Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~V7493.::L
FIELD OF THE INVENTION
The invention relates to a strip casting machina
primarily intend~d for the casting of lead ~trip
although it will be undarstood that other metals,
metal alloys, mixtures of metals and non~metallic
fillers, and also such materials as polycarbonates
and acrylics, may be able to be cast in the form of
strip by a machine embodying the invention.
S~MMARY OF THE INVENTION
Accoxding to the invention, there i9 provided a
strip casting machine including a pair of rolls,
means for supplying molten material to a spaca
between the rolls, the spacing o~ which defines a
gap through which the ma~erial is to bo fed, means
for cooling said rolls whereby to cool the molten
material carried into the gap, and means for
driving said rolls in contra-rotation to control
the feed of the material through said gap. The
means for cooling the pair of rolls may be interior
spaces within said rolls for the circulation of a
cooling fluid. The means for driving the rolls may
include means for monitoring the power consumption
of a drive motor, and means for increasing the
driven speed of the rolls in response to an
lncrease of power consumption. Alternatively,
2a7~
means for driving the rolls may include means for
sensing the force tending to separate the rolls
during the operation o the machine, and for
increasing the drivan speed of the rolls in
response to an increase in the force tending to
separate said rolls.
The machine may include a containing space for
holding the molten material above and between the
rolls, said space being enclosed at opposite ends
by respective plates urged into sliding engagement
with end surfaces of said rolls. The plates at the
opposite ends of the rolls may be urged into
sliding engagement with the end surfaces of tha
roll~ by spring means.
The machine may include ad~ustment means whereby
the distance between the two rolls is ad~ustable.
Means may be provided for maintaining a pool of
molten material above and between the two rolls at
a substantially constant level, conveniently a dip-
probe and a solenoid operated valve actuated bysaid probe. The means for maintaining the level of
said pool of molten material may comprise means for
feeding the molten material to the pool at a rate
greater than that at which the material is fed
between the rolls, and overflo~ means for returning
excess material from the pool. A holding tank may
2~7~911
be provided for feeding the molten material to the
pool of material, and there may be provided means
for maintaining the depth of molten material in
said holding tank comprising means for feeding the
material to said tank at a rate greater than that
at which the material is fed between the rolls, and
ovsrflow means in said tank for retu:rnlng excess
material therefrom.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a semi-diagrammatic view of a metal
strip casting machine embodying the invention,
Figure 2 is a diagrammatic view illustrating a
control means for the machine,
Figure 3 is a circuit diagram,
Figu~a 4 is a view slmilar to Figure 1 and
illustrating a possible modification, and
Figure 5 is a view of a further possible
modification.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1 of the drawings, the
metal strip casting machine there illustrated
includes a pair of water cooled rolls 10,10 spaced
apart side by side, as shown, and capable of being
driven, by means not shown, in contra-rotation as
indicated by the arrows. A space, generally
indicated 12, which is to contain molten metal
2~7~91~
above and between the rolls is enclosed at its
opposite ends by respective graphite plates 14
which are acted upon by spring means (not shown) to
urge them into sliding engagement with the and
surfaces of the rolls.
The arrangement is such that the molten metal
contacting the water cooled rolls is chilled and as
the rolls rotate as indicated by the arrows, a
metal strip is formed in the "nip" between the two
rolls and is carried downwards as shown by the
chain-dotted lines.
The spacing of the two rolls, that is to say the
width of the gap between them, is ad~ustable (by
means not shown) between zero and some desired
maximum, for example up to 2.5 mm. In this way
the thickness o the mstal strip being carried
downwards by the two rolls is ad~ustable. ~he
metal strip being carried downwards by the rolls is
guided towards a pair of rollers 16,16 which in
turn guide the strip towards a slitting head (not
shown).
Means are provided for maintaining the level of
the pool of molten metal between the two rolls
10,10. As shown, these means are constituted by a
dip-probe 18 and a solenoid op~rated valve 20 which
can be opened to allow the gravity flow of molten
2~ ~19:~
metal from a holding tank 22. The holding tank is
itself replenished from time to time from a melting
pot 24. A dip-probe 26 and a solenoid operated
valve 2~ are provided to monitor the level of
molten metal in the holding tank ancl to control the
flow of molten metal from the melting pot,
respectively.
The cooling flow through the rolls 10,10 takes
place through rotatable connectors (not shown)
mounted on the roll spindles. Means are provided
for controlling the rate of flow of water through
the rolls to suit the temperature o~ the molten
metal in the space 12 above and between the rolls
and the thickne3s and the rate of ~ravel o metal
strip being carried downwards between the rolls.
Referring now to Figure 2, this illustrates the
way in which, dux.ing the operation of the machine,
the molten metal carried into the gap between the
rolls is chilled by contact with the roll~.
Ideally, as shown in full lines, the molten metal
will have solidified throughout the thickness of
the strip being produced as it reaches the planP
containing the axes of the two rolls.
If the molten metal has solidified at some
distance above the plane containing the axes of
the two rolls, for example in the region indicated
.
2 ~ ~1 4 9 ~
by ~he chain-dotted lines in Figure 2, the rolls
will re~uire to act in the manner of the rolls of a
rolling mill and the powar consumption of the
electric motor (not shown in Figures 1 and 2)
driving said rolls will increase. Ther~ are
therefore provided means or monitoring the force
tending to separate the two rolls and for
increasing the driven speed of the rolls in
response to a significant increase of said force.
The means for monitoring the force tending to
separate the two rolls are constituted by a ~train
gauge 11. In Figure 3 there is illustrated the
means whereby the driven speed of the rolls is
automatically increased ~n response to a
slgnificant increase of the force tending to
separate the two rolls. The motor unit 13 for
driving the rolls is provided with a tacho-
generator 15 the outpu~ from which is fed to a
comparator circuit 17 in opposition to a signal
; 20 from the strain gauge 11. The diference, or
error, between the two signals controls the output
stage of a triac 19 which is provided for
automatically adjusting the coil excitation level
of the unit connecting the motor and roll drive.
In operation of the machine, a significant
increase of the force tending to separate the two
2 0 7 ~ 9 :L ~
rolls results in an increased speed damand
reference signal from the strain gauge. This
immediately results in an error signal being
produced so that the motor speed is corraspondingly
~ncreased. The solidlflcation point is thus
brought down towards the position shown in full
lines in Figure 2, the signal $rom the strain gauge
is automatically reduced, and the rotational speed
of the rolls is thus allowed to fall. By fine
tuning of the speed of response of the system, the
solidification of the strip being producad i9
automatically maintained substantially at the
position shown in ull lines in Figure 2.
Referring now to Figure 4, in a modi1cation of
the machine ~ust described, the meltlng pot 2~ is
located at a lower level than the holding tank, and
indeed lower than the space 12 above and between
the rolls. A pump 30 is provided for feeding the
molten metal from the melting pot 24 to the holding
tank 22 through pipe 32.
Means which in this case are provided for
maintaining the depth of molten material in the
holding tank are constituted by an overflow pipe 34
opening from the side of said tank and leading back
to the melting pot. Means which are provided for
maintaining the depth of the pool of molten
~074911
ma~erial in the space 12 above and between the
rolls are constituted by an overflow or weir 36
ormed in one of the graphite plates 14, exc~ss
material being returned ~o the melting pot through
a down pipe 38 with which said over:Low or weir
communicates.
Referring now to Figure 5, this view illustrates
a further possible modification in which the pool
of molten metal is not held in a space defined by
the surfaaas of the two rolls but in a chamber
generally indicated ~0 mounted above the rolls.
The chamber has an overflow aperture 42 in an e~nd
wall which determines the static head o molten
metal. In thls case the molten metal i~ fed to the
gap between the rolls through an elongate feed
channel 44 extending the full length of the rolls.
A wear rssistant skirt 46 extends below the lower
end of the feed channel and bears against the
surfaces of the two rolls. (The graphite and
plates 14 of Figures 1 and 4 are not shown in
Figure 5. They may or may not be required).
POSSIBLE MODIFICATIONS
Various other modifications may be made. For
example, the respective plates which in the Figure
1 and Figure 4 constructions enclose the containing
space for holding the molten material above and
2~7~19~.1
between the rolls need not necessarily be acted
upon, or directly acted upon, by sprin~ means. A
system of levers could be arranged to apply the
required forces to said plates, sa:ld levers being
5acted on either by respective springs or by weights
acting through respective bell crank leverQ to
apply the required lateral forces.
Other means may be provided for automatically
maintaining the solidification o the strip
10substantially at the po ition shown in full lines
in Figure 2. For example, there could be provided
means for monitoring the power consumption of the
roll drive motor and means for increasing the
driven speed o the rolls in response to a
15significant increase of electria power consumption.
Provision may be made for 'after cooling' of the
strip, that i9 to say for the cooling of the strip
by a water or other f luid bath or by spray a*ter
the strip has exited from the rolls.
20The rolls could conceivably be cooled by a liqu:Ld
other than water, or even by vapour, pumped through
the hollow interior of each roll.
Although the machine has been described as being
for the production of metal strip, it will be
25understood that with suitable adjustments of the
temperature controls and drive controls it could be
d .~ t
used for the production of thermoplas~ics strip,
for axample polycarbonates and acryllcs.
