Inert gas bubble-actuated molten metal pump with gas-diffusion grid

An inert gas bubble-actuated molten metal pump, for the movement of molten metal in a molten-metal bath, which obviates the necessity of a heatproof and flameproof cover to counteract splashing and spattering at the surface of the molten metal bath above the pump, comprising an inert gas diffusion means at an upper end thereof, the diffusion means having an upper surface containing a multiplicity of small upwardly-opening apertures for the breaking up of large bubbles and the diffusion of small bubbles of inert gas upwardly therethrough. The pump includes a refractory block which comprises a conveying conduit which is preferably elongated in width and a spreader cavity in communication with both a passageway in the block for providing a source of inert gas and a lower end of the conveying conduit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The field of the invention is inert gas bubble-actuated molten metal pumps 
for use in a well of a metal-melting furnace and in particular relates to 
an improved inert gas bubble-actuated molten metal pump incorporating a 
gas-diffusion grid for purposes of obviating certain disadvantages of 
known such pumps as well as certain other novel and advantageous 
characteristics, all of which will become apparent hereinafter. 
2. Prior Art 
The state of the art regarding the introduction of metal chips into a 
charge or other well of a metal-melting furnace and the conveyance of 
molten metal from one place to another within or out of a metal-melting 
furnace has been fully reviewed in the prior U.S. patents of one of us, in 
particular U.S. Pat. No. 5,735,935, issued Apr. 7, 1998, and the 
disclosure of that patent as well as of those enumerated therein is hereby 
incorporated by reference. 
At the present state of the art, the use of an inert gas bubble-actuated 
molten metal pump for moving molten metal from one place to another within 
or out of a metalmelting furnace is now well established. The term 
"actuated", with reference to an inert gas bubble "actuated" molten metal 
pump, means that the pump is put into action by the inert gas bubbles or, 
synonymously, that the pump could be said to be driven, propelled, or 
powered by the inert gas bubbles. 
Although the inert gas bubble-actuated molten metal pump of the previous 
U.S. Pat. No. 5,203,910 and others of one of us has met with considerable 
success, when such device has been employed within a metal-melting furnace 
to move molten metal from one place to another in the same well of the 
metal-melting furnace or from one well to another in a metal-melting 
furnace, for purposes of effecting circulation of the molten metal 
therein, and is a great improvement over previously-employed circulation 
pumps, several undesirable effects have been noted. In particular, undue 
spattering or splashing of molten metal at the surface of the molten metal 
mass above the exit port of the pump has been found objectionable per se, 
in addition to the fact that the splashing and spattering have caused a 
disruption of the protective metal oxide coating or dross which generally 
accumulates at the surface of the molten metal bath or pool, with the 
result that increased levels of oxidation, which would normally not be 
encountered, have occurred at the surface of the molten metal mass, and 
the solution to these problems has frequently required the presence of a 
heat-resistant and flame-resistant cover above the exit port of the 
bubble-actuated molten metal pump to reduce the resultant splashing and 
spattering at the surface of the molten metal bath or pool, as provided in 
the earlier U.S. Pat. No. 5,735,935 of one of us. 
It would be highly desirable to eliminate the necessity of such a heat- and 
flame-resistant cover while at the same time avoiding the undesirable 
spattering or splashing of molten metal at the surface of the molten metal 
mass, bath, or pool above the exit port of the pump, and the present 
invention provides a solution to the aforesaid problems as well as 
providing additional advantages due to the unique details of construction 
of the bubble-actuated molten metal pump of the present invention. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to eliminate the undesirable 
splashing and spattering at the surface of a molten metal mass, bath, or 
pool, by the provision of a unique bubble-actuated molten metal pump 
having a built-in gas-diffusion grid at the upper and exit end thereof. It 
is a further object of the invention to provide such a bubble-actuated 
molten metal pump having particular details of construction which enable 
the production and passage of relatively large inert gas bubbles through 
the conveying conduit thereof, as well as structure for the production of 
such relatively large inert gas bubbles within the molten metal pump 
itself from a single point of introduction of the inert gas employed in 
its operation, but which large gas bubbles are broken up into a 
multiplicity of small bubbles by the gas diffusion means of the invention. 
Still other objects of the invention will become apparent hereinafter and 
yet other objects will be apparent to one skilled in the art to which this 
invention pertains. 
SUMMARY OF THE INVENTION 
What we believe to be our invention, then, inter alia, comprises the 
following, singly or in combination: 
An inert gas bubble-actuated molten metal pump, for the movement of molten 
metal in a molten metal bath, which obviates the necessity of a heatproof 
and flameproof cover to counteract splashing and spattering at the surface 
of the molten metal bath above the pump, comprising: 
a block of molten metal- and high temperature- resistant refractory 
material adapted to be placed into communication with a source of inert 
gas and into a molten metal bath for movement of the molten metal therein 
by means of inert gas bubbles, 
an inert gas-feed passageway in said block for the passage of inert gas 
from a source thereof to an exit from said passageway, 
a conveying conduit in said block and in communication with said gas-feed 
passageway exit, the exit of said gasfeed passageway communicating with a 
lower end of said conveying conduit for the conveyance of molten metal and 
inert gas bubbles therein and therethrough when said block is in place in 
a molten-metal bath, 
said conveying conduit having also an upper end, an inert gas diffusion 
means at an upper end of said block and in communication with the upper 
end of said conveying conduit, said diffusion means having an upper 
surface containing a grid comprising a multiplicity of small 
upwardly-opening apertures for the breaking up of large bubbles and the 
diffusion of small bubbles of inert gas upwardly therethrough; such 
a pump wherein the refractory material is a graphite, ceramic, silica, or 
silicon carbide material; such 
a pump wherein the refractory material is graphite; such 
a pump wherein the grid in the upper surface of said diffusion means 
comprises apertures of approximately one-eighth to three-eighths inch in 
diameter; and such 
a pump wherein the number of apertures is in excess of 100. 
Moreover, such a pump wherein the conveying conduit is elongated in width 
and wherein a spreader cavity is provided in said block in communication 
with both the gas-feed passageway exit and a lower end of said conveying 
conduit, as well as such 
a pump comprising, on an upper surface of said block, apertures for the 
insertion and securement of refractory support columns therein for 
mounting of the pump in a molten metal bath; such 
a pump wherein an inert gas feed line is located within a refractory 
support column, and finally such 
a pump wherein said apertures in said block for said support columns are 
threaded.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be more readily understood from the following 
detailed description, particularly when taken in conjunction with the 
drawings, in which all of the significant parts are numbered or lettered 
and wherein the same letters and numbers are used to identify the same 
parts throughout. 
A metal-melting furnace, as shown a reverberatory furnace, of refractory 
material or having the usual refractory lining and fired by combustion 
burners fed by natural gas or fuel oil, which throw flames into the 
interior of main chamber 18 thereof through usual flame-introduction 
means, is shown in the FIGS. at 10. The furnace well comprises bottom wall 
11 and side or vertical walls 12 and 13, with a mass of molten metal, 
preferably and usually aluminum or magnesium or an alloy thereof, therein 
being shown at 26. The base portion 11 of the furnace may be supported on 
the underlying floor by means of I-beam supports, not shown. Main chamber 
18 is provided with main chamber extensions 19 in the form of intermediate 
well 20, usually referred to as the circulation well, and adjacent well 
22, which is usually but in this case need not be the charge well, 
connected with each other and with main chamber 18 by means of 
communicating passageways 24. 
Molten metal 26 is contained in main chamber 18 and is circulated from the 
hottest part thereof, indicated at 38, through intermediate well 20 into 
adjacent well 22 via communicating passageway 24. The necessary 
circulation throughout the furnace is provided by means of inert gas 
bubble-actuated molten metal pump PU, located in an opening in wall 12 
between intermediate well 20 and adjacent well 22. Separate circulating 
means in what is normally circu lation well 20 is not required. 
Conveying conduit CC of pump PU is molded in or routed out of a block of 
refractory material B, which is resistant to the molten metal 26 and the 
high temperature employed, the refractory material usually being of a 
graphite, ceramic, silica, or silicon carbide material. As shown, it is of 
graphite. Elongated conveying conduit CC is angled with an upper portion 
extending to the horizontal and a lower portion extending downwardly at an 
angle to the horizontal, the lower end thereof being designated LE and the 
upper end thereof being designated UE. The angle to the horizontal of the 
upper portion of conduit CC is a definitely preferred aspect or embodiment 
of the invention for attainment of the stated objectives, with the upper 
end UE also sometimes being referred to herein as the exit port EP of pump 
PU and conduit CC. The upper end UE of conduit CC and of the pump PU 
discharges into an extension D of the pump PU, made of the same refractory 
material B as the rest of the pump, the extension D constituting a 
gas-dispersion or gas-diffusion means having a plurality of apertures A in 
its upper surface, to cause the larger inert gas bubbles to break up into 
a multiplicity of smaller bubbles which then escape upwardly through the 
grid G thereof in a controlled manner which does not induce spattering or 
splashing of the molten metal at the surface thereof. Extension D may have 
top and side walls only, or may include a bottom, in which case it is 
tubular in nature. 
Also visible in the drawings are the surface of the molten metal mass with 
its usual layer of metal oxide or dross 25, which ordinarily collects at 
the surface of the molten metal pool or bath or mass 26, this being shown 
as present in all of the wells of the metal melting furnace 10. According 
to the usual flow path or pattern 36 in such a metal-melting furnace, as 
created by the action of the inert gas bubble-actuated molten metal pump 
PU and the conveying conduit CC thereof, circulation of molten metal 26 in 
furnace main chamber 18 is constantly and continuously moved from the 
hottest point 38 thereof in main chamber 18 through communicating 
passageways 24 into intermediate well 20 and then into adjacent well 22. 
When and if well 22 is used as a charge well of the furnace for 
introduction of metal chips into cavity 22C thereof, a chip-charger means 
will be employed in conjunction therewith, but this is immaterial 
according to the present invention. 
As is usual the flow of molten metal 26 in the pump PU is effected by means 
of bubbles of inert gas IG introduced into the conveying conduit CC at or 
adjacent its lower end LE and rising up the incline therein to emerge at 
the upper end or exit port UE/EP, at which point the molten metal 26 and 
the inert gas IG, together referred to as effluent 26/IG, moves out into 
well 22, the outlet or upper end UE and exit port EP of the conveying 
conduit CC, and thus of the pump PU, being directed into well 22 and the 
mass of molten metal 26 therein. However, instead of "shooting out" into 
the mass of molten metal 26 in well 22, as is usually the case, the larger 
bubbles of inert gas IG are broken up into many smaller bubbles as they 
pass into and through diffuser D and the apertures A in the grid G in the 
upper surface thereof, and the propellant gas is thus dissipated without 
splattering or splashing at the surface of the molten metal mass 26 in 
well cavity 22C and frequently even without disruption of the protective 
layer or skin of molten metal oxide or dross 25 at the surface thereof. 
Grid C may advantageously comprise 126 apertures, each of 3/8 inch 
diameter, and each preferably at an approximately 10 degree angle with the 
vertical, this grid comprising a substantial portion of the upper surface 
of gas-diffuser or gas-dispersion means D. 
The lower end of the inert-gas supply or feed line IGFL in the form of a 
gas-feed passageway provided in block B and in one support column SC, in 
turn connected to pipe P at pipe connector PC, provides a single outlet or 
exit port E for the inert gas, which then expands and passes through 
spreader cavity S whereafter it is released into the lower end LE of 
conveying conduit CC, in this case having internal dimensions which 
provide a substantially greater width than height to the conduit CC. The 
spreader cavity S, together with the widthwise elongated ovoid or 
oblong-shaped conduit CC, permits the formation of much larger and, for 
moving of molten metal, more efficient, inert gas bubbles than would be 
possible without the spreader cavity S and with a conduit CC having a 
circular configuration or other configurations having internal dimensions 
wherein the width thereof does not substantially exceed the height 
thereof. However, the larger size of these more efficient bubbles makes it 
all the more necessary to break them up into a multiplicity of small 
bubbles by means of the gas-diffuser or gas-dispersion means D. 
As shown in the drawings, the gas feed means comprises inlet port I and 
pipe P, in communication through PC with inert-gas feed line IGFL in the 
form of a passageway having an exit port E at its lower end, which in turn 
communicates with the lower end LE of the widthwise elongated conveying 
conduit CC of pump PU through spreader cavity S, the said passageway or 
IGFL being provided in a support column SC and in supporting block B, both 
of refractory material, which block B is also attached to support columns 
SC, the connections between support columns SC and block B involving 
threads T on support columns SC which engage with cooperating threads T in 
apertures in block B. Support columns SC are supported from hanger H, in 
turn supported by chain or cable CH connections to a ring or hook, in turn 
suitably connected to a hoist HO, not shown, for convenient introduction 
and removal of pump PU and its auxiliary fittings, supports, and inert gas 
feed line as a unit into and from their operative location in a well or 
wells of the metal-melting furnace. Support columns SC may advantageously 
be clad with or surrounded by ceramic sleeves CS, which may in turn be 
cemented to the support columns SC by means of sealant ST, advantageously 
a high-temperature graphite mortar, which may also conveniently and 
advantageously be employed to seal the joints between the support columns 
and the block B above threads T and where support columns SC abut block B 
and/or enter threaded apertures therein. Alternatively, the support 
columns SC may advantageously be flame-sprayed with ceramic prior to 
encasing them with ceramic sleeves CS as just described. 
OPERATION 
In operation, molten metal from main chamber 18 of the metal-melting 
furnace 10 is circulated throughout the furnace with the assistance of 
inert gas bubble-actuated molten metal pump PU, the pump operating within 
the furnace in the manner of previous inert gas bubble-actuated molten 
metal pumps in accord with the disclosure of the previous U.S. Pat. No. 
5,735,935 of one of us and other patents cited therein. The advantage of 
employing the pump of the present invention is the absence of splashing or 
spattering at the surface of the molten metal above the outlet end of the 
pump, because of the multiplicity of apertures A in the grid G of integral 
diffuser D. As a further advantage of the pump of the present invention, 
the provision of a single inert gas outlet, communicating with a spreader 
cavity, and thence with the widthwise elongated conveying conduit of the 
pump of the present invention, permits the more efficient molten-metal 
pumping utilization of the gas in the form of relatively larger gas 
bubbles without the necessity of a plurality of points of introduction of 
the inert gas into the pump and the conveying conduit thereof and 
accordingly increases the efficiency of the operation in this respect as 
well. In addition, upon exiting the metal-moving pump together with metal 
being moved by the same, the inert gas passes into the diffuser at the 
upper end thereof and is directed upwardly through the apertures in the 
grid located in the upper surface thereof, thereby converting large 
bubbles into a multiplicity of tiny bubbles and thereby avoiding the 
inconvenience of spattering or splashing of the molten metal at the upper 
surface thereof and sometimes even without disruption of the protective 
layer of metal oxide or dross at the said surface, thus presenting an 
overall highly efficient and yet highly economic and advantageous 
arrangement of apparatus for the circulation of molten metal throughout 
the various chambers of a metal-melting furnace. 
IN GENERAL 
The bubble-actuated molten metal pump of the invention as well as the gas 
feed means of the invention are generally constructed of or arranged so as 
to expose only high-temperature molten metal-resistant ceramic, graphite, 
silica, or silicon carbide or the like, and the hangers and support 
columns supporting the same within the metal mass may be bonded thereto as 
by welding, clamping, or ceramic or adhesive bonding around the exterior 
thereof or in some cases may be molded into the ceramic, graphite, silica, 
or silicon carbide material of construction, or in other cases may even be 
of mild or stainless or such steel coated or plated with a refractory 
material. Of course, it goes without saying that the structure and 
material of construction, as particularly described under "DETAILED 
DESCRIPTION OF THE INVENTION" herein, is preferred. 
The metal of the metal mass, pool, or bath, whenever referred to herein, 
may be of any suitable material of the type usually employed or found in a 
metal-melting furnace, including aluminum, magnesium, titanium, brass, 
iron, or steel, or an alloy thereof, or a metal for alloying one of said 
metals, and in most common practice today is aluminum or an alloy thereof. 
The molten metal may be new or previously used, including even and 
especially new and used aluminum sheet and can scrap, as is now 
conventional in the art. 
It is thereby seen from the foregoing that the objects of the present 
invention have been accomplished and that a novel, efficient, and economic 
apparatus has been provided, all accord with the OBJECTS OF THE INVENTION 
and the SUMMARY OF THE INVENTION as set forth hereinbefore. 
It is to be understood that the present invention is not to be limited to 
the exact details of operation, or to the exact compounds, compositions, 
methods, procedures, or embodiments shown and described, as various 
modifications and equivalents will be apparent to one skilled in the art, 
wherefore the present invention is to be limited only by the full scope 
which can be legally accorded to the appended claims.