Filter indexing apparatus for filtering molten metal

An apparatus and method for filtering molten metal are disclosed. The apparatus utilizes a continuous filtering medium that is serially indexed into the metal filtering area. The apparatus may be used to filter ferrous and non-ferrous metals, and provides significant cost and time savings. In one embodiment the apparatus allows automatic indexing of a new filter for each shot or pour on high production casting machines. In another embodiment the apparatus is adapted to filter large amounts of metal up to 5,000 pounds or more.

FIELD OF THE INVENTION 
The present invention relates to the filtration of molten metal. More 
particularly, the invention relates to an apparatus and method for 
filtering ferrous and nonferrous molten metals using a continuous 
filtering medium that is serially introduced into a molten metal stream. 
BACKGROUND OF THE INVENTION 
Filtration of molten cast metals has been demonstrated to be an effective 
method of improving overall casting quality. Filtration enhances the 
mechanical and physical properties of castings by removing inclusions from 
the molten metal before they can enter the mold cavity. 
There are numerous applications in foundry practice where quantities of 
molten metal are poured repetitiously into holding furnaces for 
replenishment of metal used, into die casters for each shot and in pigging 
operations. Those foundry operations that require repetitive or automatic 
pouring of molten metals, especially aluminum, into casting machines such 
as die-casters and permanent mold casting operations cannot easily utilize 
filters in their gating systems. Therefore the metal is usually filtered 
in a holding furnace dip-well prior to being poured into the machine. 
These operations typically utilize a robot to dip into the furnace 
dip-well and then pour the metal into the casting machine. Aluminum is 
usually the metal cast in these operations, and even though it is filtered 
in the holding furnace it will form dross or oxides immediately upon 
exposure to the air as it is dipped out of the dip-well. Being able to 
filter the metal as it is being poured into a casting machine would be a 
great advantage. Most of these operations are also high production. For 
example, die-casting machines typically make 30 to 60 shots per hour. 
These operations would benefit greatly by having a new filter 
automatically positioned for filtration of each shot or pour. 
There are also many operations, especially in foundries, where batch 
quantities of molten metal are treated with master alloys, ferroalloys and 
inoculants that create reaction products such as oxides, sulfides and 
slags. These impurities cause many problems in holding furnaces such as 
slag build-up on furnace walls and pouring nozzle clogging, which result 
in costly down time and excessive maintenance. 
In highly automated ductile iron foundries high production molding machines 
are used that make a mold every 10 to 15 seconds. The holding furnaces 
that feed metal to these molding lines are typically replenished with 1200 
to 3000 pounds of ductile iron every 10 to 30 minutes. Batch treated 
ductile iron is also transferred from the treatment ladle into smaller 
pouring ladles. Filtering the metal at this stage would result in much 
less maintenance of the pouring ladles plus provide cleaner metal to the 
mold line. 
Ceramic filters are extensively used in the foundry industry to improve 
casting cleanliness and to reduce the number of castings that must be 
scrapped due to the presence of unwanted impurities. Such ceramic filters 
are typically incorporated into the gating system in order to remove slag, 
dross, and other particles from the metal stream before the metal enters 
the mold cavity. The most common types of ceramic filters comprise 
hard-fired cellular ceramic structures and rigid reticulated ceramic foam. 
These filters are relatively thick and, due to their massive structure, 
tend to chill the first molten metal that reaches the filter, requiring 
relatively coarse openings to ensure reliable passage of the molten metal. 
Cellular extruded ceramic filters therefore rely on the formation of a 
filter cake on the upstream side to remove smaller inclusions that would 
otherwise pass through the openings in the filter. Ceramic foam filters, 
while providing a more tortuous path for the molten metal than cellular 
filters, also exhibit the formation of a filter cake which can become the 
controlling factor for the size of the inclusions that the filter will 
remove. 
Recently, refractory cloths made from materials such as fiberglass and 
silica have been used as metal filtration media. The most common 
refractory cloth for filtering high temperature ferrous metals comprises 
woven silica fibers. U.S. Pat. No. 5,124,040 to Hitchings, which is hereby 
incorporated by reference, discloses a silica cloth filter having a 
carbonaceous coating that produces improved filtering characteristics. 
Conventional molten metal filters are typically only able to be used once 
because of the impurities that they collect and because the molten metal 
solidifies around them after the pouring operation, particularly when they 
are used in mold gating systems. Prior art hard-fired ceramic filters and 
ceramic cloth filters are usually placed by hand before each pouring 
operation, adding significantly to processing costs. Conventional molten 
metal filtering apparatuses incorporating ceramic filters are disclosed in 
U.S. Pat. Nos. 5,202,081 to Lake et al., U.S. Pat. No. 4,990,059 to James, 
and U.S. Pat. No. 4,159,104 to Dantzig et al. 
At the present time there is no commercially available filtration equipment 
to automatically filter significant quantities of metal with automatic 
replacement of the filter media, particularly as the metal flows into a 
holding furnace or pouring ladle. The present invention has been developed 
in view of the foregoing and to overcome other deficiencies of the prior 
art. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a novel apparatus for 
filtering molten metal. 
Another object of the present invention is to provide an apparatus for 
filtering molten metal comprising an inlet for supplying molten metal, an 
outlet in communication with the inlet for receiving molten metal, a 
molten metal filter disposed between the inlet and outlet, and means for 
serially indexing portions of the molten metal filter into an area between 
the inlet and outlet to filter the molten metal. 
A further object of the present invention is to provide a novel method for 
filtering molten metal. 
Another object of the present invention is to provide a method for 
filtering molten metal comprising providing a flow of molten metal, 
contacting the molten metal with a portion of a molten metal filter, 
stopping the flow of molten metal, indexing another portion of the molten 
metal filter into the area of molten metal flow, continuing the flow of 
molten metal, and contacting the molten metal with the new portion of the 
molten metal filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings in detail, wherein like reference numerals 
represent like elements throughout the several figures, FIG. 1 shows a 
partially schematic side view of a molten metal filtering apparatus 10 in 
accordance with one embodiment of the present invention. The apparatus 10 
includes a generally tubular inlet member 11 comprising a flange portion 
12. As shown most clearly in FIG. 2, the inlet member 11 comprises a 
lining 13 that is preferably made of a refractory material such as 
magnesia (MgO), alumina (Al.sub.2 O.sub.3), silica (SiO.sub.2) or the 
like. 
The apparatus 10 also includes a generally tubular outlet member 15 
including a flange portion 16. As shown most clearly in FIG. 2, the outlet 
member 15 includes a refractory material lining 17 made of any suitable 
refractory material, as noted above. The outlet member 15 is preferably 
connected to a base member 20 by any suitable fastening means. As shown in 
FIG. 2, the outlet member 15 may be connected to the base member 20 by 
means of a casing 19 and fastening members 21 such as bolts. The casing 19 
may be connected directly to the flange 16 of the outlet member 15, or may 
be connected to an intermediate plate 18. The casing 19 may contain a 
refractory material 22 that extends into a cutout portion 28 of the base 
member 20. While the refractory lining 17 and refractory material 22 are 
shown as separate pieces in FIG. 2, it is recognized that a single piece 
of refractory material could be used. 
The inlet member 11 is preferably fastened to a plate member 30 that is 
adapted to move away from the base member 20 in order to allow a new 
portion of filter material to be advanced or indexed through the 
apparatus, as discussed more fully below. As shown most clearly in FIGS. 3 
and 5, the inlet member 11 may be fastened to the plate member 30 by means 
of fasteners 35 extending through the flange 12. The fasteners 35 may be 
bolts, rivets or any other type of suitable fastener. The plate member 30 
includes a plurality of hollow cylindrical washers 31 of generally 
T-shaped cross section adapted to slidably receive a plurality of bolts 32 
which are fastened to the base member 20. Biasing members 33 are disposed 
between the heads of the bolts 32 and the cylindrical washers 31 in order 
to force the plate member 30 toward the base member 20. While the biasing 
members 33 are shown schematically as spiral springs in the figures, other 
suitable biasing members such as leaf springs, hairpin springs, compliant 
materials such as high temperature polymers and the like may be used. 
Furthermore, the plate member 30 may be biased toward the base member 20 
by the force of gravity, without the requirement of a specific biasing 
element. 
The plate member 30 may include downwardly extending projections 34 as 
shown in FIGS. 1, 3 and 4. The projections 34 extend through cutout 
portions 29 in the base member 20, and include cam surfaces adapted for 
raising the plate member 30 away from the base member 20, as more fully 
discussed below. 
While the base member 20 is shown as a relatively flat member in FIG. 1, it 
is preferred to provide the base member 20 with reinforcements for 
preventing distortion of the shape of the base member 20 during the molten 
metal filtering operation. For example, as shown in FIG. 6, the base 
member 20 may be provided with downwardly extending edge portions 26 and 
27 that provide structural rigidity to the base member, thereby preventing 
warping upon exposure to the increased temperatures associated with molten 
metal filtration. FIG. 6 also shows the cutout portions 28 and 29 in the 
base member 20. As discussed previously, the cutout portion 28 is adapted 
to receive a portion of the refractory material 22, as shown in FIG. 2, 
while the cutout portions 29 are adapted to receive the downwardly 
extending projections 34 of the plate member 30, as shown in FIG. 3. 
The components of the present apparatus, such as the base member 20, plate 
member 30, etc., may be made from any suitable material, with high 
temperature steels being particularly preferred due to their ability to 
withstand elevated temperatures and their relatively low cost. Components 
such as the refractory linings 13 and 17 that contact the molten metal 
during the filtering operation must be capable of withstanding 
temperatures at least as high as the melting point of the metal being 
filtered, and preferably well above the melting point of the metal in 
order to allow for superheating of the metal. Thus, depending on the type 
of metal to be filtered, the metal-contacting components are selected such 
that they are able to withstand elevated temperatures at least as high as, 
e.g., the melting point of lead (328.degree. C.), aluminum (660.degree. 
C.), iron (1535.degree. C.) or any other metal to be filtered. The 
preferred refractory linings of the present invention which comprise 
magnesia, alumina, silica or the like are capable of withstanding very 
high temperatures, and are particularly suitable for handling a wide range 
of different molten metals. 
The inlet member 11 and the plate member 30 are adapted to move away from 
the outlet member 15 and the base member 20, against the force of the 
biasing members 33. As shown in FIGS. 1 and 3, cam members 40 may be used 
to move the plate member 30 away from the base member 20. The cam members 
40 are mounted on actuator rods 41 disposed on either side of the outlet 
member 15. The cam members 40 preferably include cam rollers 42 in order 
to reduce friction. However, the cam rollers 42 are not absolutely 
required, and could be replaced by a curved surface or any other suitable 
means for contacting the projections 34 of the plate member 30. The 
actuator rods 41 are preferably rotatably mounted to the base member 20 by 
means of support brackets 43. 
The cam members 40 are actuated by means of any suitable driving source. 
For example, as shown in FIG. 1, the driving source may be a pneumatic 
motor 44 connected to a pressurized air supply (not shown) by means of a 
tube 45. Driving power may thus be supplied to the cam members 40 from the 
pneumatic motor 44 by means of the actuator rods 41. While a pneumatic 
motor 44 is preferred due to the high temperatures associated with the 
molten metal filtration operation, it is recognized that any other 
suitable power source such as, for example, hydraulic or electric motors 
may be used. 
The molten metal filtering apparatus 10 includes a molten metal filter 50 
disposed between the inlet member 11 and the outlet member 15. As shown in 
FIG. 1, the filter 50 is preferably a continuous sheet of material that is 
supplied from a roll or coil 51. The filter 50 is serially advanced or 
indexed into the filtering area between the inlet member 11 and the outlet 
member 15 by means of the indexing motor 52. The indexing motor 52 
comprises opposed indexing rollers 53 and 54 that rotate in opposite 
directions to pull the filter 50 in the direction of the arrow 55. The 
indexing motor 52 may be mounted on the base member 20, or may be provided 
at any other suitable location. The indexing motor 52 is preferably 
pneumatically operated, but could also be operated hydraulically, 
electrically or the like. 
The molten metal filter 50 is preferably provided as a continuous flexible 
sheet of material that can be supplied in the form of a roll or coil. The 
term "continuous" as used herein to describe the filter 50 is meant to 
include filter materials that can be indexed, portion-by-portion, into the 
filtering area, as opposed to discrete filter elements that must be 
individually replaced. Preferably, the continuous filter is of sufficient 
length that allows multiple indexing steps without the requirement of 
frequent replacement. For example, the continuous filter may be 50 to 200 
feet long. The filter 50 may be provided as a woven or nonwoven cloth, 
with woven cloth being preferred due to the greater ability to control the 
mesh size of the cloth. A particularly preferred woven cloth comprises 
silica in a mock leno weave that contains generally square through holes 
ranging in size from about 1.times.1 mm to 2.times.2 mm. 
Preferred filter materials include fiberglass and refractory oxides such as 
silica, alumina, magnesia and combinations thereof, with silica cloth 
being particularly preferred for filtering high temperature metals such 
as, for example, irons and steels. Fiberglass filters are generally 
preferred for low melting point metals such as, for example, aluminum. 
Thus, the choice of filter material is dependent on the type of molten 
metal to be filtered. Typical metals include ferrous metals such as gray, 
malleable, white and ductile cast irons, and non-ferrous metals such as 
aluminum, lead, brass and bronze. However, it is to be understood that a 
wide range of metals can be filtered using the apparatus and method of the 
present invention. 
For the filtration of ferrous metals, coated silica cloth such as disclosed 
in U.S. Pat. No. 5,124,040 is particularly preferred for use in accordance 
with the present invention. Such coated silica cloth traps impurities in a 
manner unlike cellular or reticulated foam ceramic filters. When molten 
metal reaches the coated cloth filter, a stiffening resin encapsulating 
the fibers of the filter decomposes, forming a carbonaceous char. During 
the filtration of ferrous alloys, the decomposition products of the resin 
react with the iron to form Wustite (FeO), which in turn reacts with the 
silica fibers to form a layer of fayalite (2FeO-SiO). The molten iron 
temperatures cause the fayalite coating to become soft and sticky so that 
it captures any nonmetallic inclusions that touch it, holding them onto 
the cloth filter. Since the sticky fayalite film forms instantly, it is 
possible to filter even micron sized inclusions from the very first metal 
to pass through the filter. 
A particularly preferred embodiment of the present invention is shown in 
FIGS. 4 and 5, wherein support members 60 are connected to the plate 
member 30 on either side of the molten metal filter 50. A rod 61 is 
disposed between opposing support members 60, below the filter 50, as 
shown in FIG. 4. When the inlet member 11 and the plate member 30 are 
drawn against the base member 20 as shown in FIG. 4, the rods 61 are 
disposed within recesses 62 in the base member 20. When the plate member 
30 is moved away from the base member 20, the rods 61 contact the 
underside of the filter 50 and raise the filter along with the plate 
member 30. As discussed more fully below, such a configuration allows for 
the filter 50 to be raised from the surface of the base member 20 in order 
to facilitate advancement of the filter 50 if the underside of the filter 
includes frozen metal left over from the filtering operation. 
FIGS. 7 and 8 illustrate another embodiment of the present invention 
wherein the apparatus is adapted for filtering relatively large volumes of 
molten metal. In this embodiment, the inlet member 11 includes a filter 
box 70 in communication with a pouring box 71 by means of an opening 72. 
The filter box 70, pouring box 71 and opening 72 may be made of any 
suitable material capable of withstanding molten metal temperatures. While 
the filter box 70 and pouring box 71 are shown as being made of refractory 
material in FIGS. 7 and 8, these components could also be made of 
refractory-lined metal casings or any other suitable material. It is noted 
that the filter box 70 may extend to a greater height than shown in FIG. 8 
in order to accomodate the desired volume of molten metal. 
In the embodiment shown in FIGS. 7 and 8, the outlet member 15 is disposed 
below a refractory basin 80 that includes generally upwardly extending 
side walls and a bottom floor that is sloped toward an opening 81, which 
in turn is in flow communication with the interior of the refractory 
lining 17. A refractory material grid 82 comprising cross members 83 is 
disposed above the refractory basin 80. As discussed more fully below, the 
cross members 83 of the refractory grid 82 serve to support the filter 50 
during the molten metal filtering operation. The refractory basin 80 and 
refractory grid 82 may be made of any suitable refractory material such 
as, for example, castable ceramic. While the refractory basin 80 and the 
refractory grid 82 are preferably provided as separate pieces as shown in 
FIG. 8, it is recognized that they could be provided as a single unit. 
The apparatus shown in FIGS. 7 and 8 is particularly suited for filtering 
relatively large volumes of molten metal in amounts up to approximately 
5,000 pounds or more. For large volumes of metal, the dimensions of the 
refractory grid 82 may range from less than 1 ft..times.1 ft. to more than 
2 ft..times.2 ft. Thus, the area covered by the grid as shown in the top 
view of FIG. 7 may range from less than 1 sq. ft. to more than 4 sq. ft., 
depending on such factors as the amount of molten metal to be filtered and 
the rate at which filtering is to proceed. It is recognized that the 
embodiment shown in FIGS. 7 and 8 is not necessarily drawn to scale, and 
that considerable modification of the size and shape of the various 
elements is possible. 
The apparatus of the present invention operates as follows. Molten metal is 
introduced into the inlet member 11 by any suitable means such as a 
trough, runner, ladle, holding furnace or the like. When the molten metal 
is introduced into the apparatus, the inlet member 11 and the plate mender 
30 are disposed adjacent to the base member 20 of the outlet member 15. As 
shown most clearly in FIG. 2, the filter 50 is pressed between the 
refractory lining 13 of the inlet member and the refractory material 22 of 
the outlet member 15. This is accomplished by extending the refractory 
lining 13 slightly below the bottom of the plate member 30, and by 
extending the refractory material 22 into the cutout 28 of the base member 
20. The refractory lining 13 and the refractory material 22 thus serve to 
clamp the filter 50 in place and to protect the components of the 
apparatus, such as the base member 20 and the plate member 30, from the 
high temperatures of the molten metal. 
Molten metal introduced into the inlet member 11 flows through the filter 
50 and exits the apparatus by way of the outlet member 15. While the 
outlet member 15 is shown as a generally tubular structure in the figures, 
it is recognized that other configurations such as, troughs, runners, 
casting molds, holding furnaces and the like are also suitable outlet 
members. 
The apparatus of the present invention can be placed at any suitable 
location in the molten metal processing operation. For example, the 
apparatus may be located directly upstream from a casting mold, or over 
the inlet to a molten metal holding furnace. As a particular, non-limiting 
example, it may be advantageous to filter ferrous molten metals before the 
metal is introduced into a conventional holding furnace. Large amounts of 
batch-treated metal can be filtered. For example, ductile iron may be 
filtered when it is added to a holding furnace that supplies molten metal 
to an automated molding line. Alternatively, for smaller castings of 
non-ferrous metals such as aluminum, it may be advantageous to place the 
outlet of the apparatus directly over the inlet to a shot tube on a 
conventional die caster. In the case of die casting, the apparatus can be 
used to automatically filter the metal going into each casting directly at 
the shot tube. 
After the desired amount of molten metal is filtered through the apparatus 
10, the flow of metal is stopped to allow a new section of the filter 50 
to be indexed into the area between the inlet member 11 and the outlet 
member 15, thereby permitting a fresh portion of the filter 50 to be 
placed in the path of the molten metal stream. 
Indexing of the molten metal filter 50 is accomplished by raising the plate 
member 30 away from the base member 20 in order to allow the filter 50 to 
be freely advanced in the direction of the arrow 55 in FIG. 1. A preferred 
technique for moving the plate member 30 away from the base member 20 is 
by the use of the cam members 40. The pneumatic motor 44 rotates the 
actuator rods 41 which are disposed on opposite sides of the outlet member 
15. Rotation of the actuator rods 41 causes rotation of the cam members 40 
and cam rollers 42, as shown by the arrows 46 in FIG. 3. The cam rollers 
42 bear against the lower surfaces of the downwardly extending projections 
34 of the plate member 30 in order to move the plate member upwardly in 
the direction of the arrows 47 in FIG. 3. The plate member 30 thus moves 
upwardly against the force of the biasing members 33. As shown most 
clearly in FIG. 2, the movement of the plate member 30 away from the base 
member 20 causes the refractory lining 13 to move away from the refractory 
material 22 to thereby allow the molten metal filter 50 to move freely in 
the horizontal direction. 
In a particularly preferred embodiment as shown in FIGS. 4 and 5, the rods 
61, which are supported on the plate member 30 by means of the supports 
60, are disposed beneath the filter 50. In the closed position as shown in 
FIG. 4 the rods 61 are seated within recesses 62 in the base member 20. 
However, when the plate member 30 is raised the rods 61 contact the 
underside of the filter 50, thereby raising the filter 50 above the upper 
surface of the base member 20. This configuration is particularly 
advantageous where molten metal has frozen on the underside of the filter 
50 during the filtering operation. By using the rods 61 to raise the 
filter 50 above the surface of the base member 20, any metal that has 
solidified on the underside of the filter 50 should be provided with 
sufficient clearance so as not to impede the advancement of the filter 
during the indexing step. 
Once the plate member 30 is moved away from the base member 20, a new 
portion of the filter 50 may be indexed into place by means of the 
indexing motor 52. As shown in FIG. 1, the indexing rollers 53 and 54 
rotate in opposite directions in order to pull the filter 50 in the 
direction of the arrow 55. The length of the filter 50 that is pulled 
through the apparatus with each indexing step can be adjusted to any 
desired amount. Preferably, the filter 50 is advanced a sufficient amount 
to provide a new portion of the filter in the entire area of molten metal 
contact. As shown in FIG. 1, the filter 50 is preferably provided on a 
supply roll 51 that rotates freely when the filter 50 is pulled through 
the apparatus by the indexing motor 52. The supply roll 51 may be provided 
with a slight rotational resistance in order to provide tension on the 
filter 50 to prevent slack. 
In a preferred embodiment, the pneumatic motor 44 and indexing motor 52 are 
automatically controlled such that the pneumatic motor 44 first rotates 
the cam members 40 a sufficient amount to raise the plate member 30, 
followed by actuation of the indexing motor 52 to pull the desired length 
of the filter 50 through the apparatus, followed by actuation of the 
pneumatic motor 44 to rotate the cam members 40 to thereby lower the plate 
member 30 against the base member 20. In a particularly preferred 
embodiment, the flow of molten metal through the apparatus is also 
automatically controlled such that the flow is stopped during the indexing 
operation, and is then started once the new portion of the filter 50 has 
been indexed into place. In this manner, the molten metal filtering 
operation can be totally automated, thereby avoiding the increased cost 
and time associated with prior art molten metal filtering processes. 
Sensors may be used with the apparatus to indicate when the appropriate 
length of the filter 50 has been pulled through the apparatus and/or to 
indicate when the plate member 30 is in the raised or lowered position. 
Such sensors may be of any suitable type, including photoelectric, 
infrared, laser, mechanical and the like. 
The operation of the apparatus as shown in the embodiment of FIGS. 7 and 8 
is similar to that previously discussed, and is particularly suitable for 
filtering relatively large amounts of molten metal. For example, the 
filter box 70 as shown in FIGS. 7 and 8 may be capable of holding 5,000 
pounds or more of molten metal. In this embodiment, the molten metal is 
first introduced into the pouring box 71 and then flows into the filter 
box 70 by means of the opening 72. The pouring box 71 can be used to more 
uniformly distribute the molten metal over the surface of the filter 50, 
in comparison with directly pouring the molten metal into the filter box 
70 by means of a ladle or the like. 
Due to the relatively large surface area of the filter 50 that is exposed 
to the molten metal, the apparatus of FIGS. 7 and 8 includes the 
refractory grid 82 as a means of support. For example, the grid area shown 
in the top view of FIG. 7 may be approximately 18 inches.times.18 inches, 
in which case the filter 50 might tend to sag to an undesirable degree 
without the support of the cross members 83 of the refractory grid 82. 
While a square grid is shown in FIGS. 7 and 8, it is recognized that any 
suitable grid geometry may be used. For example, the holes between the 
cross members 83 could be circular, hexagonal, or any other suitable 
shape. Furthermore, the ratio of the area of the openings between the 
cross members 83 to the area of the cross members 83 themselves can be 
varied, with the criteria that the cross members 83 must be of sufficient 
thickness to adequately support the filter 50 during the filtering 
operation, but must not be so thick as to restrict the flow of molten 
metal to an undesirable degree. The refractory grid 82 and refractory 
basin 80 are preferably made of castable ceramic and are relatively easily 
replaced in the apparatus after they have become worn or eroded. 
The present invention achieves several advantages over prior art molten 
metal filtering processes. In typical prior art filtering operations, the 
filters, which may comprise hard-fired cellular or reticulated ceramic 
blocks or refractory cloths, must be individually placed in the molten 
metal stream. Manual placement of discrete filter elements is time 
consuming and can lead to excessive processing costs. In accordance with 
the present invention, an advantage is gained in being able to filter 
metals being poured into casting machines and permanent molds at the very 
last moment, and have a new or fresh filter index into place 
automatically. Another advantage is obtained by being able to filter large 
amounts of metal that has been treated with ferroalloys, inoculants and 
master alloys, before being placed into holding furnaces or pouring 
ladles. By providing a continuous filtering medium that is serially 
indexed into position, the present invention eliminates the problems 
associated with discrete filter elements and provides a substantially 
expedited process that can be automated, thereby significantly reducing 
costs. 
Various modifications of the presently described embodiments are possible. 
For example, the configurations of the inlet member 11 and outlet member 
15 can be varied considerably in order to conform to wide ranging molten 
metal filtration requirements. In addition, the means for moving the inlet 
member 11 away from the outlet member 15 in order to allow indexing of the 
filter 50 can be modified from the embodiments shown herein. For example, 
the inlet member 11 could be held stationary while the outlet member 15 is 
moved. Furthermore, the means for indexing the filter 50 through the 
apparatus 10 can be varied depending on such factors as the type of filter 
medium that is used and the specific filtering operation employed. 
Accordingly, it is understood that the above description of the present 
invention is susceptible to considerable modifications, changes and 
adaptations by those skilled in the art, and that such modifications, 
changes and adaptations are intended to be considered within the scope of 
the present invention, which is set forth by the appended claims.