U.S. patent number 3,598,384 [Application Number 04/856,529] was granted by the patent office on 1971-08-10 for metal vapor generators.
This patent grant is currently assigned to S.A.E.S. Getters S.p.A.. Invention is credited to Mario Zucchinelli.
United States Patent |
3,598,384 |
Zucchinelli |
August 10, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
METAL VAPOR GENERATORS
Abstract
A particle free device for releasing a metal vapor comprising: a
container having walls defining a chamber; an opening in at least
one of said walls; a particulate, metal vapor releasing substance
within the chamber; and a member within the chamber and adjacent to
the opening whereby the opening is rendered permeable to metal
vapor but impermeable to the particulate substance.
Inventors: |
Zucchinelli; Mario (Milan,
IT) |
Assignee: |
S.A.E.S. Getters S.p.A. (Milan,
IT)
|
Family
ID: |
11178050 |
Appl.
No.: |
04/856,529 |
Filed: |
September 10, 1969 |
Foreign Application Priority Data
|
|
|
|
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Sep 13, 1968 [IT] |
|
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21,185A/68 |
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Current U.S.
Class: |
266/275; 392/389;
118/726 |
Current CPC
Class: |
H01J
9/395 (20130101); H01J 9/20 (20130101); C23C
14/243 (20130101); H01J 9/12 (20130101); C22B
5/16 (20130101) |
Current International
Class: |
H01J
9/12 (20060101); H01J 9/38 (20060101); H01J
9/20 (20060101); H01J 9/395 (20060101); C22B
5/16 (20060101); C22B 5/00 (20060101); C23C
14/24 (20060101); C22b 061/00 () |
Field of
Search: |
;266/1,34R,34V,39
;118/48,49,49.1,49.5 ;219/271,275 ;117/107,107.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Publication: The Review of Scientific Instruments; Vol. 35, No. 6;
June, 1964 (Eichenbaum et al.).
|
Primary Examiner: Dost; Gerald A.
Claims
I claim:
1. A particle free device for releasing a metal vapor, said device
comprising:
A. a container having continuous walls defining a chamber;
B. the extremities of the walls juxtaposed parallel to one another
defining an opening;
C. a particulate metal vapor releasing substance within the
chamber; and
D. a member within the chamber and adjacent to the opening whereby
the opening is rendered permeable to metal vapor but impermeable to
the particulate substance wherein the chamber is completely filled
with the metal vapor releasing substance which holds the member in
place.
2. The device of claim 1 wherein the container is a material of
high electrical resistance.
3. The device of claim 1 wherein the metal vapor is that of an
alkali metal.
4. The device of claim 1 wherein the metal vapor is that of
mercury.
5. The device of claim 1 wherein the metal vapor is that of
barium.
6. The device of claim 1 wherein the metal vapor releasing
substance is a mixture of an alkali metal chromate and a reducing
agent for the chromate.
7. The device of claim 1 wherein the member is a wire having a
diameter greater than the transverse dimension of the opening.
8. A particle free device for releasing a metal vapor, said device
comprising:
A. a container having continuous walls defining a chamber;
B. the extremities of the walls juxtaposed parallel to one another
defining an opening;
C. a particulate metal vapor releasing substance within the
chamber; and
D. a wire within the chamber adjacent to the extremities of the
walls, the wire having a diameter greater than the distance between
the extremities of the walls wherein the chamber is completely
filled with the metal vapor releasing substance which holds the
wire in place.
9. A particle free device for releasing an alkali metal vapor, said
device comprising:
A. a container having continuous walls of a rectangular sheet
material of high electrical resistance defining a chamber;
B. the longitudinal extremities of the sheet material juxtaposed
parallel to one another defining an opening;
C. a metal vapor releasing substance in the chamber, said substance
comprising an alkali metal chromate and a reducing agent for the
chromate; and
D. a wire within the chamber adjacent to the longitudinal
extremities of the sheet material, the axis of the wire being
parallel to the longitudinal extremities of the sheet, the diameter
of the wire being greater than the distance between the extremities
of the sheet wherein the chamber is completely filled with the
metal vapor releasing substance which holds the wire in place.
10. A particle free device for releasing a metal vapor, said device
comprising; a container having walls defining a chamber; an opening
in at least one of said walls; a particulate, metal vapor releasing
substance within the chamber; and a member within the chamber and
adjacent to the opening whereby the opening is rendered permeable
to metal vapor but impermeable to the particulate substance wherein
the chamber is completely filled with the metal vapor releasing
substance which holds the member in place.
Description
DISCLOSURE
Devices which release metal vapors, such as those of mercury,
cesium, potassium, or sodium, in vessels such as electron tubes,
are well-known in the art as described, for example, in Italian
U.S. Pat. No. 784,903, Italian completive application 21538A/67 of
Nov. 12, 1967, and by Eichenbaum, et al., "Cesium Vapor Dispenser,"
The Review of Scientific Instruments, Vol. 35, No. 6, June 1964,
pp. 691--693. Unfortunately, the above and other prior art
generators suffer from a number of disadvantages. For example, they
frequently release small particles before and/or after metal vapor
release. These small particles are electrically conductive and can
cause short circuits, damage photosensitive surfaces and cause
other difficulties within the electron tubes. Another disadvantage
is the undesirable sorption of water vapor and gasses from the
atmosphere by that portion of the metal releasing substance within
the device which comes in contact with atmospheric air. Another
disadvantage is the nonuniform compression of the particulate metal
vapor releasing substance within the device which generally occurs
when the container of the generator is closed. The above and other
disadvantages lead to poor reproducibility of results from one
generator to another, causing numerable difficulties during
production and use of the generators.
Accordingly, it is an object of the present invention to provide
novel metal vapor generators which are substantially free of one or
more of the disadvantages of the prior art. Another object is to
provide metal vapor generators which are substantially free of
loose particles before and/or after release of the metal vapor. A
further object is to provide metal vapor generators having a
reduced tendency to sorb water vapor and gases from the air.
Another object is to provide metal vapor generators with a
uniformly compressed particulate metal vapor releasing substance
adjacent to the opening of the generator. Additional objects and
advantages will be apparent to those skilled in the art by
reference to the following detailed description and drawings
wherein:
FIG. 1 is a plan view of a generator of the present invention;
FIG. 2 is an elevation view of the generator of FIG. 1;
FIG. 3 is an enlarged sectional view taken along line 3-3 of FIG.
2;
FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG.
2; and
FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG.
1.
According to the present invention, there is provided a particle
free device for releasing a metal vapor. This device comprises a
container having continuous walls defining a chamber. The
extremities of the walls are juxtaposed parallel to one another to
form an opening. A particulate metal vapor releasing substance is
within the chamber. Also within the chamber and adjacent to the
opening is a member placed such that the opening is rendered
permeable to metal vapor but impermeable to the particulate
substance.
The container can have any convenient shape, but in one preferred
embodiment of the present invention is made from a generally
rectangular sheet of material, bent around its longer axis such
that the longitudinal extremities of the sheet material are
juxtaposed parallel to one another, and define an opening through
which the metal vapor is released. In another preferred embodiment,
the container is made of a material of high electrical resistance
permitting activation of the metal vapor releasing substance by
imposing an electrical potential across the ends of the container
to heat the container.
The particulate metal vapor releasing substance within the chamber
can be virtually any suitable material but is generally a mixture
of a compound of the desired metal and a reducing agent for the
compound. Reducible metallic compounds include, among others,
cesium dichromate, or more preferably cesium chromate, potassium
chromate, and sodium chromate. Mercuric oxide can also be employed
if mercury is the desired metal. Any suitable reducible agent such
as those described in Eichenbaum or the Italian patent supra can be
employed, examples of which include, among others, silicon and
aluminum. When the desired metal is barium, any of the well known
barium aluminum alloys can be employed. The metal vapor releasing
substance is particulate in order to provide a large surface area
for vaporization of the metal and/or chemical reaction. However if
the particles are too small they tend to escape from the device.
Generally those which pass through a U.S. standard screen of 170
mesh/inch and are retained on a screen of 450 mesh/inch, i.e. those
exhibiting a particle size of about 10 to 90 .mu., are
suitable.
The member within the chamber is located adjacent to the opening
whereby the opening is rendered permeable to metal vapor, but
impermeable to the particulate substance. According to the broadest
aspects of the invention, the member can have any suitable
geometric shape but is preferably elongated having its axis
parallel to the extremities of the walls or sheet. The cross
section can be any regular or irregular polygon and, thus, can be
triangular, square, or hexagonal but is preferably round since such
a cross section gives the best seal against loose particles. In the
most preferred embodiment of the present invention, the member
within the chamber is a wire having a diameter greater than the
distance between the extremities of the walls.
Referring now to the drawings and in particular FIGS. 1 and 2
thereof, there is shown a device 10 for generating metal vapors.
The device 10 comprises a container or tube 11 having terminals 12
and 13 in each end thereof. The terminals 12 and 13 seal the ends
of the tube 11 and together with the walls thereof, define a
chamber containing the metal vapor releasing substance 14 which
preferably fills the chamber. As shown in FIG. 3, the tube 11 is
formed from a continuous sheet of material such that the tube 11
has a lower wall 15 connected to sidewalls 16 and 17 which in turn
are connected to top walls 18 and 19. The edges of the sheet which
is comprised of top walls 18 and 19 meet in juxtaposed relationship
defining an opening 20 of width d which is generally 100 to 300
microns. Within the chamber containing the substance 14 is a member
21 which is preferably a wire of circular cross section. The wire
21 is held in place by the substance 14. As shown in FIG. 3, the
diameter of the wire 21 is greater than the dimension d. As shown
in FIG. 5, the axis of the wire 21 is parallel to the longitudinal
edge of the top wall 18 and, therefore, also the top wall 19. By
this arrangement, metal vapors produced by the substance 14 can
pass by the wire 21 and out the opening 20, whereas loose particles
in the substance 14 are kept within the chamber. Another advantage
of this arrangement is the decreased tendency for the substance 14
to sorb water vapor and other gases from the air since the chamber
is almost effectively sealed by the wire 21 minimizing entry of air
into the chamber.
A common method of producing the device 10 is to compress the
particulate substance 14 and form the walls 15, 16, 17, 18, and 19
into the general form of FIG. 3 but with the walls 16 and 17 angled
outward at a greater angle than shown, thus making d much larger.
The walls 16 and 17 are then pressed towards one another to reduce
d to the desired value. However, in the absence of the wire 21, the
compressed material 14 adjacent to the opening 20 fractures and
produces loose particles.
In a nonlimiting example of operation, the device 10 is placed in a
vessel such as an image intensifier tube in which it is desired to
introduce cesium vapor. The terminals 12 and 13 are connected to a
source of potential not shown, and the tube evacuated by any known
means. Current is then caused to flow through the nichrome tube 11
by impressing a potential across the terminals 12 and 13 until the
tube 11 is heated to about 1,000.degree. K, whereupon the substance
14, which is a mixture of one part by weight of Cs.sub.2 CrO.sub.4
and two parts by weight of Si, releases cesium vapor. No loose
particles are observed in the vessel either before or after cesium
vapor release.
Although the invention has been described in considerable detail
with reference to certain preferred embodiments thereof, it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention as described above and as
defined in the appended claims.
* * * * *