US2054221A - Electric discharge tube or the like - Google Patents

Description

SePt- 15, 1936 W. l.. KRAHL 2,054,221

ELECTRIC DISCHARGE TUBE OR THE LIKE Filed Aug. 2l, 1934 ATTORNEY Patented Sept. 1.5, 1936 l s UNITEDy STATI-.ash

PATENT OFFICE I to Hygrade Sylvania Corporation,

Salem,

Mass., a corporation of Massachusetts Application August 21, 1934, Serial No. 740,742 5 claims. (o1. 25o-27.5)

This invention relates to electric discharge tubes and more particularly to such tubes as are used in wave repeating systems or the like.

Anobject of the invention relates to an im- 5 proved form of wave repeating device.

Another object relates to an electron discharge tube having an improved form of electrode spacer.

A further object is to provide an improved rectier tube.

l A feature of the invention relates to a novel formof electrostatic shield for radio tubes or the like.

Another feature relates to a special form of insulator spacer member for radio tubes which is l treated in such a way as to cause it to act as an electrostatic shield.

A further feature relates to a tube of the socalled shield-grid type wherein part of the electrostatic shielding means also serves as an electrode spacing means, and wherein the electrostatic capacity between anode and control grid is reduced to a minimum.

A'still further feature relates to the novel organization, arrangement and relative location of g5 parts which go to make up a relatively simple and economically manufactured radio tube.

Other features and advantages not specically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims: i

While the invention will be disclosed herein as embodied inone known type and structure of electron discharge tube, it will be understood that this is done merely for purposes of explaining the invention and not by way of. limitation. Accordingly in the drawing:

Fig. 1 is a partial sectional view of a tube embodying features of the invention. l

Fig. 2 is a detailed plan viewof one of the composite shield-spacer elements according to the invention.

Fig. 3 is a partial view showing the invention embodied in the mount of a full wave rectifier tube or the like.

Fig. 4 is a top plan view of the mount of Fig. 3.

Referring more particularly to Fig. 1, the numeral I represents in dotted outline the enclosing envelope of any well known form of electrondischarge tube. While the drawing shows an envelopeprovided with a dome portion 2 and a metallic contactor cap 3, it will be understood that any other shape of envelope may be employed Merely for purposes of explanation, it will be assumed that the envelope I is provided with a re-entrant stem 4, terminating in a press 5 wherein are sealed the various electrode lead-in or support wires 6 to I4 inclusive. Wires 6 and I4 extend through a pair of spaced discs I5, I6, one of these discs being shown in plan view in Fig, 2. In accordance with the present invention, 5 each of the discs I5 and I6 consists of a sheet of insulating material such as mica or the like provided with a coating of suitable metal or conducting material such as carbon, graphite or the like. This coating may be applied in any well known l0 manner by dipping, brushing, painting, plating, or spraying for example by the Schoop process. If desired the surface of the insulator discs may be roughened or otherwise treated prior to applying the metallic coating so as to prevent the l5 coating from chipping or peeling. As shown in Fig. 2 the median portion of each composite disc is provided with a series of perforations I'I to 21 inclusive and through certain of these perforations are adapted to pass the corresponding wires 20 6 to I4 inclusive. In order that the various wires and electrodes may be insulated from one another, the median portion of each disc containing the perforations I8 to 26 is left uncoated. It will be understood of course that the disc may be 25 coated either on one side or on both sides. In the latter case both faces of the disc containing the perforations I8 to 26 should be left uncoated. The perforation 22 is adapted to receive and support the cylindrical indirectly heated cathode 28, 30 the metal sleeve of which is electrically connected to the wire 9 as shown in Fig. l. The cathode may be heated by any well-known heaterthe termin nals of which are connected to the wires I0 and I I. Surrounding the cathode 28 is a suitable con- 35 trol or signal grid 29 in thev form of a wire wound helically around the supporting posts 30, 3I The post 3I is connected by means of the conductor 32 to the metal cap 3. In like .manner surrounding the control grid is a shield-grid 33 which may be 40 in the form of a wire helically wound around the posts 34, 35, the latterpost being welded or otherwise fastened to the support wire I2. Similarly, surrounding the control grid and shield-grid is a suppressor grid 36 which may consist of a wire 45 wound helically around the posts 31, 38, post 31 being welded or otherwise fastened to the lead-in wire 8. Surrounding the suppressor grid is a hollow metal plate or anode 39 which is supported on the posts 40, 4 I, these latter posts in turn being 50 welded or otherwise fastened to the wires 1 and I 3. Surrounding the anode is a Wire mesh shielding electrode 42 which is fastened to posts 6 and I4.-

'I'he electrodes 33 and 42 constitute respectively 55 an inner and anouter shield for the electrodes '3 and 39. Likewise the composite discs i5 and i6 at opposite ends `of the electrode assembly act to substantially close 0E electrostatically, the open ends of the various electrodes, thus in effect providing a substantially complete electrostatic shield or cage between the control grid 29 and the anode 39. The metallic coatings of the discs may be electrically connected to the inner shield grid 33 and to the outer shield grid 42 in any suitable manner. Preferably however, the posts S and i4 which carry the outer shield grid pass through the coated areas of the discs as will be clear from the drawing, and if desired the perforations through which these posts pass may contain metallic eyelets which may be welded or otherwise fastened to the said posts 6 and i4. A metallic strap may then be provided between the post iii and thel post 35.

While the drawing shows one specific manner of mounting the composite shield-spacer discs i5 and i6 with respect to the ends of the electrodes, it is understood that this is merely illustrative and that any other suitable manner of mounting may be employed as long as the said discs substantially complete the shielding between the control grid and the anode. If desired, the upper disc 1 6 may be made of sufficient diameter so as to contact with the inner wall of the dome portion 2 to steady the electrode assembly at its upper end. While the drawing shows the discs i5 and I6 spaced from the upper and lower edges of the electrode 42, it will be understood of course that the said electrode 42 may be extended in length so that its lower and upper edges engage respectively the metallic coatings on the discs l5 and I6 thus completely enclosing the anode.

Referring to Fig. 3 there is shown a mount for a full Wave rectifier tube comprising a press 43 into which are sealed the lead-in and support wires 44 to 5| inclusive. Mounted on the wires 41 and 48 is a composite disc 52 consisting of a sheet of mica or similar insulating material having coatings of metal suitably deposited or applied to opposite faces of the disc. Preferably, although not necessarily, the metallic coatings on opposite faces of the disc 52 are smaller in area than the disc itself so that there vis an uncoated area around each edge of the disc. The wire 41 contacts electrically with the coating on one-side of the disc while the wire 48 contacts with ing on the opposite side of the said disc. Mounted in spaced relation to one side of the disc 52 is a suitable electron-emitting cathode 53 which, merely for purposes of explanation, is shown as an indirectly heated cathode provided with heater filament terminals connected to the wires 45 and 46 and with a tubular metal cathode sleeve 54 connected to the 'wire 44. A similar cathode 55 the coatis mounted in spaced relation to the opposite face of the disc 52. It will be understood that any well known means may be provided for maintainingthe cathodes 53 and 55 in their predetermined spaced relations with respect to the metallic coating 55 and the metallic coating 51 on disc 52. The coatings 56 and 51 therefore serve as anodes to the cathodes 53 and 55 and the insulator por- 'tion of the composite disc effectively insulates the two metal coatings from each other and also shields the cathodes from each other. Since the metallic coatings 56 and 51 are required to act as anodes, preferably although not necessarily, they are constituted of a metal such as iron, nickel or the like which is not materially affected by the heat or bombardment from the cathode.

Various changes and modifications may be made herein without departing from the spirit and scope of the invention. f

What I claim is:

1. An electric discharge tube having a pairof electrodes, anl insulator member interposed between said electrodes, and a metallic coating on the surface of said member except at the regions where said member connects with'said electrodes.

2. A tube mount comprising a press supporting a plurality of pairs of metal uprights, an electrode supported on each pair of uprights, an insulator member through which said uprights pass to insulatingly keep said electrodes apart, and a coating of metal on the surface of said member to serve as an electrostatic shield, said coating being fore-shortened with respect toV one pair of uprights.

3. A -shielding cage for radio tubes or the like comprising a hollow cylindrical metal member'and f a pair of insulator discs closing off the ends of said member, said discs being provided with localized c'onductive coatings on-their surfaces and also being provided with perforations said-coating being fore-shortened with respect to certain of said perforations. A Y

4. An electric discharge tube comprising a pair of insulator discs, an electrode assembly mounted between said discs, each of 'saiddiscs being provided with a conductive coating on its surface but with the median portions of the disc surface uncoated, projections from certain of said electrodes engaging the uncoated portions of said discs, and projections from another of said electrodes engaging the coated portions of said disc.

5'. A composite shielding and spacing member for radio tubes comprising a disc of insulating material having a conductive coating on the surface thereof, said disc being provided with perforations to receive electrode projections, the portions of said disc surface adjacent'the perforations being uncoated.

WALTER LOUIS KRAHL.

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