Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
1999-06-15
2002-09-10
Dunn, Tom (Department: 1725)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S452000, C164S437000, C164S151500, C164S154100
Reexamination Certificate
active
06446704
ABSTRACT:
TECHNICAL FIELD
This invention pertains to a non-ferrous metal mold plug activation system and bleedout detection and plug off system, which stops the flow of metal during predetermined conditions, such as during the initial introduction of molten metal to the molds or in the event a bleedout is detected in the mold.
BACKGROUND OF THE INVENTION
Metal ingots and billets are typically formed by a casting process, which utilizes a vertically oriented mold situated above a large casting pit beneath the floor level of the metal casting facility. The lower component of the vertical casting mold is a starting block mounted on starting block pedestals. When the casting process begins, the starting blocks are in their upward-most position and in the molds. As molten non-ferrous metal is poured into the mold and cooled, the starting block is slowly lowered at a pre-determined rate by a hydraulic or pneumatic cylinder or other device. As the starting block is lowered, solidified non-ferrous metal or aluminum emerges from the bottom of the mold and ingots or billets are formed.
While the invention applies to casting of metals in general, including without limitations aluminum, brass, lead, zinc, magnesium, copper, steel, etc., the examples given and preferred embodiment disclosed are for aluminum, and therefore the term aluminum will be used throughout for consistency even though the invention applies more generally to metals.
While there are numerous ways to achieve and configure a vertical casting arrangement,
FIG. 1
illustrates one example. In
FIG. 1
, the vertical casting of aluminum generally occurs beneath the elevation level of the factory floor in a casting pit. Directly beneath the casting pit floor
1
a
is a caisson
3
, in which the pneumatic or hydraulic cylinder barrel
2
for the hydraulic cylinder is placed.
As shown in
FIG. 1
, the components of the lower portion of a typical vertical aluminum casting apparatus, shown within a casting pit
1
and a caisson
3
, are a hydraulic cylinder barrel
2
, a ram
6
, a mounting base housing
5
, a platen
7
and a starting block base
8
, all shown at elevations below the casting facility floor
4
.
The mounting base housing
5
is mounted to the floor
1
a
of the casting pit
1
, below which is the caisson
3
. The caisson
3
is defined by its side walls
3
b
and its floor
3
a.
A typical mold table assembly
10
is also shown in
FIG. 1
, which can be tilted as shown by hydraulic cylinder
11
pushing mold table tilt arm
10
a
such that it pivots about point
12
and thereby raises and rotates the main casting frame assembly, as shown in FIG.
1
. There are also mold table carriages which allow the mold table assemblies to be moved to and from the casting position above the casting pit.
FIG. 1
further shows the platen
7
and starting block base
8
partially descended into the casting pit
1
with billet
13
being partially formed. Billet
13
is on starting block
14
, which is mounted on pedestal
15
. While the term starting block is used for item
14
, it should be noted that the terms bottom block and starting head are also used in the industry to refer to item
14
, bottom block typically used when an ingot is being cast and starting head when a billet is being cast.
While the starting block base
8
in
FIG. 1
only shows one starting block
14
and pedestal
15
, there are typically several of each mounted on each starting block base, which simultaneously cast billets, special shapes or ingots as the starting block is lowered during the casting process.
When hydraulic fluid is introduced into the hydraulic cylinder at sufficient pressure, the ram
6
, and consequently the starting block base
8
, are raised to the desired elevation start level for the casting process, which is when the starting blocks are within the mold table assembly
10
.
The lowering of the starting block base
8
is accomplished by metering the hydraulic fluid from the cylinder at a pre-determined rate, thereby lowering the ram
6
and consequently the starting blocks at a pre-determined and controlled rate. The mold is controllably cooled during the process to assist in the solidification of the emerging ingots or billets, typically using water cooling means.
There are numerous mold and casting technologies that fit into these mold tables. Some are generally referred to as “hot top” technology, while others are more conventional casting technologies that use floats and downspouts, both of which are known to those of ordinary skill in the art. The hot top technology generally includes a refractory system and molten metal trough system located on top of the mold table, whereas the conventional pour technology involves suspending or supporting the source of molten metal above the mold table and the utilization of down spouts or tubes and floats to maintain the level of molten metal in the molds while also providing molten metal to the molds.
These different casting technologies have different advantages and disadvantages and produce various billet qualities, but no one of which is required to practice this invention.
The metal distribution system is also an important part of the casting system. In the two technology examples given, the hot top distribution trough sits atop the mold table while the conventional pouring trough is suspended above the mold table to distribute the molten metal to the molds.
Mold tables come in all sizes and configurations because there are numerous and differently sized and configured casting pits over which mold table are placed. The needs and requirements for a mold table to fit a particular application therefore depends on numerous factors, some of which include the dimensions of the casting pit, the location(s) of the sources of water and the practices of the entity operating the pit.
The upper side of the typical mold table operatively connects to, or interacts with, the metal distribution system. The typical mold table also operatively connects to the molds which it houses.
When non-ferrous metal is cast using a continuous cast vertical mold, the molten metal is cooled in the mold and continuously emerges the lower end of the mold as the mold table is lowered. The emerging billet, ingot or other configuration is intended to be sufficiently solidified such that it maintains its desired shape. There is an air gap between the emerging solidified metal and the permeable ring wall. Below that, there is also a mold air cavity between the emerging solidified metal and the lower portion of the mold and related equipment.
Conditions may develop during the casting process which cause the molten aluminum to pass through the mold without sufficiently solidifying, such that instead of solidified metal emerging, molten metal leaks through. This is referred to as bleedout or breakout and not only creates a very dangerous condition, but causes substantial economic loss due to the physical damage that results and the downtime to the production line.
Systems directed to preventing or minimizing the effects of the bleedout situation must operate under very harsh conditions in the casting environment, conditions such as high heat, steam, exposure to molten metal, and exposure to corrosive elements in the air, to name a few.
Originally, workers were exposed to the dangerous bleedout condition because they were required to manually plug the mold entrance to prevent the further flow of molten metal through the mold experiencing the bleedout condition.
Other prior systems have been developed to attempt to remedy the well recognized problem. One example of such a prior system utilizes a relatively complicated optical sensor system which detects the presence of metal in the mold air cavity optically. Once a blockage is detected between a sensor positioned in the upper portion of the air gap and a sensor positioned in the lower portion of the air gap, a signal is sent to a controller. The optical sensors may also be positioned to detect molten metal in the mold air cavity. The controller generally receives the signal, interprets i
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