US3210145A

US3210145A - Electron gun supporting technique

Info

Publication number: US3210145A
Application number: US91498A
Authority: US
Inventors: Norman F Fyler
Original assignee: Litton Precision Products Inc
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1961-02-24
Filing date: 1961-02-24
Publication date: 1965-10-05
Anticipated expiration: 1982-10-05
Also published as: GB974902A

Description

Oct. 5, 1965 N. F. FYLER ELECTRON GUN SUPPORTING TECHNIQUE 3 Sheets-Sheet 1 Filed Feb. 24. 1961 Oct. 5, 1965 N. F. FYLER ELECTRON GUN SUPPORTING TECHNIQUE 3 Sheets-Sheet 2 Filed Feb. 24, 1961 @Z 5? g M w .M 7% 6 Mi;

mmmmmw rex Ze 1601! 7 Fry/farm Oct. 5, 1965 N. F. FYLER ELECTRON GUN SUPPORTING TECHNIQUE 5 Sheets-Sheet 5 Filed Feb. 24. 1961 United States Patent "'ice 3,210,145 ELECTRON GUN SUPPORTING TECHNIQUE Norman F. Fyler, Menlo Park, Calif., assignor to Litton Precision Products, Inc., San Carlos, Calif. Filed Feb. 24, 1961, Ser. No. 91,498 Claims. (Cl. 316-19) This invention relates to beam-type electron tubes, and more particularly to arrangements and techniques for mounting and aligning electron guns Within the envelope of such tubes.

In the past, the alignment of guns in beam-type tubes, has presented a serious problem. Thus, for example, in the case of cathode ray tube, a slight error in the alignment of the gun will produce a significant error in the position of the beam on the screen of the cathode ray tube. In some cases, compensation has been provided by the application of steady correcting voltages to the de fiection plates or coils of the tube. In other cases, various cumbersome techniques have been employed for alignment of the gun structures.

Principal objects of the present invention include the arcuate alignment and mounting of electron gun structures in a simple reliable and permanent manner.

Another object of the present invention is to eliminate the perturbations of the electric field which are characteristic of electron gun structures of the prior art which employ ceramic rods in their construction.

In accordance with the present invention, one step in the alignment of the electron gun of a beam-type tube involves melting a ring of glass and leaving a small hardened central area of glass on one side of the neck of the tube adjacent a mounting point on the electron gun structure. In practice, this alignment technique is performed after evacuation of the tube with the electron gun in operation. It the case of a cathode ray tube, the error in position of the beam is apparent from observation of the cathode ray tube screen. The tube, in accordance with an illustrative method utilizing the principles of the invention, is rotated until a torch having a circular ring of flame and a movable central plunger is aligned with the radial displacement of the beam on the cathode ray tube, with respect to the center of the cathode ray tube. The burner may then be advanced to soften a circular ring of glass on one side of the neck of the tube, leaving a relatively hard central area of glass. The plunger is then slowly advanced to engage the hardened center and move the gun structure toward alignment. Meanwhile, the operator continues to observe the face of the cathode ray tube, and continues to advance the plunger until the beam is accurately aligned with the center of the cathode ray tube. The fuel to the torch is then cut off, with the plunger remaining in position. In view of the fact that the envelope is evacuated, the melted zone or diaphragm will be drawn inwardly to engage the adjacent portion of the electron gun structure. Now that the gun is properly aligned, the glass is softened in two additional radially spaced points to secure the gun structure in its aligned position. Each end of the gun structure may be secured at three points. The components of the gun structure may be provided with flanges and each flange may be secured in the manner described above.

In accordance with a featured method of the invention, therefore, the electron gun structure of an electron 3,210,145 Patented Oct. 5, 1965 beam type tube is aligned by the steps of mounting the gun loosely in a glass neck forming part of the tube, evacuating the envelope, softening a ring of glass at one side of neck around a localized hardened area, pressing on the hardened area to deform the glass into aligning contact with the gun structure, and supporting the gun at at least two additional spaced points.

The resulting beam-type electron tube characteristically includes a neck in which the gun structure is mounted. Furthermore, the gun structure is mounted directly from the glass of the neck, and at least one of the inward protrusions by which the gun is mounted includes a central area having the same general surface configuration as the glass neck of the tube and a deformed ring of glass interconnecting the central area and the wall of the neck. The central area has the same general surface configuration as the neck because it is the hardened portion against which pressure was applied by the aligning plunger.

Turning to another aspect of the invention, in cathode ray tubes in which precision electron beams are employed, the side rods which support the component parts of the gun tend to introduce perturbations into the electric field configuration. These perturbations tend to diffuse the electron beam, and reduce the sharpness of focus.

In accordance with another feature of the invention, this undesired effect may be avoided by mounting the separate sections of the electron gun directly from the neck of the tube. In a preferred embodiment, at least one of the glass protrusions supporting the gun may be of the form described in the preceding paragraphs, for precise alignment purposes.

The novel features which are characteristic of the invention, both as to its organization and method of construction and operation, together with further objects and advantages thereof, will be better understood from the following description when taken in connection with the accompanying drawings in which illustrative embodiments of the invention are disclosed, by way of example. It is to be expressly understood, however, that the following detailed description and the drawing are for the purposes of illustration and description only, and that they do not define limitations of the invention.

In the drawing:

FIG. 1 shows a cathode ray tube in which the electron gun is mounted in accordance with the principles of the present invention;

FIG. 2 is a detailed view of a portion of the mounting arrangements for the gun of FIG. 1;

FIG. 3 is a diagrammatic showing of a torch having a ring-shaped flame distribution as employed in the present invention;

FIG. 4 shows a protrusion for securing the gun structure in position, the protrusion being formed with the ring-type burner shown in FIG. 3;

FIG. 5 is a cross-sectional view taken along lines 5-5 of FIG. 1 of the drawings;

FIG. 6 shows a mounting arrangement in accordance with the present invention in which the neck of the tube isconstricted at one point to engage one of the dielectric side rods of the gun structure;

FIG. 7 is a detailed showing of the distortion which may be produced by the difference in dielectric constant between free space and the side rods; and

FIG. 8 is another embodiment of the invention in which the supporting side rods are not used, and in which the '3 three sections of the gun structure are independently supported directly from the glass neck of the beam tube.

7 Referring to FIG. 1 of the drawings, the cathode ray tube includes a faceplate 12 hearing markings in accordance with polar coordinates and a neck portion 14 in which a gun structure 16 is mounted. The gun structure 16, per se, is generally conventional and includes three

sections

18, 20 and 22 which were held together by the dielectric side rods 24. The side rods are preferably of a low expansion material such as Pyrex, which has a composition including approximately 80 percent silica, 12 percent boron oxide and additional sodium and aluminum oxide.

The electron gun 16 is provided with

end flanges

26 and 28 by which it is mounted to the neck 14 of the cathode ray tube. The electron gun 16 is mounted in position by two sets of three glass protrusions which extend inwardly adjacent the

flanges

26 and 28. Two of the protrusions which engage flange 26 are shown at 30 and 32. The

protrusions

34 and 36 are two of the three supports for the lower flange 28 of FIG. 1.

FIG. 2 is a detailed showing of the protrusion 30 and its engagement with the flange 26. Prior to the formation of the protrusion 30, the cathode ray tube is evacuated; accordingly, there is a dilference in pressure of about fourteen or fifteen pounds per square inch (atmospheric pressure) across the glass wall of the neck 14 of the cathode ray tube. When a portion of the neck is heated by a torch, this difference in pressure will draw the glass inward into engagement with the rim 26. In accordance with the present invention, a gun such as the electron gun 16 of FIG. 1, may be properly aligned with the center of the screen 12 as it is being rigidly mounted in place. In practice, the gun is initially mounted within the neck 14 of the tube solely by its input leads to the pins 38. The tube is then evacuated and proper operating potentials are placed on the components of the gun structure 16. The gun is still relatively loose within the neck 14 and the beam will normally not strike the cathode ray tube faceplate in the center.

In order to align the gun 16 with the center of the faceplate 12, the cathode ray tube may be clamped in a vertical position. A torch such as that shown in FIG. 3 is mounted immediately adjacent the neck 14 of the cathode ray tube. The torch of FIG. 3 is a special ring type burner. It includes an outer chamber 40 for combustible gas and a central movable plunger 42. Surrounding the plunger 42 are a series of openings which provide a ring-shaped set of gas jets 44 when the torch is ignited.

When the torch of FIG. 3 is mounted adjacent the neck of the tube 14, the tube 14 is rotated about its axis until the torch is aligned with the radial displacement trace which is visible on the cathode ray tube screen. Thus, for example, with the tube as shown in FIG. 1, and the torch mounted along the neck of the tube adjacent the rim 26 of the gun 16, it will be assumed that the electron beam initially follows a path 46 so that it impinges on the screen 12 at point 48. This is a displacement from the center 50 of the screen 12 parallel to the plane of the paper, in the showing of FIG. 1. Under these initial misalignment conditions, the torch would be directed to point 52 adjacent the rim 26 to shift the position of the gun 16 so that the point 48 would be shifted to coincide with the center 50 of the cathode ray tube screen. Of course, the

protrusions

30, 32, 34 and 36 are not yet formed at the time that the initial alignment is undertaken. It should also be particularly noted that the position of the supporting protrusions in FIG. 1 indicates an initial misalignment in the radial direction extending toward the speciall formed protrusion 34, rather than in the plane of the drawing of FIG. 1.

FIG. 4 shows the structure which is produced by the ring burner of FIG. 3. The burner softens the glass along a ring generally indicated by the reference character 54. A hard central area 56 remains at the center. As the plunger 42 of FIG. 3 is advanced, it bears on this hard central section and pushes it against the rim 26 to move the gun and align it with the center of the cathode ray tube faceplate. The soft ring of glass 54 is pulled inwardly to some extent by the pressure differential mentioned above. It therefore engages the rim 26 at two spaced points. After the gun is properly lined up, the burner may be extinguished, leaving the plunger 42 in place as the glass cools. At this time the glass neck 14 of the tube may be heated and softened at two additional points spaced around the rim 26. As a result of the pressure diiference, the softened areas are drawn inwardly so that the rim 26 is supported at three substantially equally spaced points about its periphery.

A similar adjustment may then be made around the rim 28 at the other end of the gun structure. If the alignment is entirely correct, a simple torch may be em ployed to provide three protrusions which engage the rim 28. If the gun is not properly centered, the special ring burner with its associated plunger, as shown in FIG. 3, may be employed to center the rim 28 of the gun. By adjusting the engagement of the protrusions at both

rims

26 and 28, it is evident that the direction of the beam, as well as the point at which it impinges on screen 12 may be adjusted. Full freedom of motion may be provided by the use of six ring-type burners, three equally spaced about rim 26, and three equally spaced about rim 28. In practice, however, it is normally suflicient to have one special ring burner for aligning purposes, and an additional burner of the standard type having a single flame to heat the tube neck at the five additional points following the initial alignment.

FIG. 5 is a cross-sectional view taken through lines 55 of FIG. 1. The alignment depression is shown at 32. Two

additional dimples

30 and 56 are spaced approximately evenly around the periphery of the rim 26 of the anode electrode 22.

The fit between the rim 26 and the

protrusions

30, 32 and 56 will depend upon the expansion coefiicients of the glass in the neck of the tube and that of the rim 26. In a typical glass employed in cathode ray tubes, the expansion coeflicient is 96 l0 per degree centigrade. To obtain a precise fit in which zero clearance obtains throughout the entire range of operating temperatures, a titanium metal rim 26 may be employed. The expansion coefficient of titanium is approximately 85 10 per degree centigrade, and this is sufficiently close to that of the glass that no problems are encountered with a zero clearance fit. When other materials having significantly higher or lower coefficients of expansion than that of the glass neck are employed, difierent types of fits may be present. Thus, for example, Where the rim has a higher coeflicient of expansion than the glass, there will be a slight clearance between the rim and the supporting protrusions at room temperature. However, as the gun heats up during the course of operation, the rim will expand to barely engage the three aligning protrusions. In cases where the coefiicient of expansion of the rim is significantly less than that of the glass, the members have an interference fit at room temperature. This is caused by the engagement at elevated temperatures and the lesser reduction in diameter of the inner member as compared with the enclosing protrusions as the temperature is reduced.

FIG. 6 illustrates an arrangement in which the gun assembly 58 is supported at 7 points. The 7 points of support include 3 protrusions in engagement with the rim 60 at one end of the gun and three additional protrusions in engagement with the rim 62 at the other end of the gun. A seventh protrusion 64 is in engagement with one of the Pyrex side rods 66 which holds the three elements of the gun together. In the case of the arrangement of FIG. 6, the coefiicient of expansion of the end rims 60' and 62 was significantly greater than that of th glass envelope. By way of example, in one case, the rims had an expansion coefficient of about l 10-" per degree centigrade. The Pyrex side rods including rod 66, however, have a coefficient of expense of about 55 l0 per degree centigrade which is significantly less than the expansion coefiicient of the glass envelope. After the gun had been aligned at an elevated operating temperature, the tube was allowed to cool off. Under these conditions, a slight clearance was present between the rims and 62 and their associated alignment protrusions. The

additional protrusions

64 and 65 in engagement with the Pyrex side rods served to remove the remainder of the available space. As the temperature of the tube is increased in the course of operation, the rims 60 and 62 are accurately aligned as they engage their respective alignment protrusions. Following the mounting steps as outlined above, the neck mounting may be heated to several hundred degrees centigrade, to relieve the stresses where the glass has been deformed.

FIG. 7 indicates, schematically, the perturbations of the electric field which are caused by Pyrex side rods. More specifically, FIG. 7 shows a cathode assembly 68 and an accelerating electrode 70 which are mounted on Pyrex side rods 72 and 74. The electrons pass through the

openings

76 and 78 in the

structures

68 and 70, respectively. In the science of electron beam formation, it is particularly important that the electric fields to which the beam is subjected are symmetrical. Where Pyrex rods are employed, however, significant perturbations of the electric field may occur between

electrodes

68 and 70 in the vicinity of the side rods 72 and 74. These perturbations are indicated by the

curved lines

80 and 82.

The arrangement of FIG. 8 is designed to avoid the adverse efifects of the side rods, which were described above in connection with FIG. 7. In the structure of FIG. 8, the gun includes the cathode assembly 84, a first accelerating electrode or grid 86, and a principal accelerating and focusing electrode 88. Instead of using Pyrex rods of the type shown in FIG. 6, the

gun elements

84, 86 and 88 are mounted directly from the wall of the neck 90 of the cathode ray tube. Thus, the cathode assembly 84 is supported both by the leads which extend to the base 92 and by the supporting protrusions 94, 96. Similarly, the electrode 86 is mounted in place by the

protrusions

98 and 100. In the case of the pairs of

protrusions

94, 96 and 98, 100, it is to be understood that at least one additional protrusion is associated with each of the indicated pairs, so that each electrode in question is supported at at least three points spaced around its periphery. The longer accelerating and focusing electrode 88 may be supported by six dimples or protrusions. These are arranged in two sets. Two of the

protrusions

102 and 104 of one set are located at the lower end of the electrode 88 and the

protrusions

106 and 108 form two of the three evenly spaced protrusions which support the upper end of electrode 88.

In practice, the gun of FIG. 8 is formed by mounting the three

electrode assemblies

84, 86 and 88 on a suitable jig within the neck 90 of the cathode ray tube. While they are mounted in this manner, the

electrodes

84 and 86 are secured in position by the sets of protrusions as shown in FIG. 8. The electrode 88 is also secured in position but only loosely through the set of protrusions at its lower end, including the

protrusions

102 and 104, and by its connecting lead. Following this preliminary mounting and alignment step, the jig is removed from the electrodes.

The electrode assemblies are connected by suitable conductors to the pins 110 which extend from the base of the vacuum tube. In this regard, it may be noted that the lead 112 which is connected to electrode 88 extends radially from electrode 88 to the side wall of the neck and then directly down along the wall to the base of the tube. Similarly, the connecting lead wire 114 to electrode 86 extends radially from electrode 86 to the wall of the neck 6 90, and along the wall to the base of the tube. In this manner, the electron beam passing through the center of the gun structure is not-affected by the fields associated with

wires

112 and 114.

The cathode ray tube is now evacuated and energized. Following the assembly of the three electrode assemblies forming the gun as described above, it is aligned to a first approximation with the cathode ray tube screen, which is not shown in FIG. 8. Minor changes in the direction of the beam may now be made by slight movements of the outer end of electrode 88. The process as described above in connection with FIGS. -1 through 4 of the drawings is now applied to the arrangement of FIG. 8. Thus, the misalignment of the electron beam is determined by viewing the faceplace. A ring-type torch such as that shown in FIG. 3 is employed to make the broad protrusion shown at 106 in FIG. 8, and to correct any slight misalignment. Two additional protrusions including the protrusion 108, are then provided to support the electrode 88 firmly in the aligned position.

It is to be understood that the above-described arrangements are illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art Without departing from the spirit and scope of the invention. Thus, by way of example and not of limitation, the aligning protrusions may be made through the use of an element of glass having a higher melting point than the glass in the wall of the neck, instead of by the use of a special torch as shown in FIG. 3. Four protrusions could, of course, be employed instead of three in each case. Accordingly, from the foregoing remarks it is to be understood that the present invention is to be limited only by the spirit and scope of the claims.

What is claimed is:

1. A method for aligning the gun structure of a beamtype tube having an envelope, comprising mounting said gun structure loosely in a glass neck forming part of the envelope of said tube, evacuating the air from within said envelope, softening a ring of glass at one side of said neck around a localized hard central area, pressing on the localized hardened area to deform the glass into contact with said gun structure, and softening the glass in said neck at two additional spaced points to engage the gun structure.

2. A method for aligning the gun structure of a beamtype tube having an envelope comprising mounting said gun structure loosely in a glass neck forming part of the envelope of said tube, evacuating the air from within said envelope, softening a ring of glass in said neck around a localized hard central area adjacent a support member on the electron gun structure, pressing on the localized hard area to deform the glass into contact with said gun structure, and softening the glass in said neck at two additional spaced points to engage the gun structure.

3. A method for aligning the gun structure of a beamtype tube having an envelope comprising mounting said gun structure loosely in a glass neck forming part of the envelope of said tube, evacuating the air from within said envelope, energizing the gun structure, providing an indication of the path of the electron beam emerging from said gun, softening a ring of glass in said neck around a localized hard central area, pressing on the localized hardened area to deform the glass into contact with said gun structure, moving the gun structure to optimize the indication, and softening the glass in said neck at two additional spaced points to engage the gun structure.

4. A method for aligning the gun structure of a beamtype tube having an envelope comprising mounting said gun structure loosely in a glass neck forming part of the envelope of said tube, evacuating the air from said envelope, energizing the gun structure, providing an indication of the path of the electron beam emerging from said gun, softening a ring of glass on one side of said neck around a localized hard central element which is sealed to the glass forming said ring, pressing on the localized hardened element to deform the glass into contact with said gun structure to optimize the indication, and softening the glass in said neck at two additional spaced points to engage the gun structure.

5. A method for forming a beam-type electron tube comprising the steps of aligning a plurality of electrode assemblies to form an electron gun by engagement with a jig, enclosing the electrode assemblies in the neck of a vacuum tube, melting individual protrusions from said glass neck into engagement with the electrode assemblies forming said electron gun, disassembling the jig from the electrodes, sealing and evacuating the envelope of the vac uum tube, and precisely aligning at least one of the electrode assemblies after sealing and evacuating said envelope by melting an additional individual protrusion from said glass neck into engagement with said one of the electrode assemblies.

References Cited by the Examiner UNITED STATES PATENTS 2,123,957 7/38 Orth 313291 X 2,219,111 10/40 Nicoll 31382.1 2,395,991 3/46 Chilcot et a1. 313253 2,417,061 3/47 Chilcot et al 313288 X 2,716,584 8/55 Retzer 31619 2,745,981 5/56 Sanabria et a1 313254 3,03 4,846 5/ 62 Rose 3 16-23 FRANK E. BAILEY, Primary Examiner.