U.S. patent number 3,600,625 [Application Number 04/853,174] was granted by the patent office on 1971-08-17 for projection picture tube with rotating fluorescent screen.
This patent grant is currently assigned to Tokyo Shibaura Electric Co., Ltd.. Invention is credited to Masao Ando, Kuramatsu Hayakawa, Shinichi Sawagata, Asahide Tsuneta.
United States Patent |
3,600,625 |
Tsuneta , et al. |
August 17, 1971 |
PROJECTION PICTURE TUBE WITH ROTATING FLUORESCENT SCREEN
Abstract
A projection picture tube comprising an evacuated envelope, an
electron gun assembly disposed therein, a metal target member with
a fluorescent film thereon which is to be scanned by electron beams
emitted by the electron gun assembly, a motor for rotating the
target member without causing the electron beams to be affected by
an external magnetic field, and an optical system for enlarging the
image produced on the fluorescent film.
Inventors: |
Tsuneta; Asahide (Kawasaki-shi,
JA), Hayakawa; Kuramatsu (Kawasaki-shi,
JA), Sawagata; Shinichi (Tokyo, JA), Ando;
Masao (Kawasaki-shi, JA) |
Assignee: |
Tokyo Shibaura Electric Co.,
Ltd. (Kawasaki-shi, JA)
|
Family
ID: |
26416166 |
Appl.
No.: |
04/853,174 |
Filed: |
August 26, 1969 |
Foreign Application Priority Data
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|
|
|
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Aug 31, 1968 [JA] |
|
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75008/68 |
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Current U.S.
Class: |
313/149; 313/474;
348/808; 313/30; 348/743; 348/776; 348/E9.025 |
Current CPC
Class: |
H04N
9/31 (20130101); H01J 29/24 (20130101) |
Current International
Class: |
H01J
29/18 (20060101); H01J 29/24 (20060101); H04N
9/31 (20060101); H01j 001/44 (); H01j 029/02 ();
H01j 007/24 () |
Field of
Search: |
;313/146,149,30,92 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Segal; Robert
Claims
What we claim is:
1. A projection picture tube comprising an evacuated envelope
having a transparent faceplate, a bearing member fixed in the
envelope, a rotary anode member rotatably coupled to the bearing
member and having a central shaft, a motor disposed on the back
portion of the envelope, coupling means airtightly coupling the
motor and the central shaft of the anode member, said coupling
means including an insulating crankshaft member coupled to the
motor, a second crankshaft member coupled to the central shaft of
the anode member, a universal joint coupling the crankshafts
together, and bellows disposed airtightly on the back side of the
envelope and surrounding the insulating crankshaft member, a
fluorescent film formed on the surface of the rotary member which
faces the faceplate, an electron gun assembly received in the
envelope for impinging electron beams on the fluorescent film, and
an optical system for enlarging and projecting an image produced on
the fluorescent film by electron beam impingement.
2. The projection picture tube according to claim 1 wherein said
fluorescent film is a color fluorescent film.
3. The projection picture tube according to claim 2 wherein said
fluorescent film includes a plurality of fluorescent areas formed
from fluorescent materials displaying three primary colors, those
of said areas which are associated with the same color being
arranged at equal spacings, the boundary between adjacent areas
being bent at intermediate points in a direction opposite to the
rotating direction of the rotary member, so that each of said areas
has a shape progressively broadening from the center to the
periphery of the rotary member.
4. The projection picture tube according to claim 1 comprising an
aluminum film on the fluorescent film.
5. The projection picture tube according to claim 1 wherein said
motor is an air motor.
6. The projection picture tube according to claim 5 wherein said
second crankshaft member is metal and said bellows is metal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to picture tubes, and more
particularly to a projection picture tube.
The projection picture tube is intended optically to optically
enlarge the image produced on the fluorescent film or plane by
electron beams from the electron gun assembly and project the
enlarged image on a screen. It is used, for example, by a theater
or broadcasting station to allow a large number of people to see
television images at the same time.
Since the projection picture tube is required to produce pictures
of high intensity, the fluorescent film is impinged by particularly
accelerated electron beams. Impingement of accelerated electron
beams on the fluorescent film results in its increased temperature,
reducing the amount of light beams or intensity generated
therefrom.
According to the prior art, the fluorescent film is generally
deposited on a glass envelope. Since the glass envelope has poor
heat release characteristics, the temperature rise of the
fluorescent film is unavoidable, imposing a limitation on the
increase of intensity and in consequence failing to produce an
image of desired clearness.
SUMMARY OF THE INVENTION
It is accordingly the object of the present invention to provide a
projection picture tube wherein a substrate on which there is
mounted a fluorescent film consists of metal to improve heat
release from the film, and the substrate is rotated without
affecting the electron beams by a magnetic field, to prevent the
same part of the film from being continuously impinged by electron
beams, thereby preventing the temperature rise of the film and
increasing the intensity of an image produced thereon.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1 is a sectional view of a projection picture tube according
to the embodiment of the present invention, wherein the drive means
consists of an air motor;
FIG. 2 is a sectional view of a projection picture tube according
to another embodiment of the invention, wherein the drive means
consists of an electric motor;
FIG. 3 is a section view of a projection picture tube according to
still another embodiment of the invention, particularly adapted to
project color television images; and
FIG. 4 is a plan view of the arrangement of a plurality of sections
representing the three primary colors of the fluorescent film
disposed on the rotary member involved in the projection picture
tube.
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment shown in FIG. 1 of a projection picture tube 1,
there is contained in a cylindrical envelope 2 a metal rotary
member 5 prepared by coating a fluorescent film 3 and vapor
depositing thereon an aluminum film 4. The envelope comprises a
transparent face plate and a blind cylindrical member made of
glass. At the corner of the faceplate of the envelope 2 is formed a
projecting neck portion 6, in which there is sealed an electron gun
assembly for ejecting electron beams at an angle of 45.degree. with
respect to the central axis of the rotary member 5. An air motor 8
for driving the rotary member 5 is fixed by rivets 10 to a support
frame 9 formed on the periphery of an opening perforated at the
central part of the backwall of the envelope 2. The driving source
of said air motor 8 is constant pressure air supplied at one end of
a duct 11 and discharged at the other. Said air rotates a plurality
of rotary vanes projecting from a movable vane shaft 12. To the
movable vane shaft 12 is rotatably fitted one end of a crankshaft
13 by a pin 14. Said crankshaft consists of a rod made of
insulating material, for example, Bakelite. The other end of the
crankshaft 13 is connected to one end of another crankshaft 16 made
of metal, for example, stainless steel by means of a universal
joint 15. The other end of the metal crankshaft 16 is rotatably
connected to the central shaft 18 of the rotary member 5 by a pin
17. To finish up the aforesaid connecting mechanism, there is
provided a washer type flange plate 19 at the opening in the back
plate of the envelope 2. Said opening is sealed airtight with
bellows 20 made of metal, for example, stainless steel which
extends from the universal joint 15 to the flange plate 19 in a
manner to cover the crankshaft 13. The flange plate 19 consists of
seal metal, such as SNC (Sylvania No. 4) or KOV, which is selected
according to the material of the envelope used. On the periphery of
the envelope 2 are arranged at equal spacings a plurality of (three
in this embodiment) bearings 21 concurrently acting as terminals.
To these bearings are securely fixed from the interior of the
envelope 2 a cylindrical bearing frame by means of a spring washer
22 and stainless steel bolt 23. The bolt 23 is effected by
inserting a driver through a hole perforated in said bearing frame.
To the central part of the bearing frame 24 is fixed a bearing
frame 25 by a pin 26. The bearing frame 25 contains a stainless
steel ball bearing 27. The central shaft 18 of the rotary member 5
is inserted into the ball bearing 27 and stopped by a stopper 28
disposed at the top of said bearing 27 to be prevented from being
urged in the axial direction. Between the rotary member 5 and the
bottom of the bearing frame 24 is interposed a thrust bearing 29 in
a manner to surround the central shaft 18. Said thrust bearing 29
allows the rotary member 5 smoothly to rotate in a horizontal
plane. On the bottom wall of the bearing frame 24 are radially
formed a plurality of beads 30 to increase its mechanical strength
and prevent its vibration thereby to ensure the smooth rotation of
the rotary member by the force of the air motor 8. When, under such
arrangement, the air motor 8 is operated, the rotary member 5 is
rotated by the gyroscopic motion generated collectively by the
crankshafts 13 and 16, universal joint 15 and bellows 20. With the
view of preventing to some extent the temperature rise of the
fluorescent film 4 resulting from scanning by accelerated electron
beams, the rotary member has a thickness adapted to absorb and
expel the heat generated in said film 4, for example, 5 mm. in this
embodiment. The rotary member is preferably formed on nonmagnetic
metal having a magnetic permeability of less than 1.005.mu., for
example stainless steel of the Cr16 percent--nil14 percent type.
With a projection picture tube of ordinary size, a rotary member 5
mm. thick weighs about 0.3 to 0.8 kg. and can rotate most stably at
a speed of 60 to 1200 r.p.m.
For impingement of accelerated electron beams on the fluorescent
film 4, the rotary member 5 is impressed with high voltage. Said
voltage is supplied through one of the aforesaid plurality of
bearings 21 concurrently acting as terminals which are disposed on
the sidewall of the envelope 2. Since the crankshaft 13 is made of
insulating material, the voltage is not conducted to the upper part
of the envelope 2. Though said voltage is supplied up to the
universal joint 15, the support frame 9 serves as a safety cover,
so that there is absolutely no danger of the high voltage section
being contacted from the outside.
Outside of the envelope 2 is positioned an optical system 31, for
example, a Schlieren optical system, in a manner to face the face
plate of said envelope 2 or the fluorescent film 3.
Before the necessary parts are fitted to the interior of the
envelope 2, said envelope 2 is cut on the indicated broken line A-A
in upper and lower portions. After said fitting is complete, the
divided parts are sealed together to finish a projection picture
tube by a known process.
There will now be described the operation of a projection picture
tube according to the present invention. Air having a constant
pressure adjusted by a pneumatic pressure adjuster is introduced at
one end of the duct 11 of the air motor 8 to rotate it and in
consequence the rotary member 5 at a prescribed speed. Then the
bearings 21 are impressed with a prescribed high voltage to
energize the electron gun assembly 7 disposed in the neck portion 6
and scan the fluorescent film 4 mounted on the rotary member 5 with
electron beams, obtaining a television image. Said image is
enlarged by an enlarging optical system 31 provided outside of the
picture tube and projected on a screen. The apparatus of the
aforementioned embodiment involves an air motor and needs no
magnetic shielding means as is required when there is used an
electric motor.
There will now be described by reference to FIG. 2 a projection
picture tube according to another embodiment of the invention. In
the cylindrical envelope 2 is disposed a rotary member 5. On one
side of the rotary member 5 is mounted a fluorescent film 3 on
which there is superposed an aluminum film by vapor deposition. In
the lower corner of the envelope 2 or at the end portion of the
face plate is formed a projective neck portion 6 at an angle of
45.degree. with respect to the central axis of the rotary member 5.
To the interior of the neck portion 6 is fitted an electron gun
assembly 7 for ejecting electron beams. A motor for driving the
rotary member 5 is fitted to the upper portion of a cylindrical
shield 32 so formed as to cover the back plate of the envelope 2.
Said motor is of an induction or pulse type 33. The rotary shaft of
the motor 33 is connected through an annular member 35 made of
insulating material to the shaft 36 fitted to the central part of
the rotary member 5. Said shaft 36 has a floating rotary plate 37
coaxially fitted to the center thereof. Further, said shaft 36 is
supported by a cylindrical bearing stand 34 welded to a flange
plate 19 sealed to the periphery of an opening in the envelope 2.
To that side of the bearing stand 34 which faces the flange plate
19 is welded airtight one end of bellows 20. To the other end of
the bellows 20 is sealed a packing 38 made of tetrafluoro resin or
silicon rubber. Said packing 38 is slidably attached to the
floating rotary plate 37 by means of a spring 39 concentrically
disposed between the bearing stand 34 and bellows 20, thereby
keeping the interior of the envelope 2 airtight. Between the
floating rotary plate 37 and bearing stand 34, as well as between
said bearing stand 34 and rotary member 5 are positioned a pair of
thrust bearing 40 to ensure the smooth rotation of the rotary
member 5. Said member 5 is fixed by bolt 43 to a shield plate 42
made of stainless steel or permalloy with a ceramic spacer 41 lying
therebetween. Said shield plate 42 is supplementally intended
unfailingly to shut off a floating magnetic field introduced from
the outside. For the purpose of the present invention, it is
preferred that all metal materials excluding the seal metal be of a
nonmagnetic type having a magnetic permeability of less than
1.005.mu., for example, Cr16percent--Nil14percent stainless steel.
The required high voltage is supplied at a terminal 44 drawn out of
the flange plate 19. The motor 33 is insulated from a source of
said high voltage by the annular insulating member 35 interposed
between said motor and shaft 36.
Since the motor 33 involves a great deal of magnetic material, it
is necessary to shield said magnetic field. To this end, there is
fitted a cylindrical magnetic shield 32 over the peripheral surface
of the envelope 2 with spacers 45 and 46 interposed therebetween.
Said cylindrical magnetic shield 32 consists of metals, for
example, permalloy which have a great magnetic shielding effect to
an external field. Said cylindrical magnetic shield 32 is so
positioned as to cover the upper surface of the envelope 2 at a
space of 10 to 15 mm. from the rotary member 5. Referring to the
intervening spacers 45 and 46, there will be obtained a good effect
if the side spacer 45 is 3 mm. thick and the upper spacer 46 is 10
mm. thick.
There is further provided another cylindrical magnetic shield 47 in
a manner to surround the peripheral area of the motor 33, which is
fixed to the aforesaid cylindrical magnetic shield 32 by rivets 48.
When parts are assembled to manufacture the subject picture tube,
the envelope 2 is cut on line B-B before the fitting of the
cylindrical magnetic shields 32 and 47. After said assembly, the
cut apart parts of the envelope 2 are welded or sealed together. A
projection picture tube thus assembled is finished up by the known
method.
The aforementioned arrangement enables a magnetic field to be fully
shielded even when there is used an ordinary electric motor like an
induction or pulse type which involves large amounts of magnetic
material, and in consequence a satisfactory television picture to
be projected.
The preceding two embodiments relate to an apparatus for
monochromatic television pictures. If, however, the rotary member
is fitted with a fluorescent film producing three primary colors,
there will be obtained a picture tube for use in color television.
There will now be described a color television picture tube by
reference to FIGS. 3 and 4.
In FIG. 3, the envelope 2 is prepared from a cylindrical form of
glass, in which there is disposed a rotary member 5. On one flat
plane of the envelope 2 is concentrically formed a projecting
portion 49. At the end part of the faceplate is formed a neck
portion 6 at an angle of 45.degree. with respect to the central
axis of said rotary member 5. To the interior of the neck portion 6
is fitted an electron gun assembly 7. A motor 50 for driving the
rotary member 5 comprises a rotor 51 rotatably disposed in the
projecting portion 49 and a field coil 52 formed around the
projecting portion 49. Around the field coil 52 is provided a cover
53. The shaft of the rotor 51 is connected to the rotary member 5
by a metal stopper 54. The field coil 52 is supplied with a
revolving magnetic field. To avoid the effect of the revolving
magnetic field of the field coil 52, there is fitted to the shaft
of the rotor 51 a blind magnetic shielding member 55 in a manner to
cover the back and side of the rotary member 5. Further, there is
provided a magnetic shield 56 in a manner to surround the upper
peripheral portion of the envelope 2.
The surface of the rotary member 5 is divided into six equal
sections. In these sections are formed two groups of fluorescent
films each of which involves three sections representing three
primary colors of blue, red and green and arranged in the order
mentioned as viewed in the rotating direction of said member 5. On
the surface of the rotary member 5 are formed by the known etching
process, as shown in FIG. 4, six depressed areas 57 0.05 to 0.08
mm. deep progressively broadening radially from the center to the
periphery of the rotary member 5, so as to allow the aforesaid six
fluorescent films to be deposited thereon. These depressed areas 57
are separated from each other by six projecting partition band 58
0.3 to 0.5 mm. wide which were left unprocessed during the etching
operation. In this case, the partition bands 58 are bent in two
stages opposite to the rotating direction of the rotary member 5.
That portion of each band which accounts for 55 percent of the
entire length thereof extending from the center to the periphery is
formed along the radial line. The second portion of the band
accounting for 15 percent of the entire length extends at an angle
of 30.degree. with respect to the radial line, and the last portion
reaches the periphery of the rotary member at an angle of
50.degree. with respect to the radial line. Considering
requirements for the bonded strength of a fluorescent film and the
resolution grade of the image produced, it is preferred that the
surface of the depressed area 58 be finished with a roughness of 2
to 5 microns. Further, the angular portion defined by the side
plane of the projecting partition band and the top plane of the
depressed area which intersect each other is formed into a curved
plane having a curvature corresponding to the meniscus or crescent
shape appearing on the edge of a fluorescent film when it is
disposed in said depressed area, in order to make the surface of
said film completely flush with the surface of the projecting band.
The rotary member 5 is made of metals, for example, Cr16
percent--Nil14 percent stainless steel which have a magnetic
permeability of less than 1.005.mu. and consequently are most
preferable in respect of electrical and physical properties. As
described above, on the six depressed areas of the rotary member 5
are deposited two groups of fluorescent films, each of which
comprises three sections representing three primary colors of blue,
red and green and arranged in the order mentioned as viewed in the
rotating direction of the rotary member 5. The formation of
fluorescent films of three primary colors is carried out, for
example, in the following manner. First, over the entire surface of
the rotary member 5 is applied a fluorescent material displaying
one color, for example, red. Only the prescribed portion of said
fluorescent material which will later constitute the red section is
exposed to light for baking and other unnecessary unexposed
portions are washed off. Such operation is repeated three times,
namely, each time a fluorescent material representing one of the
three primary colors is coated.
Electron beams from the electron gun assembly 7 scan at an angle of
45.degree. the different fluorescent sections of blue, red and
green in turn, according as the fluorescent plane travels due to
the rotation of the rotary member 5, thereby presenting a color
television picture.
The projection picture tube of the present invention having the
aforesaid arrangement enables a color television picture to be
projected on a screen with high intensity and resolution. To the
field coil of said projection picture tube used as a drive means is
connected a 144c/s source exactly synchronizing with the vertical
synchronizing pulse of image signals. And the rotor or rotary
member 5 is rotated at a speed of 1440 r.p.m. At this time electron
beams from the electron gun assembly scan the fluorescent sections
of blue, red and green at the rate of 144 fields per second,
producing a color television picture on the fluorescent plane.
The rotating speed of the rotary member and the fluorescent
sections have a certain relationship. That is, the number of the
fluorescent sections is defined by an integral multiple of three,
and the rotating speed of the rotary member is chosen according to
said number.
In the projection picture tube described in the aforesaid three
embodiments of the present invention, the electron gun assembly is
intended to generate a single flux of electron beams or a single
image. However, there may be used a plurality of such assemblies to
produce a plurality of images on the fluorescent plane by supplying
them with different image signals. Thus it is possible to enlarge
these images separately for projection or combine them to form a
composite picture. To this end, To is also possible to incorporate
a plurality of electron guns into an assembly at such different
angles to the fluorescent plane as produce divergent fluxes of
electron beams or different images.
As mentioned above, the present invention allows the substrate of a
fluorescent film or a rotary member to be made of metal, thus
releasing heat effectively. Further, the rotation of said rotary
member permits the parts of the fluorescent film scanned by
electron beams to be constantly shifted in position, thereby
preventing the undue local temperature rise of said film.
Accordingly, the present invention has an advantageous effect of
protecting the fluorescent film to improve its light producing
efficiency and projecting a distinct enlarged image on a screen due
to increased intensity. Experiments show that the life of a
projection picture tube according to the present invention has been
doubled as compared with that of the prior art type because the
fluorescent film is prevented from being deteriorated.
Moreover, the fluorescent film is deposited on a disk substrate
made of metal, for example, stainless steel. This eliminates the
generation and transmission of X-rays as is observed in the case
where there is formed a fluorescent film on the surface of glass
material used in the conventional picture tube. Also there do not
occur other drawbacks, for example, that the glass surface turns
brown with the resultant low intensity and resolution and dark
images.
* * * * *