Note: Descriptions are shown in the official language in which they were submitted.
P-PWUa235
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DEVICE FOR INJECTING PREHEATED AIR INTO A SHAFT FURNACE AND
PROCESS FOR MANUFACT~7RING BALL-AND-SOC1KET JOINTS
The present invention relates to a device for injecting
preheated air into a shaft furnace, consisting of a
plurality of separate cylindrical elements, each consisting
of an external steel easing and an internal refractory
lining and comprising at least one central tubular element
connected, on one side, by a first ball-and-socket
articulation and a first expansion joint to an upper
connection piece integral with a preheated air feeding
bustle pipe surrounding the furnace and, on the other or
opposite side, by a second ball-and-socket articulation and
a second expansion joint to a lower connection piece
extended by an elbow and a blast nozzle, the latter being
articulated on a tuyere installed in the wall of the
furnace, and in which device the ball-and-socket joints
comprise a convex ball-part formed by the end of one of the
connection segments and pivoting in a concave socket-part
formed by the end of the adjacent connection segment and a
soft refractory joint interposed therebetween.
These devices, more generally known under the name of
"tuyere-stock", are subject to problems of mobility and
sealing. In fact, as a result of high temperature of the
preheated air (a temperature of the order of 1200°C or
more) and of the high temperature prevailing inside the
furnace, the wall of the latter and the bustle pipe and the
tuyere-stock are subject to thermal expansions and
deformations which cause significant relative displacements
between the bustle pipe and the wall of the furnace. The
tuyere-stock must therefore be capable of compensating for
these relative displacements, whilst at the same time
preventing leaks of gas or preheated air.
To meet these requirements, US Patent 3,766,868
provides a tuyere-stock of the type described in the
introduction. This tuyere-stock has since been improved by
the design of universal ball-and-socket joints like those
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described in the German patent specification DE-C2-2218331.
The three joints of this tuyere-stock make it passible to
compensate all the relative movements between the bustle
pipe and the wall of the furnace. Sealing in the region of
the joints is obtained by means of bellows expansion
joints, whilst mechanical stability is ensured by means of
cardan connections associated with the two opposite ends of
the central tubular element in the region of the two
universal joints.
The most stressed and most critical part is always
located in the place of the joints . In fact, the mobility
of the ball-part with respect to its socket often leads to
irreversible distortions of the soft joints and to
frictions among refractory materials. In addition, given
the difficulties to machine refractory steel, it is not
possible to extend the armouring, forming the casing of the
ball-part, to the tip of the latter. That is the main
reason why microcracks are often formed in the refractory
of the tip of the ball-part, causing disturbing
circulations and whirls.
To these quality criteria of a reliable tuyere-stock
are added the concern for a competitive manufacturing
price, for the possibility of easy and rapid dismounting,
for the possibility to easily renew the refractory material
if necessary, etc. It is obvious that all those criteria
often tend to oppose each other, thus forcing the designer
and manufacturer to choose a reasonable compromise.
The object of the present invention is to provide a new
device of the type described in the introduction, which is
more resistant to wear at the place of the joints, which
owing to its numerous alternative solutions, adapts itself
perfectly to the requirements of the user, while permitting
a reasonable manufacturing price.
In order to achieve this object, the device according
to the present invention is characterized essentially in
that the radius of curvature of each ball-and-socket joint
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3
is in an order of magnitude of half the diameter of the
different connection elements and in that the convex ball-
parts of the ball-and-socket joints comprise a protective
sheath or sleeve made of refractory steel and which extends
to the diametrical base of the ball-part. The reduction of
the radius of curvature of the ball-and-socket joints
allows a better guiding of the ball-parts in their sockets,
while reducing the risks of shock and wear of the soft
joints by permmitting to keep always the same width for a
joint.
The reduction of the radius of curvature of the joints
and the fact that the metallic armouring or casing, which
at this place, forms the sheath of the ball and extends to
the base of the latter, allows to maintain a uniform width
of the joint slot or groove during the pivotments.
The present invention also provides a new process for
manufacturing a convex ball-part of ball-and-socket joints
of a device far injecting preheated air into a shaft
furnace, said process consisting in first fabricating the
ball sheath or sleeve of refractory steel and to provide
it with an inner refractory lining, and being characterized
in that the end of a refractory steel pipe is distorted
until it has the form of a convex dome with a central
opening and a convex spherical surface extending between
the central opening and the cylindrical surface of the
pipe, in that the sheath thus formed is placed on a
support, in that a cylinder having a diameter slightly
inferior to the diameter of said central opening, is placed
axially inside, and in that refractory material is cast
between the cylinder and said sheath by using the latter as
a mould.
According to a first embodiment of a tuyere-stock
according to the invention, the ball-parts are formed by
the lower ends of the upper connection element and of the
central tubular element.
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The ball--part of the central tubular element can either
be an integral part of this element, or be separated from
the latter by a transverse junction filled with an annular
joint.
The armouring of the central tubular element and the
one of the lower connection pipe can be connected directly
to each other through an expansion joint, or by means of a
flange or an detachable weld.
The socket of the lower joint can be formed into the
refractory lining cast in a cylindrical sheath made of
refractory steel and arranged coaxially inside the
armouring of the lower connection piece.
The soft refractory joint can be fixed partially to the
armouring and partially to the rim of the socket. It can
also be partially fixed to an inner seat of the cylindrical
sheath and partially to the refractory material.
Alternatively, it can also be attached partially to the
refractory material and partially to a seat delimited by
the upper part of the sheath and by a ring welded inside
the armouring.
According to a second embodiment, the sockets of both
ball-and-socket joints are arranged at the two opposite
ends of the central tubular element, whilst the convex
ball-parts are arranged in the upper and lower connection
pieces.
Other particular features and adavantages of the
invention will be appreciated and understood by those
skilled in the art from the following detailed description
of several embodiments, with reference to the accompanying
drawings in which:
- Figure 1 shows a view, in vertical section, of a
conventional foyers-stock according to US Patent 3,766,867;
- Figure 1a shows an alternative embodiment of the
lower joint of the tuyere-stock according to Figure 1;
- Figure 2 shows the details of a joint of a tuyere-
stock as disclosed in German Patent DE-C2-2218331;
5
- Figures 3 and 3a illustrate in juxtaposition and in
axial section a ball-and-socket joint according to the
present invention;
- Figure 4 illustrates schematically the process making
a sheath of refractory steel, for a ball-part of a joint
connection according to the present invention;
Figure 5 shows diagrammatically an axial section
through the vertical section of a first embodiment of a
tuyere-stock according to the present invention;
- Figure 5a illustrates schematically an alternate
execution of the lower joint of the tuyere-stock according
to Figure 5;
- Figures 6a, 6b and 6c illustrate schematically the
different manufacturing steps of the refractory lining of
the different elements of the tuyere-stock depicted in
Figure 5;
- Figure 7 is a similar view to that of Figure 5 of a
second embodiment of a tuyere-stock according to the
present invention;
- Figures 8, 9 and 9a illustrate different alternate
embodiments of the lower joint connection of the tuyere-
stock according to Figure 7;
- Figures 10a, 10b and 10c illustrate schematically the
different manufacturing steps of the refractory lining of
the different elements of the tuyere-stock depicted in
Figure 7;
- Figure 11 illustrates schematically a third
embodiment of a tuyere-stock according to the present
invention;
- Figures 12a, 12b et 12c illustrate schematically the
different manufacturing steps of the refractory lining of
the tuyere-stock depicted in Figure 11;
- Figure 13 illustrates schematically a fourth
embodiment of a tuyere-stock according to the present
invention and
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- Figures 13a, 13b and 13c illustrate schematically the
different manufacturing steps of the refractory lining of
the tuyere-stock depicted in Figure 13.
The known tuyere-stock, designated by the reference 20
in Figure 1, connects a main bustle pipe 22, arranged
around a blast furnace, to the wall 24 of the blast
furnace. This tuyere-stock 20 comprises a straight oblique
section consisting of a central tubular element 26
articulated with its upper end on a connection piece 28
fixed to the bustle pipe 22 and at its lower end on a
connection piece 30 flanged to an elbow 32. This elbow 32
is extended by a nozzle 34, the end of which is articulated
on a tuyere 36 fastened in the wall 24 of the furnace. The
upper joints 38 and lower joints 40 between the central
tubular element 26 and the two connection pieces 28 and 30
are universal joints allowing relative shifts or movements
between the bustle pipe 22 and the wall of the furnace 24.
Sealing in the region of the joints 38 and 40 is obtained
by means of bellows expansion joints 44, 46 fixed
respectively to the tubular element 26 and the adjacent
connection pieces 28 and 30. Mechanical stability is
ensured by means of cardan joints 48, 50 likewise
connecting the central element 26 to the adjacent
connection pieces 28 and 30. All these elements of the
tuyere-stock consist of an outer-metal armouring or
housing 52 provided with an inner refractory lining 54,
through which passes a supply channel or conduit 56
ensuring the passage of the preheated air.
each one of the two joints 38, 40 consists of a convex
part called ball and of a concave part called socket. In
the upper joint 38, the ball is part of the upper
connection piece 28 and penetrates into the socket formed
by the upper end of the central element 26. The lower part
of the latter constitutes the ball-part of joint 40 and
penetrates into the socket formed by the upper part of the
lower connection piece 40.
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In the embodiment of Figure 1, the ball-part of the
joint 40 is integral with the central element 26, that is,
its refractory lining extends, without interruption, from
the upper end to the tip of the ball-part. This design of
the central element 26 makes its manufacture easier,
compared with the alternative solution illustrated in
Figure 1a, where the ball-part is separated from the rest
of the central element and is connected to the latter in
the region of the flange, which is provided for the ,
fastening of the cardan 50a. The alternative solution
illustrated on figure 1a presents however the advantage of
allowing the separate dismounting of the lower part, which
consists of the tubular connection piece 30 and the
joint 40a, from the upper part consisting of the rest of
the central element 26 and the upper joint 38 with the
tubular connection piece 28. It shall be noted that the
upper joint 38 must necessarily be designed as shown in
Figure 1a, so that the tuyere-stock can be disconnected
from the bustle pipe 22.
Figure 2 shows a known embodiment of a joint connection
as disclosed in the German patent DE-C2-2218331. This
embodiment is different essentially from that one depicted
in Figure 1 in that the joints are spherical, as shown by
the joint between the ball part 58 and the socket of the
connection piece 30. In this embodiment, the ball-part 58
is also separated from the central element 26, following
the example of Figure 1a. The embodiment according to
Figure 1 is, nevertheless, also feasable here.
Another difference as compared with the embodiment of
Figure 1 is the arrangement of soft resilient joints in the
region of the ball-and-socket joint. A first sealing
ring 62 consisting, for example, of ceramic fibers is
incorporated in the refractory of the socket 60 and closes
the pasage way between the socket 60 and the tip of the
ball-part 58. Another soft seal 64, also made of ceramic
fibers, is arranged in the annular space between the lower
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end of the metallic sheath 68 of the ball-part 58 and the
cylindrical connection sleeve of the expansion joint 44.
This seal 64 is wedged between the edge of the socket 60
and a peripheral collar 66 welded to the sheath 68.
The purpose of these joints 62 and 64 is essentially to
stop or to reduce the penetration of hot air inside the
expansion joints 44 in order to provide them a better
protection against high temperatures. when the ball-part 58
is subjected to an axial shift relative to the connection
piece 30, the lower edge of the sheath 68 may distort or
even crush the seal 64 on one side, whereas on the opposite
side, the collar 66 tends to compress the seal 64 in the
axial direction. Given that the refractory joints are
lacking elasticity, there is a risk that these shifts cause
irreversible distortions, thus reducing their efficiency.
The device according to Figure 2 shows another
handicap, in so far as the refractory-steel sheath 68 is
only extending to the limit of the cylindrical part of the
ball-part 58. The refractory tip of the ball-part 58 is,
therefore, rapidly overladen with micro-cracks which are at
the origin of a rapid wear and a breaking of the tip of the
ball-part. The lack of support for the refractory of the
tip of the ball-part 58 needs, furthermore, a relatively
large radius of curvature R to avoid that the convex tip,
which is not supported by the sheath 68, has been tapered
too much. This, an its turn, is at the origin of the sharp
edge between the cylindrical part and the convex part of
the ball-part 58, and which risks to crush the seal 64
during the angular movements of the articulation.
Figures 3 and 3a show each one half of an articulation
according to the present invention, the Figures being shown
close to each other, so as to show an entire joint, of
which the left part shows the version with the ball-part
separated from the central conduit segment and of which the
right part shows the ball-part being part of the central
conduit segment.
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9
The Figures 3 and 3a show that the ball-part of the
articulation according to the present invention 70, 70a is
completely envelopped by its refractory-steel
sheath 72, 72a, which extends to the base of the ball-part
around its convex section. The manufacture of such a
refractory sheath 72, 72a, in a single piece with a convex
section is rendered possible by an artful manufacturing
process, explained more in detail hereinafter. Compared to
the state of the art exemplified in Figure 2, the ball-part
of the present invention has a less important radius of
curvature, in the order of magnitude of half a diameter of
the connection conduit segments of the tuyere-stock, which
improves its mobility. A seal 74, for example made of
ceramic fibers, is provided between the ball-part 70, 70a
and the refractory of the tubular connection piece 76. This
seal can, for example, be cemented to the armouring of the
tubular connection piece 76 between two support
rings 78, 80. The seal 74 adapts perfectly to the shape of
the tip of the ball-part and extends to the major part of
the convex section of the latter. In case the tuyere-stock
is designed to accomodate to a maximum axial misalignement
of 7°, the ball-part 72, 71 can deviate of 3,5° on both
sides from its neutral position illustrated on the
Figures 3 and 3a by the angles a and 13. During such an
extreme pivoting movement, the seal 74 always forms a thick
sealing pad or cushion without being compressed by the
ball-part 70, 70a, owing to the tact that the width of the
slot or grap remains constant during the relative
swivelling.
With reference to Figure 4, the process according to
the present invention for making the refractory-steel
sheath of a ball-part, will now be described. To this
effect, a cylindrical pipe 82 made of refractory steel is
used, which might be provided with a small peripheral
flange 84, in the case of the embodiment shown in Figure 3.
All around the opposite side of the flange 84, at regular
10
distances, cuttings following the generating line are made,
with a depth corresponding to the length of the convex
section of the ball-part to be made. These cuttings 86 thus
define identical tongues 88. These tongues 88 are then
folded down towards the axis of the pipe 82 until the
cuttings 86 are completely closed, in order to define a
spherical dome with a central opening 90 formed by the
frontal bevels 92 of the tongues 88 juxtaposed to each
other. This crimping of the tongues 88 can be carried out
in a mould with a spherical bottom. The sheath 72 is then
finished by welding the different tongues 88 one to the
other over the whole length of the cuttings.
Figure 5 illustrates a first embodiment of the oblique
section of a tuyere-stack with two identical ball-and
socket joints 94 and 96, each of which comprising a ball
part enveloped by a sheath made of refractory steel
manufactured according to the process described with
reference to Figure 4. Figure 5 as well as the following
Figures do not show, for reasons of simplicity, the means
for obtaining mechanical stability to the joints 94 and 96.
These means, although present in a specific embodiment, can
be means known per se, like cardan- joints or tension rods
as disclosed in the European Patent EP-A1-0363576.
Figure 5a shows an alternative embodiment already
described hereinbefore, according to which the ball-part of
the lower joint 96a is separated from the central tubular
conduit element 98a.
In both the embodiments of Figures 5 and 5a the sealed
connection between the central element 98 and the lower
tubular connection piece 100 is performed by means of a
flange 102 at the upper end of the sheath of the ball-part.
The central element 98 comprises also an upper flange 104
beyond the expansion joint of the upper articulation 94 to
conect the tuyere-stock to the bustle pipe (not shown).
In the embodiment of Figure 5 these flanges 102 and 104
are, moreover, necessary for manufacturing the three
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11
elements separately, namely the central element 98, the
lower connection piece 100 and the upper connection piece
106, which consists simply of the ball-part of the ball-
and-socket joint 94. This manufacturing will now be
described and illustrated with reference to Figures 6a, 6b
and 6c.
Figure 6a shows the manufacturing of the refractory of
the ball-part 106. For this purpose, the sheath 72
manufactured according to the process described with
reference to Figure 4, is overturned onto a support 108,
made for example of wood, the central opening 90,
preferably directed downwards. A cylindrical form 110, made
for example of expanded synthetic material, is then
introduced into the sheath 72 and hold in place, for
example, by a plug 112 fastened to the support 108 and
penetrating into an axial channel of the form 110. The only
thing that remains to be done is casting the refractory
material 114 into the annular space delimited by the
form 110 and the sheath 72, by using the latter as a mould.
Figure 6b shows the manufacturing of the central
conduit element 98. For this purpose, the assembly formed
by the armouring 116 of the central element with the sheath
of the lower ball-part and the upper expansion joint is
overturned, the flange 104 to the bottom, onto a
support 118; the ring 120 which delimits the placement of
the joint of the upper articulation 94 closing the opening
around the support. The upper profile of the support 118 is
complementary to the form of the socket of the
articulation 94. Thereupon a cylindrical form 122 made of
expanded synthetic material is axially placed onto the
support 118, and held in place by a plug 124. The only
thing that remains to be done is to fill the annular space
around the form 122 with refractory material.
Figure 6c shows the manufacturing of the lower
connection piece. As in the case of Figure 6b, the
armouring 126 of this tubular connection piece, including
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12
the expansion joint of the lower articulation, is
overturned, the upper flange to the bottom, onto a
support 128 identical to the support 118 used previously.
Then a form made of expanded synthetic material 130, of
which the outer form corresponds to the inner channel of
the finished tubular connection piece 100, is placed
axially onto the support 128, and the space around the
form 730 is filled with refractory material. It shall be
noted that the three forms made of synthetic
material 110, 122 and 130 may remain in place when
assembling the tuyere-stock, since they will be consumed
automatically when the tuyere-stock is put into operation.
Figure 7 shows a second embodiment of a tuyere-stock
with a central tubular element 132, a lower connection
piece 134 and a ball-part 136, however, unlike the
embodiment of Figure 5, the armouring of the central
element 132 is connected by means of the expansion joint of
the lower articulation to the armouring of the tubular
connection piece 134. The flange 102 of the embodiment of
Figure 5a consequently disappeared, which allows a
reduction of the manufacturing costs of the tuyere-stock.
On the other hand, since the tubular connection piece 134
cannot be separated from the central element 132, the
manufacturing step shown by Figure 6c is no more possible
and other ingenious methods have to be employed in order to
be able to cast the socket of the lower joint. To this
effect, the refractory of the connection piece 134 is cast,
in the example shown, in two successive operations,
symbolized by the interruption 138. This will also affect
the design of the lower joint, particular of the socket of
the tubular connection piece 134. Figures 8 and 9 show
several embodiments.
Figure 8 shows the details of the ball-and-socket
joint 140 between the central element 132 and the lower
connection piece 134. The ball-part 142 is identical with
the one of the previous embodiment, that is, provided with
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13
a refractory sheath made according to Figure 4. On the
other hand, the socket 144 of the articulation 140 formed
by the upper part of the refractory lining of the
connection piece 134 is modified. In fact, as shown in
Figure 8, the refractory lining forming the socket 144 is
cast inside the cylindrical sheath 146 made of refractory
steel and fitted coaxially inside the metal armouring of
the tubular connection piece 134. The sheath 146 can be
held in place by means of two rings 148 and 150 fixed
respecti~rely to the inner wall of the armouring and to the
outer wall of the sleeve 146. The thermal insulation is
obtained by means of a thick seal 152 made of ceramic
fibers which is cemented to the inner surface of the
armouring of the connection piece 134 and extends to the
bottom between the ball-part 142 and the socket 144. Two
annular supports 154 and 156, which are welded to the
armouring or housing, ensure the support of the seal.
In the alternative embodiment according to Figure 9,
the socket 144 is also arranged inside a sheath 158 made of
refractory steel, which compared to the embodiment of
Figure 8 is longer than the sheath 146. The part of the
sheath 158 which exceeds the refractory lining, is designed
as a housing for the seal 160 made of ceramic fibers. The
embodiment of Figure 9 in relation to that of Figure 8, has
the advantage that the seal 160 can be put in place before
assembling the tuyere-stock, and can be inserted together
with the socket 144. On the other hand, the embodiment of
Figure 8, compared to that of Figure 9, has the advantage
of a better thermal insulation because of a seal 152 that
is thicker than the seal 160.
Figure 9a shows a compromise solution between the
embodiments of Figures 8 and 9 in that the sheath 162 is
also used as a housing for the seal 164, but is associated
with an annular collar 160, which is welded to the inner
surface of the armouring. The seal 164 can thus also be put
in place onto the socket before assembling of the tuyere-
~~ r.-~' ~a~ rl
14
stack, as is the case in Figure 9, but unlike the latter
the collar 166 forms a thermal b:cidge contributing to the
heat dissipation from the seal 164 to the outer armouring.
With reference to Figures 10a, 10b and 10c, the
manufacturing steps of the different elements of the
tuyere-stock of Figure 7 will now be described, as it has
been done previously with Figure 5, by also refering to
Figures 6a to 6c. By way of example, it will be referred to
the use of the embodiment shown in Figure 9.
Figure 10a shows the casting of the refractory into a
sheath according to Figure 4 to make the upper
ball-part 136. This step is identical to the one described
with reference to Figure 6a and does not have to be
explained further.
At this instant however the intermediary step
illustrated in Figure 10b is applied. This Figure shows the
separated casting of the socket 144 of the lower
articulation joint 140. First, the sheath 158 is placed
onto a mould 168 made of wood, the housing provided far the
seal 160 (Figure 9) being directed to the bottom. The
profile of the upper front of this mould 168 is
.complementary to that of the refractory lining of the
socket 144. Then a form 169 made of expanded synthetic
material corresponding to the opening of the socket 144 is
placed axially inside the sheath 158 onto the support 168,
and the refractory material is cast between this form 169
and the sheath 158. Following the casting and the removal
of the mould 168, the seal 160 (Figure 9) can be cemented
in its housing inside the sheath 158.
With a view to the casting of the central element 132,
its metal armouring which is fixed to that of the
connection piece 134 by means of the expansion joint, is
overturned onto the upper flange. The casting itself of the
element 132 is identical to the casting described with
reference to Figure 6b, and the same moulds and forms will
be used. When this casting is completed, the socket 144
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cast as explained with reference to Figure 10b and after
the seal has been put in place, is introduced into the
armouring of the connection piece 134 in order to place it
on the ball-part 142 where it is held by the abutments 148
5 and 150. When the socket 144 is in place a form, not shown,
defining the channel of the tubular connection piece 134,
is placed on this socket 144, and the casting of the
connection piece 134 is finished by filling the annular
space between said form and the armouring of the tubular
10 connection piece 134 with refractory material.
Figure 11 shows a third embodiment similar to the one
shown in Figure 7 which comprises a central tubular conduit
element 170 connected through an upper ball-and-socket
articulation 176 to a ball-part 172 and thourgh a Lower
15 ball-and-socket articulation 178 to a tubular connection
piece 174. The lower connection piece 174 and the lower
articulation 178 are identical with the embodiment of
Figure 5 and, thus, do not have to be described further.
The central element 170 is analogous to the one of the
embodiment of Figure 7 insofar as it does not comprise a
flange for its connection to the tubular connection
piece 174. In order to solve, in the embodiment of
Figure 11, the manufacturing and assembly problems as
explained with reference to Figure 7, a removable or
detachable link or connecting piece is provided between the
armouring of the central element 170 and that of the
tubular connection piece 174. As shown by Figure 11, an
upper end 180 of the expansion joint 182 is welded to the
armouring of the central conduit element 170 through a
metallic shoulder member 184 onto which is also welded the
sheath of the ball-part of articulation 178. The solidity
of the welding of the member 180 to the shoulder 184 must
be a compromise between the necessity to be able to remove
the welding in case of dismounting, on the one hand, and
the necessity to ensure the sealing and to restrain the
internal pressure, on the other hand.
~i~:~~'~~~
16
The embodiment of Figure 11 has the advantage of the
same simplicity in manufacture as the embodiment of
Figure 5, that as, there is no need to cast the lower
connection piece in two steps, and it also has the
advantage the advantage of the embodiment of Figure 7, to
save the linking flange between the central element and the
lower connection piece. However, the embodiment of
Figure 11 needs a welding that must resist the internal
pressure.
The different casting steps of the elements of the
embodiment of Figure 11 as illustrated by Figures 12a, 12b
and 12c, correspond exactly to those disclosed with
reference to Figures 6a, 6b and 6c, and thus do not have to
be explained further; the same forms and moulds being used.
The only difference lies in the absence of a flange on the
connecting element 180 of the expansion joint 182 and in
the absence of a flange on the central element 170, which
is replaced by shoulder 184. Following the casting of the
three elements 170, 172 and 174 according to
Figures 12a, 12b and 12c, the seal of the lower
articulation 178 is put in place by cementing it to the
housing provided at the inner surface of the armouring of
the connection piece 174 above the expansion joint 182.
Then the connection piece 174 is attached to the ball-part
of the central element 170 and the peripheral welding
between the connecting element 180 and the shoulder 184 is
made.
With reference to Figure 13 a fourth embodiment will
now be described, which combines all the advantages of the
three previous embodiments. The embodiment according to
Figure 13 also comprises a central tubular element 200
connected through an upper ball-and-socket joint to a ball-
part 202 and through a lower ball-and-socket joint 208 to a
lower connection piece 204. However, contrary to the
previous embodiments, the two sockets of the
articulations 206 and 208 are provided at opposite ends of
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17
the central element 200, the ball-part of the lower
articulation 208 forming a part of the connection
piece 204. The upper and lower articulations are thus
positioned in opposite directions, as disclosed in the
European Patent EP-A1-0363576, which also gives the
advantages described in this document.
As shown in Figure 13, this embodiment saves the flange
of the central element 200, without having to provide a
removable weld between the armouring of the latter and the
armouring of the lower connection piece 204 and without
having to cast the tubular connection piece 204 in two
steps as indicated in the description of the different
manufacturing steps, which will be described hereinafter
with reference to Figures 13a, 13b and 13c.
The manufacture of the ball-part 202 illustrated by
Figure 13a is in accordance with the manufacture of the
ball-parts of the previous embodiments.
Figure 13b shows the manufacture of the central
element 200. The metal armouring of the element 200, which
makes part of the one of the lower tubular connection
piece 204, is placed onto a mould made of wood which holds
it through the housing of the seal of the lower
articulation 208. The mould 210 is supported by a base 212
which is, preferably, provided with a base element
supporting, the armouring of the connection piece 204
through an inner stop 216 which will thereafter serve as a
fixing support for the sheath of the ball-part. The profile
of the upper front of the mould 210 is complementary to
that of the socket of the lower articulation Thus, a
form 218 made of expanded synthetic material and
corresponding to the inner channel of the central
element 200, has merely to be placed axially inside the
armouring of the element 200 and on the mould 210. Then the
annular space between the form 218 and the armouring has to
be filled to the brim of the housing of the seal of the
upper articulation 206. The profile of the socket 220 of
18
the upper articulation is formed in the cast refractory
material by removing the cast material before it hardens,
for example with a strickle having a profile complementary
to the one of the socket 220. The structure thus made in
accordance with Figure 13b is then turned over and placed
on a base 222 which consists preferably of a mould made of
wood used to model the socket of the articulations. The
structure is carried by the socket 220 on the mould 222.
The seal 224 is subsequently put in place by cementing it
in its housing provided to this effect on the inner surface
of the armouring of the element 200. A disc 226 made of
expanded synthetic material is then placed at the bottom of
the socket-part previously formed by the mould 210 in
Figure 13b, the thickness of the disc corresponding to the
axial width of the transverse slot of the articulation 208
between its ball-part and socket. The sheath of
ball-part 72 is then introduced from above into the
armouring of the connection piece 204 by placing it and
welding it by its edge 84 onto the stop device 216 provided
on the inner surface of the armouring. A form made of
expanded synthetic material is then placed axially on the
disc 226, the configuration of the form corresponding to
the passage channel of the tubular connection piece 204.
All that needs to be done then is to cast the refractory
material into the annular space around that form, by using
the sheath 72 as a mould. After the removal of the
mould 222 and of the plugs 228 and 330 used to maintain the
inner forms during the casting, the central element 200 and
the tubular connection piece 204 are ready for assembly,
the inner forms as well as the disc 226 can stay in place
given that they will be used up automatically when the
tuyere-stock is put into operation.
