Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
Lance holder with multiple-tolerance clamping head
The invention concerns a lance holder for lance tubes used in the iron and
steel
industry having a clamping head which has a fixing part and a clamping part,
to
which a sealing sleeve clamping and thus sealing the lance tube introduced is
allocated.
Lance holders with a clamping head and a slag non-return safety device or
backburn safety device serve to hold the lance tube required for oxidation
securely
and an the other hand to prevent slag from running back to the oxygen inlet
when
the blasting process is completed or interrupted. According to DE 23 27 595C,
a
gas-permeable sintered metal disc, which prevents slag return, is arranged
shortly
before the oxygen hose. This mechanical barrier to slag return does not always
fulfil requirements, particularly if high volumes of oxygen have to flow
through,
because then a sintered metal disc naturally leads to difficulties. The
upstream
valve arrangement also performs a sort of slag-return prevention function,
closing
when the gasket arranged above has been burned due to returning slag. The
lance tube inserted into the lance holder is held by a clamping head with a
collet
arranged therein. The effect of the teeth of the collet holds the lance tube
inserted
in the lance holder. A sealing sleeve is arranged behind this collet and is
affected
by the inserted tube and deformed so that it is in close contact with the
outside of
the lance tube. This close contact due to deformation of the sealing sleeve
has the
initial disadvantage that the sealing sleeve may stick to the lance tube, so
that the
remainder of the lance tube can only be removed with difficulty or by removing
the
sealing sleeve as well when the collet is opened. This problem and the
particular
configuration of the collet have the disadvantage that the diameter of the
respective lance holder must be quite precisely matched to the diameter of the
lance tubes to be inserted and held. Currently, lance holders are in use which
can
accept and fix imperial tubes and others which can accept metric lance tubes.
Only very narrow tolerances are possible due to the movement of the collet and
ultimately also the sealing sleeve, usually in the range of 0.2 mm. As these
lance
tubes are consumables, businesses are ultimately forced to purchase them with
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both imperial and metric tube diameters, causing problems for staff, because
they
are usually depend on lance holders which accept only a few tube diameters.
This
means that damage and accidents occur repeatedly, because the lance holder
components which are crucial to fixing and sealing are damaged during
operation
with a diameter of tube which is too great or too small, rendering the lance
holder
unusable. As these lance tubes introduce oxygen into the melt and usually have
to
be curved for this purpose, the molten steel can endanger operators,
particularly if
the lance tubes slip out or if other problems occur. Even if the operators are
protected by protective clothing and hard hats, protection against molten
steel is
inadequate, so that injuries and detrimental effects can occur repeatedly.
The invention is based upon the problem of creating a lance holder for
multiple
and simultaneously as many dimensions as possible, and which is safe to
operate
and easy to handle.
The problem is solved according to the invention by the fixing part comprising
the
inserted lance tube is provided with a leading bevel in which pressure
elements
distributed around the circumference are guided which are displaceable at
right
angles to the longitudinal axis of the lance tube and by means of which fixing
part
a clamping part having a pressure bevel corresponding to the leading bevel is
arranged and formed in an influenceable manner.
By means of a lance holder designed in such way it is first of all possible to
hold
the inserted lance tube precisely and securely, because it is held precisely
by the
pressure elements, when operating the clamping head or particularly the
clamping
part which is pushed onto the fixing part. The sealing sleeve is relieved
simultaneously. This ensures that once the lance tube is inserted, it can only
be
removed by deliberate operation of the clamping part. However, the lance tube
is
securely held throughout operation, the sealing sleeve being protected against
sticking by further measures described below and itself having a diameter
which
allows the use of lance tubes of different diameters. The range of acceptance
of
different lance tube diameters is restricted by the leading bevel and the
correspondingly-designed clamping part, but a considerable reduction in the
sizes
of the lance holder is possible. The tolerance range is increased to
approximately
0.5 - 3.00 mm by the design according to the invention, depending upon the
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structure of the lance holder. The number of lance tubes currently in use, for
which
a variety of lance holders, tailor-made to the respective dimensions were
necessary, can thus be reduced to 6-7. This is rendered possible because the
displaceable pressure elements act and take effect as soon as lance tubes of
the
sizes intended for the respective lance holder are inserted, whilst fixing a
lance
tube with a smaller external circumference still remains possible, because the
displaceable pressure elements then only take effect after a corresponding
displacement path and fix the lance tube.
A purposeful embodiment of the invention provides for the pressure elements
all
being formed and arranged to be displaced simultaneously and uniformly by the
pressure bevel against the wall of the lance tube. Insertion of the respective
lance
tube does not cause tilting or other problems with the smallest possible lance
tube
diameters, because the individual pressure elements are stressed and pressed
against the wall of the lance tube evenly and simultaneously.
A further purposeful embodiment provides for the pressure elements being
formed
so as to generate punctiform and/or linear load pressure on the wall. Pressure
elements are thus used which do not exercise pressure across the surface of
the
lance tube, but punctiform or linearly, so that a higher, more targeted
pressure or
load pressure may be generated.
A particularly purposeful embodiment provides for the pressure elements being
formed as balls, so that the aforementioned punctiform load pressure can be
generated in such a way that the lance tubes are held optimally, the lance
tubes
usually consisting of mild steel, e.g. St 37, whilst the balls are made of a
hardened
material, thus being capable of a long useful life.
Particularly even and secure fixing of the lance tubes in the lance holder is
provided if three balls are evenly distributed around the circumference in the
leading bevel of the fixing part, as pressure elements. Bores are then
purposefully
present in the leading bevel, through which the respective ball may be pressed
onto the surface of the lance tube by the clamping part pushed on or displaced
and its pressure bevel. For this purpose, the clamping part has, as
aforementioned, a matched pressure bevel which extends uniformly, ensuring
that
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all three balls are moved towards the inserted lance tube in their bores
simultaneously, to hold it securely and thus fix it permanently.
Lengthwise deformation of the sealing sleeve, i.e. compression, is waived, to
prevent it from sticking when it contacts the inserted lance tube. Deformation
would have to involve the application of considerable force, particularly for
lance
tubes with greater tolerances. This is avoided by the solution according to
the
invention, in accordance with which the fixing part has a wedge on the side
opposite the leading bevel, insertable between the external wall of the
sealing
sleeve and the surrounding protective casing. Said wedge acts on the sealing
sleeve and ensures that the latter is in sufficiently close contact with the
external
wall of the lance tube, ensuring a secure seal, advantageously without
compression in the longitudinal direction being necessary. For this purpose,
the
wedge is displaced longitudinally, pressing the sealing sleeve against the
wall of
the lance tube, as desired. If the fixing part and its wedge are withdrawn
when
released, the sealing sleeve will be relieved, can regain its shape and
separate
from the rest of the lance tube, so that the lance tube can be removed from
the
lance holder easily. Such even pressure on the lance tube has the additional
advantage that consistently superficial contact is possible, which would not
be
guaranteed if the sealing sleeve were compressed.
Displacement of the clamping part on to the fixing part purposefully takes
place by
the clamping part of the clamping head having a clamping sleeve which encloses
the clamping part and is formed on an external thread of the protective casing
such that it can be displaced. It may thus be ensured that the clamping part
can be
correspondingly pushed onto the fixing part and the balls thus pressed against
the
wall of the lance tube with little force. This process takes place simply by
turning
the clamping sleeve, which may be further facilitated by roughened contact
surfaces and the like.
Ease of movement of this displacement process is specifically enhanced by
arranging a ball bearing between the front wall of the clamping part and the
clamping wall of the clamping sleeve. Said ball bearing between the clamping
sleeve and clamping part reduces the friction which occurs in the clamping
process so that it may take place without the application of great force.
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The lance tube must be inserted far enough into the lance holder, i.e. through
the
sealing sleeve. To ensure this, provision is made for a check valve to be
arranged
between the sealing sleeve and a backburn safety device, with a stop which
perceptibly restricts potential insertion. The lance tube inserted as far as
the stop
then releases the gas flow when clamped. Operation therefore cannot commence
when the lance tube has been inserted in the lance holder until it has been
inserted far enough to achieve precise sealing by the sealing sleeve. The
check
valve is opened simultaneously. The check valve is then held open by the lance
tube until the lance tube is or has to be removed, when a spring then moves
the
valve back into its closed position automatically.
Further provision is made for a non-return valve, to be opened by the gas
flow, to
be provided on the opposite side of the backburn safety device, to render the
entire lance holder safe. This ensures that the gas flow can enter the lance
holder
at the requisite pressure and is cut off again automatically if the pressure
falls too
far. Precise, safe operation of the lance holder is thus guaranteed.
In order to make it possible to install and maintain the parts downstream of
the
lance holder itself separately, the invention also provides for the backburn
safety
device with the valves to be allocated to a safety casing removably connected
to
the protective casing. Both casings are preferably bolted together.
It has already been stated above that the number of sizes required can be
reduced
considerably by the lance holder according to the invention. According to the
invention provision is made for the fixing part, clamping part and sealing
sleeve to
be formed having tube tolerances of 3-4 mm for group dimensions admitting both
metric and imperial tubes. This makes it possible, as already mentioned above,
to
cope with about seven holder sizes, whilst currently far more than 15 such
holder
sizes have to be considered in order to make fairly reliable lance holder
operation
possible. Reliable operation is always guaranteed by the new lance tube fixing
system.
The invention is particularly distinguished by the creation of a lance holder
which
can be used in both the iron and steel industries without an unnecessary
potential
hazard to the operators by mishandling or operation of the lance holder, or
due to
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inadmissible lance tube diameters. Firstly, the lance tube inserted in the
lance
holder is optimally fixed therein, simultaneously ensuring that the lance tube
is
always inserted far enough into the lance holder in operation, i.e. as far as
the
stop. When the stop is reached, or shortly before, during clamping, the check
valve blocking the inflow of gas is opened and the gas can flow through the
lance
holder into the lance tube previously held in the sealed lance tube. The
necessary
sealing of the lance tube no longer takes place by means of a sealing sleeve
deformed longitudinally, but by the sealing sleeve being pressed evenly and
securely against the respective lance tube by a wedge. This creates the
possibility
of using sealing sleeves with a larger diameter than the external diameter of
the
lance tube. The purposeful design of the clamping head with pressure elements
in
the form of balls displaceable at right angles to the longitudinal axis
primarily
ensures punctiform application of the load pressure and thus optimal fixing of
the
lance tubes inside the lance holder. This ensures that the lance tube cannot
rotate
in the lance holder, the lance holder being fixed by the clamping head and the
sealing sleeve, but so securely by the clamping head that any detrimental
effect
whatsoever on the fixing of the lance tube is precluded. Secure retention is
also
provided for deformed lance tubes, because sufficient force can always be
applied
by the punctiform or linear fixing of the lance tubes in the lance holder.
Suitable
marking can visibly and easily establish the tube diameters for which the
respective lance holder is intended for the operators. This precludes any
hazards
whatsoever.
Further details and advantages of the subject of the invention emerge from the
following description of the relevant drawing, which shows a preferred
specimen
embodiment with the necessary details and individual components.
Figure 1 is a side view of a lance holder with a moulded rotary valve;
Figure 2 is a cross-section of the lance holder with a 13.2 mm diameter tube
clamped in;
Figure 3 is a perspective representation of the lance holder shown in Fig. 2;
Figure 4 is a cross-section of a lance holder with a tube with a circumference
of
17.5 mm clamped in, and:
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Figure 5 is a cross-section of a lance holder in its relaxed state, without a
lance
tube.
Figure 1 is a side view of a lance holder 1. A lance tube 2 is inserted in the
clamping sleeve 25 from the front. The clamping sleeve 25 and the clamping
head
3 contain a fixing part 4 and a clamping part 5 not shown here, which
cooperate
with the sealing sleeve 6 and are accommodated in the clamping head 3 formed
as a protective casing 9. The adjacent safety casing 10 accommodates the
requisite valves which will be considered below. A rotary valve 11 is screwed
onto
this safety casing 10, which bears the manufacturer's name 40.
A cross-section through the lance holder 1 shown in Fig. 1 is shown in Fig. 2,
where it may be seen that the lance tube 2 is inserted far into the lance
holder 1
through the clamping head 3. The aforementioned sealing sleeve 6 is pressed
against the wall 18 of the lance tube 2 by a wedge 22 so that full sealing is
achieved. Said wedge 22 forms the end 21 of the fixing part 4 opposite the
leading
bevel 14. When the clamping head 3 or the clamping sleeve 25 is operated, the
wedge 22 is pushed in between the outer wall 23 of the sealing sleeve 6 and
the
protective casing 9 so that the sealing sleeve 6 is deformed and is in close
contact
with the wall 18.
Whilst the opposite end 21 of the fixing part 4 causes the deformation and
presses
the sealing sleeve 6 against the wall 18, the front end has a leading bevel
14, in
which pressure elements 16 are arranged which may be displaced at right angles
to the longitudinal axis 15 of the lance tube 2. Said pressure elements 16 are
affected by the pressure bevel 17 of the clamping part 5, which is pushed onto
the
correspondingly formed leading bevel 14 when the clamping sleeve 25 or the
clamping head 3 is turned. The pressure elements 16 are formed as balls 20, as
shown in Fig. 2 and Fig. 3, the balls 20 being pressed directly against the
wall 18,
so that secure fixing of the lance tube is guaranteed. Three such balls 20,
20' are
distributed around the circumference, all of which are affected uniformly and
simultaneously by the pressure bevel 17. In order to make this movement
sequence, i.e. the displacement of the clamping part 5 by the clamping sleeve
25
as uniformly as possible, the balls of a ball bearing 30 are arranged between
the
front wall 28 of the clamping part 5 and the clamping wall 29 of the clamping
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sleeve 25 or clamping head 3. This minimises friction so that the necessary
forces
can be applied without problems by the external thread 27 on the protective
casing
9 and the internal thread 26 of the clamping sleeve 25, to ensure uniform,
simultaneous displacement of the pressure bevel 17 onto the pressure elements
16 or the balls 20.
When the lance tube 2 is inserted in the lance holder 1, the check valve 32
arranged between the sealing sleeve 6 and the backburn safety device 7 is
opened. At this point, the outside wall 8 or 23 of the sealing sleeve 6 has
not yet
been stressed by the wedge 22, so the lance tube 2 can easily be inserted
correspondingly far. When the stop 33 is reached, the check valve 32 is, as
described, displaced against the force of a spring so far that gas can now be
fed
into the lance holder 1, although the fixing measures have to be taken first.
Only
then can the gas flow 34 be released, which opens the non-return valve 36
arranged on the side 35 opposite the backburn safety device 7. For this
purpose, a
release and check valve not shown here must first be operated.
Fig. 3 shows the lance holder 1 with the lance tube 2 of the smallest diameter
in
the working position, i.e. non-return valve 36 can now be opened by the gas
flow
34, to allow the gas to flow through. The illustration in Fig. 3 emphasizes
that the
pressure elements 16 used in the form of balls 20 are advantageously suitable
for
exercising punctiform pressure on the lance tube 2 and fixing it securely.
Fig. 4 shows a lance holder 1 with a lance tube 2 of the largest possible
diameter,
17.5 mm, intended for this type of lance holder inserted. In comparison with
Fig. 2
it will be clear that the particular shape of the sealing sleeve 6 ensures
that secure
sealing still takes place at this considerably larger diameter. The wedge 22
is
pushed up far enough to achieve this, wherein the balls 20 can already
exercise
their fixing effect, although the pressure bevel 17 is only having a small
effect on
them. In contrast, it may be recognised from the illustration in Fig. 2 that
the balls
20 have only reached the secure position on the wall 18 by correspondingly far
displacement of the pressure bevel 17 of the clamping part 5.
The non-return valve 36 can also now be opened in the position shown in Fig. 4
by
opening the gas path, to allow the gas flow 34 to pass through the lance
holder 1
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and enter the lance tube 2.
Finally, Fig. 5 is a cross-section of a lance holder 1 in its relaxed state,
because no
lance holder 2 has yet been inserted.
The check valve 32 is moved into its closed position by the allocated spring
and
the stop 33, which is affected by the lance tube 2 to be inserted, is pushed
back
correspondingly far here. The lance tube 2 is inserted into the insertion
channel 37
as far as this stop 33 and the entire component then displaced so that the
check
valve 32 opens.
It may be seen from Fig. 5 that the balls 20 are borne in bores 38 so that
they may
be displaced at right angles to the longitudinal axis 15 of the lance tube 2.
This
particular embodiment makes precise fixation of the inserted lance tube 2
possible, including when lance tubes with the diameters shown in Fig. 4 or
Fig. 2
are to be introduced. Appropriately formed lance holders must be used for
other
diameters, the advantage of the lance holder according to the invention
predominantly being regarded as being that tube tolerances of 3-4 mm can be
handled safely, as aforementioned. It is also advantageous that the oxygen or
gas
can only flow if the lance tube 2 is pushed into lance holder 1 as far as the
stop 33.
The lance holder 1 has a considerably reduced overall weight and a very
compact
design. The clamping head 3 is hardened and can have a long useful life. It is
also
advantageous that the lance holder 1 can be assembled and dismantled easily,
making it particularly well suited to work in the iron and steel industries.
lo
