[0001] The present invention refers to a device to collect and dump the smoke and dust generated
during a scarfing operation of slabs.
[0002] It is well known that slabs, and other metallurgical semifinished products in general,
must be scarfed before any successive operations, that is to say, the defective surface
material must be removed.
[0003] This is done by means of a 100 mm diameter torch, which, through the spark-starting
of a voltaic arc, forms a bath of molten steel on the surface, which it pushes along
the entire slab surface, by the pressure of the oxygen and the longitudinal traverse
of the apparatus. The transverse and longitudinal inclinations of the nozzle render
such an operation easy.
[0004] should be noted that such scarfing operation is carried out by sliding the scarfing
head described above, along two rails located on the sides of a bench, or of a supporting
surface on which the slabs to be scarfed are arranged. It is known that, in order
to remove the dust and smoke generated by the scarfing operation from the working
area, the operating head is equipped with a hood, integral to said operating head
while the latter moves. Said hood is placed over the slab surface to be scarfed, and
is connected to a sliding seal, acting as a hood, which directs the smoke and dust
into a manifold directly connected to the exhaust fan.
[0005] The above described known device has the drawback that it sucks in and removes from
the working area only a part of the dust and smoke generated during the scarfing operation.
The residual dust and smoke, thus, remain in the working area, negatively affecting
the working conditions; further damages to machinery in the working area are to be
ascribed to the effects of the smoke and dust which have not been sucked in by the
hood.
[0006] t Hence, the purpose of the present invention is to eliminate such drawbacks, by
using a retractable tunnel of a particular shape, which can move together with the
operating head and makes it possible to collect all the dust and smoke generated during
the scarfing operation.
[0007] Moreover, as such dust and smoke often cause the plant to be stopped because of the
impossibility for the staff to work there, therefore causing a loss in production,
the present invention is a thorough solution to said problems.
[0008] It should also be remembered that scarfing is very noisy (because of the oxygen blast)
and the retractable tunnel has also the function of lowering noise level.
[0009] The retractable tunnel, according to the invention is secured at one end to a wall
placed near the end of the bench and on which the suction duct begins for the smoke
sucked in by a suitable exhaust fan. At its other end, the retractable tunnel is secured
to the scarfing head by means of a firm metal structure, and follows its movement,
contracting while said head operates and expanding when it goes back to its start
position for a new operation cycle.
[0010] The retractable tunnel according to the invention has the shape of a bellow, suitably
supported.
[0011] The essential characteristics of the invention are summed up and described in the
claims; its advantages and objects will also be discussed in the following specification,
with respect to embodiments chosen by way of example only and with particular reference
to the enclosed drawings, in which:
Figure 1 shows a side perspective view of the retractable tunnel according to the
invention, in the expanded position;
Figure 2 shows a top view of the retractable tunnel according to the invention, in
the closed position;
Figure 3 shows a longitudinal vertical section view of one of the two side raceways
in which the bottom parts of the tunnel sides project, so as to form a hydraulic seal
against the flow of smoke. Said figure dealing in particular with the means necessary
to remove the dust and deposits which continuously settle in said raceways;
Figure 4 shows a view of the scarfing head according to plane IV-IV figure 2;
Figure 5 and 6 show a cross section of two possible positions of the above mentioned
raceways.
[0012] With particular reference to figure 1, 2 and 3: 10 indicates a long shaped base on
which the slabs to be scarfed are to be placed; said base 10 has, on its sides, two
rails 11, on which the supporting means of the scarfing head and of the bellow shaped
retractable tunnel slide, all of which having reference number 20.
[0013] Along the internal side of the two tracks 11, there are two raceways 12 full of water,
in which the lower parts of the retractable tunnel 20 project, so as to form a hydraulic
seal.
[0014] The retractable tunnel 20 is formed by a number of folds 21, made of fire and abrasion
proof material. It results in a bellow shape which enables the retractable tunnel
to change from the expanded position, shown in figure 1, to the contracted position
shown in figure 2
[0015] In order for it to stiffen up transversally, the bellow shaped retractable tunnel
is provided with frames 22, substantially shaped like an upside down U, located at
pre-set spaces, for example, constant ones.
[0016] Said frames are connected to joints 32 of the articulated arms 32 of a pair of pantographs
30, placed at both sides of the tunnel. Joints 32 of arms 31 suitably slide along
frames 22 of the bellow shaped retractable tunnel.
[0017] Furthermore, the bellow shaped retractable tunnel 20 is suspended from a pair of
portals 40, provided with feet 41, which, by means of wheels 42 move along said rails
11. Arms 31 and joints 32 of pantograph 30 allow for uniform length variations of
the retractable tunnel.
[0018] The bellow shaped retractable tunnel is also supported on its front part, by the
supporting frame 60 of the scarf ing head, said frame being supported by a carriage
61, provided with moving equipment.
[0019] On its rear part, which is fixed, the retractable tunnel is secured to a wall, for
example a plain concrete wall 43, through which the dust and smoke suction duct 44
goes, which terminates against said wall.
[0020] The operation is therefore very simple: when the tunnel is in its contracted position
(see figure 2), slabs 70 to be scarfed are placed on base 10. As in its contracted
position the tunnel according to the invention has an extremely short length, depending
substantially on the size ¡of feet 41 of supporting portals 40, the area of the base
10 available for the slabs 70 to be scarfed is used in the best way.
[0021] When the slabs 70 to be scarfed are arranged, the retractable tunnel 20 and the scarfing
head 62 are pulled back to cover the slabs 70 which have just been arranged on base
10. The retractable tunnel 20 reaches here its maximum length (see figure 1).
[0022] The scarfing head 62 is then started, together with a fan, not shown in figure, which'sucks
in the smoke generated inside the tunnel, through duct 44 (see figure 1).
[0023] As the scarfing head 62 moves forward, the length of the tunnel 20 decreases until
it reaches the final position shown in figure 2.
[0024] As the lower ends of the side walls of the tunnel move in the water contained in
raceways 12, a perfect seal of the tunnel is obtained, preventing the dust and smoke
from leaking through into the working area surrounding the tunnel. .
[0025] The opening between the front part of the tunnel and the supporting and transporting
structure of the head, does not allow for a flow of smoke as, due to said fan, through
said opening a strong current of air flows in.
[0026] In figure 3 are shown the cleansing means for raceways 12: they consist of paddles
45 supported articulately by feet 41 of the mobile suspension portals of the tunnel.
[0027] Said paddles have a cross section which is substantially equal to the cross section
of the raceways 12. If the working direction of the scarfing head is that shown by
arrow F1, they are provided with pawl means preventing a rotation towards the right
beyond the vertical position shown in the right part of figure 3: in this way, they
gather the dust and deposits which settle on the bottom of raceways 12, and direct
them to a system of collection tanks and hydroseparators indicated schematically with
reference number 46.
[0028] As said paddles can freely rotate towards the left, with respect to figure 3, they
scrape the upper surface of the deposits settled in raceways 12, during the return
of the retractable tunnel from the position shown in figure 2 to the position shown
in figure 1 (see arrow F2 in figure 3).
[0029] Therefore, raceways 12 are cleaned automatically and continuously.
[0030] With particular reference to figures 1, 2 and 4: in order to protect the retractable
tunnel walls from the jets of red-hot material caused by the scarfing head work, the
latter is equipped with a side deflector 51, and with an upper deflector 52. Thus,
the jets of red-hot material caused by the scarfing head work, are deviated in the
longitudinal direction of the tunnel, so as to protect its side and upper walls.
[0031] Moreover, the part of the tunnel facing the scarfing head, is made of two suitably
hardened iron sheets: an upper iron sheet "53", and a side iron sheet "54".
[0032] In this way, the jets of red-hot material which the deflectors 51 and 52 might have
failed to intercept, would not touch the flexible walls of the tunnel bellow, but
said protection iron sheets 53 and 54.
[0033] Deflectors 51 and 52, and iron sheets 53 and 54 are placed only on one side, in view
of the fact that, as shown in figures 1, 2 and 4, the scarfing head faces downwards
and sideways.
[0034] With particular reference to figures 5 and 6, they show the two possible positions
of the guide rails 11 with respect to raceways 12, respectively 112.
[0035] The position of raceways 12, shown in figure 5, corresponds to the embodiment shown
in figures 1, 2 and 4, with the retractable tunnel frame external to the tunnel itself.
[0036] Such solution has the advantage that the tunnel supporting structures are protected
against dust'and jets of molten metal and slag caused by the scarfing head.
[0037] The solution shown in figure 6, on the other hand, would allow for an increase of
the distance between the tunnel walls and the slabs, thereby increasing the tunnel
wall durability.
1. Device to collect and dump the smoke and dust generated during a scarfing operation,
particularly of slabs, and other metallurgical, unfinished products, of the type providing
a supporting bench for the slabs to be scarfed and a scarfing head, sliding on rails
along said bench, in which suction means for the smoke and dust generated during the
scarfing operation are also provided, and characterized by the fact that it prbvides
a retractable tunnel., preferably in the shape of a bellow, secured on one of its
ends to one end of said bench, where the suction duct of a smoke exhaust fan is located,
and on its other end integral in its movement to a scarfing head, wherein suitably
supporting means for said retractable tunnel are located at pre-set spaces along the
tunnel.
2. Device, according to the previous claim, characterized by the fact that said bellow
shaped retractable tunnel is provided with hardening frames with the shape of an upside
down U, located at pre-set spaces, along whose sides the trunnions slide vertically,
trunnions which are placed on the ends of the arms of a pantograph, secured, on one
of its ends, to the fixed securing element of said tunnel, and, on its other side,
to the supporting and transporting structure of the scarfing head.
3. Device, according to the previous claims, characterized by the fact that said tunnel
is suspended from one or more portals, sliding on rails or pulled by the articulated
joints of the arms of said pantograph.
4. Device, according to the previous claims, characterized by the fact that the lower
parts of the retractable tunnel side walls project into two raceways filled with water,
so as to create a hydraulic seal.
5. Device, according to the previous claims, characterized by the fact that said sliding
portals are equipped with inclinable paddles which, when the tunnel is contracting,
scrape the bottom.of said raceways, removing the deposits, while, when the tunnel
is expanding, fold back freely upwards, so as to drag the deposits from said raceways
in one direction only.