The document describes a patent for improvements in the production of molds and cores. It involves a process of blowing a mixture of sand and gas-hardenable binder into a mold or core box while applying a gaseous hardening agent. Specifically, it applies the hardening agent at points where the air pressure driving the mixture has reduced, so that the gas is prevented from flowing backwards. The invention also provides an apparatus for this process using a blowing plate with vents to introduce the hardening gas into the mixture stream.

1. * GB780039 (A)
Description: GB780039 (A) ? 1957-07-31
Improvements in or relating to the production of moulds and cores
Description of GB780039 (A)
PATENT SPECIFICATION
Inventor: DONALD HORACE SNELSON 780,039 Date of filing Complete
Specification Nov. 10, 1955.
" Application Date Nov. II, 1954. No. 32717/54.
Complete Specification Published july 31, 1957.
Index at acceptance:-Class 83(1), F(5B: 8J4B: 13BX).
International Classification:-132Zc.
COMPLETE SPECIFICATION
Improvements in or relating to the Production of Moulds and Cores Wie,
FOUNDRY SERVICES LIMITED, of Long Acre, Nechelils, Birmingham 7, a
British Company, do hereby declare the invention, for which we pray
that a patent may be granted to us, and the method by which it is to
be performed, to be particularly described in and by the following
statement:-
The present invention relates to improvements in the formation of
moulds and cores o10 by the process which consists in blowing sand
into a mould or core box by air pressure. Such a process is used to
enable mould or core boxes to be filled and formed rapidly.
It is known to incorporate a binder, such as waterglass, in the sand
to be blown into the mould or core box and to apply a gas, such as
carbon dioxide, vhich reacts with the binder to effect rapid hardening
and render the mould or core stronger.
According to the present invention, a method of making a mould or core
comprises blowing a mixture of sand and gas hardenable binder into a
mould or core box and applying a gaseous hardening agent thereto as
the mixture is entering the mould or core box.
According further to the present invention, a method of making a mould
or core by the method just set forth comprises applying air pressure
to a mixture of sand and gas-hardenable binder to cause the mixture to
pass through a passageway into a mould or core box and applying a

2. gaseous hardening agent at a point or points in the passageway where
the pressure initially exerted on the mixture has become reduced, the
gaseous hardening agent being applied at a pressure equal to the
initial air pressure or between the initial air pressure and the
reduced air pressure, whereby the gaseous hardening agent is prevented
from passing through the passageway in the reverse direction to the
sand/binder mixture.
The invention also provides apparatus for use in making a mould or
core by blowing a mixture of sand and gas-hardenable binder into a
mould or core box and applying a gaseous hardening agent thereto as
the mixture [Price 3s. 6d.] is entering the mould or core box,
comprising a blowing plate to be mounted upon the moula or core box
and to support a container for the 50 mixture, which plate comprises
wails defining an orifice and means for feeding gaseous hardening
agent into said orifice. In a preferred form of the invention the
orifice is surrounded by a hollow chamber for receiving the gaseous 55
hardening agent and one or more vents are provided in the walls of the
orifice for allowing the gaseous hardening agent to be introduced into
the orifice.
In order that the invention may be readily 60 understood, reference is
made to the drawings accompanying the provisional specification in
which: Fig. 1 shows the equipment used in the imown mould Or core
blowing process employing a single-orifice blowing plate; Fig. 2 shows
equipment suitable for carrying out the present invention; Fig. 3
shows the actual pressure gradient between container and mould or core
box 70 entrance; Fig. 4 illustrates one alternative form of equipment
to that shown in Fig. 2; and reference is also made to the drawings
accompanying the present specification, in 75 which:Fig. 5 illustrates
diagrammatically a form of apparatus for use in illustrating the
principle of the invention; Fig. 6 illustrates theoretically the
pressure 80 gradient within the container, blowing plate and meuld or
core box during the blowing process.
Referring to Fig. 1, the normal method of blowing moulds or cores
makes use of a container la which' has a blowing plate lb attached to
the lower open end thereof, an orifice lc being provided in the
blowing plate lb, which is clamped over a mould or core box Id. The
container la is filled with sand g0 by hand and lair pressure at
approximately lbs. par sq. in. is applied to the surface of thle sand
in the container la to inject the sand through the orifice lc into the
mould or core box ld and thereby form the desired mould or core.
If COO is to be introduced with the sand at the same time, using a
normal blowing plate, the pressure of CO2 will necessarily be greater
than the pressure of the air used to blow the core, i.e. greater than
100 lbs. per sq. in. The result of this is that CO. will pass not only

3. into the mould or core box ld but also into the container la and will
therefore harden the residual sand which is in excess of that required
to fill the mould or core box ld.
In carrying out the invention, CO. is injected into the sand/air
mixture entering the core box at such a pressure that it will not blow
back into the sand/air mixture remaining in the container which is at
approximately lbs. per sq. in.
In accordance with one embodiment of the invention, the blowing plate
is formed with an orifice in the shape of a venturi tube, i.e.
a tube having a smaller aperture at the container end than at the
mould or core box end and is provided with an aperture or aperLS tures
in the wall of the orifice located where the cross-section of the
orifice lies intermediate the cross-sections at the twvo ends, and
preferably nearer the mould or core box end.
Conveniently the biowing plate is formed as illustrated in Fig. 2.
where the orifice 2c takes the form of a venturi tube, the walls of
which form part of a hollow plate 2b including a chamber 2e extgnding
round the orifice 2c and having vents 2f passing through the watlls at
a point near the under end of the orifice 2c ant; preferably inclined
so that the direction of flow of gas therethrough from the chamber 2e
into the orifice 2c has a component in the direction of flow of the
air/sand mixture through the orifice. The only entrance to the chamber
2e is through an opening 2g which ienabies carbon dioxide to be
admitted under pressure.
There will be a continuous fall of pressure from point 1 where
the:air/sand mixture enters the orifice 2c and point 2 where the air/
sand mixture leaves the orifice 2c. At point 1, the pressure is
approximately 100 lbs. per sq.
in., namely the pressure prevailing in the sand container 2a, while at
point 2 it has fallen to a lower fi.ure, as illustrated in Fig. 3,
where P1 indicates the pressure in the container 2a, P2 the pressure
of carbon dioxide in the chamb'er 2e and P3 is the pressure where the
apertres 2f enter tire orifice 2c, which pressure it will be noted is
only slightly greater than the pressure at the mould or core box end
of the orifice 2c.
If CO is injected into the stream passing through the venturi orifice
2c at the apertures 2f at a pressure greater than at point 2 but less
than the pressure at point 1 (say 100 lbs.
F.per sq. in.), CO. will be drawn into the air/ sand stream. but will
not penetrate into the sand container 2a. By this means, CO. will be
drawn into the mould or core box 2d, but at the same time it wvill not
enter into the container.
It is of course possible to introduce CO, m other ways utan tuirough
tme walls ot the venturi tuoe oliltce in tne biowing plate. inmce 70

4. the pressure in mte orifice is approximately unitorm at any
cross-section, the CO2 may be intio/uced at any point of a
cross-section ot the venturi tube orifice. T1his is illustrated in
Fig. 4, where a sand container 4a is supported 75 on a solid blowing
plate 4b having a venturi tube oriice 4c tnerein. CO is introducea
through a tube 4g passing through the wall of the container 4a and
having its outgoing end terminating vertically downwardly and
coentrally withlin the orifice 4c in the blowing plate 4b.
Alternatively, a central tube, such as the tube 4g just described may
be used in association with a hollow blowing plate such as that shown
in Fig. 2, so that CO2 is introduced at 85 the same pressure both by
way of the tube 4g ani by way of the apertures 2f in the walls ot the
orifice 2c.
Fig. 5 ot the drawing accompanying the present specification shows a
jorm of apparatus 90 suitable for iliustrating the process ot mould or
core inmaKing according to the invention. A mould or core box 10 is
mounted upon a suitable support 11 anid carries at its upper end a
blowing plate 12. 'ihis is of the hollow type 95 shown in Fig. 2 ot
the drawings accompanying the provisional specification. The blowing
plate 12 supports a cartridge or sand container 14 in which is
provided a sand/binder mixture for forming the desired mould or core.
A 1l0 core blower 16 is mounted at the upper end of the container 14
and comprises an upright hollow cylinder having a spring-loaded valve
17 in the bottom closure wall thereof. The stein 18 of the valve 17 is
pivotally connected 10:
to one end of a lever 19 fulcrumed to a suitably rigid part 20. A tube
21 connects the interior of the core blower 16 to a compressed air
line 22. Carbon dioxide at a pressure of approximately 750 lbs. per
sq. in. is contained 11o in a bottle 24 provided with the usual outlet
valve 25, which is connected by a tube 26 to a pressure-operated
reduction valve 27. The latter is connected by a tube 28 to a gas
reservoir 29, the pressure in which is adjustable 11' by means of a
relief valve 30, and the reservoir 29 is connected bya turbe 31 to a
solenoidoperated valve 32. which controls the supply of CO, by way of
a tube 34 to the blowing plate 12. A micro-switch 35 is mounted so
that 124 its rocker arm 36 is controllable by the lever 19 of the core
blower valve 18 and the switch is coupled by an electrical lead 37 to
the solenoid valve 32. The reduction valve 27 is connected to the air
line 22 by way of a tube 12'.
38.
Operation of the lever 19 to open the valve 17, whereby the
sand/binder mixture 15 is subjected to the air pressure in the line 22
and blown into the mould or core box 10, also 131 780,039 he orifice
ysed in the blowing plate and will be best ascertained as a result of

5. experiment.
In certain circumstances, it may be desirabie to aomit further (GL,
alter tne core or mouki is iully formed, provided the air pressure is
maintained.
It will also be appreciated that the CU2 may icbe admitted through a
hole or holes extenaing round the outlet of the blowing plate instead
of the passageway, provided tmat tie 75 pressure of the CO, at tmat
point is less than the pressure of air applied to the sand and binder.
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