Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ELECTRODE SLIPPING DEVICE
FIELD OF THE INVENTION
The present invention relates to an electrode slipping
device.
BACKGROUND OF THE INVENTION
In prior art, e.g. documents WO 2015/001180 Al and WO
2015/001179 Al disclose an electrode slipping device.
Also Figure 1 shows this kind of an electrode slipping
device having, on the left side encircled with a dot-
and-dash line denoted with A, two prior art clamping
devices 5' mounted on the upper holder ring 2 and on
the lower holder ring 3. Figure 2 shows such a prior
art clamping device 5'. The clamping device 5' com-
prises a frame element 6' which is attachable to a
holder ring 2 and/or 3 to be stationary in relation to
the holder ring. A cylinder portion 7' is stationary
in relation to the frame element 6'. A plunger 8 is
arranged to be engaged with a clamping shoe (not
shown). The plunger 8 comprises a cylindrical housing
9' and an end plate 10' (not shown). A pressing spring
(not shown) is arranged inside the cylindrical housing
9' to act between the frame element 6' and the plunger
8' for urging the plunger 8' towards the clamping shoe
and for pressing the clamping shoe against the elec-
trode E. Four tension bars 12' are arranged outside
the cylindrical housing 9' inside which the pressing
spring is located. Each tension bar 12' has a first
end which is releasably attached to the end plate 10'
of the plunger 8'. A piston element (not shown) is ar-
ranged movable inside the cylinder portion 7' to form
a hydraulic power means 16' wherein the piston element
can be moved by hydraulic pressure of hydraulic fluid
which is arranged to be guided to a space between the
piston element and the cylinder portion. Movement of
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the piston element by hydraulic pressure of the hy-
draulic fluid causes the tension bars 12' to pull the
plunger 8 against the spring force of the pressing
spring to move the clamping shoe from a clamping posi-
tion to a release position.
As mentioned, the four tension bars are located out-
side the cylindrical housing which accommodates the
pressing spring. This kind of arrangement of tension
bars makes the clamping device bulky and heavy. The
end plates, to which the tension bars are attached,
must be both wide and thick to be sturdy enough to
withstand the bending force caused by the pressing
spring acting on the central region of the end plate
and at a distance from the support points to tension
bars, in order to avoid bending of the end plates. The
clamping device also has many parts making it compli-
cated and expensive to manufacture and difficult to
service.
OBJECTIVE OF THE INVENTION
The objective of the invention is to alleviate the
disadvantages mentioned above.
In particular, it is an objective of the present in-
vention to provide an electrode slipping device having
a clamping device which has a simple, compact and
light-weight structure with few parts, easy to mainte-
nance and cheap to manufacture.
SUMMARY OF THE INVENTION
According to an aspect of the invention, the present
invention provides an electrode slipping device com-
prising an upper holder ring and a lower holder ring,
the upper holder ring and the lower holder ring con-
taining one or more clamping assemblies including a
clamping shoe and a clamping device arranged in co-
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operation with each other, so that the clamping shoe
is operable between a clamping position, where an
electrode is clamped, and a release position, where
the electrode is unclamped. The clamping device corn-
prises a frame element fixedly attachable to a holder
ring to be stationary in relation to the holder ring.
The clamping device comprises a cylinder portion, the
cylinder portion being arranged stationary in relation
to the frame element. The clamping device comprises a
plunger, the plunger comprising a cylindrical housing
and an end plate arranged to be engaged with the
clamping shoe. The clamping device comprises a press-
ing spring arranged inside the cylindrical housing to
act between the frame element and the plunger, for
urging the plunger towards the clamping shoe and for
pressing the clamping shoe against the electrode. The
clamping device comprises a tension bar having a first
end releasably attached to the end plate of the plung-
er, and a second end. The clamping device comprises a
piston element arranged movable inside the cylinder
portion to form a hydraulic power means wherein the
piston element can be moved by hydraulic pressure of
hydraulic fluid which is arranged to be guided to a
space between the piston element and the cylinder por-
tion. Movement of the piston element by hydraulic
pressure of the hydraulic fluid causes the tension bar
to pull the plunger against the spring force of the
pressing spring to move the clamping shoe from the
clamping position to the release position.
According to the invention the clamping device com-
prises one and single tension bar arranged centrally
in relation to the frame element, the plunger, the
pressing spring and the piston element.
The advantage of the invention is that due to one and
single central tension bar the clamping device can be
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a simple, compact and light-weight structure with few
parts, being easy to maintenance and cheap to manufac-
ture. The single centrally arranged tension bar ena-
bles that a thick end plate is not needed since the
tension bar does not exert bending forces to the end
plate, as happens in the prior art device. For exam-
ple, a prior art clamping device having a pressing
force 60 tn may have a weight 450 kg. The weight of
the clamping device according to the invention with
the same pressing force may be less than 300 kg. Re-
duction of weight is considerable.
In an embodiment of the electrode slipping device, the
frame element, the plunger and the pressing spring
each have a central hole to receive the tension bar
therein.
In an embodiment of the electrode slipping device, the
end plate has a central hole having an inner thread,
and that the first end of the tension bar has a first
outer thread threaded to the inner thread of the end
plate.
In an embodiment of the electrode slipping device, the
second end of the tension bar has a second outer
thread on which a lock nut is threaded.
In an embodiment of the electrode slipping device, the
clamping device comprises two or more cylinder por-
tions and piston elements disposed radially around the
tension bar to form two or more hydraulic power means
around the tension bar.
In an embodiment of the electrode slipping device, the
clamping device comprises three or four cylinder por-
tions and piston elements disposed radially around the
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tension bar to form three or four hydraulic power
means around the tension bar.
In an embodiment of the electrode slipping device, the
5 clamping device comprises a second end plate to which
the piston elements are attached, the second end plate
comprising inlets and outlets for guiding the hydrau-
lic fluid to and from the two or more hydraulic power
means.
In an embodiment of the electrode slipping device, the
cylinder portion and the piston element are both annu-
lar thereby forming an annular hydraulic power means
which is concentric in relation to the tension bar.
In an embodiment of the electrode slipping device, the
frame element comprises an inlet and an outlet for
guiding the hydraulic fluid to and from the annular
hydraulic power means
In an embodiment of the electrode slipping device, the
pressing spring consists of a plurality of conical
disc spring washers.
In an embodiment of the electrode slipping device, the
lower holder ring comprises a single clamping device
configured to releasably press one clamping shoe
against the surface of the electrode. Further the low-
er holder ring comprises a contact shoe made of elec-
trically conductive material for supplying current to
the electrode, the contact shoe being arranged at an
opposite side of the lower holder ring in relation to
the position of the clamping shoe.
In an embodiment of the electrode slipping device, the
upper holder ring is attached to a stationary struc-
ture, and that the lower holder ring is suspended from
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the stationary structure by vertical hydraulic cylin-
ders.
It is to be understood that the aspects and embodi-
ments of the invention described above may be used in
any combination with each other. Several of the as-
pects and embodiments may be combined together to form
a further embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to pro-
vide a further understanding of the invention and
constitute a part of this specification, illustrate
embodiments of the invention and together with the de-
scription help to explain the principles of the inven-
tion. In the drawings:
Figure 1 shows an axonometric view of an electrode
slipping device provided with clamping devices accord-
ing to prior art A and according to a first embodiment
of the invention B,
Figure 2 shows an axonometric view of a prior art
clamping device,
Figure 3 shows an axonometric view of a clamping de-
vice of a first embodiment of the electrode slipping
device of the invention,
Figure 4 shows an axonometric view of an electrode
slipping device according to a second embodiment of
the invention,
Figure 5 shows a cross-section V-V from Figure 4,
Figure 6 shows a side view of a clamping device of
Figure 5,
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Figure 7 shows an end view VII-VII of the clamping de-
vice of Figure 6,
Figure 8 shows a cross-section VIII-VIII from Figure
6,
Figure 9 shows a longitudinal cross-section of a fur-
ther embodiment of a clamping device in a clamping po-
sition I wherein the hydraulic power means is unpres-
surized, and
Figure 10 shows the clamping device of Figure 9 in in
a release position wherein the hydraulic power means
is pressurized.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows an electrode slipping device 1 which is
for holding and slipping of a self-baking Soderberg
electrode E. The slipping device 1 comprises an upper
holder ring 2 and a lower holder ring 3. The upper
holder ring 2 and the lower holder ring 3 both com-
prise several clamping assemblies including a clamping
shoe (not shown in Figure 1) and a clamping device 5
arranged in co-operation with each other. The clamping
shoe is operable between a clamping position where an
electrode E is clamped and held in its position and a
release position where the electrode E is unclamped
and can be moved. The operation principle of the
clamping device 5 is explained in more detail with
reference to Figure 9 and 10.
The operation principle of the slipping device 1 is
known from the prior art. The slipping device allows
controlled displacement of the electrode. The upper
and lower holder rings 2, 3, are sequentially operated
and moved to extend the electrode as the tip of the
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electrode is consumed in use in the furnace. The two
holder rings 2, 3 are connected with vertical hydrau-
lic cylinders 100 that enable relative movement be-
tween the upper and lower holder rings. This action
enables slipping through of the electrode whilst al-
ways maintaining a positive grip on the outer surface
of the electrode.
In Figure 1 the clamping devices 5 according to the
invention are installed in the upper and lower holder
rings 2, 3 and are shown on the right side and encir-
cled by a dot-and-dash line denoted by B. The clamping
device 5 is also shown in Figure 3. When compared to
the prior art clamping device 5' shown in Figure 2,
Figure 3 shows that the new clamping device 5 is a
more simple, compact and light-weight structure with
fewer parts.
The structure of the clamping device 5 is disclosed in
more detail with reference to Figures 5 to 10 in the
following.
As shown in Figures 5, 9 and 10 the clamping device 5
comprises a frame element 6 which is fixedly attached
to a lower holder ring 3 to be stationary in relation
to the holder ring. A cylinder portion 7 is arranged
stationary in relation to the frame element 6. The
cylinder portion 7 may be a separate part in relation
to the frame element 6 whereby the cylinder portion 7
is attached to the frame element 6. The clamping ele-
ment 5 comprises a plunger 8. The plunger 8 comprises
a cylindrical housing 9 and an end plate 10. The end
plate 10 can be engaged with the clamping shoe 4 to
press it. A pressing spring 11 is arranged inside the
cylindrical housing 9. The pressing spring 11 acts be-
tween the frame element 6 and the end plate 10 of the
plunger 8 urging the plunger 8 towards the clamping
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shoe 4 and for pressing the clamping shoe 4 against
the electrode E.
One and single centrally disposed tension bar 12 is
releasably attached to the end plate 10 of the plunger
8. The end plate 10 has a central hole 19 having an
inner thread 20. The first end 13 of the tension bar
12 has a first outer thread 21 which is threaded to
the inner thread 20 of the end plate 10 to provide a
releasable attachment.
A piston element 15 is arranged movable inside the
cylinder portion 7 of the frame element 6 to form a
hydraulic power means 16. The piston element 15 can be
moved by hydraulic pressure of hydraulic fluid which
is guided into a space S between the piston element 15
and the cylinder portion 7. Movement of the piston el-
ement 15 by hydraulic pressure of the hydraulic fluid
causes the tension bar 12 to pull the plunger 8
against the spring force of the pressing spring 11 to
move the clamping shoe 4 from the clamping position I
(Figure 9) to the release position II (Figure 10).
As shown in Figure 9, in the clamping position I the
hydraulic power means 16 is unpressurized and the
pressing spring 11 urges the plunger 8 to press the
clamping shoe (not shown) against the electrode (not
shown). In this position an end E of the cylinder
portion 9 of the plunger 8 is at a distance from a
stopper F formed by a surface of the frame element 6.
As shown in Figure 10, in the release position II the
hydraulic power means 16 is pressurized and the press-
ing spring 11 is pulled by the tension bar 12 to a
shortened state wherein the end E of the cylinder por-
tion 9 of the plunger 8 abuts against stopper F. In
this position the clamping shoe (not shown) is pulled
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away from contact to the electrode (not shown) and the
electrode is free to be moved.
The one and single tension bar 12 is arranged central-
5 ly in relation to the frame element 6, the plunger 8,
the pressing spring 11 and the piston element 15. The
frame element 6, the plunger 8 and the pressing spring
11 each have a central hole 17, 18, 19 to receive the
tension bar 12 therein. The second end 14 of the ten-
10 sion bar 12 has a second outer thread 22 on which a
lock nut 23 is threaded.
Figures 5 to 8 show an embodiment of the clamping de-
vice 5 which comprises four cylinder portions 7 and
four piston elements 15 disposed radially around the
tension bar 12 to form four hydraulic power means 16
around the tension bar 12. The clamping device 5 com-
prises a second end plate 24 to which the piston ele-
ments 15 are attached. The second end plate 24 corn-
prising inlets 25 and outlets 26 for guiding the hy-
draulic fluid to and from the two or more hydraulic
power means 16. Preferably the inlet 25 is at a lower
level than the outlet 26 in order to prevent formation
of air bubbles in the hydraulic fluid. In
Figure 7
can be seen that the four hydraulic cylinder means are
connected in series so that the hydraulic fluid flows
through all four hydraulic power means 16.
Figures 9 and 10 show another embodiment wherein the
cylinder portion 7 and the piston element 15 are both
annular thereby forming one annular hydraulic power
means 16 which is concentric in relation to the ten-
sion bar 12. An annular hydraulic power means 16 is
compact and can provide a great force. In this embod-
iment the cylinder portion 7 comprises an inlet 25 and
an outlet 26 for guiding the hydraulic fluid to and
from the annular hydraulic power means 16. Preferably
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the outlet 26 is above the level of the inlet 25 in
order to prevent formation ofairb bubbles in the hy-
draulic fluid.
In the embodiments shown in Figures 5, 9 and 10 the
pressing spring 11 consists of a plurality of conical
disc spring washers 27, so-called Belleville washers,
arranged as a stack.
The hydraulic power means 16 of the clamping devices 5
of both embodiments of Figure 5 and Figure 9 can be
easily detached for service simply by removing the
lock nut 23 and by unthreading the tension bar 12 from
the end plate 10 whereby the frame element 6, plunger
8 and the pressing spring can remain in its place to
press the clamping shoe 4 while the cylinder portion 7
and the piston element 15 are detached.
Reference is now made to Figures 4 and 5. Figure 4
shows an electrode slipping device 1 designed for
graphite electrode. The lower holder ring 3 comprises
a single clamping device 5 arranged to releasably
press one clamping shoe 4 against the surface of the
electrode E (shown in Figure 5). The lower holder ring
also comprises a single contact shoe 28 made of elec-
trically conductive material for supplying current to
the electrode. The contact shoe 28 is arranged at an
opposite side of the lower holder ring 3 in relation
to the position of the clamping shoe 4. AS can be seen
in Figure 4, the upper holder ring 2 is attached to a
stationary structure 29. The lower holder ring 3 is
suspended from the stationary structure 29 by vertical
hydraulic cylinders 30.
Although the invention has been the described in con-
junction with a certain type of the slipping device,
it should be understood that the invention is not lim-
ited to any certain type of the slipping device. While
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the present inventions have been described in connec-
tion with a number of exemplary embodiments, and im-
plementations, the present inventions are not so lim-
ited, but rather cover various modifications, and
equivalent arrangements, which fall within the purview
of prospective claims.
