[0001] The present invention relates to a power supply cable for arc furnaces.
[0002] It is known that the supply of electric power to arc furnaces, which are used particularly
for the production of steel and of ferrous alloys, is performed by means of appropriately
designed cables which connect a transformer to electrode-bearing arms located at the
cover of said furnaces and arrange themselves in a sagging configuration due to their
own weight.
[0003] Said cables comprise a plurality of water-cooled plaits which conduct the electric
current, are connected to two terminals and are contained in a tube which is made
of an elastic material, such as rubber, extending from one of said terminals to the
other.
[0004] In the known art, said rubber tube is clamped at its ends on heads which are comprised
within the terminals, so that it cannot perform any movement with respect to said
heads, and this fact is the cause of rather unsatisfactory functional situations.
[0005] It is in fact known that when the cover of the furnace is opened, the electrode-bearing
arms rotate about a vertical axis which causes a rotation of the terminal of the cable
which is connected thereto, whereas the terminal of the cable which is connected to
the transformer remains fixed; this leads to a torsion of the cable with all of its
components, i.e. with the current-conductive plaits and with the rubber covering tube,
which is unfavorable both as regards the strength of said tube and as regards the
force to which the structures of the furnace are subjected.
[0006] The aim of the present invention is therefore to provide a power supply cable for
arc furnaces which allows to obtain improved functional conditions but maintains great
constructive simplicity.
[0007] The proposed aim is achieved by a power supply cable for arc furnaces, according
to the invention, which comprises water-cooled current-conductive plaits which are
connected to two terminals and are contained in a tube which is made of a rubber-like
material extending from one of said terminals to the other, characterized in that
said tube is clamped, at at least one terminal, on a bush which is associated with
a head of said terminal so that it can rotate.
[0008] Further characteristics and advantages will become apparent from the description
of a power supply cable for arc furnaces, illustrated only by way of non-limitative
example in the accompanying drawings, wherein:
figure 1 is a view of a terminal of a cable according to the invention, shown partially
in cross-section with the locking straps not yet tightened and partially in a side
view with said straps tightened;
figure 2 is a schematic view of a cable according to the invention during use in two
different positions, one indicated in solid lines and the other one indicated by dot-and-dash
lines.
[0009] With reference to the above figures, the reference numeral 1 generally designates
a power supply cable for an arc furnace, which is intended to connect the output of
a current transformer 2 to an electrode-carrying arm 3.
[0010] While the terminal 4 of the cable 1 which is connected to the output of the transformer
2 is of a conventional type, the terminal 5 connected to the electrode-carrying arm
3 is executed according to the invention and is described in detail with reference
to figure 1.
[0011] Within said terminal, is thus noted the presence of the head, generally designated
by the reference numeral 6, which comprises a milled portion 6a which has a rectangular
cross-section, a cylindrical portion 6b, a first ridge 6c and a second ridge 6d to
which the current-conductive plaits, such as 7, converge.
[0012] The reference numeral 8 furthermore designates a tube, made of an elastic material
such as rubber, which extends from one to the other of said terminals 4 and 5 of the
cable 1 while it is locked on the head of the terminal 4 in a conventional manner,
so that it is unable to perform any movement with respect thereto, it is associated
with the head 6 of the terminal 5 with the interposition of the bush 9, which is suitable
for rotating about the axis of the portion 6b of said head.
[0013] More precisely, said tube 8 is locked on the outer surface of the bush 9 by means
of the clamps 10, 11 and 12 which are arranged at regions delimited by the circumferential
ridges provided on said surface.
[0014] Seats for containing the gaskets 13 for providing a seal against the water for the
cooling of the current-conductive plaits are provided at the inner surface of the
bush 9; in a known manner, by means of ducts not shown in the figure, said water reaches
the space portion 14 delimited by the ridges 6c and 6d of the head and by the tube
8.
[0015] Finally, the reference numeral 15 designates a non-magnetic steel ring which is inserted
between the brass bush 9 and the ridge 6c of the head 6, which is made of copper,
in order to protect the surfaces of said elements against excessively rapid wear.
[0016] From what has been described it is evident that the functional condition which the
invention allows to provide is optimum: in fact, when the electrode-carrying arm 3
rotates upon the opening of the furnace cover, moving the cable 1 from the position
shown in solid lines in figure 2 to the position shown in dot-and-dash lines, the
head of the terminal 5 performs the rotation about its own axis shown in said figure
2, producing torsion of the assembly of the electric power-conductive plaits but not
of the tube 8, since a relative rotation, allowed by the bush 9, occurs between said
tube and said head.
[0017] The tube 8 is thus not subjected to torsion, as occurs in known cables, and this
leads to greater durability of said tube and to a reduction of the stresses induced
in the structures of the furnace; possible negative effects of the torsion of the
tube 8 on the assembly of the electric power-conductive plaits are also eliminated.
[0018] In the practical execution of the invention, all the details may be replaced with
other technically equivalent elements; the materials employed, as well as the shapes
and dimensions, may furthermore be any.
[0019] Where technical features mentioned in any claim are followed by reference signs,
those reference signs have been included for the sole purpose of increasing the intelligibility
of the claims and accordingly such reference signs do not have any limiting effect
on the scope of each element identified by way of example by such reference signs.
1. Power supply cable for arc furnaces, comprising water-cooled current-conductive plaits
which are connected to two terminals and are contained in a tube which is made of
a rubber-like material and extends from one of said terminals to the other, characterized
in that said tube is clamped, at at least one terminal, on a bush which is associated
with a head of said terminal so that it can rotate.
2. Cable according to claim 1, characterized in that said bush has, at its inner surface
which is intended for contact with the head of the cable terminal, seats for containing
gaskets for providing a seal against the water for the cooling of said cable, and
is provided, at its outer surface, with circumferential ridges which are suitable
for delimiting regions at which said tube is suitable for being secured by means of
locking clamps.
3. Cable according to one or more of the preceding claims, characterized by the presence
of a ring made of non-magnetic steel interposed between the surface of the bush which
is directed toward the cable and a ridge of the head of the terminal of said cable
with which said bush is associated.