US2910608A - Grid support wedges - Google Patents

Description

.between the electrode support rods.

GRID SUPPORT WEDGES Wenfoo George Woo, West Newton, Mass., assignor to Raytheon Company, a corporation of Delaware Application June 13, 1955, Serial No. 514,820

8 Claims. (Cl. 313 -260) This invention relates to electron discharge devices and their construction, and more particularly to wedges for retaining grid supports in place in separators.

In electron discharge devices any change in the relative positions of the electrodes, particularly of the grids, will cause variations in the electrical output of the tube. This appears as noise in the output of an operating tube. A common cause of such changes in the relative positions of the electrodes is the play of the support rods within the holes in which they are mounted in separators, usually of mica. This can be prevented by tightening the tolerances to which the holes for the support rods are drilled in the mica. However, if this is done, the already difiicult task of inserting the support rods of theelectrodes into the holes in the spacer is made even more ditficult with the result that production is slowed down and made more 1 expensive. In fact, the more play that can be tolerated, the easier is the assembly operation. Another diiiiculty with making the holes in the spacers for the support rods to close tolerances, is that the holes are enlarged in the process of pushing the rods through them. Furthermore, 1

when the cathode sleeve heats during processing and operation, it will distort the openings. Stakes have been used to give added rigidity to the electrode supports, but this construction is expensive and in the subrniniature size of tube there is no room to spare on the separator for stakes. Another approach has been to insert small metal springs This again is an expensive construction. In addition, the metal of the springs is likely to lose its temper when the mount is heated, either during processing or during the operation of the tube and cease to perform its function of forcing the electrode supports toward the sides of the holes in the separators, thus permitting the play to take place and create noise. A possibility is to melt glass about the electrode supports as they protrude from the spacer. While this is effective in stopping play, it is expensive.

By the construction of the invention, a piece of mica,

or other insulating material is formed with a region of a dimension determined by the desired spacing of the electrode supports and formed by two opposing notches of a depth and width determined by the radius of the support rods to be separated. The notches are preferably trapezoidal in shape, although they may be of other shapes, such as triangular or semicircular. The wedge is inserted edgewise between the electrode supports and turned fiat as it approaches the spacer. It is held down and in position by a second spacer inserted about the electrode supports over the wedges. The result is that the electrodes are retained in their relative spacing even when the holes in the mica are formed to greater than their normal tolerances. These larger tolerances speed up assembly of the mounts making the construction cheaper. Tubes constructed with the wedges of the invention produced no vibration output that could be traced to motion of the grid or gn'ds. In a representative case, microphonic output was reduced from 300 millivolts to millivolts.

2,910,608 l atented Oct. 27, 1959 ice The foregoing and other advantages of this invention will be better understood from the following description taken in conjunction with the accompanying drawing wherein:

Fig. l is an exploded isometric view of a tube mount assembled with the wedges of the invention; v

Fig. 2 is a view takenalong the line 2-2 of- Fig. 3 of a mount with the wedges of the invention inserted within an envelope (only a part shown);

Fig. 3 is a View taken along the line 3'-3 of Fig. 2 partially broken away of a tube with the wedges of the invention; and

Figs. 4a, 4b and 4c are plan views of three forms of the wedges of the invention.

In Fig. 1 the reference numeral 10 designates the lower of two upper spacers of insulating material, preferably mica, formed with openings through which are inserted the electrode supports 11, 12, 13, 14, 15 and 16, the cathode sleeve 17 and two tabs 18 and 20 formed integral with the anode 21. The support rods 13 and 14 support the first grid 22, best seen in Fig. 3. The supports 12 and 15 support the screen grid 22a, and supports 11 and 16 support the suppressor grid 22b, also best seen in Fig. 3. Two wedges 23 are formed of insulating material, preferably of mica, each with a notch 24 in each side, leaving a restricted region 25. These wedges may be of. any of the shapes shown in Figs. 4a, 4b and 4c. Fig. 4a shows the preferred configuration. in which the notch is of trapezoidal shape. The depth a, an outer b, and

an inner c widths of this notch are determined by the radius of the associated rods at the region of contact. The width of the restricted region 25 is determined by the desired spacing between the associated. rods. Mica is suificiently soft so that if the dimension d is mades'lightly larger than the desired spacing, the rod will fracture off enough mica to complete the cutting of the notch and give a tight fit without buckling or weakening the mica. The notches of the trapezoidal shape, shown in Fig. 4a, are easier to form in the mica than the semicircular notches 24a of radius r, considerably greater than the radius of the associated rods shown in Fig. 4b. However, a semicircular notch accommodates a rod of circular cross section better than the triangular notches 24b, shown in Fig. 40. This particular type of notch is the easiest to make, but it is necessary to make the dimension d considerably smaller for the same spacing of the associated grid support ro'ds, than for either of the other two shapes. This weakens the wedge. Thus the form of the wedge shown in Fig. 4a has been found to be best, but other constructions for achieving the region of 7 reduced width, such as those shown in Figs. 4b and 40, can be used.

When the wedges are inserted, they are held in place by a second spacer 26 formed with an opening 27 to receive the support rods 11 through 16, and with an enlargement 27a at .the center to receive the cathode sleeve 17. It is also formed with slots 28 and 30 to receive the tabs 18 and 20 that support the anode 21. Individual openings might be formed in the spacer 26 for each electrode support, but all that is needed is a means for holding down both those portions of each wedge that protrude beyond the space between the electrode supports. Separate openings would require each electrode support to be inserted in its opening, slowing assembly and increasing cost. The result of the construction of the invention is the sandwich shown in Fig. 3' where the spacer 10 forms the bottom layer with the electrode supports 11 through 16, the cathode sleeve 17, and the tabs 18 and 20 passing through it. The wedges 23, shown in cross section as the middle layer, are inserted between their associated support rods 12 and 13, and 14 and 15, respectively. It will be seen that when the mount is inserted in the envelope 31 the protrusions 32, formed on the spacers and 26, serve to support the mount transversely in the envelope without conducting excessive heat to the regionof contact. Other spacer configurations can of course be used. Wedges of the invention may be used between the lower ends of the electrode supports as well.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordinglydesired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. An electron discharge device including a plurality of electrodes with support members inserted in openings in spacer members, wedge members placed between at least two adjacent electrode support members where they protrude from at least one of the spacer members, said wedge members comprising a flat strip of insulating material of a hardness less than that of the support members having a region of reduced width, said width being slightly greater than that required by the desired separation of the adjacent electrode supports, said region of reduced width being formed by opposing notches of a width and .depth determined by the cross-sectional dimensions of the adjacent electrode supports at the region of contact, the width of said notches reducing with depth.

2. An electron discharge device includinga plurality of electrodes with support members inserted in openings in spacer members,.wedge members placed between at least two adjacent electrode support members where they protrude from at leastone of the spacer members, said wedge members comprising a flat strip of insulating material of a hardness less than that of the support members having a region of reduced width, said width being slightly greater than that required by the desired separation of the adjacent electrode supports, said region of reduced width being formed by opposing semicircular notches of a radius determined by the cross-sectional dimensions of the adjacent electrode supports at the region of contact.

7 3. An electron discharge device including a plurality of electrodes with support members inserted in openings in spacer members, wedge members placed between at least two adjacent electrode support members where they protrude from at least one of the spacer members, said wedge members comprising a-flat strip of insulating material of a hardness less than that of the support members having a region of reduced width, said width being slightly greater than that required by the desired separation of. the adjacent electrode supports, said region of reduced width being formed by opposing notches of a triangular shape with a width and depth determined by the cross-sectional dimensions of the adjacent electrode Y supports at the region of contact.

wedge membe 5. comprising a fiat strip of insulating material of a hardness less than that of the support members having a region of reduced width, said width being slightly greater than that required by the desired separation of the adjacent electrode supports, said region of reduced width being formed by opposing notches of a trapezoidal shape with dimensions determined by the cross-sectional dimensions of the adjacent electrode supports at the region of contact, the width of said notches reducing with depth.

5. Wedge members for separating the electrode supports of electron discharge devices formed of a flat strip of insulating material of a hardness less than that of said supports with a region of reduced width, said width being slightly greater than that required by the desired separation of the electrode supports to be separated, said region of reduced width being formed by opposing notches of a width and depth determined by the cross-sectional dimensions of the electrode supports with which the wedge is to be adjacent at the region of contact, the width of said notches reducing with depth.

6. Wedge members for separating the electrode supports of electron discharge devices formed of a fiat strip of insulating material of a hardness less than that of said supports with a region of reduced width, said width being slightly greater than that required by the desired separation of the electrode supports to be separated, said region of reduced width being formed by opposing semicircular notches ot a radius determined by the crosssecti-onal dimensions or" the electrode supports with which the Wedge is to be associated at the region of contact.

7. Wedge members for separating the electrode supports of electron discharge devices formed of a flat strip of insulating material of a hardness less than that of said supports with a region of reduced width, staid width being slightly greater than that required by the desired separation of the electrode supports to be separated, said region of reduced width being formed by opposing notches of a triangular shape with a width and depth determined by the cross-sectional dimensions of the electrode supports with which the wedge is to be associated at the region of contact.

8. Wedge members for separating the electrode sup ports of electron discharge devices formed of a'fiat strip of insulating material of a hardness less than that of said supports with a region of reduced width, said Width be ing slightly greater than that required by the desired separation of the electrode supports to be separated, said region of reduced width being formed by opposing notches of a trapezoidal shape with dimensions determined by the cross-sectional dimensions of the electrode supports with which the wedge is to be associated at the region of contact, the width of said notches reducing with depth.

References Cited in the file of this patent UNITED STATES PATENTS 289,166 Strohm Nov. 27, 1883 1,801,451 Parker Apr. 21, 1931 1,867,390 Thompson July 12, 1932 1,886,991 Van Horne Nov. 8, 1 932 2,057,115 Rothe Oct. 13, 1936

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