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Патент USA US3026446

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March 20, 1962
T. P. WARNE, JR
3,026,438
GRID-CATHODE ASSEMBLY FOR CATHODE RAY TUBES
Filed June 5, 1958
Z
913 42
IN VEN TOR.
THums P WARNEJR.
United States Patent O?ice
1
3,026,438
Patented Mar. 20, 1962
2
assembly employing the ceramic disk and the retainer;
3,026,438
and
FIG. 5 is a perspective view of the ceramic disk in—
GRID-CATHODE ASSEIVLBLY FOR CATHODE
RAY TUBES
corporating the ramps.
Thomas P. Warne, Jr., Trout Run, Pa., assignor to Radio
The same reference characters are used to denote simi
Corporation of America, a corporation of Delaware
'
lar elements throughout the drawing.
Filed June 5, 1958, Ser. No. 740,082
FIG. 1 of the drawing illustrates an embodiment of
6 Claims. (Cl. 313—82)
the invention in which a grid-cathode assembly comprises
a metallic grid cylinder 1, a metallic spacer cylinder 3,
This invention relates to cathode ray tubes, and in
particular to a novel structure for controlling electrode
a ceramic disk 5 and a cathode 7. The spacer cylinder
spacing and a novel method of assembly of electrodes. 10 3 and the ceramic disk 5 serve as support structure for
The exact spacing and alignment of a grid electrode
supporting the cathode 7 relative to the grid cylinder 1.
aperture with relation to an emitting cathode electrode
The metallic grid cylinder 1 has a closed end 9 with a
face is very important because it determines the e?ective
relatively small circular aperture 11 centrally located
control of the grid. The grid aperture alignment and
therein. Three elongated bosses 13 radially positioned
spacing from the cathode emitting face must be accurate 15 120° apart are formed in the grid endwall 9. The elon
because it forms part of the ?rst electron lens system by
gated bosses 13 are clearly shown in FIG. 2 of the draw
which the beam is formed and focused. Since it is neces
ing.
sary to have precision in the spacing and alignment of the
The metallic spacer cylinder 3 is an integral structure
cathode and grid, and because uniformity of the close
having a lower cylinder portion 15, and a smaller diam
spacing of these two electrodes in each tube is required 20 eter tubular portion 17 coaxially positioned and con
in mass production of tubes of the same type, the me
chanical design of a grid-cathode unit of an electron gun
represents one of the important problems in gun design.
nected by a shoulder or annular section 19. The lower
process of assembling many small parts in proper rela~
tionship. The process also involves ?xing several sub~
wall adjacent the open end. The smaller tubular por
tion 17 has a ?anged end 23 on which three gradient
portion 15 ?ts closely into the grid cylinder 1 to allow
rotational and longitudinal motion of the metallic spacer
The construction of a grid-cathode structure of a con
3 against the grid cylinder Wall. The lower portion 15,
ventional type of electron gun has involved the di?icult 25 which is open-ended, has a pair of spaced slots 21 in the
assemblies in predetermined spaced relationships involving
critical distances subject to small tolerances.
sections or ramps 25 are formed.
The dis
Each of the ramps 25, illustrated in FIG. 3, delineates
tances between parts are generally measured by a microm 30 a 120° arc of the generally annular pattern formed by
eter dial gave and spacing adjustments are made by insert
the ?ange 23. Each ramp 25 slopes in the same direc
ing spacers of various thickness. This method is tedious
tion along its are at the same angle. Ramps which slope
and time-consuming.
.030 inch in 100° of are have been found to be satis
Furthermore, in a conventional electron gun assembly,
factory. The ?anged end 23 is provided with a large aper
35
the heating of the cathode sometimes causes the cathode
ture 27 through which the cathode 7 may be projected.
emitting surface to move closer to the grid aperture. This
The cathode 7 includes a conventional hollow metallic
change in grid-cathode spacing results ?'om the expan
cylinder 29, closed at one end by a cap portion 31. The
sion of the cathode cylinder when the heater is turned
outer surface of cap portion 31 is coated with an emitting
on. Warping of the grid cylinder due to changes in pres
layer 33 of thermionic emitting material, such as a mix
sure or temperature may also a?ect the alignment and
ture of strontium and barium oxides. This material is
spacing of the grid-cathode.
well known and is recognized as that which easily emits
An object of this invention is to simplify the spacing
electrons, when heated to high temperatures.
adjustment between electrodes of a cathode ray tube.
Another object of this invention is to provide an im
Mounted
within the cathode cylinder 29 is a heater ?lament 35
which is coated with a layer of insulating material. The
?lament 35 is twisted in a coil formation to provide a uni
directional ?eld when ?lament 35 is heated with alternat
ing current. The cathode cylinder 29 is supported within
which is stable under varying operating conditions.
a central aperture 39 of the ceramic support disk 5 by
According to this invention electrodes have co-operat
peripheral beads 41 pressed out of the wall of the cathode
ing means on adjacent surfaces to provide a spiral action 50 cylinder 29 into contact with opposite surfaces of the
with respect to each other upon relative rotation. Spac
ceramic disk 5.
ing of the electrodes is controlled by rotation of one
During assembly of the grid-cathode unit, the cathode
electrode with respect to another electrode.
cylinder 29 and attached ceramic disk 5 are inserted into
According to one embodiment of the invention, which
the grid cylinder 1 so that the disk 5 rests against the
is described in detail in the following speci?cation, a grid 55 shoulder or annular section 19 of the spacer 3. The
cathode assembly includes co-operating means which con
cathode 29 is so positioned within the ceramic disk 5 so
proved structure for accurate control of the spacing from
cathode to grid.
Another object is to provide a grid-cathode ‘assembly
sist of bosses co-operating with ramps. During assembly
of the electron gun the bosses and ramps are engaged
and a rotation of the cathode with respect to the grid
provides spacing adjustment.
that the cathode emitting layer 33 projects from the rela
tively large aperture 27 of the spacer. A portion of
60
The invention is more fully described in the following
detailed description when read with the drawing in which:
FIG. 1 is an elevational view partially in section show
ing the grid-cathode assembly employing the metallic
spacer cylinder;
the wall of the spacer 3 adjacent and below the inserted
ceramic disk 5 is then crimped to rigidly ?x the ceramic
disk 5 within the spacer cylinder 3 against the shoulder
or annular section 19. When so ?xed, the cathode 7
and the metallic spacer 3 are spaced in insulated relation
65
ship.
FIG. 2 is a section taken along the line 2—2 of FIG. 1
The metallic spacer cylinder 3 securing the ceramic
disk 5 which supports the cathode 7 is telescoped into
showing one form of the bosses, according to the inven
the grid cylinder 1 thereby engaging the ramps 25 of the
tion;
spacer 3 with the bosses 13 of the grid 1. Projections 42
of a rubber ended mandrel 43 engage the pair of slots
70
cylinder showing the ramps;
21 at the open end of the spacer 15. By rotating the
FIG. 4 is a vertical section showing the grid-cathode
mandrel 43 the spacer cylinder 3 rotates relative to the
FIG. 3 is a perspective view of the metallic spacer
3,026,438
3
grid end wall 9. Rotation of the spacer cylinder 3 While
4
scribed above, may be employed. The rotation of the
ceramic disk 51 while the ramps 55 contact the bosses
13 moves the ceramic disk 51 with the cathode 49 to
spacer cylinder 3 to move along its longitudinal axis and
wards or away from the grid aperture 11 depending-upon
thus varies the spacing from cathode to grid.
the direction of rotation. The spacing from cathode
The desired spacing between the cathode emitting layer
to grid is thus adjusted to a desired distance. The metallic
33 and the grid aperture 11 may be determined by an
grid cylinder 47 and the. metallic retainer ring 53 are then
electric spark method, or an optical method, or any other
fastened, as by welding, to permanently ?x the cathode
suitable method. In the optical method, a microscope
49 with relation to the grid 47 .
I
45 is positioned above the grid aperture 11 whereby the
spacing from the grid end wall 9 and grid aperture 11 10 According to this invention, a fully adjustable control
of grid to cathode spacing during assembly is provided.
to the cathode emitting layer 33 may be viewed and
the ramps 25 and the bosses 13 are engaged allows the
measured. The microscope 45 is so ?xed that when the
layer 33 is viewed in sharp focus, the desired spacing
from cathode to grid has been effected. Alternatively,
in the electric spark method, the cathode 7 and spacer
3 are moved axially within the grid cylinder 1 toward
the grid aperture 11 until a point is reached at which a
predetermined potential applied between the cathode 7
A cathode assembly is provided which is free ?oating
with respect to the grid aperture. The simpli?ed design
and construction lends itself readily to automatic assembly,
with a resultant saving in manufacturing time and cost.
Better operating e?iciency of the grid-cathode assembly
in an electron gun of a cathode ray tube is also provided.
It should be understood that the scope of the invention
encompasses the use of any number of grid end wall
20 bosses for engagement with a corresponding number of
31 of the cathode to the grid end wall 9.
ramps for space adjustment. Three ramps and corre
When the desired spacing is obtained, the cylindrical
sponding bosses, as illustrated, insures proper alignment.
wall, of the metallic grid cylinder 1 and the close-?tting
The gradient portions need not be in ramp design, but may
metallic spacer 3 are welded together. A desiredrspacing
take another form, such as studs of varying height. The
and relationship between the grid aperture 11 and the
25 bosses, described as elongated in the above examples, may
cathode emitting face 31 is ?xed in this manner.
be dimples which are circular or rectilinear.
Changes in temperature may cause warpage of the elec
What is claimed is:
trodes. Since both grid end wall 9 and the spacer ?ange
l. A cathode grid assembly for an electron ‘gun includ
2-3 remain in direct contact and respond to warpage as an
ing a tubular cathode closed at one end and having an
integral ‘structure, changes in temperature do not effect
emitting surface on said closed end, a tubular grid having
their spacing. This construction of the grid-cathode unit
an apertured transverse wall adjacent said emitting sur
affords a substantially constant spacing and alignment of
face, and tubular ‘supporting means insulatingly support
the grid aperture 11 relative to the cathode emitter.
ing said cathode within said grid, said grid and said
In another embodiment of the invention, illustrated in
tubular supporting means having co-operating means on
FIGS. 4 and 5, the assembly comprises a grid cylinder
and grid 1 causes an electric spark from the closed end
47, a cathode 49, a ceramic spacer or disk 51, and a C13 C21 adjacent surfaces thereof for providing a spiral action
metallic retainer ring 53. The cathode 49 is substantially
‘the same as cathode 7 shown in the above embodiment.
The ceramic disk 51 has three gradient portions or
relative to each other upon relative rotation for adjusting
the spacing between the emitting surface in said cathode
and said apertured transverse wall.
2. A gridécathode assembly for an electron gun com
These ramps are similar in
structure to the ramps 25 described above, but may be 40 prising a grid cylinder with an apertured end wall, a
ramps 55 on one surface.
metallize'd to provide a smooth, uniform surface for
allowing the bosses 13 of the grid cylinder 47 to slide
freely on the‘ ramps 55. The other side of the disk 51
has a pair of spaced slots ‘57 which in one form may be
two rectilinear grooves ‘180° apart.
The cathode 49 is positioned within a central aperture
59 of the ceramic disk 51 and is supported by peripheral
beads 61 pressed out of the cathode cylinder wall into
contact with opposite surfaces of the ceramic disk 51.
cathode having an emitting face adjacent the aperture in
The ceramic disk 51 serves as support structure for sup
prising a grid cylinder with an apertured end wall, a
cathode having an emitting face, and a spacer cylinder
supporting said cathode within said grid cylinder, said
spacer cylinder having a predetermined number of ramps
porting the cathode 49 relative to the grid cylinder 47.
The metallic retainer ring 53 is a metallic annulus
which snugly ?ts into the grid cylinder 47, and which
may freely be moved against the grid cylinder wall. On
one surface, the retainer ring 53 has a pair of protuber
ances 65 which may be tightly ?tted into the slots 57
of the ceramic disk 51 to allow a close engagement of the
retainer ring 53 and the disk 51. On the other annular
said end wall, and means supporting said cathode within
said grid cylinder, said supporting means having a num
lber of ramps, said grid end wall having a number of
spaced bosses in engagement with said ramps whereby
upon relative rotation of said cathode with respect to said
grid cylinder therspacing between said cathode and said
grid dome is adjusted.
3. A grid-cathode assembly for an electron gun com“
on one surface, said grid end wall having a number of
spaced projections corresponding to said ramps, said
spacer cylinder being adapted to be rotated with respect to
said grid cylinder to provide spacing adjustment between
said grid end wall and said cathode emitting face.
4. A grid-cathode assembly for an electron gun com‘
67 into which a tool, such as a mandrel 43, may be 60 prising a grid cylinder with an apertured end wall, a
spacer with an annular end, and a cathode assembly, said
inserted.
surface of the retainer ring 53, there are two spaced slots
in manufacture, the ceramic disk 51 supporting the
cathode 49 is interlocked with the retainer ring '53 by
means‘of the disk slots 57 and the corresponding retainer
protuberances 65. The cathode 49 and ceramic disk 51
are inserted into the grid cylinder '47 with the cathode
emitter 63 facing the grid aperture. The retainer 53 is
next inserted into the grid cylinder 47 so that the pro
cathode assembiy being supported by said spacer and in
sulated from said grid cylinder, said end wall having a
number of bosses therein, said annular end having a
number of ramps, said ramps and said bosses being
capable of slidable engagement, ‘means to rotate said
spacer and said cathode assembly with respect to said grid
cylinder when said ramps and said bosses are engaged
thus displacing said spacer and said cathode assembly
tuberances 65 engage the slots 57 of the ceramic disk 51.
The metallized ramps 55 of the ceramic spacer 51 engage 70 with respect to said ‘grid end wall, and means to fasten
said spacer in relation to said grid cylinder when a desired
and grid bosses 13. The mandrel 43 is linked with the
grid-to-cathode spacing has been effected.
retainer slots 67 and rotated slowly, thus rotating the
5. A grid-cathode assembly ‘for an electron gun com
retainer ring 53 and the attached structure which includes
prising a metallic grid cylinder, a metallic spacer cylinder
the ceramic disk 51 and the cathode 49. The same meth
ods of measuring the grid to cathode spacing, as de
which closely ?ts into said grid Cylinder, a cathqqg assem.
3,026,438
5
bly including an emitting face, and a ceramic disk having
a central aperture wherein said cathode assembly is posi
tioned, means for fastening said ceramic disk and said
cathode assembly within said spacer cylinder, said grid
6
disk and said cathode being joined and movable as an
assembly, said assembly being telescoped into said grid
cylinder whereby each of said gradient portions engage
a corresponding one of said bosses, said assembly being
cylinder having a closed end with a number of spaced 5 adjustably rotatable with respect to the grid aperture to
bosses, said spacer cylinder including a ?anged end, hav
vary the distance from the grid aperture to the cathode.
ing a number of ramps, said ramps engaging said bosses,
and slot means for rotating said spacer cylinder within
References Cited in the ?le of this patent
said grid cylinder to adjust the distance between said grid
UNITED STATES PATENTS
aperture and said cathode emitting face, and means for 10
fastening said cylinders in ?xed relationship.
6. A grid-cathode assembly for an electron gun includ
ing a grid cylinder, a cathode, a ceramic disk and a re
tainer; said grid cylinder having a closed end with an
aperture therein, said closed end having a number of 15
spaced bosses, said ceramic disk having an aperture where
in said cathode is ?xed, a surface of said disk having a
number of gradient portions, said number of gradient
portions corresponding to said number of bosses; said
2,157,718
2,345,642
2,380,946
2,476,060
2,481,648
2,658,393
2,717,974
2,808,527
2,810,851
Mutscheller ____________ __ May 9,
Varian ________________ __ Apr. 4,
Cooke ________________ __ Aug. 7,
Moss ________________ __ July 12,
Dehn ________________ __ Sept. 13,
Woods _______________ __ Nov. 10,
Wihtol _______________ __ Sept. 13,
McKenzie ______________ __ Oct. 1,
Johnson ______________ __ Oct. 22,
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