U.S. patent application number 14/126553 was filed with the patent office on 2014-04-17 for chop gate and nozzle.
This patent application is currently assigned to VESUVIUS GROUP, S.A.. The applicant listed for this patent is Jean-luc Renard. Invention is credited to Jean-luc Renard.
Application Number | 20140103080 14/126553 |
Document ID | / |
Family ID | 46397151 |
Filed Date | 2014-04-17 |
United States Patent
Application |
20140103080 |
Kind Code |
A1 |
Renard; Jean-luc |
April 17, 2014 |
CHOP GATE AND NOZZLE
Abstract
A shop gate and a nozzle are suitable for being coupled with the
bottom floor of a tundish, said nozzle comprising a hollow tube
with an axial bore extending from an inlet opening at a first end
of the nozzle to an opposite outlet opening at or adjacent the
second, opposite end, and comprising a flange extending
substantially normal to the axis of the tube and located between
said first and second ends, characterized in that the flange
comprises a lower, guiding surface facing towards the second end of
the tube, said guiding surface being flat and substantially normal
to the tube.
Inventors: |
Renard; Jean-luc;
(Saint-Symphorien, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Renard; Jean-luc |
Saint-Symphorien |
|
BE |
|
|
Assignee: |
VESUVIUS GROUP, S.A.
Ghlin
BE
|
Family ID: |
46397151 |
Appl. No.: |
14/126553 |
Filed: |
June 27, 2012 |
PCT Filed: |
June 27, 2012 |
PCT NO: |
PCT/EP2012/002695 |
371 Date: |
December 16, 2013 |
Current U.S.
Class: |
222/596 ;
222/591 |
Current CPC
Class: |
B22D 41/28 20130101;
B22D 41/34 20130101; B22D 41/50 20130101; B22D 41/24 20130101; B22D
41/22 20130101; B22D 41/502 20130101; B22D 41/44 20130101 |
Class at
Publication: |
222/596 ;
222/591 |
International
Class: |
B22D 41/50 20060101
B22D041/50 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2011 |
EP |
11171655.1 |
Claims
1-15. (canceled)
16. Chop gate device comprising a frame defining an upper portion,
a mid portion, and a lower portion, and further comprising (a) a
nozzle comprising a hollow tube with an axial bore extending from
an inlet opening at a first end of the nozzle to an opposite outlet
opening at or adjacent the second, opposite end, and comprising a
flange extending substantially normal to the axis of the tube and
located between said first and second ends, thus defining a first,
inner nozzle portion extending from the flange and the inlet and a
second, outer nozzle portion extending from the flange to the
outlet, wherein the flange comprises a top, clamping surface facing
towards the first, inner nozzle portion, and a lower, guiding
surface facing towards the second, outer nozzle portion, said
guiding surface being flat and substantially normal to the tube,
said nozzle being coupled to the frame such that the first inner
portion extends above the frame upper portion, the flange is
clamped to the frame mid portion by a clamp, and the second, outer
portion extends below the frame lower portion, (b) a chopper
comprising a plate defining a first and second opposite major
surfaces separated by the thickness of the plate, and a sharp
chopping leading edge, said plate being slidingly mounted in the
frame lower portion, such that the first main, sealing surface
thereof is parallel to and contacts the flange guiding surface of
the nozzle, and such that the chopping leading edge is configured
to contact one side of the second, outer portion of the nozzle and
is configured to be driven parallel to the flange guiding surface
across to the other side of the second outer portion; and (c) a
pusher configured to force the chopping leading edge through the
second outer portion of the nozzle and thus sever it off from the
nozzle flange and first inner portion, such that the first main
surface of the chopping plate seals the bore at the level of the
flange guiding surface.
17. Chop gate device according to claim 16, comprising a presser
resiliently pressing on the chopper to form a tight and sealing
contact between the chopper sealing surface and the flange guiding
surface.
18. Chop gate device according to claim 16, comprising a clamp
configured to applying a clamping force onto the flange clamping
surface and configured to fix in place the nozzle to a receiving
surface of the frame.
19. Chop gate device according to claim 18, wherein the clamp
comprises three clamping elements, the centroids of said three
clamping elements forming the summits of a triangle having two
summits on either side of the diameter of the cross section of the
axial bore passing by the third summit and wherein the nozzle
clamping surface comprises three separate support rims jutting out
and distributed around the perimeter of the tube, which centroid
form a triangle which summits match the summits of the triangle
formed by the clamping elements.
20. Chop gate device according to claim 16, wherein the outer
nozzle portion comprises a weakening notch at the interface between
the flange guiding surface and the second outer portion, leveled
with the leading edge of the chopper.
21. Chop gate device according to claim 18, wherein the flange
clamping surface of the nozzle is slanted, reducing the thickness
of the flange away from the tube.
22. Tundish comprising a chop gate device according to claim 16,
wherein the chop gate device is fixed to the outside of the bottom
floor of the tundish, such that the first inner portion of the
nozzle protrudes through an opening in the floor of the tundish and
is embedded within the refractory layer lining the inner walls of
the tundish.
23. Nozzle suitable for being used in the chop gate device of claim
16, said nozzle comprising a hollow tube with an axial bore
extending from an inlet opening at a first end of the nozzle to an
opposite outlet opening at or adjacent the second, opposite end,
and comprising a flange extending substantially normal to the axis
of the tube and located between said first and second ends, thus
defining a first, inner nozzle portion extending from the flange
and the inlet and a second, outer nozzle portion extending from the
flange to the outlet, wherein the flange comprises a top, clamping
surface facing towards the first, inner nozzle portion, and a
lower, guiding surface facing towards the second, outer nozzle
portion, said guiding surface being flat and substantially normal
to the tube, wherein the outer nozzle portion comprises a weakening
notch at the interface between the flange guiding surface and the
second outer portion.
24. Nozzle according to claim 23, wherein the flange clamping
surface is slanted, reducing the thickness of the flange away from
the tube.
25. Nozzle according to claim 23, wherein the second, outer portion
forms a shroud nozzle and the outlet is formed by at least one
window opening to ambient and being distributed around the
peripheral wall of the second outer portion adjacent the second end
thereof.
26. Nozzle according to claim 23, wherein the second outer portion
forms a pouring nozzle and the outlet opens axially at the second
end of said second outer portion.
27. Nozzle according to claim 23, wherein the weakening notch
extends around substantially the whole perimeter of the outer
nozzle portion.
28. Nozzle according to claim 23, wherein the nozzle clamping
surface comprises three separate support rims jutting out and
distributed around the perimeter of the tube, the centroids of said
three support rims forming the summits of a triangle having two
summits on either side of the diameter of the cross section of the
axial bore passing by the third summit.
29. Nozzle according to claim 23, wherein the flange is partly clad
with a metal casing with the exception of the guiding surface.
30. Nozzle according to claim 28, wherein the three separate
support rims are part of the metal casing.
31. Chop gate device of claim 21, wherein the slanting angle is
comprised between 30 and 60.degree. with respect to horizontal.
32. Chop gate device of claim 21, wherein the clamping means apply
a clamping force substantially normal to the slanting clamping
surface of the flange.
33. Nozzle according to claim 24, wherein the slanting angle is
comprised between 30 and 60.degree. with respect to horizontal.
34. Nozzle according to claim 25, wherein the outlet comprises
pairs of opposed windows.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to metal forming
lines such as continuous metal casting lines. In particular, it
relates to a pouring nozzle design allowing a safe and reproducible
emergency sealing of the through bore thereof in case of problem
during the casting operation.
[0003] 2. Description of the Related Art
[0004] In metal forming processes, metal melt is transferred from
one metallurgical vessel to another, to a mould or to a tool. For
example, as shown in FIG. 1 a ladle (11) is filled with metal melt
out of a furnace and transferred to a tundish (10). The metal melt
can then be cast through a pouring nozzle (1) from the tundish to a
mould for forming slabs or to a mould for forming billets or
ingots. Flow of metal melt out of a metallurgic vessel is driven by
gravity through a nozzle system (1, 111) located at the bottom of
said vessel. In particular, the tundish (10) is provided at its
bottom floor (10a) with a nozzle system (1, 100) comprising an
inner nozzle portion (4A) embedded in a refractory lining of the
tundish floor (10b) and an outer, pouring nozzle portion (4b)
extending outside of the tundish as best seen in FIG. 4.
[0005] In case of emergency, it must be possible to seal the
through bore of the nozzle system (1) to interrupt the casting of
metal melt. Some tundishes are equipped with a nozzle exchange
device. In such devices, the inner nozzle and the outer pouring
nozzles are two separate parts, which are mounted on either side of
the frame of the nozzle exchange device in tight contact with one
another, In case of emergency, the outer nozzle can be replaced by
a new one or by a blank plate sealing the through bore of the inner
nozzle.
[0006] An alternative solution to nozzle exchange devices is to
chop off the outer nozzle portion (4b) of an integral nozzle system
(i.e., comprising both inner and outer nozzle portions in one
piece) with a chopper or chopping means. The integral nozzle is
fixed to the tundish floor by embedding the inner nozzle portion
thereof in the refractory lining of the tundish. The outer nozzle
portion of the integral nozzle, protruding out of the tundish is
engaged in a chopping device (100) comprising a sliding knife
having a sharp leading edge resting on a wall of the tubular
portion of the outer section of the nozzle and able to slide across
the nozzle tubular portion chopping it off by actuation of a
pneumatic, hydraulic, or mechanical arm. A blank plate follows the
leading edge to theoretically seal the gaping through bore of the
upstream section of the nozzle left intact. The problem with such
chopping devices is that in order to have a tight contact between
the blank plate and the cut off section of the nozzle tubular
portion, the edges of the cut need be smooth and straight. This is
seldom the case with state of the art chopping devices (100), which
generally produce jagged cut sections. Such devices are therefore
able to stop the flow of metal melt but rarely to stop it properly
allowing metal infiltration and fins around the sealing area and
the mechanism.
[0007] The present invention proposes a solution for the formation
of a tight contact between the edges of the chopped off tubular
portion of a nozzle and the plate of the chopper or chopping means
of a chopping device. These and other aspects of the present
invention are discussed in continuation.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention is defined by the attached independent
claims. The dependent claims define advantageous embodiments. In
particular, the present invention concerns a chop gate device
comprising a frame defining an upper portion, a mid portion, and a
lower portion, and further comprising [0009] (a) A nozzle
comprising a hollow tube with an axial bore extending from an inlet
opening at a first end of the nozzle to an opposite outlet opening
at or adjacent the second, opposite end, and comprising a flange
extending substantially normal to the axis of the tube and located
between said first and second ends, thus defining a first, inner
nozzle portion extending from the flange and the inlet and a
second, outer nozzle portion extending from the flange to the
outlet, wherein the flange comprises a top, clamping surface facing
towards the first, inner nozzle portion, and a lower, guiding
surface facing towards the second, outer nozzle portion, said
guiding surface being flat and substantially normal to the tube,
said nozzle being coupled to the frame such that the first inner
portion extends above the frame upper portion, the flange is
clamped to the frame mid portion by clamping means, and the second,
outer portion extends below the frame lower portion, [0010] (b) A
chopper or chopping means comprising a plate defining a first and
second opposite major surfaces separated by the thickness of the
plate, and a sharp chopping leading edge, said plate being
slidingly mounted in the frame mid portion, such that the first
main, sealing surface thereof is parallel to and contacts the
flange guiding surface of the nozzle, and such that the chopping
leading edge can contact one side of the second outer portion and
can be driven parallel to the flange guiding surface across to the
other side of the second outer portion; and [0011] (c) A pusher or
pushing means capable of forcing the chopping leading edge through
the second outer portion of the nozzle and thus sever it off from
the nozzle flange and first inner portion, such that the first main
surface of the chopping plate seals the bore at the level of the
flange guiding surface.
[0012] In order to ensure an excellent, tight and sealed contact
between the sealing surface of the chopper or chopping means and
the guiding surface of the nozzle flange, the device frame
comprises a presser or pressing means resiliently pressing on the
chopper or chopping means to press the chopper or chopping means
sealing surface against the flange guiding surface or flange
guiding means.
[0013] The frame of the chop gate device is provided with a clamp
or clamping means for fixing the nozzle to the frame. In an
advantageous embodiment, said clamp or clamping means are designed
to apply a clamping force onto the flange clamping surface and thus
fix in place the nozzle to a receiving surface of the frame. The
clamping force may be substantially normal to the clamping surface
of the flange. In an advantageous embodiment, the clamping surface
of the flange is slanted with respect to horizontal, and the clamp
or clamping means apply a clamping force substantially normal to
said slanting clamping surface. This geometry allows the nozzle to
be centered within the frame of the chop gate device by the
clamping forces applied on various sides of the nozzle to said
slanting clamping surface.
[0014] Unlike the state of the art integral nozzles, the present
nozzle is coupled to the frame of the chop gate device by clamping
thereto the flange of the nozzle. This ensures a perfect alignment
of the nozzle with the frame and chopper or chopping means mounted
on the same frame. It is only after clamping the nozzle to the
frame that the inner nozzle portion of the integral nozzle is
embedded in the lining of the tundish.
[0015] In an advantageous embodiment, the clamp or clamping means
comprise three clamping elements, the centroids of said three
clamping elements forming the summits of a triangle having two
summits on either side of the diameter of the cross section of the
axial bore passing by the third summit. Such clamping elements are
to be used with a nozzle which clamping surface comprises three
separate support rims jutting out and distributed around the
perimeter of the tube, which centroid form a triangle which summits
match the summits of the triangle formed by the clamping
elements.
[0016] In order to achieve as clean a cutting surface as possible
when chopping the tube off, it is advantageous if the outer nozzle
portion comprises a weakening notch at the interface between the
flange guiding surface and the second outer portion, leveled with
the leading edge of the chopper or chopping means.
[0017] The present invention also concerns a tundish comprising a
chop gate device as discussed supra fixed to the outside of the
bottom floor thereof, such that the first inner portion of the
nozzle protrudes through an opening in the floor of the tundish and
is embedded within the refractory layer lining the inner walls of
the tundish.
[0018] Finally, the present invention also concerns a nozzle
suitable for being coupled with the bottom floor of a tundish, said
nozzle comprising a hollow tube with an axial bore extending from
an inlet opening at a first end of the nozzle to an opposite outlet
opening at or adjacent the second, opposite end, and comprising a
flange extending substantially normal to the axis of the tube and
located between said first and second ends, thus defining a first,
inner nozzle portion extending from the flange and the inlet and a
second, outer nozzle portion extending from the flange to the
outlet, wherein the flange comprises a top, clamping surface facing
towards the first, inner nozzle portion, and a lower, guiding
surface facing towards the second, outer nozzle portion, said
guiding surface being flat and substantially normal to the tube,
characterized in that, the outer nozzle portion comprises a
weakening notch at the interface between the flange guiding surface
and the second outer portion. In one embodiment, the weakening
notch may extend around a portion only of the perimeter of the
outer nozzle portion. In order to obtain an even cleaner cut,
however, the weakening notch may extend around substantially the
whole perimeter of the outer nozzle portion.
[0019] In one embodiment the flange clamping surface (5a) is
slanted, reducing the thickness of the flange (5) away from the
tube. The slanting angle may be comprised between 30 and 60.degree.
with respect to horizontal, and may be 45.degree.. In an
advantageous embodiment the second, outer portion forms a shroud
nozzle and the outlet is formed by at least one window, and may be
formed by two or four windows opposed two by two and opening to
ambient and being distributed around the peripheral wall of the
second outer portion adjacent the second end thereof. In an
alternative embodiment, the second outer portion forms a pouring
nozzle and the outlet opens axially at the second end of said
second outer portion.
[0020] In a particular embodiment, the nozzle clamping surface
comprises three separate support rims jutting out and distributed
around the perimeter of the tube, the centroids of said three
support rims forming the summits of a triangle having two summits
on either side of the diameter of the cross section of the axial
bore passing by the third summit.
[0021] In order to mechanically strengthen the flange of the nozzle
some or all the flanges surfaces, bar the guiding surface, are at
least partly clad with a metal casing. For a nozzle comprising
three rims as discussed supra, it is advantageous that the three
separate support rims be part of the metal casing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Various embodiments of the present invention are illustrated
in the attached Figures:
[0023] FIG. 1: shows schematically a typical continuous casting
line.
[0024] FIG. 2: shows two embodiments of shroud nozzles according to
the present invention. (a) and (b) show a cross section thereof,
and (c) shows a perspective view of the nozzle illustrated in
(a).
[0025] FIG. 3: shows two embodiments of short pouring nozzles
according to the present invention. (a) and (b) show a cross
section thereof, and (c) shows a perspective view of the nozzle
illustrated in (a).
[0026] FIG. 4: shows a side view of a nozzle as illustrated in FIG.
3(b) mounted in a chopping device coupled to a tundish: (a) before
chopping, (b) after chopping.
[0027] FIG. 5: shows a front view of a nozzle mounted on a chop
gate device according to the present invention
[0028] FIG. 6: shows chopping means suitable for the chop gate
device of the present invention.
[0029] FIG. 7: shows a nozzle embodiment with three clamping
rims.
[0030] FIG. 8: shows a top view of the nozzle of FIG. 7 clamped in
a chop tube device according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] As can be seen in FIGS. 1 and 2, a nozzle according to the
present invention is an integral nozzle in that a single tube forms
both inner and outer portions (4a, 4b) of the nozzle tube (4) with
a single through bore running from an outlet (2a) opening at the
end of a first portion (4a) forming the inner nozzle, to an outlet
(2b) opening at or adjacent the second portion (4b) forming the
outer nozzle. The inner and outer nozzle portions (4a, 4b) are
separated by an external flange (5), extending normal to the axis
of the tube and comprising a first, guiding surface (5b) facing
towards the outlet (2b) and an opposite second, clamping surface
(5a) separated from the first surface by the thickness of the
flange. The flange runs around the whole circumference of the tube
and serves to fix the nozzle in its casting position.
[0032] The flange (5) of a nozzle according to the present
invention has several functions. First, the flange is used to clamp
the nozzle to a matching receiving surface of the frame of the chop
gate device (100) by applying a clamping force by a clamp or
clamping means (104) to the second, clamping surface (5a) of the
flange. This ensures that the nozzle be perfectly aligned with the
frame and sliding chopper or chopping means (101). The clamping
forces may be applied substantially normal to the clamping surface
(5a) of the flange. As illustrated in FIG. 5, the clamp or clamping
means (104) may be disposed on at least two opposite sides of the
flange. It is also possible to have a clamp or clamping means
disposed on four sides of the flange, opposite two by two. In an
embodiment illustrated in FIGS. 2(a), 3(a), and 5, the clamping
surface (5a) of the flange is comprised of two distinct slanted
clamping surfaces, the thickness of the flange (5) reducing away
from the tube. The slanting angle may be comprised between 30 and
60.degree. with respect to horizontal, and the slanting angle may
be about 45.degree..+-.3.degree.. The clamp or clamping means (104)
apply a clamping force substantially normal to said slanted
clamping surface (5a), which help centring the nozzle with respect
to the receiving surface of the frame (cf. FIG. 5).
[0033] Second, the flange first guiding surface (5b) has the
function of guiding the chopper or chopping means as it runs across
the tube. This is achieved by the first surface (5b) facing towards
the outlet (2b) which acts as a guiding surface, and as such is
flat and substantially normal to the tube.
[0034] Third, the guiding surface (5b) ensures a tight contact
between the remaining portion of the nozzle and the chopper or
chopping means, thus sealing the through bore of the inner nozzle
portion (4a) and stopping the flow of metal melt altogether.
Indeed, the chopper or chopping means (101) comprise a plate
suitable for sliding along a plane substantially normal to the axis
of the nozzle. Said plate comprises a leading edge (101c) which is
sharp and hard enough to cut the way of the plate through the tube
bringing a main, sealing surface (101b) of the plate vis-a-vis the
through bore of the upstream portion of the nozzle still in place.
The combination of a straight course of the chopper or chopping
means during the chopping operation, and the tight contact between
the chopping plate (101) and the guiding surface (5b) of the flange
(5) ensure that in case of emergency, the flow of metal melt can
reliably be interrupted altogether at any time by actuation of the
chopper or chopping means (101). In order to ensure a tight contact
between the sealing surface (101b) of the chopper or chopping means
(101) and the guiding surface (5b) of the nozzle flange (5), the
frame of the chop gate device is provided with a presser or
pressing means (105) resiliently pressing on the chopper or
chopping means (101) to form a tight and sealing contact between
the chopper or chopping means sealing surface (101b) and the flange
guiding surface or flange guiding means (5b). As illustrated in
FIG. 5, the presser or pressing means may be oriented with an
angle, and may be about 45.degree. with respect to horizontal, to
apply a force substantially normal to two opposite chamfered edges
of the chopper or chopping means (101). Since the chopper or
chopping means (101) must be able to slide along one direction
through the nozzle tube, the sealer or sealing means must apply
their force to two edges parallel to the chopping means trajectory.
The application of forces at about 45.degree. on two opposite edges
of the chopper or chopping means (101) allows not only to ensure a
good contact between the sealing surface (101b) and the guiding
surface (5b), but also to centre the chopper or chopping means
(101) during the whole chopping process.
[0035] Fourth, the geometry of the flange perimeter may help to
control the angular orientation of the nozzle with respect to its
central axis. This is particularly important for nozzles having
outlets opening laterally on the wall of the tubular portion of the
nozzle, as illustrated in FIG. 2. In such cases, the orientation of
the outlets may be very important and can be controlled by ensuring
that the flange geometry matches the receiving surface of the frame
only in the desired orientation. The perimeter of the flange may
have a geometry having the same number of axes of symmetries as the
allowed positions of the lateral outlet windows. In particular, if
the flange perimeter is a quadrilateral, a trapezium ensures a
single allowed position, a rectangle allows two different
North-South positions of the nozzle and a square allows four
equivalent positions (two North-South and two East-West positions).
In summary, if the flange must help orienting the nozzle, the
flange perimeter should not be circular.
[0036] FIG. 2 shows two embodiments of nozzles according to the
present invention. Both have in common that the second, outer
portion (4b) of the nozzle is substantially longer than the first
inner portion (4a). They are both provided with four windows (2b)
opening on the side walls adjacent the end of the nozzle portion
(4b). This kind of outer nozzle is called a shroud nozzle and is
suitable for continuous casting of billets or bloom. It allows to
protect the metal melt ("shroud") from any contact with air as it
emerges from the nozzle through the lateral outlet windows (2b). In
many cases, two opposite, lateral windows only are provided. The
orientation of the respective windows is very important for the
quality of the cast parts, and can be controlled with the flange
geometry as discussed supra.
[0037] FIG. 3, on the other hand shows two embodiments of pouring
nozzles which are generally shorter than a shroud nozzle and the
outlet (2b) opens in the axis of the tube. Such pouring nozzles are
suitable for casting blooms and billets in moulds. The embodiments
of FIGS. 2(a)& 3(a) differ from the corresponding embodiments
of FIGS. 2(b)& 3(b) in that in the former two, the second,
clamping surface (5a) opposite the guiding surface (5b) and facing
towards the inlet (2a) is slanted with respect to the latter,
whilst it is parallel to the first, guiding surface (5b) in the
latter two. The geometry of the second, clamping surface (5a)
depends on the design of the clamp or means for clamping the nozzle
to the chop gate device (100). A slanted second, clamping surface
(5a) allows for a better centring of the nozzle in the device. Both
embodiments, however, have in common that: [0038] a) the guiding
surface (5b) is flat and substantially normal to the axis of the
nozzle tube, in accordance with the present invention, and [0039]
b) the tundish nozzle is aligned with respect to the frame of the
chop gate device trough the clamping means and not, as in
traditional designs, aligned with respect to the floor of the
tundish. This innovative concept allows the nozzle and chopper or
chopping means to be systematically in perfect alignment.
[0040] The flange, like the rest of the nozzle is made of a
refractory material to resist the high temperatures of a metal
melt. The flange (5) is at least partly clad with a metal casing
for reinforcing it as it is submitted to clamping stresses applied
by the clamp or clamping means (104) of the chop gate device. The
guiding surface (5b), however, shall not be clad with a metal
casing (22) because in case of actuation of the chopper or chopping
means, said surface must form a tight, heat resistant contact with
the chopping plate (101). If the guiding surface (5b) were clad
with a metal casing (22) it may contact metal melt and melt itself
thus provoking leaks.
[0041] In order to promote the formation of a "clean" chopped off
surface, the tubular portion of a nozzle according to the present
invention must comprise a weakening notch (6) at the interface
between the flange guiding surface (5b) and the second outer
portion (4b). The notch may run around the whole circumference of
the tube as illustrated in FIGS. 2(c) and 3(c). It may run as a
continuous notch or, alternatively, it may run as an intermittent
(e.g., dashed) notch, around a portion only or substantially the
whole perimeter of the outer portion of the nozzle.
[0042] As illustrated in FIG. 4, a chop gate device (100) according
to the present invention comprises a frame defining an upper
portion, a mid portion, and a lower portion, a nozzle according to
the present invention can be clamped in the frame by clamp or
clamping means (104), such that the first, inner portion (4a) of
the nozzle extends above the frame upper portion, the flange (5) is
fixed to the frame mid portion by clamp or clamping means (104),
and the second, outer portion of the nozzle extends below the frame
lower portion, The device (100) further comprises a chopper or
chopping means (101). The chopper or chopping means (101) comprise
a plate defining a first and second opposite major surfaces
(101a&b) separated by the thickness of the plate, and a sharp
chopping leading edge (101c). The plate is slidingly mounted in the
frame mid portion, such that the first main, sealing surface (101b)
thereof is parallel to and contacts the flange guiding surface (5b)
of the nozzle, and such that the chopping leading edge (101c) can
contact one side of the second outer portion (4b), as illustrated
in FIG. 4(a). From said position, which allows casting of a metal
melt to proceed, the plate can be driven in case of emergency
parallel to the flange guiding surface (5b) and across to the other
side of the second outer portion (5b), thus chopping the nozzle
second outer portion (4b) of the nozzle, as shown in FIG. 4(b). A
tight and sealing contact between the top, sealing surface (101b)
of the chopper or chopping means and the flange guiding surface is
assisted by pressing forces applied by presser or pressing means
(105) onto the plate of the chopper or chopping means. It is
advantageous that the forces are applied on two opposite sides of
the chopper or chopping means plate, or with an angle of the order
of 45.degree..+-.3.degree. (although other angles are possible) so
that the plate is continuously being centred with respect to the
nozzle even when the chopper or chopping means (101) are in motion.
As illustrated in FIG. 5, in this embodiment, the plate of the
chopper or chopping means must have two opposite edges chamfered to
an angle mating the orientation of the presser or pressing means.
It is clear that the presser or pressing means (105) must be
positioned so as to clear the way to the chopper or chopping means,
when the latter is activated.
[0043] The plate is usually made of casting steel but it may also
be made of a refractory material as, in case of use, the main top,
sealing surface (101b) thereof will seal the through bore of the
nozzle extending upstream from the flange (5) and thus be in
contact with metal melt. The leading edge, on the other hand, may
be reinforced with a hardened material, such as carbides and the
like. The guiding surface (5b) of the flange of the nozzle serve
both as guiding surface to ensure that the leading edge (101c)
follows the desired course, but also as sealing surface in matching
collaboration with the sealing surface (101b) following gapless
downstream of the leading edge (101c). Both flange guiding surface
(5b) and sealing surface (101b) should be made of bare refractory
material (i.e., not clad with a metal casing), lest a metal leak
would melt a portion of casing cladding such surfaces.
[0044] FIG. 6 shows an embodiment of a chopper or chopping means
(101) suitable for the chop gate device of the present invention.
In the illustrated embodiment, it can be seen that a hole (102)
encloses the outer portion (4b) of the nozzle (see dashed lines
indicating the position of the nozzle), with the downstream edge of
the hole forming the leading edge (101c) that will run through and
chop the tube in case of emergency. Directly downstream of said
leading edge, a sealing plate (101b) is provided with no gap
between the leading edge (101c) and sealing surface (101b) to seal
the gaping hole of the chopped tube. This geometry decreases the
amount of metal melt spillage during the chopping operation to a
minimum.
[0045] Actuation of the chopping plate is driven by a mechanical,
pneumatic, or hydraulic arm (102), able to push the chopper or
chopping means (101) from a casting position, allowing the metal
melt to flow undisturbed (cf. FIG. 4(a)), to a sealing position,
wherein the leading edge (101c) thereof is driven by a distance, d,
to the other end of the nozzle tube, chopping the portion of tube
(4b) extending downstream of the flange guiding surface (cf. FIG.
4(b)). The plate main top, sealing surface (101b) contacts tightly
the flange guiding surface (5b), thus interrupting the flow of
metal melt by sealing the gaping bore (2) at the flange level.
[0046] A chop gate device (100) as defined supra is fixed to the
outside of the bottom floor (10a) of a tundish (10). A nozzle as
defined supra can then be clamped into position onto the frame of
the device (100) by the action of a clamp or clamping means on the
flange clamping surface (5a). The first inner portion (4a) of the
nozzle (1) protrudes through an opening in the floor (10a) of the
tundish thus forming an inner nozzle, which can then be embedded
within the refractory layer (10b) lining the inner walls of the
tundish. The refractory layer may comprise a well block for housing
the inner portion (4a) of the nozzle. The flange (5) and second
outer portion (4b) of the nozzle, on the other hand, stand outside
of and below the tundish. A tundish thus equipped is safe to use as
the casting operation can easily be interrupted in case of
emergency and the flow of metal melt stopped almost instantly. This
is rendered possible by the use of a nozzle according to the
present invention that comprises a specific flange guiding surface
(5b) capable of guiding a chopper or chopping means linearly along
a well defined trajectory to chop a portion of the nozzle along a
straight plane. On the other hand, the sealing surface (101b) of
the plate of the chopper or chopping means (101) also acts as blank
plate, sealing the bore (2) of the nozzle portion still in place,
i.e., standing upstream from the guiding surface (5b), with the
advantage that there is no gap between the leading edge (101c) and
the sealing surface (101b).
[0047] In the embodiment illustrated in FIG. 7, the clamping
surface (5a) of the flange (5) comprises three separate rims (30a,
30b, 30c) for wedging the inner nozzle against the frame of chop
tube device, the three rims projecting from and being distributed
around the perimeter of the tube. The term "separate rims" refers
to separated, non-adjacent rims. Each wedging rim has a so-called
bearing surface intended to be in contact with the frame of the
chop tube device, extending along a substantially horizontal plane,
referred to as the bearing plane, and a so-called clamping surface
(5a) to cooperate with the clamp or clamping means of the chop tube
device. The so-called clamping surface is arranged facing the
bearing surface so that the clamping system and the frame sandwich
the wedging rim under the action of the clamping system. The
wedging rims are advantageously entirely made of metal and are part
of the metal casing of the nozzle. The bearing surfaces or clamping
surfaces are advantageously planar. Alternatively, the surfaces may
have various shapes, for example, inclined, convex or grooved.
[0048] The centroids of the three support rims form the summits of
a triangle having two summits on either side of the diameter of the
cross section of the axial bore (2) passing by the third summit. In
other words, the inner nozzle comprises a vertical central
longitudinal plane, wherein the three wedging rims are arranged in
a Y shape on the periphery of the nozzle, the base of the Y being
arranged in the central longitudinal plane and the two arms of the
Y being arranged on either side of said plane. The second and third
wedging rims have second and third clamping surfaces (5a), each of
said second and third surfaces being arranged on either side of the
longitudinal plane and having a centre positioned at an angle
between 30 and 45.degree. in relation to the longitudinal plane,
with reference to the centre of the inner nozzle. Although not
essential, it is advantageous that said second and third clamping
surfaces of the nozzle be arranged symmetrically in relation to the
longitudinal plane. The first clamping rim comprises a first
clamping surface, said surface passing through the longitudinal
plane and extending substantially symmetrically in relation to said
plane, in a surface included in an angular sector between 14 and
52.degree. with reference to the centre of the inner nozzle.
[0049] As illustrated in FIG. 8, a nozzle comprising three rims as
discussed supra can be used with a chop tube device according to
the present invention comprising three clamping elements (50a, 50b,
50c), the centroids of said three clamping elements forming the
summits of a triangle having two summits on either side of the
diameter of the cross section of the axial bore (2) passing by the
third summit, at positions matching the positions of the clamping
rims (30a, 30b, 30c) of the nozzle.
[0050] Numerous modifications and variations of the present
invention are possible. It is, therefore, to be understood that
within the scope of the following claims, the invention may be
practiced otherwise than as specifically described.
* * * * *