Note: Descriptions are shown in the official language in which they were submitted.
13~4S~o
- 1 - FS 1390
FEEDER SLEEVES
This invention relates to feeder sleeves
for use in the casting of molten metals and
particularly to feeder sleeves for use in the
casting of molten ferrous metals.
During solidification cast metals under-
go a reduction in their volume. For this reason,
in the casting of molten metals into moulds it is
usually necessary to employ feeder heads located
above or at the side of the castings in order to
compensate for the shrinkage which occurs when
the castings solidify. It is common practice to
surround a feeder head with an exothermic and/or
thenmally insulating feeder sleeve in order to
retain the feeder head metal in the molten state
for as long as possible and thereby to improve
the feeding effect and to enable the feeder head
volume to be reduced to a minimum. Such feeder
sleeves are usually of circular or oval horizontal
cross-section.
When casting molten metals and particu-
larly when casting molten ferrous metals into sand
moulds it is often des1rable to include in the
mould some means for preventing inclusions from
being ~ncorporated ~n castings produced in the moulds.
With grey and malleable ~rons inclusions
can be formed due to refractory particles and/or
slag being carr1ed over from a furnace or a ladle
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into the mould cavity or due to particles of sand
from the running system being washed into the mould
cavity.
Inclusions are most prevalent in ductile
s or nodular irons because in addition sticky
magnesium silicate slags, often associated with
particles of magnesium oxide and magnes~um
sulph~de, are formed during the nodularising
process and these are difficult to remove prior
to pouring the molten metal into the mould,even
though special precautions such as a fluxing '.
treatment, the use of a teapot ladle or the use
of a specially designed running system incorporat-
ing slag traps are adopted.
Strainer cores are often used in moulds
in malleable and grey iron foundries and in some
ductile iron foundries, but their principal
function is as a means for controlling the flow
of a molten iron into the mould and they have
only a limited filtering effect.
: . In recent times it has become common
practice to incorporate filters, for example,
ceramic foam filters, into the running systems of
moulds, e~ther in the runner itself or in the
sprue. It is also known to locate a filter at
~ the bottom of a feeder cav~ty or at the bottom of
j a feeder sleeve cav~ty, ad~acent the cast1ng cavity
~ of the mould.
;
According to the present lnvent~on
there is provided a feeder sleeve having an upper
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- 3 - FS 1390
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end and a lower end and having fixed in its cavity
a filter located at least 0.5 cm from its lower
end.
The filter is preferably located at
least 1 cm from the lower end of the sleeve.
Expressed in terms of the overall height of the
sleeve the filter is preferably located above the
lower end of the sleeve by at least 10% and no
more than 75% of the height of the sleeve.
The feeder sleeve of the invention may
be formed from exothermic, heat-insulating or
exothermic and heat-insulating material.
The filter may be for example a metal
mesh, a cloth made from glass or other inorganic
fibres, a honeycomb type of structure having pores
which extend from one face to an opposite face, or
a structure having interconnecting pores such as a
ceramic foam.
Ceramic foam filters are preferred and
such filters may be made using a known method of
making a ceramic foam, in which an organic foam,
usually polyurethane foam, is impregnated with an
aqueous slurry of ceramic material containing a
binder, the impregnated foam is dried to remove
water and the dried impregnated foam is fired to
burn off the organic foam to produce a ceramic
foam.
The feeder sleeve may be for example,
circular or oval in horizontal cross-section and
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it may be for example cylindrical, an inverted
frusto-conical shape or funnel shaped. The sleeve
may be formed around the filter, the filter may be
fixed in position inside the sleeve cavity, for
example by means of an adhesive, or the sleeve may
have a ledge or shoulder on its inner surface for
locating the filter in the desired position.
Alternatively the sleeve may be formed in two
parts and one end of each of the two parts may be
fixed to one face of the filter, for example by
means of an adhesive.
When the feeder sleeve of the invention
is used it is located in the mould above the mould
cavity and molten metal is poured into the sleeve
so that it flows through the filter and into the
mould cavity. After pouring and as the metal in
the mould cavity solidifies and contracts, molten
metal is fed from the feeder sleeve cavity through
the filter to compensate for the contraction and
to produce a sound casting. After solidification
the casting is removed from the mould and the
feeder is removed.
In order to insert and locate the sleeve
in a preformed feeder cavity in a mould it is pre-
ferred that the outer surface of the sleeve istapered and that the feeder cavity has a corres-
ponding taper, the direction of taper depending on
whether the sleeve is to be inserted in the feeder
cavity from above or below. It is also preferred
that the outer surface of the sleeve or the mould
surface surrounding the feeder cavity has means
for holding the sleeve firmly in position once it
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- 5 - FS 1390
has been inserted in the feeder cavity. The means
may be for example protrusions such as ri bs on the
lateral surface of the sleeve or protrusions such
as ribs formed on the feeder cavity of a sand mould
by the use of a recessed former during mould pro-
duction.
In order to make it easy to remove the
feeder a breaker core may be located between the
lower end of the feeder sleeve and the mould
cavity in accordance with normal practice. The
breaker core may be fixed to the base of the feeder
sleeve if desired, for example by means of an
adhesive or by shaping the breaker CQre so that
part of the breaker core can be push fitted into
the sleeve.
The use of a feeder sleeve according to
the invention enables moulds of simpler design to
be used because a separate sprue and the running
system which is normally used can be eliminated.
The rate of casting production can therefore be
improved because only the feeder needs to be
removed from the casting and the casting process
is also more economic because less metal needs to
be melted and cast for producing a particular casting.
Furthermore as the filter is not in
contact with the casting itself, potentially delet-
erious effects on the casting surface by the
filter are obviated and when the filter is a cloth
or mesh filter, distortion of the filter downwards
into the mould cavity due to the filter becoming
flexible at the metal casting temperature is avoided.
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- 6 - FS 1390
The invention is illustrated with
reference to the accompanying drawings in which
Figures 1 - 3 are vertical cross-sections of
feeder sleeves according to the invention and
Figure 4 is vertical cross-section of a mould
incorporating a feeder sleeve according to the
invention.
Referring to Figure 1 a cylindrical
feeder sleeve 1 formed from two parts 2 and 3 has
a cloth filter 4 made from inorganic fibre fixed
by means of an adhesive to the lower end 5 of the
top part 2 and the upper end 6 of the bottom part
3. The filter 4 is located above the lower end 7
of the sleeve 1 by approximately 33% of the overall
lS height of the sleeve 1.
Referring to Figure 2 a feeder sleeve 11
of circular horizontal cross-section has an upper
portion 12 which is funnel shaped and a lower
portion 13 which is cylindrical. A filter 14 of
ceramic foam having a taper from top to bottom
corresponding to the taper of the funnel shaped
portion 12 of the sleeve 11 is located at the
bottom of the funnel shaped portion 12 and above
the lower end 15 of the sleeve by approximately
28% of the overall height of the sleeve 11.
Referring to Figure 3 a feeder sleeve
21 of circular horizontal cross-section has an
upper portion 22 which is funnel shaped and a
lower portion 23 whose wall thickness is greater
than that of the upper portion so as to produce
a ledge 24. A filter 25 of ceramic foam is located
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- 7 - FS 1390
on the ledge 24 and above the lower end 26 of the
sleeve by approximately 26% of the overall height
of the sleeve 21.
Referring to Figure 4 a cylindrical
feeder sl~eve 31 tapering from 75 mm inner diameter
at the top down to 40 mm inner diameter at the
base is fitted with a circular ceramic foam filter
32 of 55 mm diameter held in place by the tapered
sleeve wall. The sleeve is located in a sand
mould 33 such that the sleeve 31 provides the sole
means of entry for metal into mould cavity 34
which is used to produce a plate casting measuring
26 x 26 x 3 cm in ductile iron.
When molten iron was poured into the
feeder sleeve so as to fill the mould cavity and
the sleeve cavity, the total weight of metal
poured was 16.3 kg. After the plate casting had
solidified the cast;ng was removed from the mould
and the feeder was knocked off. 2 mm of the
surface of the plate was removed by a skimming
operation and the plate was inspected by a dye
penetration technique. Very few inclusions were
present. For comparison a similar casting was
produced in a mould having a sprue, a runner
system and a feeder lined with a sleeve of refrac-
; tory heat-insulating material 75 mm in diameter
and 100 mm in height. The total weight of metal
cast was 23.15 kg which is 6.85 kg more than the
weight cast when using the feeder sleeve of the
invention. Furthermore, examination of the plate
casting by the dye penetration technique after
1 removal of 2 mm of the surface revealed the
presence of a number of inclusions.
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