US2006807A - Audion tube construction - Google Patents

Description

July 2, 1935. A. s. HOPPING AUDION TUBE CONSTRUCTION Filed Nov. 26, 1928 r 7 .rrrrrrrrr f1 Patented July 2, 1935- AUDION TUBE CONSTRUCTION Alvin Samuel Hopping, Bloomfield, N. J., assignor, by mesne assignments, to Radio Corporation of America, a corporation of Delaware Application November 26, 1928, Serial No. 321,830

4 Claims.

This invention-relates ingeneral to improvements in the construction of vacuum tubes by means of which the characteristics of cheapness, ease of assembly, reproducibility, uniform char acteristics,-lightness, and ruggedness are secured.

One of the objects of this invention involves the construction of the anode or plate electrode of electron discharge devices of the type known as audions in the form of a spiral winding of wire.

Another object of this invention involves the construction of the elements of devices of the above type of apparatus which are very simple in structure and adapted for production in large quantities, which parts are so made as to be assembled in the correct relation only.

A further object of this invention is the production of vacuum tube elements of this nature which in assembled relation produce a unit which is very light and yet exceedingly strong, thus eliminating a tendency to the production of microphonic noises and displacement of the elements under shock.

A further object of this invention contemplates a structure which may be made of substantially gas free materials which can, upon treatment, be completely degasified.

A further object of this invention involves a structure including coil, grid and plate by means of which heat dissipation is increased and the danger of back emission is eliminated.

These and other objects, as will appear from the following disclosure, are secured by means of this invention.

This invention resides substantially in the combination, construction, arrangement, and relative location of parts, all as will be set forth in considerable detail in the following disclosure and defined in the appended claims.

Referring to the drawing- Figure 1 is an elevational view of the device showing the relative arrangement of parts;

Fig. 2 is an elevational view taken at right angles to Fig. 1;

Figure 3 is a cross sectional view taken on the line 33 of Fig. 1 looking in the direction of the arrows; and

Fig. 4 is an enlarged cross sectional view of the heater element of the tube taken on the same line.

The disclosure in the drawing of this invention is that of what is known as an indirect heate'r type of A. C. tube but it is, of course, apparent that many of the features of construction of the device as disclosed are applicable to all forms of electron discharge devices. It is usual in the present construction of these devices to employ an anode or plate electrode consisting of a sheet of metal formed into a cylinder of circular or other cross sectional configuration. The metal usually employed for the plate electrode is nickel which is used extensively because of its cheapness, this being the main consideration since nickel is not the best metal for the plate electrode when considered with respect to its electrical characteristics. The best common metals electrically for the plate or anode of an electron discharge device are tungsten and molybdenum. Heretofore, these metals have not been used in solid plate construction because of their high cost, difiiculty of preparation, and inadaptability for the operations thereof trans forming them into plates. conservatively it may be said that a tungsten or molybdenum plate of average size would cost in the neighborhood of several dollars which, of course, is prohibitive. One of the features of this invention is the employment of tungsten or molybdenum in the form of a small wire shaped to form a helical coil. It is now relatively easy and cheap to produce tungsten or molybdenum in the form of fine wires. Thus a plate electrode comprising a fine coil of tungsten or molybdenum wire would only cost a few cents to construct. In addition, such a plate electrode is strong, exceedingly light, and adapted to readily dissipate the heat generated by the cathode or heater. It has been known before to construct plate electrodes in the form of a fine wire mesh but the wires in the mesh are usually not closer than five thousandths of. an inch, while the wound helical plate may have the wires as close as one thousandth of an inch. In addition, fine mesh grids have a tendency to buckle and do not as readily dissipate the heat generated. Other improved features of construction will be apparent from the following detailed disclosure.

Referring to the drawing in which one embodiment of this invention has been given, the device is shown comprising a socket I having the depending contact prongs 2, 3, 4, 5 and 8. These prongs are connected to the various electrodes of the device in a manner well known in the art and need not be gone into in detail in this case. Cemented in the socket l is the evacuated vessel 1 having reentrant stem tube 8 in the press of which is supported in a vertical position all of the electrodes. The two main supports comprise two straight wires 9 and i0 securely held in the press of the stem tube and extending vertically therethrough.

Mounted transversely on the two supporting wires 9 and I through which they pass are the insulating plates II and I2. These insulating plates, which in the best form of construction are .made of mica, have a number of holes punched therein so that they may slide over the supports 9 and I 0. The lower spacer or plate ll may contact with flattened portions of the support to limit its downward movement. other holes in the spacers I I and [2 are two short straight rods l3 and I 4 around which is wound the wire l6 forming the plate electrode of the tube. In actual construction the turns will be much closer together but have been shown as they have in the drawing so as to not confuse them with the grid coil. These turns, as is usual in the art, are welded to the supporting wires. The supporting wire l3 has a curved extension l which is welded to the support 9 which, together with the lead in wire and corresponding prong, provides a circuit to a point external of the tube for the plate. In a similar manner the grid is mounted on two wire supports l1 and I8 extending through holes in the spacers. Support I1 has a curved extension I9 which is welded to the support I 0 which, together with the lead in wire and corresponding prong, provides a circuit external to the tube for the grid. The grid comprises a winding of wire each turn 20 of which is welded to the supports. These two helical coils are made of tungsten or molybdenum in accordance with the principles of this invention.

The heater in this case comprises a resistance wire 2| which is mounted in a ceramic enclosing member 23. This ceramic enclosing member or support comprising a small solid rod of some insulating material, such as isolantite, which has two parallel longitudinal boresextending therethrough through which the resistance wire 2! bent in the form of a hairpin is threaded. The terminals of this resistance wire,- which forms the heater, extend to two of the depending prongs. The insulating supporting rod 23 is covered for the greater part of its external surface with a suitable metallic sleeve 30 which in turn is covered with any suitable electronically active material forming a coating 24 in the manner now well known in this art. As shown in Fig. 2 the coating 24 is in electrical contact with this sleeve 30 of conducting material 25 which is welded to a short projecting wire 25, which is in turn welded to a wire 22 fastened to the press. This wire 22 is likewise connected to one of the prongs of the base. The construction of the heater and cathode surface is shown in better detail in Fig. 4. Also welded to the supporting wire 9 is a short wire 26 which supports at its lower end a small metallic open ended cup 21 in which the getter" is placed. This small cup opens downwardly so that when the getter is flashed to remove any residual gases within the tube the interor surface of the vessel 1 is not coated so as to make it In the bestpractice this small opaque to light. container 21 will have the plane of its open end below the plane of the top edge of the socket so that the so-called silvering effect will not occur on any substantial portion of the vessel which extends above the socket.

The advantages of this construction as pointed out at the beginning of this disclosure are now apparent. I am, of course, well aware that many changes in the details of construction and relative arrangement of parts will readily occur to those skilled in the art ,and I do not, therefore, desire to be limited to this detailed disclosure which has been given for purposes of illustration but rather to the principles and scope of the invention as it is defined in the appended claims.

What I seek to secure by United States Letters Patent is:

1. An electron discharge device comprising a central sleeve-like cathode, a first wound wire electrode surrounding said cathode, a second wound wire electrode surrounding said cathode, a first insulator member for spacing the upper ends of all said electrodes, a second insulator member for spacing the lower ends of said electrodes, each of said insulators having a perforation through which the opposite ends of said cathode pass for maintaining said cathode central with respect to said wound electrodes.

2. An electron discharge device comprising an evacuated container having a press portion, a

' sleeve-like metal cathode, a pair of wound wire grid-like electrodes surrounding said cathode, a pair of metallic wires serving as the sole support for said grid-like electrodes from said press, and an insulator disc through which said cathode passes for maintaining said cathode central with respect to said grid-like electrodes.

3. In a vacuum tube a pair of spaced apart insulators, a cathode extending between said insulators, a grid having a supporting rod between said insulators and extending through an opening in one of them, the end of said grid rod being bent at an angle at'the opposite side of said insulator, a press, a plurality of support rods sealed in said press andpassing through aligned openings in said insulating members, the bent end of said grid support rod being welded to one of said support rods.

4. An electron discharge device comprising an enclosing glass envelope, a metallic tubular cathode having an exterior coating of alkaline earth oxides thereon, a heater element disposed in said cathode, current conducting leads for said heating element extending through said envelope, a perforated anode, and a dielectric shield member disposed between said anode and said heating element current conducting leads.

ALVIN SAMUEL HOPPING.

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