US2055897A - Mount for electron discharge devices - Google Patents

Description

Sept. 29, 1936. J H|RMANN 2,055,897

MOUNT FOR ELECTRON DISCHARGE DEVICES Filed June 26, 1934 INVENTOR JULIUS H IRMANN ATTORNEY Patented Sept. 29, 1936 UNITED STATES MOUNT FOR ELECTRON DISCHARGE DEVICES Julius Hirmann, Hillside, N. J assignor to Radio Corporation of America, a corporation of Delaware Application June 26, 1934, Serial No. 732,404 4 Claims. (Cl. 25047.5)

My invention relates to improvements in electron discharge devices and more particularly to improved means for firmly and accurately positioning the electrode mount within the envelope 5 of a tube. 1

In modern tubes such as tubes having dome type bulbs or envelopes, it is found desirable to hold the electrode assembly firmly in place in the envelope to prevent transverse movement of the mount. To this end the dome or other constricted portion of the tube is utilized to Steady the electrode assembly against transverse movement and to keep the assembly more firmly in position than when the assembly is support- 5 ed and steadied only from the stem press. The mount should be steadied sufficiently to avoid noises, such as clicking, due to contact between the electrode assembly and the envelope when the tube is jarred or vigorously vibrated. The

steadying means or mount spacer should be sufficiently resilient to avoid the stresses and distortion of the mount assembly produced when a mount with rigid steadying means is forced into a bulb dome slightly smaller than usual.

Metallic spring spacers are resilient and easily made and attached to the mount, but the use of such metallic springs to steady the mount has not heretofore been favored because strain checks and cracks were often produced in the glass bulb during exhaust at the points where the metal touched the glass. The usual practice is to attach to the mount, mica mount spaces either in the form of a plate or disc extending'transversely of the dome portion of the envelope or in the form of vertical oblong shaped micas attached to the mount intermediate their ends and with their ends in contact with the walls of the bulb. Mica mount spacers also have some disadvantages, as commercial mica 40 varies from .008" to .020" in thickness and the resiliency of the mica spacers also varies considerably with the result that the mounts are not always positioned centrally of the tube. Attaching the vertical micas to the mount is sometimes difficult and various ways of attaching the micas have been devised. Furthermore, mica may split under stress and sometimes it blisters during high frequency heat treatment. A metallic spring mount spacer would in many cases be preferable to a mica spacer if it could be used without harm to the bulb or to the tube.

The principal object of my invention is to hold firmly and accurately the free end of an electrode mount within the bulb of an electron dis charge device by metallic springs secured to the mount and engaging the interior walls of the bulb without injury to the mount during assembly or to the bulb during exhaust.

The novel features which I believe to be char- 5* acteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in m which Figure 1 is a view in perspective with parts broken away to show details of construction of an electron discharge device embodying my invention, and Figure 2 is an enlarged horizontal cross section taken along line 22 of 15 Figure 1.

The electron discharge device as shown in Figure 1 has a dome type bulb l0 provided with the usual stem press I l and base I2. The mount l3 comprises the usual electrode assembly including a cathode, grid and anode and extends at its upper end into the tubular portion or dome of the bulb Ill. The mount'has secured on its upper end by strips l4 welded to the mount, a sheet insulator or electrode spacer 15, preferably of mica, which extends transversely of the mount and of the tubular portion or dome of the envelope II. A rigid member constituting part of the mount,'such as the anode side rods l6, which extend upwardly thru the mica spacer l5 and f into the dome of the bulb, carries the mount spacer or steadying means for holding the mount centered in the dome.

In view of the fact that the envelopes are not all of exactly the same diameter, rigid mount spacers on the upper end of the mount to fit snugly in the dome are not feasible. If the mount spacers are rigid and fit the largest envelope, the mount will be stressed and distorted whena smaller envelope is placed over the mount assembly; while if the spacer fits the smaller envelope it will be loose in the large envelope and clicking will result.

In accordance with my invention I provide a mount spacer comprising metallic spring spacers 4 ll, each having a loop portion l8 intermediate its ends and substantially perpendicular to the spring for fastening the spring spacers to a rigid mount member, such as the side rod l6, and each having its outer end curved, preferably on a radius 50 less than that of the dome to form bowed in portions 19 at its ends, so that the bowed portions have a substantially line contact with the interior wall of the tubular portion of the bulb. The spring spacers I! are positioned between the 55 side rods and extend transversely of the tube with their bowed ends in contact with the inner walls of the tubular portion of the envelope ID to resiliently support and steady the mount and center it in the envelope. These metallic spring spacers may be made, for example, of thin flat or ribbon material of tinned steel, tungsten or the like, it being obvious that the spring spacers may also be made of very small diameter resilient wire.

I have obtained very good results with tinned steel .012" thick and .073 wide, the overall length of the spring spacer being about 1.150", the length of the loop about .140" and the radius of curvature of the bowed ends .140". spring spacers were used in a bulb having a dome portion about 1.30 in diameter, the side rods being spaced about 1.02 apart.

By providing the loop portion I8, the bowed portions of the spring spacers may be disposed between the side rods to extend toward each other and the springs may be provided with an overall length nearly equal to the diameter of the tubular portion of the bulb. This results in long resilient springs having a greater resiliency and capable of adapting themselves to wider variations of bulb diameter than the usual mica spacers. When the bulb is placed over the mount the ends of the spring spacers are flexed inwardly toward each other to an extent depending on the inner diameter of the dome of the bulb. These springs act to resiliently center the mount from the walls of the tubular portion of the envelope and prevent clicking of the tube.

While I do not wish to be restricted to any particular theory, I believe that the success of the metallic spring spacers is due to the fact that because of their small mass they absorb very little heat from the bulb during the sealing operation and because of their thinness they do not rapidly conduct heat toward or away from the bulb. On the other hand due to the fact that the spring spacers are mounted at the top of the side rods the spacers are not in the intense high frequency field while the plate is being heat treated to degas it and since the ends of the spring spacers are not joined to form a closed circuit, little if any high frequency heating of the springs results. Very little if any heat is conducted from the plate to the spring fingers thru the side rods because of the extremely small cross section of the side rods. Checks and strains in the glass envelope are apt to occur if there is a large temperature differential between the envelope and metallic spring spacers in contact therewith, as, for example, when heat is rapidly conducted from the metallic springs to the mount when heating the envelope during sealing or when heat is rapidly conducted to the metallic springs from the mount during the high frequency heat treatment. With the metallic spring spacers made in accordance with my invention the temperature of the ends of the metallic spring spacers in contact with the wall of the tube is always so nearly the same as the temperature of the glass envelope that the temperature differential between the metallic spring spacers and the wall is practically negligible, thus preventin checks and strains.

While I have indicated the preferred embodi- These ments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is,-

I. An electron discharge device comprising an envelope having a tubular portion, a mount enclosed by said envelope and having rods extending into the tubular portion, metallic ribbon spring spacers, each of said spacers being provided intermediate its ends with a loop enclosing and securedto a different one of said rods and having its ends in engagement with the walls of the tubular portion of the envelope to resiliently steady the mount from the walls of the tubular portion of said envelope.

2. An electron discharge device comprising an envelope having a tubular portion, a mount enclosed by said envelope and comprising an electrode assembly provided with a pair of oppositely disposed rods extending within the tubular portion of the envelope, metallic spring spacers, each of said spacers being provided with a loop intermediate its ends for encircling and engaging a different one of said rods for positioning the spring spacers intermediate the side rods, each of said metallic spring spacers separately extending transversely of the tubular portion of the envelope and having bowed-in ends in contact with the walls of the tubular portion of the envelope to resiliently steady the mount from the walls of the tubular portion of said envelope.

3. A metallic spring spacer for engaging a side rod of a mount of an electron discharge device positioned within an envelope provided with a tubular portion. and comprising a metallic spring having a'substantially perpendicular looped portion intermediate its ends for encircling and engaging said side rod to extend transversely of the tubular portion of the envelope, and reversely curved ends on said spring adapted to contact the walls of the tubular portion of the envelope to resiliently steady the mount from the walls of the tubular portion of the envelope.

4. An electron discharge device comprising an envelope having a tubular portion, a mount enclosed by said envelope and comprising an electrode assembly provided with a pair of oppositely disposed side rods extending within the tubular portion of the envelope, metallic ribbon spring spacers provided with a loop portion intermediate their ends for engaging said side rods to position the spring spacers intermediate the side rods, said metallic spring spacers extending transversely of the tubular portion of the envelope and having their ends curved in toward each other on a radius less than that of the tubular portion of the envelope to have a substantially line contact with the walls of the tubular portion of the envelope to resiliently steady the mount from the tubular portion of said envelope.

JULIUS HIRMANN.

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