US2250647A - Shielded radio tube and the like - Google Patents

Description

July 29, 1941. c. F. MILLER SHIELDED RADIO TUBE AND THE LIKE Filed Dec. 4, 1957 HUN Mam

INVENTOR BY r1 4;

A ORNE Patented July 29, 1941 SHIELDED RADIO TUBE AND THE LIKE Carl F. Miller, Emporium, Pa.,

grade Sylvania Corporation,

assignor to Hy- Salem, Mass., a

corporation of Massachusetts Application December 4, 1937, Serial No. 178,039

3 Claims.

This invention relates to electron discharge tubes and more especially to tubes of the electrostatically shielded type.

A principal object of the invention is to provide an improved electrostatically shielded radio tube of the top cap-contact type.

Another object is to provide an electrostatical- 1y shielded radio tube of the top cap-contact type, whereby connection to the said contact can be made in an improved manner.

A feature of the invention relates to a radio tube of the top cap-contact type having as an integral part thereof, a special form of electrostatic shielding envelope whereby the said contact can be electrically connected to associated apparatus by a substantially straight wire connection, thus reducing the possibility of undesirable electromagnetic pick-up through the connecting Wire.

Another feature relates to an improved structure of top cap-contact for radio tubes and the like.

A further feature relates to an improved form of connector clip which is especially designed to facilitate connection to the top cap-contact of a radio tube through the outer enclosing electrostatic shield.

A still further feature relates to the novel organization, arrangement and relative location of parts which constitute an improved electrostatically shielded radio tube having a top cap-contact.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

Inasmuch as the present invention is concerned mainly with the manner of electrostatical- 1y shieldinga radio tube and the manner of connecting the electrodes thereof in circuit, the internal structure of the tube will be shown diagrammatically, it being understood that this electrode structure or mount may be of any wellknown type. Accordingly in the drawing,

Fig. 1 is an elevational view partly in vertical section of a tube and connector arrangement according to the invention.

Fig. 2 is an enlarged detail view of the top -c ac o h tube of Fi 1.

Fi 3 is a sectional plan view of Fig. 1 taken along the line 3-3 thereof, viewed in the direction of the arrows.

Fig. 4 is a detailed view, partly in section, of the imp o ed onnect r cl p accordin o the invention.

Fig. 5 shows a modification of the tube of Fig. 1.

Referring to Fig. 1 there is shown a glass bulb I having the wellknown form of reentrant stem 2 terminating in a press 3 wherein the various lead-in and support Wires 4, 5, 6 and l are sealed in a vacuum-tight manner. Supported from the press by one or more of the said wires is any well-known form of radio tube mount diagrammatically indicated by the numeral 8. For a detailed description of a typical electrode mount that may be used, reference may be had to Patent No. 2,084,734. In certain types of tubes, for example those employing a shield-grid electrode, it is the usual practice to bring out the connection from the control grid of the mount, by means of a conductor 9 sealed in a vacuum-tight manner through the top portion of the envelope I. In accordance with the present invention, the exterior connection to the lead 9 is made by means of a metal cap l0 having a circumferential groove I! for purposes to be described. Cap I0 is fastened in any suitable manner to the top of the bulb, as for example by cement l2, and the lead-in wire 9 is soldered or otherwise electrically connected to the cap as shown in Fig. 2.

After the mount including the stem and the electrode assembly carried thereby, is sealed into the bulb I, the latter is evacuated through the usual exhaust tubulation l3, which is subsequente ly tipped-off in any Wellknown manner. While the tube may be provided with any wellknown form of contact base, it is preferred in the embodiment of Fig. 1 to employ a disc M of insulating material such as Bakelite, fibre, ceramic or the like, wherein are fastened the tubular metal contact prongs I5. While the drawing shows only two of these prongs, it will be understood as many prongs are provided as are required to connect the various electrodes and other elements of the electrode assembly in circuit. Preferably also there is attached centrally to the disc M a hollow tubular metal boss l6 having a guiding key I! fastened to, or integrally formed thereon. As will be seen, the disc I4 is also provided with a central opening to accommodate the exhaust tubulation I3, which is protected by the member [6.

In order to shield electrostatically the tube with its electrode assembly and lead-in wires, there is provided an inverted cup-shaped metal member l8 completely closed at the top by a metal cap 18a, member 18 being fastened in any suitable manner at its lower end to the rim of disc M, as for example by crimping the rim of member l8 against disc [4. If desired the meme her [8 may extend downwardly below the disc l4 and the overhanging rim of member 18 may be spun back against the disc. For detailed descriptions of other manners of fastening the pronged base to the member [8, reference may be had to U. S. Patent No. 2,238,025.

Prior to fastening the member 18 to the base, there is applied either to the outer face of bulb l or to the inner face of shield 18 a ring of cement 19 which upon later heating and drying, anchors the bulb within the shield. In accordance with the invention, the shield I8 is provided near its upper end with a series of circumferentially spaced slots 20 which are arranged to be in horizontal alignment with the groove ll so that the connector clip 2| can be inserted in a straight line through any convenient one of the said slots, and into spring engagement with the cap l0. Preferably the spring clip is of the character shown in detail in Fig. 4 and comprises a round spring wire 22 bent back upon itself to form a bifurcated forward end defining a substantially circular cap embracing portion 23, the extreme outer ends 24, 25 of the bifurcated portion diverging as shown in Fig. 4 so as to facilitate gripping engagement between the cap it! and the connector. Preferably the connector is designed so that the circular portion 23 is normally slightly smaller in internal diameter than the outer diameter of the grooved portion ll of cap [0, and the flexible character of the two arms of the clip maintain the latter in spring pressed contact with the cap I0. A flexible conductor 26 is soldered or otherwise fastened to the bend in the clip, the

conductor 26 being provided with the usual insur lating sheath or coating 21. Preferably, although not necessarily, a short length of flexible insulating tubing 28 is fitted over the clip and insulation 21 to avoid short-circuiting the clip on the edges of the slot 20. If desired, the tubing 28 and insulation 21 may be covered with a braided metal sheath which can be grounded in any suitable manner.

In most types of radio receivers, the tubes are located as close as possible to the adjacent tuning units such as coils or condensers. Heretofore where top cap-contact tubes have been employed, connection has been usually made to the top contact of the tube by means of a small cup-shaped metal member which must be pressed vertically downward on to the top cap-contact. This usual arrangement is open to a number of objections which are entirely overcome by the present invention. For example with the conventional type of connector it is necessary to arch or partially loop the wire leading from the tuning unit to the top cap of the tube. Secondly the top cap with its contact thereon, is practically completely exposed in order to enable the cap-contact to be applied thereto. The former, may result very frequently in broken connections between the flexible load and the cup-contact; and the latter, may result in appreciable electromagnetic pick-up by the looped or partially looped connecting wire. Furthermore with the usual type of cup-contact, it is very diflicult to provide a resilient or spring pressed contact between the cup and the top cap. By employing a shield 18 which is completely closed at the top and by employing the special form of spring connectors described, in conjunction with the grooved top cap 10, it is possible to make contact to the said cap in an expeditious manner and by employing a perfectly straight connection between the tuning unit 29 and the cap ID as shown in Fig. 1. Furthermore the diill verging ends 24, enable the clip to be inserted through the most convenient one of the slots 20 with the assurance that the clip will resiliently and firmly engage the top cap III as shown in Fig. 3. By reason of the spring engagement between the clip and the top cap, and by reason of the fact that the portion 23 of the clip lies Within the groove l I, there is very little likelihood of the clip being jarred loose, once it has been inserted in place. It will be understood of course, that the members H and [8 are grounded when the tube is plugged into its associated socket, thus providing a substantially complete electrostatically shielded tube, without employing the separate removable metal cans or the like which are usually provided over the ordinary glass tubes in radio receivers.

Fig. 5 shows the invention applied to a, tube of a somewhat different construction. In this embodiment the base I4 is eliminated, and the glass bulb 3D enclosing the electrode assembly 3|, is sealed to a specially formed glass closure member 32 having rigid metal rods 33 sealed directly therethrough, the outer ends of these rods serving as contact prongs, and the inner ends serving as electrode support and lead-in wires for the mount. Preferably the closure 32 is formed with a downwardly depending annular rim 34 which has its lower face flattened as shown. Fastened to the bottom of the tube as for example by a ring of cement 35 is a metal cup-shaped member 35 having a series of openings 31 in its bottom to allow the rods 33 to pass therethrough. The said bottom is also provided with a central opening 38 to accommodate the tipped-off exhaust tubulation 38, and welded or otherwise fastened to the said bottom is a hollow metal boss 40 with its lateral guiding pin 41. The remaining parts of the tube of Fig. 5 are the same as the corresponding parts of the tube of Fig. l and bear the same designation numerals. The arrangement of Fig. 5 has the advantage over that of Fig. 1 in that the electrostatic shielding is more complete by reason of the elimination of the separate insulator base with its contact prongs, and is less expensive to manufacture.

While certain specific embodiments have been illustrated and described, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What I claim is:

1. An electron discharge tube having an evacuated glass bulb enclosing an electrode mount, a cap-contact fastened exteriorly to the top of the bulb, a tubular metal member enclosing said bulb and carrying at its lower end a metal disc having openings for contact prongs, a metal boss carried by said disc and surrounded by the base prongs, and a slot in the peripheral wall of said member in line with said cap-contact.

2. A unitary substantially completely shielded radio tube comprising an evacuated glass envelope the bottom wall of said envelope having directly sealed therein a plurality of rigid metal rods to serve as contact prongs for the tube, a metal disc fastened exteriorly to said bottom wall and having a plurality of perforations to allow said prongs to pass therethrough while shielding adjacent prongs electrostatically, an inverted metal cup-shaped member having its lower end fastened to said disc and its upper end closed off, a hollow metal boss downwardly depending from and conductively connected to said disc, 9. contact member fastened exteriorly to the top of the enfor the passage of contact prongs and a central metal boss downwardly depending therefrom and conductively connected thereto, and a plurality of circumferentially spaced slots in the peripheral Wall of said cup-shaped member adjacent the upper end thereof.

C FMI RA

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