U.S. patent number RE33,036 [Application Number 07/125,605] was granted by the patent office on 1989-08-29 for closure mechanism with gas seal.
This patent grant is currently assigned to Didier-Werke AG, Voest-Alpine AG. Invention is credited to Herbert Bumberger, Bernhard Schiefer.
United States Patent |
RE33,036 |
Schiefer , et al. |
August 29, 1989 |
Closure mechanism with gas seal
Abstract
A closure mechanism includes a conical discharge nozzle and a
shielding tube fitted over the exterior of the discharge nozzle. A
snug conical joint is formed by closely complementary conical
surfaces of the discharge nozzle and the shielding tube. At least
one ring-shaped seal is provided in such joint to prevent exterior
air from entering between the discharge nozzle and the shielding
tube into the interior of the shielding tube. The ring-shaped seal
comprises an annular recess formed in one of the conical surfaces,
thereby defining an annular chamber, and an inert gas filling such
chamber.
Inventors: |
Schiefer; Bernhard (Cincinnati,
OH), Bumberger; Herbert (Linz, AT) |
Assignee: |
Didier-Werke AG (Wiesbaden,
DE)
Voest-Alpine AG (Linz, AT)
|
Family
ID: |
6168262 |
Appl.
No.: |
07/125,605 |
Filed: |
November 25, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
512127 |
Jul 8, 1983 |
04555050 |
Nov 26, 1985 |
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Foreign Application Priority Data
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Jul 12, 1982 [DE] |
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3226047 |
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Current U.S.
Class: |
222/597; 222/606;
164/437; 285/332 |
Current CPC
Class: |
B22D
41/42 (20130101); B22D 41/502 (20130101) |
Current International
Class: |
B22D
41/42 (20060101); B22D 41/22 (20060101); B22D
41/50 (20060101); B22D 041/08 () |
Field of
Search: |
;222/591,600,603,597,602,544,566,606 ;164/337,437 ;285/332,332.2,41
;266/236 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0048641 |
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Mar 1982 |
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EP |
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2733665 |
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Feb 1979 |
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DE |
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1474632 |
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Mar 1967 |
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FR |
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WO82/01836 |
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Jun 1982 |
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WO |
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Primary Examiner: McDowell; Robert
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
We claim:
1. In a closure mechanism of the type operable alternately for
discharging molten metal from a molten metal containing vessel and
for blocking such discharge, said closure mechanism being of the
type including a conical discharge nozzle and a shielding tube
fitted over the exterior of said discharge nozzle, the improvement
of means for preventing exterior air from entering between said
discharge nozzle and said shielding tube into the interior of said
shielding tube, said preventing means comprising:
a conical joint formed by conical surfaces of said discharge nozzle
and said shielding tube, said conical surfaces of said discharge
nozzle and said shielding tube being closely complementary .[.and
in abutment.]. .Iadd.without an open space therebetween.Iaddend.,
thereby forming a snug said conical joint; and
at least one ring-shaped seal in said joint, said ring-shaped seal
comprising an annular recess formed in one of said concial
surfaces, thereby defining an annular chamber, and an inert gas
filling said chamber.
2. The improvement claimed in claim 1, wherein said recess is
formed in said shielding tube.
3. The improvement claimed in claim 1, wherein said recess is
formed in said one conical surface to a uniform depth.
4. The improvement claimed in claim 1, wherein said recess is
wedge-shaped.
5. The improvement claimed in claim 1, further comprising an inert
gas connection opening extending through said shielding tube and
opening into said chamber.
6. The improvement claimed in claim 1, further comprising a second
ring-shaped seal of refractory fibrous material positioned between
said discharge nozzle and said shielding tube.
7. The improvement claimed in claim 6, wherein said shielding tube
has therethrough a discharge passage defining with said conical
surface tube a step, and said second ring-shaped seal is positioned
between said step and the outer end of said discharge nozzle.
8. The improvement claimed in claim 7, wherein said discharge
passage is defined by an inner cylindrical surface of said
shielding tube.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a closure mechanism of the type
operable alternately for discharging molten metal from a molten
metal containing vessel and for blocking such discharge, the
closure mechanism being of the type including a conical discharge
nozzle and a shielding tube fitted over a portion of the exterior
of the discharge nozzle.
In molten metal containing vessels, such as casting ladles and
tundishes, a molten metal, for example a steel melt, may be
discharged through a closure mechanism, for example a stopper lock
or a sliding gate closure unit, into an intermediate vessel or to a
continuous casting mold assembly. Closure mechanisms of this type
include a lower discharge nozzle, for example attached to a sliding
plate of a sliding plate closure unit. To this discharge nozzle is
attached a protective tube or shielding tube for the purpose, inter
alia, of preventing the environmental atmosphere from oxidizing the
discharged molten metal. Conventionally there is provided a conical
snug fit or joint between the discharge nozzle and the shielding
tube to ensure a reliable seal and to prevent the entrance of
surrounding air. Nevertheless, unavoidably some air enters into the
interior of the shielding tube along such conical joint. The result
is that some of the molten metal passing through the shielding tube
becomes oxidized, thereby deteriorating the degree of purity of the
molten metal, for example steel.
In the past, various proposals have been advanced to attempt to
overcome this problem. Thus, it has been attempted to place gas
permeable inserts in the shielding tube beneath the discharge
nozzle and to supply a shielding gas, such as an inert gas, to such
insert. French Pat. No. 1,474,632 discloses a device in which a
snug fit between the discharge nozzle and the protective tube is
not required, and rather wherein an open boundary zone therebetween
is filled with a protective or shielding gas. This solution however
is complex structurally and requires a considerable consumption of
the protective gas.
SUMMARY OF THE INVENTION
With the above discussion in mind, it is the object of the present
invention to provide a closure mechanism structure of the type
discussed above, but which is of a structure which prevents, with a
high degree of accuracy, exterior air from entering into the
interior of the shielding tube.
This object is achieved in accordance with the present invention by
the provision of a snug conical joint formed by closely
complimentary conical surfaces of the discharge nozzle and the
shielding tube. At least one ring-shaped seal is provided in this
joint. In accordance with a preferred arrangement of the present
invention, this ring-shaped seal comprises an annular recess formed
in at least one of the conical surfaces of the discharge nozzle and
the shielding tube. Such recess defines an annular chamber which is
filled with an inert gas. Preferably, the recess is formed in the
shielding tube. The recess may be formed to be of a uniform depth,
or alternatively the recess may be wedge-shaped. An inert gas
connection opening may extend through the shielding tube and open
into the annular chamber. Such connection opening may be connected
to a supply source of the inert gas.
In accordance with a further embodiment of the present invention,
an additional ring-shaped seal of refractory fibrous material may
be positioned between the discharge nozzle and the shielding tube.
Specifically, the shielding tube may have therethrough a discharge
passage defining with the conical surface of the shielding tube a
step, and the ring-shaped seal formed of refractory fibrous
material may be positioned between the step and the outer end of
the discharge nozzle. The discharge passage through the shielding
tube may be an inner cylindrical surface of the shielding tube.
In accordance with the present invention, air is prevented from
passing through the conical joint between the discharge nozzle and
the shielding tube by the provision of the annular, inert gas seal.
Particularly, after repeated uses of the shielding tube, such that
the conical surfaces no longer are closely complementary, the
annular seal of inert gas still prevents exterior air from passing
between the conical surfaces. In accordance with the present
invention, relatively little inert gas is consumed, since the
shielding or protective gas flows only along actual leaks between
the conical surfaces into the interior of the shielding tube. As
long as these areas of leakage between the conical surfaces are
leakproof, only a slight amount of inert gas will be consumed.
The annular chamber is of a simple construction, since only a
single annular recess need be formed. Such recess may be formed in
the outer conical surface of the discharge tube or in the inner
conical surface of the shielding tube. However, advantageously the
connection opening to the inert gas supply line always should be
provided in the body of the shielding tube.
In the embodiment of the present invention employing a refractory
fibrous ring-shaped seal between the outer end of the discharge
nozzle and a step in the shielding tube, there are provided a
number of advantages. Thus, there is provided an increased
resistance to the entry therethrough to the interior of the
shielding tube. Additionally, this arrangement prevents the buildup
of solidified metal, thereby making it possible to use the
shielding repeatedly without the necessity of burning out
solidified metal. Burning out of solidified metal would chance
damage to the annular recess formed in the conical surface of the
shielding tube.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention
will be described in further detail below, with reference to the
accompanying drawings, wherein:
FIG. 1 is a cross-sectional view of the lower portion of a
discharge nozzle and the upper portion of a shielding tube in
accordance with one embodiment of the present invention;
FIG. 2 is a view similar to FIG. 1, but of a second embodiment of
the present invention; and
FIG. 3 is a view similar to FIGS. 1 and 2, but of a third
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 1, there is shown the lower portion of a
discharge nozzle 1 employable in a closure mechanism of the type
operable alternately for discharging molten from a molten metal
containing vessel and for blocking such discharge. The further
structure of the closure mechanism is not shown, and it is intended
that the present invention be employable with any known and
conventional such closure mechanism structure. Discharge nozzle 1
has therethrough a discharge opening 3, and discharge nozzle 1 has,
at least on the lower portion thereof, an exterior conical surface
2. A protective or shielding tube 4 has an upper portion 5 having
an inner conical surface 6 joining a lower discharge passage which
conventionally is cylindrical. The conical surfaces 2 and 6 are
closely complementary to define a tight or snug conical joint
between elements 1 and 4. The lower end of shielding tube 4 is not
illustrated, but is intended to extend into an intermediate vessel
or a continuous casting mold, as is known in the art.
At least one ring-shaped seal is provided in the joint between
conical surfaces 2, 6. Specifically, such ring-shaped seal is
defined by an annular chamber 8 formed by an annular recess formed
in at least one of the conical surfaces 2, 6. In the arrangement
illustrated, the recess is formed in the conical surface 6 of
shielding tube 4, and such recess is a ring-shaped recess 10 of
uniform depth. An inert gas connection opening 9 passes through
upper portion 5 of shielding tube 4. Opening 9 is adapted to be
connected to an inert gas supply line and opens into annular
chamber 8. Accordingly, annular chamber 8 is filled continually
with inert gas.
The apparatus of FIG. 1 operates in the following manner. Thus,
when molten metal passes through outlet opening 3 and enters the
interior of shielding tube 4, a reduced pressure condition is
created because of the cross-sectional expansion of the interior of
shielding tube 4 with respect to the lower end 7 of discharge
nozzle 1. This has the tendency to cause external environmental air
to be drawn inwardly along the conical joint, i.e. generally
downwardly as shown in FIG. 1. However, the ring-shaped seal formed
by the inert gas filled annular chamber 8 prevents air from being
drawn inwardly. This protects the metal discharge passing through
shielding tube 4 from oxidation.
If the joint between the conical surfaces 2, 6 is not entirely
leakproof, which especially can happen after repeated uses of the
shielding tube 4, the shielding or protective inert gas supplied
from opening 9 and into chamber 8 will be caused to flow inwardly
only between those areas of the conical surfaces actually having
leaks. By increasing the supply pressure of the inert gas, an
effective purging of inert gas, for example argon, can be achieved
through the shielding tube 4 into the intermediate vessel to
eliminate non-metal inclusions.
FIG. 1 shows relative dimensions of the location of the ring-shaped
seal. Thus, H.sub.2 indicates the total length of the joint, i.e.
the total length through which exterior environmental air would
have to pass to reach the interior of shielding tube 4. H.sub.1
indicates that a substantial portion of the length H.sub.2 is
protected by the inert gas in annular chamber 8.
The embodiment of FIG. 2 is similar to the embodiment of FIG. 1,
with the exception that the chamber 8 is defined by a wedge-shaped
recess 11 formed in the inner conical surface 6 of the shielding
tube 4. Recess 11 is somewhat easier to form that recess 10.
Otherwise, the embodiment of FIG. 2 operates in the same manner, as
the embodiment of FIG. 1.
It also is possible in accordance with the present invention to
provide an additional ring-shaped seal of a refractory fibrous
material positioned between the discharge nozzle and the shielding
tube. Such an arrangement is shown in the embodiment of FIG. 3.
Thus, shielding tube 4 has formed in the interior thereof a step 12
defined between conical surface 6 and the discharge passage of the
shielding tube. A ring-shaped seal 13 formed from a compressable
ceramic refractory fibrous material is positioned on step 12, and
the outer end 7 of discharge nozzle 1 rests on seal 13. Those of
ordinary skill in the art will understand the type of materials
which may be employed to form seal 13. The embodiment of FIG. 3
operates substantially in the same manner as the embodiment of FIG.
1. Seal 13 improves sealing between the discharge nozzle and the
shielding tube, i.e. between annular chamber 8 and the interior of
the shielding tube. If the shielding tube is used repeatedly, a new
seal 13 can be inserted after each use. FIG. 3 shows the diameter
of the discharge passage through shielding tube 4 being smaller
than that of outlet opening of discharge nozzle 1. However, such
diameters may be the same, since they are both cylindrical.
Thereby, during the discharge of molten metal, the reduction in
pressure will be less, such that the sealing requirements will be
less stringent, as there will be less of a tendency for exterior
air to be drawn into the interior of the shielding tube.
In the devices of the present invention, it is possible to achieve
reliable sealing without the provision of gas permeable inserts in
the annular chamber 8.
The present invention has been described and illustrated with
regard to particularly preferred embodiments thereof. However, it
is to be understood that various changes and modifications may be
made to the specifically described and illustrated structure
without departing from the scope of the present invention.
* * * * *