US2151811A - Mount for electron discharge devices - Google Patents

Description

March 28, 1939.

N. R. SMRTH MOUNT FOR ELECTRON DISCHARGE DEVICES -Filed Feb. 1, 1934 I INVENTOR NEWLL R .SMI'TH ATTORNEY Patented Mar. 28, 1939 PATENT OFFECE MOUNT FOR ELECTRON DISCHARGE DEVICES Newell R. Smith, Bloomfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application February 1, 1934, Serial No. 709,267

4 Claims.

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

In modern tubes, such as a tube having the dome type bulb or envelope, it is found .desirable to firmly hold the electrode assembly in theenvelope 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 vibration and to keep the assembly more firmly established in position than when the assembly is supported and steadied only from the stem press. The mount should be steadied sufiiciently to avoid noises such as clicking which is caused by contact between the electrode assembly and the envelope when the tube is jarred or vigorously vibrated. The supporting means should be sufliciently resilient to avoid stresses and distortion of the mount assembly which are produced when rigid supporting means are provided for the mountand' the mount is forced into the domeof a bulb slightly smaller than the usual size. Attempts to steady the'mount by metal braces which touch the bulb have not been successful as such braces produce strain checks and cracks in the glass during exhaust at points where the metal touches the glass,

The principal object of my invention is to firmly hold and accurately position the free end of an electrode mount within the bulb of an electron discharge device by resilient means engaging the interior walls of the bulb without producing a deleterious efiect on the mount during assembly or injuring the bulb in any way during exhaust.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention will be best understood by reference to the following description taken in connection with the accompanying drawing in which:

Figure 1 is a View in perspective and partly broken away of one form of an electron discharge device embodying my invention;

Figure 2 is an enlarged horizontal cross-section taken along the line 2-2 of Figure 1;

Figure 3 is an enlarged partial vertical section taken along the line 3-3 of Figure 2;

Figure 4 Ban enlarged View of a mica spacer made in accordance with my invention;

Figure 5 is an enlarged View of a portion of the collar of Figure '1 showing details of the slot for holding the mica spacer shown in Figure 4; and

Figure 6 is an enlarged partial view of the collar with the mica spacer in place.

The electron discharge device shown in Figure 5 1 has the usual base I0 on a dome type bulb or envelope I I and a contact cap I2 electrically connected to a control grid, not shown, but forming a part of the mount assembly I3. Within the tubular portion or dome of the bulb I I is a shield 10 M in the shape of a fiat bottomed cup having in the bo tom a re-entrant shallow recess I5 in which the circular mica spacer I6 fits snugly, covering a rectangular slot I! in the bottom of the shield I4. At the ends of the slot I6 are up- 15 turned ears I8 which are welded to support rods I9 extending from the press of the tube. The upper ends of the cathode 20 and of the grid rods 2| extend through the mica spacer, which holds them in alignment in the middle of the slot I1 and 20 spaces them laterally.

As the bulbs are not all of exactly the same diameter, rigid spacers on the upper end of the mount to fit snugly in the dome are not entirely satisfactory. If the spacer is rigid and fits the 25 largest bulb, the mounts will be stressed and distorted when a smaller bulb is placed over the mount assembly, while if the spacer fits the smaller bulbs, it will beloose in the larger bulbs, and clicking will result.

In accordance with my invention the collar-like or cylindrical portion I4 of the shield I4 is provided with a plurality of slots 22 of the shape shown most clearly in Figure 5, into which the spring mica spacers or fingers 23 are fitted and 35 with which they are interlocked. The mica fingers 23 engage the interior wall of the dome to resiliently space the mount within the dome portion of the bulb. The resilient mica spacers are stilt enough to steady the mount, but will not 40 cause stresses or distortion of the mount. The mica spacer 23 is shaped as best shown in. Figure 4. The lower end contacts the wall of the bulb, the upper portion being fitted through the wide portion of the slot 22 and then tilted into the po- 5 sition shown most clearly in Figures 3 and 6 to interlock with the collar portion I4. The angle assumed by the spacer with respect to the vertical collar portion I4 is determined by the radius R indicated in Figure 4. The smaller this radius 50 the more acute the angle between the collar and the spacer. The length and thickness of the spacer determines the flexibility of the spacer.

One specific form of the spacer 23 which I have found satisfactory has an overall length of 55 about thirty-five thousandths of an inch, the radius R about two tenths of an inch, and its center spaced about seven thousandths of an inch away from. the upper edge of the spacer on the dotted line passing through the center of the spacer, as indicated in Figure 4. The width of the mica spacer at the lower or tongue portion is about 25 hundredths of an inch and its narrowest dimension at the shoulder about two tenths of an inch. The slot 22 in the collar is about four thousandths of an inch wide, its longer portion about twenty-six one thousandths of an inch, and its shorter portion about two tenths of an inch the width of each of the two portions of the slot being equal, that is about two one thousandths of an inch. The bottom of the slot is preferably located about one eighth of an inch from the top of the collar, which is conveniently about three tenths of an inch in height and about nine tenths of an inch in outside diameter, the mica spacer making an angle of about 20 degrees with the portion l4 collar when mounted in the tube.

While I show three such fingers it is obvious that two or more than three could be used. When the bulb is placed over the mount the fingers are flexed downward slightly and to an extent dependent upon the inner diameter of the dome of the bulb. These fingers. resiliently center the electrode assembly firmly and accurately within the envelope and prevent clicking in the tube.

While I have indicated the preferred embodiment of my invention of which I am now aware and have also indicated specific applications for which my invention may be employed it will be apparent that my invention is not 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:-

1. An electron discharge device having an envelope provided with a tubular portion at one end thereof, a mount comprising an electrode assembly positioned in the other end of said envelope and provided with a member having a collar-like portion extending within the tubular portion of the envelope said collar-like portion having slots spaced around its periphery, sheet mica springs interlockingly engaged in said slots and extending outwardly from said mount at an angle to the longitudinal axis of the tubular portion of said envelope to facilitate the insertion of said mount into the envelope of the tube and to engage the interior wall of the tubular portion of said envelope to resiliently and firmly position said mount within said envelope.

2. An electron discharge device having an envelope provided with a tubular portion at one end thereof, a mount comprising an electrode assembly in the other end of said envelope and provided with a member having a collar-like portion extending within said tubular portion, said collarlike portion having slots spaced around its periphery, sheet mica springs interlockingly engaged in said slots and set at an angle to the longitudinal axis of the tubular portion of said envelope to facilitate the insertion of said mount into the envelope of the tube and to engage the interior wall of the tubular portion of said envelope to resiliently and firmly position said mount within said envelope.

3. An electron discharge device having an envelope provided with a tubular portion, a mount comprising an electrode assembly positioned within said envelope, a member on said assembly having a cylindrical portion extending within the tubular portion of said envelope coaxially therewith and provided with apertures spaced around its periphery, insulating sheet springs mounted in said apertures and fastened to said cylindrical portion of said member with one end only of each spring angaging the interior wall of the tubular portion of said envelope to resiliently and firmly position to mount in said envelope.

4. An electron discharge device having an envelope provided with a tubular portion, a mount comprising an electrode assembly positioned in said envelope, a member on said assembly having a collar-like portion extending within the tubular portion of said envelope coaxially therewith and provided with spaced slots around its periphery, sheet mica springs having inner and outer ends and interlockingly engaged in said slots the outer end only of each mica spring contacting the inner wall of the tubular portion of the envelope to resiliently and firmly position said mount within said envelope.

NEWELL B. SMITH.

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