US2284495A - Electron tube mount of the shielded element type - Google Patents

Description

y 1942 "G. L. RISHELL 2,284,495

ELECTRON TUBE MOUNT OF THE SHIELDED ELEMENT TYPE Filed April 10, 1941 2 Sheets-Sheet l GEORGE L. RISHELL INVENTOR May 1942- e. L. RISHELL 2,284,495

IIIJEICTRON TUBE MOUNT OF THE SHIELDED ELEMENT TYPE Filed April 10, 1941 2 Sheets-Sheet 2 GEORGE L. RISHEILL INVENTOR Patented May 26, 1942 r ELECTRON TUBE MOUNT OF THE SHIELDED ELEMENT TYPE George L. Rishell, Emporium, Pa., assignor to Hygrade Sylvania Corporation, a corporation of Massachusetts Emporium, Pa.,

Application April 10, 1941, Serial No. 387,839

13 Claims.

This invention refers to electron discharge devices and in particular to discharge tubes in which several sections are mounted in a single evacuated envelope.

The simplest example of a multisectional discharge tube of this type is a combination of a diode section with a triode section, one section being mounted above the other, and having a common thermionic cathode extending through the length of both sections. Usually the diode section is at the lower end of the tube; that is, at the end nearest to the stem or header, through which the lead-in conductors are sealed. Tubes of this kind are quite commonly used as detector-amplifiers. The triode section serves as amplifier for the high frequency signals demodulated by the diode section. The amplifier section may be a pentode as well as a triode, and frequently, two diodes are mounted in the diode section, one of which may be used for AVC, the other for demodulation.

In order to insure electrical independence of the two sections of the tube from each other, a box or barrel-shaped metal shield is usually applied, which prevents undesirable electric stray fields of one section from penetrating into the discharge space of the other. A shield of this kind is preferably so designed, that it reduces the exposure of the leads coming from the electrodes of one section to those of the other section to a minimum. a I

The application of electrostatic shields between sections of multisectional tubes is, of course, not restricted to the case of diode-triodes, but is quite essential in many other multiple section tubes, as in triode-hexodes or triodeheptodes, in short in all multiple-section tubes in which a complete electrostatic shielding of one section from the other is desirable.

In all these cases, the designer is faced with a number of problems, which partly originate from the difficulty of welding the increased number of metallic connections within the small space available for the purpose, partly from the difficulty of insuring a uniform spacing between the different sections, so as to obtain a construction which will give a uniform product with respect to electrical characteristics and geometrical dimensions in line with the requirements of modern mass production methods.

The present invention solves some of these problems for multisectional tubes substantially by so designing one of the elements of one section of a multisectional tube that it serves simultaneously the purposes of shielding one section from the other, spacing two sections from each other, and partly for mechanically locking together the parts of a unitary mount which forms another section of the tube.

The invention also takes care of a free passing of the exhaust gases developed in breaking down the cathode coating. It has been noted in many cases, that the breakdown of the cathode coating of a well shielded tube section is delayed because the gases developed in this section meet too much resistance in their flow toward the exhaust tubulation and finally into the exhaust system. By the particular shape of the spacing members, which are rigidly attached to the shielding member, a free flow of these gases out of the shielded section is insured according to the invention, without sacrificing any of the good shielding properties required for the electrical independence of the different tube sections.

Accordingly, it is a principal object of the invention to devise a multisectional tube in which one tube element performs different functions for which the prior art has employed several elements.

A feature of the invention refers to an electrostatic shield, which is so designed that it automatically spaces two sections of a multisection tube accurately from each other.

Another feature of the invention refers to the partial support given to the unity of the mount of one of the sections, which prior to the invention had to be secured by separate means.

Another principal object of the invention refers to the simplification of the mounting operation of multisectional tubes.

One feature of the invention refers to the automatic and accurate spacing of two sections of a tube, which avoids the necessity of using special gauges for securing uniform spacing between sections.

Another feature of the invention is the reduction of the number of welding operations heretofore considered necessary during the mounting of the tube.

Another important feature of the invention refers to the comparative freedom of the exhaust path for the gases developed in the diode section.

Finally, it is the object of the invention to design an electrostatic shield for use between two sections of a multisectional tube, which can easily be formed from a single piece of sheet metal.

The invention is described in detail in connection with the drawings, in which Fig. 6 shows a view of another embodiment of' the invention.

Fig. 7 shows a side view of a complete tube incorporating the invention. 4 Fig. 8 is an enlarged detail view of part of Fi 1. I

Fig. 9 shows a modification oi the diode shield of Figs. 1-8.

For the sake of simplicity, the drawings show embodiments of the invention as applied to a double-diode triode. Evidently the simplification in mounting and the elimination of separate supports, eyelets, straps, mounting jigs and gauges, as well as the improved appearance of the mount, all of which are characteristic of the invention are independent of the specific structure of the sections forming the tube; and may also be obtained, by the means disclosed herein, for tubes containing more than two sections. It will, therefore, not be necessary to enumerate the different combinations of two and more sections within a single envelope to which the principles of the invention can be equally well applied.

Referring now to Figure 1, numeral I represents a glass header or stem with eight rigid lead prongs sealed through it in a vacuum tight manner. To two of the leads, 2 and 3, are welded the rigid mount supports 30, (H, which carry the diode mica spacer 29 at the bottom on rectangular bends 32 and 33, which are in a plane parallel to the disc-shaped part of header I. The bottom diode spacer is provided with holes through which the upright parts 40 and 4| oi the mount supports are threaded. This diode spacer also has holes through which the diode supports extend, and a hole in the center for taking up the cathode 5. A box-like diode shield I! is Welded to the mount supports 33 and 3!. Diode shield I1, and the diode plates (not shown), bottom spacer 29 and the lower part of cathode 5 form together the bottom or diode-section of the tube. An opening 21 is provided in the center of the top section of diode shield I! '(see Figure 3) to permit the cathode to pass through the top wall of the diode shield. The diode shield I1 is provided with ears or tabs 24, 25, by which the bottommount spacer I3 of the-top section 9 of the tube is supported. Bottom spacer I3 of triode section (top section) '9 is preferably of a construction disclosed in Patent No. 2,250,409. As explained in 'said application, the use of this mount spacer allows a rigid centering of the cathode without any danger of scratching off any cathode coating from the lower section of the cathode during the operation of mounting the cathode into the spacer. A detailed description of the steps of mounting the cathode and of slipping the spacer I3 over the mount supports 30, 3| is given in the above quoted Patent No.

' 2,250,409.. Holes and slots in spacer I 3 are provided to take up the tabs I4 of plate I0 and the side rod support of grid II. Top spacer I2 is provided with similar slots and holes too for spacing grid, plate and cathode at the top. (A

getter support and container 43 may be welded to one of supports 30 or 3|.)

Connectors are provided from the different electrodes to the respective lead-in conductors of header I in known manner. One or both of the plate tabs I4 may be bent at the bottom of mount spacer I3, but it is not necessary to bend over any of the plate tabs I4 on the top spacer I2 in order to insure a rigid unitary mount of top section 9. g It is suflilcient to weld the cathode tab 42 to one of the mount supports 30 or 3| in order to prevent top spacer I2 from slipping upward on the supports 30 and 4|. This connection from cathode to one of the mount supports is desirable also for the purpose of making the ground or cathode connection to the diode shield.

It will be noticed, that the top section forms a unitary mount between the two mount spacers I2 and I3, and that not a single eyelet, strap or other element is used which elements ordinarily fulfill no other duty than merely to insure a longitudinal spacing of the different top section elements, or an interlocking of this section in itself. The bottom spacer rests firmly on the diode shield ears 24 and 25. These ears form an integral part of the diode shield, and serve in addition for the correct longitudinal spacing of the diode shield top surface from the mount spacer I3. The cathode tab, welded to the top end of one of the supports 3!) or 3| near to and above mount spacer I2 prevents the longitudinal motion of this top spacer. The main function,

of this welded connection is, however, the formation of the metallic contact between cathode and the diode shield. In this way it comes about that a complete rigid top section is formed by grid II, plate I0 and mount spacers I2 and I3 without the usual applications of straps or eyelets welded to at least one of the supports for the only purpose of securing a rigid longitudinal spacing of the parts forming that section of the tube.

The invention is not limited to the elimination of holding means for the mount to the extent described above. Swedging of the supports 36 and ti (not shown in the drawings) may be used to prevent the top mica spacer I2 from slipping away from the top mount. If desired, the plate tabs I4 may be bent over on the top mount spacer I2, in order to insure longitudinal spacing of the top section 9 in itself.

Fig. 2 shows another embodiment ofthe invention. Here, again the bottom mount spacer I3 rests on the ears 24 and 2-5 of shield ll, but separate support wires 20 and 21 are used for supporting the diode plates (not shown) and separate supports 22 and 23 are provided for shield II, while the plate supports I3, I9, support only the top section. The connections between the electrodes of the tube and the lead-in conductors may be made in any known way. The idea 1 of the invention, in this embodiment, being the use of ears 24 and 25, rigidly connected to the shield IT for supporting the topsection 9, and,

and 50, with flaps 45, 46 and 41 and 4B andears 24 and 25, arecut out. Channels 28-(see Figure 3) are formed from flaps 45, 46, 41 and 48 in successive operations, as well as a number of strengthening ribs 52.

If desired, channels 23 may be closed at any points along their lengths by pinching (see Figures 2 and 5, points marked A), or by allowing the ears 24 and 25 to extend horizontally over the channels before bending them upward, so as to form stops for the support rods 22 and 23 as shown in Fig. 9.

The free passage of the break-down gases developed by that section of the cathode which is covered by the shielding element IT is insured according to the'invention by providing the ears 24 and 25 of the diode shield at the left and right side of the mount between spacer l3 and top surface 44 of the diode shield. This leaves the entire front and back surface between spacer I3 and top surface 44 free for the passage of these gases.

Fig. 7 finally shows an elevational view of a complete tube made substantially as described in connection with Fig. l, the corresponding parts in Figs. 1 and 6 bearing the same designation numerals. In Fig. 7, the bulb B is of glass and is provided with a special plug-in shielding and supporting base 5i such as described in detail in Patent No. 2,250,184.

What I claim is:

1. In an electron tube mount, a pair of uprights, a plurality of electrode sections in superposed relation, a box-like shield for one of said sections rigidly fastened to said uprights, said shield having a plurality of integral vertically extending struck out tabs extending therefrom and in engagement with the adjacent end of the superposed section, and upon which the Weight of said superposed section is carried,

2. In an electron tube mount, a pair of uprights, a plurality of electrode sections, means to support said sections in end-on relation but spaced longitudinally from each other, a boxlike shield for one of said sections said shield being rigidly fastened to said uprights and carrying integral vertically extending struck out projections having their ends in abutting relation with the adjacent end of the other section to predetermine the longitudinal spacing of said sections, the weight of said other section being carried by said projections.

3. In an electron tube mount, a plurality of electrode sections, a pair of uprights for supportsaid sections in superposed relation, a box-like shield substantially enclosing the lower section, said shield having a plurality of integral vertically extending struck out projections at its upper end abutting against the lower end of the other electrode section to fix the spacing between the two sections, the weight of said upper section being carried by said projections.

4. In an electron tube mount, a pair of parallel uprights, a pair of superposed electrode sections each having at its lower end a transversely extending electrode spacer member and through which said uprights pass, means to limit the downward movement of the spacer for the lower section, a box-like shield substantially enclosing said lower section, and means to limit the downward movement of the spacer member of the upper section, the last-mentioned means comprising a pair of integral tabs vertically extending from said shield and abutting the last-mentioned spacer member, said tabs supporting the weight of said upper'section.

5. An electron tube mount according to claim 4 in which said box-like shield has at opposite sides lugs through which said parallel uprights pass.

6. An electron tube mount according to claim 4 in which the said box-like shield rests at its lower end on the first-mentioned spacer member.

7. In an electron tube mount, a bottom electrode spacer, a top electrode spacer, an intermediate electrode spacer, all said spacers being parallel and extending substantially transverse to the vertical axis of the tube, a pair of parallel uprights extending through the three spacers, an electrode section located between the bottom and intermediate spacers, another electrode section located between the top and intermediate spacers, means to fix the spacings of said sections on said uprights, the last-mentioned means comprising a box-like shield substantially enclosing said lower section and having upwardly extending integral lugs abutting against said intermediate spacer and carrying the weight of said other electrode section, and means to limit the downward and upward movement of the sections and spacers on said uprights.

8. An electron tube mount according to claim 7 in which the last-mentioned means comprises an oilset portion on the uprights engaging the bottom spacer, and a projection from one of said uprights engaging the top spacer.

9. An electron tube mount according to claim '7 in which the means for limiting the movement of the sections on the uprights consists substantially entirely of means engaging the bottom spacer and means engaging the top spacer.

10. A shield member for electron tubes consisting of a box-like metal portion having lateral lugs for slidably assembling the shield on a pair of uprights and a pair of integral upwardly extending struck out lugs at the top of the shield, the Windows left by said struck out lugs providing substantially free vertical paths for the passage of gases developed during evacuation of the tube.

11. A shield member according to claim 10 in which said box-like metal portion has at opposite sides a pair of channels to receive support rods, and means cooperating with said channels to locate said shield member on said rods.

12. A shield member according to claim 10 in which said box-like metal portion has at opposite sides a pair of channels to receive support rods, and said lugs extend outwardly above said channels to limit the downward movement of said shield member on said support rods.

13. An electron tube mount comprising a header, a pair of parallel spaced uprights carried by said header, another pair of parallel spaced uprights carried by said header, an electrode assembly supported by and between the first-mentioned uprights, a second electrode assembly supported by and between the second pair of uprights in superposed spaced relation to the first electrode assembly, and means to fix the spacing of said assemblies comprising a box-like shield substantially enclosing the first assembly and having integral upstanding projections abutting against the second assembly and upon vsghch the Weight of said second assembly is carr e GEORGE L. RISHELL.

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