Metallurgical apparatus – With means treating or handling gases exhausted by treating... – Hood
Reexamination Certificate
2002-03-14
2003-08-05
Andrews, Melvyn (Department: 1742)
Metallurgical apparatus
With means treating or handling gases exhausted by treating...
Hood
C266S271000, C266S236000, C222S604000
Reexamination Certificate
active
06602461
ABSTRACT:
BACKGROUND OF THE INVENTION
When copper is melted under ambient conditions, the pourable melt tends to take up from the ambient air gases that can disadvantageously influence the material's properties. Although the pourable melt can be covered by, for example, charcoal or carbon black, experience indicates that contact with ambient air is not completely prevented. A number of possibilities have therefore been presented in the existing art in order nevertheless to prevent gas uptake from the ambient air.
German Patent 41 36 085 C2 proposes that in the production of oxygen-free copper wire, the melting and pouring operation be made to take place in a shielding gas atmosphere. For that purpose, provision is made to enclose a melting furnace, a downstream holding furnace, a launder, and a pouring trough in a housing, and to operate these devices in a shielding gas atmosphere. For this purpose, all the devices are to be as completely sealed as possible, and can be inductively heated as opposed to the otherwise usual gas heating.
European Patent 0 352 356 B1 describes a method for continuous casting of steel in an atmosphere of an inert nontoxic gas such as argon; the pouring operations during which the liquid steel is in contact with this atmosphere are performed in a sealed, oxygen-free chamber. The technical outlay for setting up such a chamber is considerable, and moreover associated with the disadvantage that only with special breathing apparatus is it possible for operating personnel to enter the chamber to control the pouring process.
European Patent 0 259 772 B1 discloses an arrangement for pouring a copper alloy having an outflow tube leading to a pouring trough, the pouring trough and outflow tube each being enclosed by a hermetically sealable housing in which a non-oxidizing atmosphere made up of a shielding gas is present.
It is not unproblematic to transfer a pourable melt from a melting furnace into downstream arrangements without major losses of the shielding gas atmosphere due to leakage. In this connection, GB 1,181,518 proposes the use of a hearth-type melting furnace, mounted on rollers and having a horizontal longitudinal axis, in which upon pivoting, the melt emerges from the hearth-type melting furnace at the end in the direction of the longitudinal axis. A pouring tube, movably mounted in a gas-tight joint for transferring the pourable melt, allows relative motion of the hearth-type melting furnace with respect to the downstream arrangements without admitting oxygen.
OBJECTS OF THE INVENTION
Proceeding from the existing art, it is the object of the invention to create an arrangement for pouring a pourable melt made up of a copper alloy which makes possible the pouring of copper alloys with little gas uptake and oxide contamination, and which can be coupled with relatively little complexity to a wide variety of melting furnaces that are tiltable about a horizontal pivot axis.
According to the present invention, the achievement of this object encompasses a melting furnace that is pivotable about a horizontal pivot axis, having a pouring tube which discharges a pourable melt and through which the pourable melt can be conveyed under a shielding gas atmosphere to a filling end of a launder. The pourable melt passes out of the launder through an outlet into a downstream mold. What is essential to the invention is that at least the filling end of the launder can be covered by a hood that seals off the pourable melt from the atmosphere, the hood being arranged in principle detachably from the launder. A seal arrangement that is arranged between the pouring tube (which engages in pivotably movable fashion into the hood) and the hood is important in this context. This seal arrangement ensures that upon pivoting of the melting furnace, the pourable melt can be transferred into the launder in a shielding gas atmosphere.
Considerable demands are made on the seal arrangement, since it must be very robust and reliable for pouring operations. The invention advantageously takes into consideration the fact that gas uptake, in particular oxygen, occurs predominantly during filling of the launder, but that oxygen can also be taken up from atmospheric moisture and the launder environment as flow occurs through the launder. These sensitive regions of the pouring arrangement are now protected in technically advantageous fashion by the apparatus according to the present invention. In order to maintain a shielding gas atmosphere, it is necessary in principle in this context to equip the melting furnace, which preferably is an induction furnace, with a gas-tight furnace cover. The most difficult region in terms of sealing technology, however, is the pouring tube engaging in pivotably movable fashion into the hood, which in order to minimize the leakage of shielding gas must be sealed with respect to the hood in every angular position that is provided for.
For that purpose, according to the invention a two-part seal arrangement can preferably be provided, encompassing an upper seal unit provided above the outflow tube and a lower seal unit located below the outflow tube.
An advantageous approach to implementing the sealing units is the seal arrangement having at least one seal unit, associated with the pouring tube, whose surface describes a circular arc about the pivot axis upon pivoting of the melting furnace. For that purpose, the pivot axis of the melting furnace must lie in the region of the seal arrangement.
Suitable in particular as seal units pivotable with the pouring tube are those having an at least partially rotationally symmetrical surface shape. These can be cylindrical segments or hollow cylindrical segments. Spherical segments are also suitable; advantageously, these make possible a further degree of freedom of the seal arrangement. The aforesaid cylindrical or hollow cylindrical segments and spherical segments can be guided in oppositely matching receptacles of the hood; the emergence of shielding gas can be reliably prevented by way of a corresponding gap seal between the hood and the seal unit. Alternatively, a seal element similar to a wiper can be positioned on the hood; the surface of the rotationally symmetrical seal unit moves along this upon pivoting, and seals the hood against shielding gas leakage.
A further advantageous approach is having the seal unit configured as a collar having a seal element at the rim. In the simplest case this can be a plate whose radially external end describes a circular arc (when viewed in cross section) upon pivoting, and which, with an incorporated seal element, is guided in the hood in a receptacle of oppositely matching configuration, i.e. a receptacle of circular arc shape.
In one embodiment, at least one seal unit encompasses a flexible packing seal made of a heat-resistant material.
In addition, the packing seal can be held in a special receptacle so that it can better adapt at all times to the pivoting motion of the pouring tube.
In another embodiment at least one seal unit is configured as a flexible mat made of heat-resistant material. The mat can be made of a textile or felt. Also alternatively conceivable are individual heat-resistant plates that are flexibly interconnected by joints. Because of the flexibility of such mats, it is not absolutely necessary to arrange them above and below the pouring tube. If installation conditions allow, they can also be arranged to the sides of the pouring tube.
In one embodiment, at least one seal unit is configured as a bellows or bellows tube; this of course must be made of a heat-resistant material. A “bellows tube” is also to be understood as a corrugated tube, made of metal or another material, that possesses sufficient flexibility for use as a seal unit.
In another embodiment, the pouring tube is subdivided into two portions of which a first portion is associated with the melting furnace and a second portion with the hood. The two portions can be coupled to one another via an intermediate seal. Although the pouring tube can fundamentally be configured in one piece, two-part
Brüning Hubertus
Frankenberg Ralph
Hecht Meinhard
Helmenkamp Thomas
Krause Andreas
Andrews Melvyn
Kenyon & Kenyon
KM Europa Metal AG
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