Ion trap and method of making it

March 13, 1951

B. M. NASE

ION TRAP AND METHOD OF MAKING IT

2,544,934

Filed June 14, 1947

Sheets-Sheet 1

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ATTORNEYS

March 13, 1951

B. M. NASE

ION TRAP AND METHOD OF MAKING IT

2,544,934

Filed June 14, 1947

Sheets-Sheet 2

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Patented Mar. 13, 1951

2,544,934

UNITED STATES PATENT OFFICE

2,544,934

ION TRAP AND METHOD OF MAKING IT

Benjamin M. Nase, Lederach, Pa., assignor to Superior Tube Company, Norristown, Pa., a corporation of Pennsylvania

Application June 14, 1947, Serial No. 754,729

Claims. (Cl. 250—27.5)

This invention relates to electrodes for the electron guns of cathode ray tubes, and is particularly concerned with the construction and manufacture of ion traps employed to prevent disintegration or blackening of the fluorescent ⁵screen coating by ion bombardment.

In accordance with the present invention, an ion trap and its mounting rings are formed from a single sleeve or tube whose ends are flared . or rolled, preferably after a preliminary chamfer- ¹ing operation, to form the mounting rings, and which is thereafter diagonally severed intermediate its ends to form a pair of electrodes jointly forming an ion trap. Preferably before the sleeve is severed, or at least before its re- ’ lease from a clamp holding it during the severing operation, an alignment mark or scratch is made longitudinally thereof, so that in subsequent assembly of the electrodes in an electron gun, the pair of them may be brought into proper angular relation to leave between them for proper ion trapping action a diagonal slot of constant Width.

The invention further resides in the ion trap ₂₅and the method of making it herein described and claimed.

For a more detailed understanding of the invention, reference is made to the accompanying drawings, in which:

Figs. l to 4 illustrate an ion trap at successive 30 stages of its formation from cylindrical stock;

Fig. 5 is a sectional view illustrating the step of forming the mounting rings;

Fig. 6. .is a perspective view of clamping blocks used in the preferred method of forming the ion 35 traps;

Fig. 7, in perspective, illustrates the step of diagonally severing the sleeve to form a pair of ion-trap electrodes;

Fig. 8 is a sectional view showing the incor- 40 poration of the ion trap electrodes in an electron gun assembly;

Fig. 9 is a fragmentary detail view on enlarged scale of parts appearing in Fig. 8;

Fig. 10 is an exploded view of the components 45 of one-half of the ion-trap assembly; and

Fig. 11 is a perspective view of the ion-trap assembly.

Referring to Fig. 1, the sleeve 10 is cut from thin walled metal tubing of diameter corre- 50 sponding with the desired diameter of the finished ion-trap electrodes. The ends thereof are slightly internally chamfered as indicated at 11 for reasons which later appear. The cutting and chamfering operations may be performed on a M lathe having a hollow spindle suited to pass a length of tubular stock having, beyond the chuck at the forward end of the spindle, a projecting portion or tip to be cut off to form a sleeve 10. One end of the sleeve may be chamfered before it is severed from the parent stock.

At the next stage or station, a sleeve 10 is positioned between the pair of forming dies 12 and 13, Fig. 5, one or both of which may be moved in direction axially of the sleeve, the opposite ends of which are respectively received by semi-circular grooves 14 and 15 in the opposed faces of the dies. The inner diameter of each, of the grooves corresponds with the inner diameter of the sleeve. Preferably, for ease in alignment of the sleeve, the central portions 16, Π of the dies bounded by the grooves extend an appreciable distance in front of the corresponding die face. As the dies f2, ί3 are moved toward one another, the ends of the sleeve 10 are each forced outwardly and then back to form a peripheral flange or bead to be used in mounting of the electrodes formed from the sleeve.’ The internal chamfering of the sleeve at its opposite ends facilitates the flaring of the ends of the tubes during the formation of the beads 18. Upon completion of this step, the sleeve has the appearance and is of the construction or configuration shown in Fig. 2.

The partially formed electrode structure is then disposed between a pair of clamping blocks 19, 19, Figs. 6 and 7, with the beads or rings (8 of the electrode structure nesting in the rounded grooves 20, 21, Fig. 6, spaced longitudinally of the bore or opening 22, Fig. 7, formed by the complementary semi-circular recesses 23, 23, Fig. 6, of the pair of blocks. The diameter of the bore 22 corresponds with the external diameter of sleeve 10 and the pairs of grooves 20, 20 and 21, 21 snugly fit the rings IS, 18 at the ends of the sleeve. With the flanged sleeve in position between them, the blocks 19, 19 are held together as by clamping screws or by their disposition in a vice or clamp, firmly to hold the sleeve 10 and so prevent its rotation or axial movement. The upper faces of. the blocks 19 are provided with complementary notches 24 located between the grooves 20, 21 and extending through the upper faces of the blocks to the recesses 23, thus to expose a longitudinal section of the sleeve. While the sleeve is firmly held by the blocks, a mark or scratch 25 is made longitudinally thereof, Figs. 3 and 4, by insertion of a scribing tool, or equivalent, through the slot formed by the notches 24, 24, the

2,644,934 sides of the slot serving as a straight edge or guide for the marking tool.

This marking step is performed preferably before the sleeve is diagonally cut, as later described, or in any event before the sleeve is released from the blocks (9, (9.

The clamping blocks (9, (9 are also provided with slots 26, 26 extending entirely across them from the upper face thereof to a substantial distance below the lowermost portion of the sleevereceiving recess 23. When the two blocks 19, 19 are brought together with their respective grooves 20 and 21 in alignment firmly to hold a sleeve between them, the pair of slots 26 of the respective blocks form a single continuous slot extending diagonally through and across the sleevereceiving bore 22. The slot 26, 26 serves accurately to guide a saw blade 27, preferably a circular saw, as it is moved relatively to the blocks to sever the sleeve and form the pair of electrodes 28, 2S, Fig. 4, having opposed diagonally cut and spaced ends and so suited to form an ion-trap.

After the matched pair of electrodes 28, 29 are released by unclamping of the blocks 4 9, 49, any burrs or rough edges caused by the sawing may be removed by a buffing or smoothing operation.

As shown by comparison of Figs. 3 and 4, the length of the mark or scratch 25 is such that a portion of it remains on each of the pair of electrodes 28 and 29 after their, severance from a common sleeve i 0. These marks are of material assistance when the pair of electrodes are assembled in an electron gun because facilitating positioning of them in their original and proper angular relation for which the trapping slot or gap 34 between them is of constant width between the opposed peripheries of the axially and angularly aligned electrodes 28, 29.

As shown in Fig. 8, and more clearly in Figs. 9 to 11, the integral peripheral ring 18 formed at the end of each ion-trapping electrode 28, 29 is received by the complementary grooved portions 30 of a pair of clamping ring members 3 i. Each of the semi-circular ring members 31 is provided with wing extensions 40 projecting from opposite sides thereof and shaped to form the glide sections 41. In assembling the ion-trap, the adjacent ends of the wing extensions are secured to each other, as by welding, and the electrodes 20, 2-9 adjusted to proper position by sliding them along rods 42 embraced by the glide sections and by rotating them within the ring members 3 i to proper angular position. The parts are then permanently held in place as by spot-welcing the ring members of each pair in the regions between the glide sections 41 and the electrode-clamping section.

Preferably, and as shown most clearly in Fig. 9, an apertured disk 32 at the end of each of the trap electrodes 28, 29 is provided with a turned back rim 33 which nests between the mounting ring 18 of the associated trap electrode 28 or 29 and the grooved portions 30 of the associated pair of clamping members 31.

The ion-trap electrodes 28, 29 are held to rods 42, Fig. 11, in axial alignment wdth other cylindrical electrodes of the gun assembly, Fig. 8, including the “2nd” anode 35, the “1st” anode 36, the accelerating electrode 37, and the cathodegrid assembly 38, with the apertures in discs 32 of the ion-trap electrodes in alignment with the apertures of the discs 39 of the other electrodes.

It shall be understood that the invention is not limited to the particular construction disclosed and that changes may be made within the scope of the appended claims.