US2814223A - cheatle - Google Patents

Description

Nov. 26, 1957 w. R. CHEATLE CATHODE SPREADER FOR FLAT CATHODES Original Filed. July 10. 1953 INVENTOR WILFRED R. CH EATLE'.

United States Patent "ice 2,814,223 1 CATHODE SPREADER FOR FLAT CATHODES Wilfred R. Cheatle, Emporium, PaL, assignor to Sylvania Electric Products, Inc., a corporation of Massachusetts Original application July 10, 1953, Serial No. 367,261.

. Divided and this application November 13, 1956, Serial claims. ((31. 8115) This inventionrelates to tools for use during the mannfacture of anelectron tube and particularly for use with a hollow element within the tube which is to be reshaped by bowing of the sides thereof.

In particular, the invention relates to a tool for insertion within a cathode sleeve which is placed within ,a wound grid in order to bring surfaces of the sleeve very close to the wound grid.

In order to obtain certain characteristics in a tube, it is sometimes necessary-to have the distance between electrodes very small. having a high mutual conductance or Gm, the distance between control grid and cathode should be made very small. In assembling such tubes where adjacent electrodes are of the final desired dimensions, one electrode is apt to rubagainst the other'with possible injury to the electrodes or their coatings.

It is an object of this invention to provide a tool for carrying out the method so that there is much less likelihood of injury to the tube components during assembly than heretofore, while yet providing for a simple method of finally forming the assembled parts to obtain desired positional relationships of the parts.

Fora better understanding of my invention, attention is directed to the following specification and claims and the accompanying drawings in which:

Fig. 1 is a perspective view of a typical mount of a tube having a high transconductance, parts being broken away to expose salient portions of the mount, and with the cathode bowing exaggerated to better illustrate the construction of the type of tube here involved.

Fig. 2 is a diagrammatic plan view of the triode portion of the mount.

Fig. 3 is a diagrammatic plan View of the cathode, grid and a fragment of a support wafer prior to spreading of the cathode, the opening in the wafer for reception of the cathode being exaggerated as to minor axis diameter.

Fig. 4 is a view similar to Fig. 3, but with the cathode spread, the figure also showing, in section, the tool utilized in the process.

Fig. 5 is a view of one form of a tool employed in the process, showing the proportion of parts.

Fig. 6 is a very much enlarged perspective view of one form of tool utilizable in the manufacture of the mount, the handle being broken away.

Fig. 7 is a section through the tool at its spreader portion, taken along the line 77 of Fig. 6.

Fig. 8 is a view similar to Fig. 6 showing a modified form of tool.

Fig. 9 is a view showing a modified form of mounting the tool, only a portion of the tool being shown.

Referring to Fig. 1 there is shown a vacuum tube mount 10 with cathode 12, grid 14 and anode 16. For exemplification, the tube disclosed is a 6J4WA type which requires exceedingly close cathode and grid. The cathode is suitably held between a pair of insulating wafers 24, and the grid is supported by grid side rods 26, which may In the case of a grid controlled tube 6 slightly distend the large area faces of the cathode.

, 2,814,223 Patented Nov. 26, 1957 rectangle are bowed outwardly very slightly. An exaggerated bow in the Wafer 24 is shown in Fig. 3 at 30.

In assembling themount, the bottom wafer has first assembled on it the cathode 12 in its parallepipedon form and the anode assembly 16. Then the grid structure 12 is slipped over the cathode and mounted on the lower wafer, and the top insulating wafer, provided with openings similar to the bottom wafer, is applied to the mount. The parts are then fastened together. In the case of manufacture of diodes, the anodes might be mounted very close to the cathode so that were an attempt made to mount parts to occupy their final positions, damage to the electrodes, particularly to the coating on the cathode, may well take place. Therefore, even in the assembly of a diode mount, it is desirable to follow the teaching of this inventor. Following such teaching, the cathode to be mounted should be of a cross section, not necessarily'rectangular, such that it may be spread to bring parts of it closer to the anode or anodes.

To complete the mount assembly, a cathode spreading tool, about to be described, is inserted into the cathode along the axial center of the cathode and is rotated to In the process, because the distention is slight, no damage "is done to the cathode coating; the insulating wafer, if

provided with a rectangular opening, will yield the slight amount necessary. Where the wafers hai e bowed wall openings, the distention of the cathode may be more freely accomplished without injury to the wafers. It has been found in practice, that by utilization of the tool following the teachings of this invention, the losses in manufacture are far below those where the assembly is effected without tools and with prebowed cathodes. In the prior art method damage to the cathode coating or distortion of other electrodes is a quite frequent occurrence resulting in considerable tube losses or shrinkage.

The tool 32 comprises a socketed handle 34 and a needle 36 secured in the handle by any convenient means such as a set screw 38 threaded into the handle and engaging the needle portion lying in the socket of the handle. The needle 36 itself is comprised of a cylindrical portion 40 and a second spreader portion 42 of reduced diameter with respect to the cylindrical portion to provide a shoulder 44 for a purpose to be described. The free end of the needle may be tapered as shown at 45.

The spreader has two parallel fiat sides 46 spaced apart a distance barely under the minor diameter of the unspread cathode and two opposed rounded surfaces 48 whose maximum spacing is equal to the desire-d final distended internal minor dimension of the cathode. The handle 34 has a flat portion 50 parallel to the fiat face 46 of the spreader to indicate, to the operator by feel, the angular position of the spreader flat faces. Instead of the needle being mounted in a socketed handle, it may obviously project upwardly from a flat base 60, as is shown in Fig. 9, resting on a suitable support such as a table.

In use, after the parts of the tube have been mounted as described above, the spreader is inserted into the cathode at about its medial longitudinal axis and thrust in until the shoulder 44 engages the edge of the cathode.

Then the tool and the cathode are relatively rotated 180 or more, thus causing the rounded edges of the needle to engage the cathode walls to be bowed. Since the maximum distance between the rounded ends of the tool is greater than the distance between the walls to be bowed, there Will be effected a spreading of the cathode to bring the outer face of the cathode closer to the grid. After the cathode has been spread, the tool is retracted. The mount then is further processed, as is usual in the art.

If desired, particularly where wafers with rectangular openings for the cathode are provided and in order to prevent possibility of breakage of the wafer when the cathode is enlarged, the form of spreading tool shown in Fig. 8 may be employed.

This tool differs from the tool previously described in that not only the free end 52 of the spreader, but also the end 54 adjacent to the shoulder 56 have their rounded cylindrical sides approach each other very slightly. Thereby neck portions are formed at both ends of the needle. As a result, when the tool is inserted in a rectangular cathode and rotated, the cathode will spread between the wafers; at the level of the wafers, the spread will be exceedingly little, if at all, thus reducing any tendency for the wafer to crack or crumble. Where the wafers are provided with rectangular holes, the cathode is slightly bulged between the wafers and held against excessive longitudinal movement with respect to the wafers when the parts are cold. The length of the operative surfaces of the needle is proportioned to the length of cathode between wafers to secure this result.

This application is a division of application Serial No. 367,261, filed July 10, 1953.

Having thus described the invention, what is claimed as new is:

1. A spreading tool comprising a generally cylindrical handle and a needle member supported by the handle. the needle member comprising a portion whose boundary is generally elliptical with parallel flat walls and cylindrical connecting walls between the edges of the fiat walls, there being a fiat surface on the handle member parallel to a fiat wall on the needle portion to facilitate positioning the tool.

2. A spreading tool comprising a handle and a needle member supported by the handle, the needle member comprising a cylindrical portion adjacent the handle and an elongated following portion, ellipsoidal in cross section, the length of the major axis of the ellipsoid throughout its length and at its juncture with the cylindrical portion being less than the diameter of the cylindrical portion to form a collar on the end of the cylindrical portion and whose minor axis terminates in a pair of parallel sides.

3. A tool for spreading cathodes comprising a mounting and a needle portion carried thereby, said needle portion including an elongated part generally cylindrical but having two parallel plane surfaces, the rounded surfaces at spaced points along the elongated part approaching the axis of the cylinder to form neck portions.

4. A tool for spreading cathodes comprising a mounting and a needle portion carried thereby, said needle por- {tion comprising a cylindrical portion attached to the handle and a second portion in axial alinement with the cylindrical portion and forming a prolongation thereof, said second portion being generally cylindrical but with parallel plane walls, the cylindrical wall portions adjacent the ends of the second portion approaching the axis of the cylinder to form reduced neck portions, there being a shoulder at the juncture of the two portions of the needle.

5. A tool for spreading cathodes comprising a mounting and a needle portion carried thereby, said needle portion including an elongated part generally cylindrical but having two parallel plane surfaces, an end of the part having its rounded surfaces approach the axis of the cylinder to form a portion of a smaller cross-sectional diameter.

References Cited in the file of this patent UNITED STATES PATENTS 437,177 Deaton Sept. 30, 1890 1,376,811 Hood May 3, 1921 1,677,572 Walkley July 17, 1928 FOREIGN PATENTS 18,702 Great Britain of 1913

Images