode structure comprising an anode of rectilinear form, a cathode consisting of a plurality of straight parallel tensioned filaments which at one end are anchored in the required position with respect to the anode, a spacing member to which the other ends of said filaments are secured, a blade member connected at one.

part thereof to said spacing member and located in a plane substantially perpendicular to the axes of the filaments, said blade member having a width considerably g than its thickness and an eflective length considerably greater than the changes in length of the cathode, so as to be flexible only in the direction of the cathode axis, and a rigid anchor member connected to another part of said blade member and locating the latter so that said other end of the cathode is held in the required position with respect to the anode.

7 A vacuum tube electrode structure comprising an anode of rectilinear form having longitudinal passages for cathode filaments, a pair of spaced apart straight parallel tensioned cathode filaments which are located in said anode and having means at one end for anchoring them in the required position with respect to the anode and means at their other ends for electrically connecting them together, a blade member having a hook-shaped end engaging and holding the electrically connected ends of said filaments, said blade member being located in a plane substantially perpendicular to the plane containing the two filaments and having a width considerably greater than its thickness and an etl'ective length considerably greater than the changes in length of the cathode, so as to be flexible only in the direction of the cathode axis, and a rigid anchor member connected to another part of said blade member and locating the latter so that said other end of the cathode is held in the required position with respect to the anode.

In testimony whereof I have hereunto subscribed my name this ninth day of May 1924-.

ERNEST YEOMAN ROBINSON.

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