Dispensing – Molten metal dispensing – Flow controllers or assists
Patent
1993-07-06
1997-02-18
Kastler, Scott
Dispensing
Molten metal dispensing
Flow controllers or assists
222594, 266236, B22D 4108
Patent
active
056038593
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to the casting of molten metal and in particular to vessels for molten solids, e.g. molten metal, and to outlets for said vessels.
Problems occur when molten solids are poured through an outlet from a vessel, for example when pouring molten metal. In a foundry, it is known to fit an outlet through the floor of a vessel for molten metal, e.g. a foundry ladle, and to provide a so-called stopper rod above the vessel. The rod is lowered or raised to close or open the outlet. The rod comprises a metal shaft surrounded by a refractory sleeve. This arrangement has disadvantages. For example, the rod becomes distorted in use; if it is used as a throttle, the stream of metal breaks up affecting the quality of the casting; and there is a relatively long turn around period when changing the refractory sleeve of the stopper rod.
An alternative device is a so-called sliding gate valve. This is mounted externally below the bottom outlet and is used on bulk steel ladles where the liquid metal is discharged in a few pours. In the foundry, however, the outlet is opened and closed a greater number of times and there can be long intervals between one opening and the next. When the sliding gate valve is closed, a slug of metal forms in the outlet above the closed valve and is unable to circulate, even though it is communication with the bulk of the molten metal, and the slug tends to freeze if the time between successive pours is too great. This causes metal to freeze on the sliding gate valve which is thus not suitable for use with foundry ladles. The sliding gate valve is also not without problems in relation to liquid steel which is particularly prone to this "freezing-off" and there is thus a serious risk of valve blockage.
It has been realised that there should be advantages in having a rotary valve mechanism instead of a stopper rod system or a sliding gate valve system. The mechanism comprises a valve in a seating therefor in the vessel outlet. A passage is present in the valve member which has inlets in the head portion thereof. A drive mechanism is present outside the vessel and used to rotate the valve member with respect to the seating member therefor, the seating member being shaped so that when in one position the inlet is closed off and in another open. Such a system is disclosed in WO88/05355 published in July 1988; in GB-A-2226263 published in June 1990; and in WO 90/14907 published in December 1990. More specifically, GB-A-2226263 discloses an outlet comprising a rotary valve member and a seating therefor, the valve member having at least one passage for conducting molten solid from inside to outside the vessel, the valve member sealing with a wall of the seating member, the wall having a first section sufficiently high that when the valve member is rotated to align an inlet end of the passage therewith the passage is closed by the first section, the wall having a second section of less height so that if the valve member is rotated to align the inlet end of the passage therewith, the inlet end is open. The outlet is normally installed so that the top of the second section of the wall is level with the inside surface of the floor of the vessel. The first section does not extend round the periphery of the wall significantly further than necessary to close the outlet. The majority of the valve member is therefore exposed so that, in contrast to the conditions when a sliding gate valve is closed, the molten metal is able to circulate around the closed valve member and there is no slug of trapped metal liable to freeze between pours.
In each of these prior disclosures, insufficient attention has been paid to the practical problems of operating such a rotary valve mechanism. It has now been discovered that in order to reliably and repeatedly rotate the valve member it is necessary to shape the sealing faces as described herein and arrange the valve so that there are no dead zones wherein molten solid can be trapped; and preferably also shape the exit p
REFERENCES:
patent: 3651998 (1972-03-01), Rocher
patent: 3760992 (1973-09-01), Bieri
patent: 4200210 (1980-04-01), Riegler et al.
patent: 4840295 (1989-06-01), Hartley
patent: 4932570 (1990-06-01), Gimpera
Foseco International Limited
Kastler Scott
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