U.S. patent number 3,777,210 [Application Number 05/302,219] was granted by the patent office on 1973-12-04 for electron gun and method of assembly.
This patent grant is currently assigned to RCA Corporation. Invention is credited to Richard Le Roy Spalding.
United States Patent |
3,777,210 |
Spalding |
December 4, 1973 |
ELECTRON GUN AND METHOD OF ASSEMBLY
Abstract
An electron gun of the type comprising a series of electrodes in
alignment along a gun axis. At least one of the electrodes
comprises a support member with an aligned opening. An apertured
member is inserted in the support member, the aperture being in
alignment with the gun axis. The configuration of an inside portion
of the support member is mechanically matched to the configuration
of an outside portion of the apertured member, whereby the relative
orientations of the members are mechanically determined on
insertion of the apertured member into the support member by
intimate physical contact of the inside and outside portions. Also
disclosed is a method of aligning an electron gun comprising the
above electrode. The support member opening is fixed in alignment
with other associated electron gun components. At least a portion
of the apertured member is then inserted into the support member
opening, the configurations of the members being such whereby an
aperture in the apertured member is mechanically aligned along the
gun axis by the inserting.
Inventors: |
Spalding; Richard Le Roy
(Lancaster, PA) |
Assignee: |
RCA Corporation (New York,
NY)
|
Family
ID: |
23166813 |
Appl.
No.: |
05/302,219 |
Filed: |
October 30, 1972 |
Current U.S.
Class: |
313/256; 313/257;
313/456 |
Current CPC
Class: |
H01J
29/82 (20130101); H01J 29/488 (20130101) |
Current International
Class: |
H01J
29/82 (20060101); H01J 29/48 (20060101); H01j
001/88 (); H01j 019/42 () |
Field of
Search: |
;313/256,257,82,DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rolinec; Rudolph V.
Assistant Examiner: Chatmon, Jr.; Saxfield
Claims
I claim:
1. An electron gun of the type comprising a series of electrodes in
alignment along a gun axis, at least one of said electrodes
comprising:
a. a support member comprising a cup having a central opening in
alignment along said gun axis in the bottom thereof;
b. an apertured member inserted in said support member and having
an aperture in alignment with said gun axis, said apertured member
comprising:
i. an outer aperture cup with a centrally apertured cup-shaped
depression in the bottom, said depression being inserted fully into
said support cup opening, the outside dimensions of said depression
being sufficiently matched mechanically to the inside dimensions of
said support member opening to prevent axial and radial play
between said outer cup and support member;
ii. an inner aperture cup with an aperture in the bottom thereof
fixed inside said outer cup, the outside dimensions of said inner
cup being sufficiently less than the inside demensions of said
outer cup to permit radial movement between said outer and said
inner cups, said inner cup aperture being aligned with said outer
cup aperture; and
iii. the configuration of an inside portion of said support member
being mechanically matched to the configuration of an outside
portion of said apertured member, whereby the relative orientations
of said members are mechanically determined on insertion of said
apertured member by intimate physical contact with said inside and
outside portions, wherein said inside portion of said cup is the
inside bottom surface and portions of the inside surface of said
central opening in the bottom.
2. The electron gun defined in claim 1 wherein said central opening
is shaped generally like an equilateral triangle with rounded
corners.
3. The electron gun defined in claim 1 wherein said aperture of
said inner cup is in a metal foil which is fastened to the bottom
of said inner cup over a larger opening in the bottom of said inner
cup.
4. The electron gun defined in claim 3 wherein said support cup
opening is such as to form an interference fit with the cup-shaped
depression of said outer cup.
5. An electron gun of the type comprising a series of electrodes in
alignment along a gun axis, at least one of said electrodes
comprising:
a. a cup-shaped support member having a central opening shaped
generally like an equilateral triangle with rounded corners in the
bottom thereof, said opening being in alignment along said gun
axis;
b. an apertured member inserted in said support member, the
aperture of said apertured member being in alignment with said gun
axis, whereby said triangular opening of said support member
mechanically holds said apertured member in position by intimate
physical contact therewith.
Description
BACKGROUND OF THE INVENTION
The invention relates to electron guns and their alignment. It is
particularly applicable to electron guns having a very fine
aperture, but is not limited thereto.
Two or more apertures may be considered in perfect alignment with
one another when they lie in parallel planes and have their centers
located on a single, straight line perpendicular to those planes,
that line being considered the axis along which they are aligned.
In the manufacture of electron guns, it is a common practice to
align the central apertures in a series of electron gun electrodes
along a gun axis by inserting an internal beading mandrel through
the apertures to hold the electrodes in alignment, and then fixing
the electrodes relative to one another by applying a molten glass
bead to tab members extending from the electrodes.
Some electron guns, however, include electrodes with apertures so
small that it is not feasible to align the apertures mechanically
by internal beading mandrel. Such apertures are generally aligned
optically. Typically, a number of other associated gun components
which have apertures large enough for mechanical alignment are
aligned by an internal mandrel and beaded to form a partially
assembled gun. Among these components is a support member having a
relatively large clearance opening. A separate member having a
small aperture is then placed on the support member and optically
aligned thereon with the gun axis. The optical alignment is done
manually by an operator who views the aperture through a
microscope, centering it with respect to the clearance opening or
other nearby apertures, and then fixes the small-aperture member to
the support member by spot welding. Various electron gun
structures, as well as techniques of assembly and alignment, are
disclosed for instance in the following references:
U.s. pat. No. 2,128,581, issued to B. C. Gardner Aug. 30, 1938,
entitled "Fine Beam Electron Gun," (U.S. Cl 250-27.5).
U.s. pat. No. 3,500,520, issued to F. G. Oess Mar. 17, 1970,
entitled "Method of Obtaining Aperture Alignment in an Electron Gun
Construction," (U.S. Cl 29-25.16).
U.s. pat. No. 3,510,926, issued to F. G. Oess May 12, 1970,
entitled "Electron Gun Alignment Device," (U.S. Cl 29-25.19).
Rca technical Note:
Note No. 406, January 1971, entitled "Internal Beading Mandrel," by
C. C. Turner et al.
Optical alignment of a small aperture on a partially assembled gun
is a time-comsuming, expensive step in electron gun manufacture.
For some electron gun structures, intervening electrodes prevent
desirable close proximity of the optical alignment microscope to
the small aperture, making alignment more difficult. Furthermore,
the clearance opening in the support member through which the
beading mandrel passes, is much larger and less precise than the
small aperture, since the mandrel must be large enough in diameter
for sufficient rigidity. The necessarily large diameter of the
clearance opening adds to the difficulty of optical alignment,
since its center is not as readily determined optically as the
center of a smaller opening.
SUMMARY OF THE INVENTION
The novel electron gun has at least one electrode comprising a
support member and an apertured member, the members having
configurations whereby an aperture in the apertured member is
mechanically aligned on insertion of the apertured member into the
support member by intimate physical contact of inside and outside
portions of the members.
The novel gun may be assembled by a novel method comprising
aligning an opening in the support member, fixing the support
member in position with respect to the other gun components, and
inserting at least a portion of the apertured member into the
opening, whereby the aperture is mechanically aligned along the gun
axis by the inserting.
When an electron gun comprising the novel electrode is assembled by
the novel method, optical alignment of the small aperture may be
performed on a member or sub-assembly separate from the partial gun
assembly without the necessity of optical alignment with associated
gun components after beading.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged side, sectional view of an electron gun
comprising a preferred embodiment of the novel electrode assembly
and aligned in accordance with the novel method of alignment.
FIG. 2 is a greatly-enlarged side, sectional view of the outer and
inner aperture cup sub-assembly of the novel electrode of FIG.
1.
FIG. 3 is a greatly-enlarged top view of the outer aperture cup of
the sub-assembly of FIG. 2.
FIG. 4 is a less-enlarged, top view of the support cup of the novel
electrode of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
STRUCTURE -- One embodiment of the invention is a vidicon color
television camera tube electron gun 10, shown in FIG. 1. The gun 10
includes a heater support 12, a cathode mount 14, a G1 electrode
16, a G2 electrode assembly 18 and a G3 electrode 20, all
mechanically fixed together by two glass beads 22 sealed to strap
members of the components. The electrodes are of drawn stainless
steel sheet. The G1 electrode 16 has a central limiting aperture 24
about 30 mils in diameter. The G2 electrode assembly 18 consists of
a support cup 26, an outer aperture cup 28, and an inner aperture
cup 30. The G3 electrode 20 is a hollow cylinder about one-quarter
of an inch in diameter inside.
The outer aperture cup 28 and the inner aperture cup 30 are shown
enlarged as a sub-assembly in FIG. 2. A top view of the outer
aperture cup 28 alone is shown in FIG. 3. The outer cup 28 is of 5
mils thick stainless steel sheet and has an outside diameter of
0.245 inches .+-. 5 mils. Four equally spaced slots 31 about 25
mils wide extend longitudinally along the wall of the outer
aperture cup 28 to permit a radial springing action of the wall. A
cup-shaped depression, or snout 32, having closely controlled
outside diameter of one-tenth inch .+-. one-half mil and having a
central outer cup aperture 34 about 30 mils in diameter, is
provided in the bottom of the outer cup 28, thereby resulting in a
shoulder 36 about one-tenth inch down from the rim of the outer cup
28. The diameters of the snout 32 and the outer cup aperture 34 are
concentric to within one-half mil.
The inner aperture cup 30 is of 5 mils thick stainless steel and
has outside diameter of 0.204 inch .+-. 2 mils. The inside depth is
about 50 mils. Centrally located in the bottom of the inner cup 30
is an opening 38 about 30 mils in diameter. A thin electroformed
nickel aperture disc 40 about 1.5 mils thick and with an inner cup
aperture 42 about 2 mils in diameter is spot welded to the outside
bottom of the inner aperture cup 30, the aperture 42 being centered
over the larger opening 38 in the bottom of the inner cup 30. The
inner aperture cup 30 is spot welded in place on the shoulder
portion 36 of the outer cup 28, the inner cup aperture 42 being in
alignment with the outer cup aperture 34.
FIG. 4 shows a top view of the support cup 26, which is provided
with a triangular guide opening 44 in the bottom. The inside edges
of the guide opening 44 are chamfered and the corners rounded. The
size of the guide opening 44 is such that upon insertion therein of
the snout 32 of the outer aperture cup 28, the sides of the guide
opening 44 will be flexed outward slightly and will seize the
snout, thereby locking it in alignment by interference fit.
METHOD -- For assembly of the gun, the heater support 12, cathode
mount 14, G1 electrode 16, the support cup 26 alone of the G2
electrode assembly 18, and the G3 electrode 20 are mechanically
aligned along a gun axis by an internal beading mandrel. This
aligns the guide opening 44 in the bottom of the support cup 26
with the gun axis. The glass beads 22 are then applied molten to
the strap members extending from opposite sides of the electrodes,
and rigidly fix the electrodes in alignment upon cooling.
The outer and inner aperture cups 28, 30 are prealigned optically
independently of the other components of the gun 10 by rigidly
holding the outer aperture cup 28 upright about the outside surface
of the snout 32 while centering the reticle of a microscope on the
center of outer cup aperture 34. The microscope is then rigidly
locked in position while inner aperture cup 30 is inserted into
outer aperture cup 28 so that it rests on the inside surface of
shoulder 36. The inner aperture cup 30 is then moved as necessary
over the shoulder 36 to achieve centering of the inner cup aperture
42 with the reticle of the microscope. The inner aperture cup 30 is
then spot welded to the shoulder 36 of the outer aperture cup 28 to
form a pre-aligned aperture cup sub-assembly as in FIG. 2. Now the
snout 32 of the pre-aligned aperture cup assembly is pressed into
the guide opening 44 of the support cup 26 of the gun 10 so that
its shoulder 36 rests firmly on the inside bottom surface of
support cup 26. The outer cup aperture 34 and the inner cup
aperture 42 are thereby mechanically aligned with the axis of the
gun 10. The wall of the outer aperture cup 28 is spot welded to the
inner wall of the support cup 26 to prevent loss of alignment by
thermal stressing during operation of the gun 10.
GENERAL CONSIDERATIONS
While the support member of the preferred embodiment is a round cup
with a triangular opening in the bottom, numerous other
configurations would be suitable for mechanical alignment of an
apertured sub-assembly. As a practical matter, however, the support
member is likely to be round with a centrally located opening, as
such a configuration is readily aligned by internal beading
mandrel. Also, it is advantageous to use the inside bottom surface
of the support cup about the opening for determining the plane of
the opening. Alternatively, the inside cup wall or other portions
of the support member may be used for this if the precision of the
support member is adequate to assure relative orientation of the
wall and bottom.
For the preferred embodiment, that portion of the support member
which by its configuration mechanically determines the alignment of
the aperture member is the flat bottom portion of the support cup,
including the inside edge of the opening. The opening centers the
aperture of the aperture member or sub-assembly on the gun axis,
and the flat bottom portion about the opening determines the
perpendicular orientation of the aperture by precisely orienting
the outer cup shoulder.
The apertured member may have one or more prealigned apertures.
That is, the apertures are aligned relative to the geometry of the
guide portion of the apertured member so that they will be aligned
upon assembly of the apertured member to the support member. In the
configuration of the preferred embodiment, for example, the
apertures of the sub-assembly are oriented parallel to the flat
shoulder surface of the outer cup and concentric with the outside
diameter of the snout.
The respective portions of the configurations of the support member
and the aperture member are matching if they determine completely
the relative orientations of the members on assembly, so that if
the configuration of the matching portion of the support member is
correctly oriented with respect to the gun axis, the apertured
member is necessarily aligned on insertion into the support member
by virtue of the mechanical match of the members to one another.
Insertion of the apertured member into the support member means
insertion of any portion of the apertured member into any portion
of the support member.
While the novel electrode assembly is useful primarily for electron
guns having apertures too small for mechanical alignment by
internal beading mandrel, it is to be understood that the novel
electrode structure is not limited to such guns, but may also be
used where, for instance, the relative sizes of succeeding
apertures are such that an internal mandrel becomes so complex as
to be impractical. For instance, where apertures go from larger to
smaller to larger, a complex expanding internal mandrel would be
required. For such a structure, a pre-aligned aperture electrode
assembly as described would be advantageous.
Although, the gun described in the preferred embodiment has only
three electrodes, the novel electrode structure may, of course, be
used with a gun having any number of electrodes, and more than one
of the electrodes may be of the novel type.
A special feature of the novel electrode assembly as described in
the preferred embodiment is improved heat sinking for the inner cup
aperture, thus permitting operation of the gun with relatively high
beam currents. The foil disc in which the inner cup aperture is
formed is firmly sandwiched between the shoulder of the outer
aperture cup and the bottom of the inner aperture cup over the
entire surface of the foil, nearly to the perimeter of the aperture
itself. Thus, beam electrons which impinge on the foil do not cause
excessive local heating, since the entire G2 electrode assembly
makes good thermal contact to the foil and provides a relatively
massive heat sink.
Another feature of the electrode of the preferred embodiment is
that the apertured round metal foil disc may be electroformed to
relatively high precision dimensions at relatively small cost. The
outside diameter of the round foil piece may thus be closely
matched to the outside diameter of the inner aperture cup. The
inner aperture cup may be placed open-end-down in a closely fitting
cylinder and the apertured metal foil disc simply dropped into the
cylinder on top of the inner aperture cup, thus being constrained
precisely on the center of the inner aperture cup so that the
aperture in the foil is concentric with the opening in the bottom
of the cup. The foil is then spot-welded in place to the bottom of
the inner aperture cup.
While the support cup opening of the electrode of the preferred
embodiment is triangular, other configurations of openings may be
used. For instance, the opening may be a round one with spring tabs
extending a short distance from the edge to the center, the spring
tabs bending outwardly upon insert of the snout of the outer
aperture cup, thus locking it in place. Various designs for
interference fit in a metal sheet opening are readily apparent. It
is an important feature of the triangular opening of the preferred
embodiment electrode support cup, that the force for flexing wall
portions outward as the snout is pressed into the guide opening is
a higher exponent function than linear functions generally
associated with leaf springs. The force for flexing a uniform
tongue-like leaf-spring member is approximately a constant times
the tangential distance which the end tongue is displaced. For the
flexing of the triangular wall portions, on the other hand, the
force needed to flex the wall increases rather rapidly, the
function associated with the force needed for the flexing being one
having an exponent greater than one. As a result, centering of the
snout is more precise with the triangular configuration for the
opening than it is for leaf-spring types of configurations. The
advantageous aspects of an interference fit of the snout in the
opening is that the opening need not be made to high precision,
since the flexing triangular sides will compensate for variations
in the size of the triangle, while still accurately centering the
snout. While a triangle appears to be particularly useful
configuration for the guide opening, other polygon configurations
would have similar advantages.
Since the outer cup aperture is aligned with the inner cup aperture
independently of the other associated electron gun structures, the
size of the outer cup aperture is relatively unimportant
mechanically. No mandrel need pass through it, and optical
alignment of the inner cup aperture with it need not be performed
by viewing the inner cup aperture through the outer cup apertures,
but may be performed as described above in the preferred embodiment
of the novel method. For some electron guns it may be desirable to
make the outer cup aperture of a smaller diameter, on the same
order as the inner cup aperture.
The inner aperture cup includes the apertured metal foil member
across the bottom of the cup. For the preferred embodiment, the
inner cup aperture is the aperture in the metal foil. The opening
in the bottom of the inner aperture cup is provided for clearance
about the foil aperture. It is understood, however, that the inner
aperture cup may be simply one piece, with the working aperture
provided centrally in the bottom, instead of in a separate metal
foil member.
The novel method of electron gun assembly, made feasible by the
novel electrode, has a number of distinct advantages. One advantage
is that it permits optical alignment of the outer cup aperture and
inner cup aperture as a sub-assembly, independent of the beaded and
fixed associated gun structures. Alignment is thus simplified, in
that handling of the main portion of the gun is reduced, closer
proximity of the microscope for optical alignment to the aperture
being aligned is possible, and the optical alignment is greatly
speeded up by the availability of faster techniques for aligning a
small sub-assembly, since it can be viewed from either end and at
any distance desired. Another advantage is that the cathode,
heater, and tube stem may be assembled as the associated gun
structures are beaded, where with other alignment techniques they
often must be assembled separately after alignment, since for
alignment the apertures are viewed from the cathode end of the
gun.
* * * * *