TITLE: A VALVE FOR VENTILATING CASTING DIES OR MOULDS
European Patent Application EP0209505 A3

ABSTRACT:
Abstract of EP0209505
The present invention relates to a ventilating valve for a die or mould
intended to be filled with a casting mixture of a polymer material and
a ballast material. According to the invention the ventilating valve
includes a valve pipe (7) which can be screwed into the die or mould
and which has an outlet passage (12) arranged eccentrically in relation
to the screwing axis (A-A). One end of the outlet passage communicates
with the interior of the die or mould, while the other end of the
passage is connected to a net disc having a mesh such as to permit the
polymer material present in the casting mixture to pass through the net
while preventing the ballast material from leaving the valve pipe.
Subsequent to curing of the casting material, the hardened flash or
stalk in the valve pipe can be pressed out therefrom, this being
facilitated by the fact that the outlet passage (12) diverges in a
direction away from the die or mould cavity.

INVENTORS:
Lundmark, Gunnar

APPLICATION NUMBER: EP19860850236
PUBLICATION DATE: 03/23/1988
FILING DATE: 06/27/1986

ASSIGNEE: AB GUSTAVSBERG
INTERNATIONAL CLASSES: B29C33/10; (IPC1-7): B29C33/10
EUROPEAN CLASSES: B29C33/10

CLAIMS:
1. A ventilating valve for a die or mould intended to be filled with a
mixture of a polymer material and a ballast material, characterized by
a valve pipe (7) capable of being screwed into the die or mould and
having an outlet passage (12) which is arranged eccentrically in
relation to the screwing axis (A-A) and which communicates at one end
thereof with the interior of the die or mould and which is closed at
the other end thereof with a net disc (13) having a me sh which allows
polymer material present in the casting mixture to pass through the net
while preventing the ballast material from leaving the valve pipe.
2. A valve according to Claim 1, characterized in that the outlet
passage (12) in the valve pipe diverges in the outlet direction.
3. A valve according to Claim 1, characterized in that the net
structure of the net disc (13) is such as to cause silica sand to
agglomerate thereon to form a pressure-tight plug.
4. A valve according to Claim 2, characterized in that the end (10) of
the valve pipe facing towards the interior of the die or mould is
conical in shape; and in that the valve pipe can be screwed into a
sleeve (5), the end of which facing the interior of the die or mould
has a conical seat (6) against which said end (10) of the valve pipe is
intended to abut sealingly when screwing in the valve pipe.
5. A valve according to Claim 4, characterized in that the end of the
valve pipe remote from the die or mould has an external screwthreaded
section (16); and in that a lock nut (15) which secures the net disc is
screwed onto said end of the valve pipe.
6. A valve according to Claim 5, characterized in that a piece of hose
is connected to the lock nut, said hose piece having located in one end
a sinter-metal plug which is permeable to air but impermeable to
casting material.

DESCRIPTION:
A valve for ventilating casting dies or moulds
The present invention relates to a ventilating valve for ventilating
casting dies or moulds, the valve being of the kind defined in the
pre-characterizing clause of Claim 1.
It is now possible to cast sanitary products, such as sinks, wash
basins and like articles from polymer materials with ballast. Such
polymer materials function as binders for silica sand of cristobalitic
structure. A curing agent, preferably in the form of an organic
oxidizing agent, is added to impart sufficient hardness to the
material. The casting compound or material can be caused to harden, or
set, at a selected elevated temperature, e.g. 90 DEG C, by selecting a
suitable combination of the aforesaid substances. The composition of
the curing agents used also controls the setting time, which for
practical reasons is selected between 15 and 45 minutes. The cast
article is held in the die or mould during the setting period, with the
die parts held together under the requisite pressure.
Manufacture is commenced with mixing the starting materials together in
a pressure tank at room temperature. When mixing of the starting
materials is complete, the tank is closed and subjected to a pressure
of approximately 2 bars. The simplest method of maintaining this
pressure is to introduce pressurized air into the tank. The pressurized
air then forces the mixture of starting materials through an infeed
conduit leading from the pressure tank to the forming tool. The forming
tool, i.e. the die or mould, comprises in its simplest form two parts,
i.e. an upper and a lower half. The die or mould halves are brought
together laterally, with the article cast on end. When casting, the
casting material is introduced into the die from beneath, with the air
present between the die halves rising upwards and being released
through a ventilating valve.
Hitherto this valve has included a transparent, reinforced, robust
plastic hose or riser. When the casting material has advanced up into
the hose, the supply of casting material is stopped by closing a gate
valve. The plastic hose connected to the ventilating valve is then
folded back through 180 DEG and sealingly closed with a ring in its
folded state. Hardening of the casting material is then initiated, by
heating the die halves. Because the hose connected to the ventilating
valve is sealed, it has been possible to press the die halves together
with the aid of hydraulic cylinders, to a pressure of about 10 bars.
This provides a cast article with maximum surface smoothness.
When the cast article has solidified or hardened throughout, the die
halves can be separated and the sprue and exit flash or stalk
subsequently removed from the article. In this regard,the flash is
knocked-off,and the mark left behind is smoothed and polished. Since it
is practically impossible to remove the hard core of casting material
from a hose of the aforesaid kind, the hose cannot be used more than
once.
For the purpose of eliminating the necessity of scrapping a section of
the hose, and for the purpose of simplifying the operation of filling
the mould or die with casting material, there is provided in accordance
with the invention a die-ventilating valve having the characteristic
features set forth in Claim 1. When using a valve constructed in
accordance with the invention, all that need be scrapped subsequent to
casting is a small net disc having an area of some very few square
centimeters, e.g. 2 cm<2>.
So that the invention will be more readily understood an exemplifying
embodiment of a ventilating valve according to the invention will now
be described in more detail with reference to the accompanying drawing,
the single figure of which illustrates one such valve in cross-section.
The valve 1 is firmly mounted on one of the die or mould halves 2,3,
preferably the upper die half 2, as illustrated in t he drawing. The
die and the valve are both made of steel. The upper die half includes
an attachment part 4 for an attachment sleeve 5 which extends through a
leadthrough or bushing in the attachment part and passes sealingly
through a valve opening in the inner wall of the die half 2. The
attachment sleeve 5 terminates flush with the inner surface of the
inner wall of the upper disc half 2, and the lower end of the sleeve is
provided with an inwardly directed part which converges towards the
longitudinal axis A-A of the sleeve 5 and which forms a conical seat 6
for a valve pipe 7.
The upper part of the sleeve 5 has a screwthreaded section 8 in the
bushing or leadthrough which can be effected, for example, by attaching
a securing nut above the attachment sleeve.
The bottom end 10 of the valve pipe 7 is bevelled to a form which
corresponds to the form of the conical seat 6 of the sleeve 5. The
valve pipe has provided at the top thereof an external screwthreaded
section which enables the valve pipe to be screwed into the sleeve
until the bevelled end of the pipe lies against the conical seat 6. As
will be seen from the drawing, the respective screwthreaded sections of
the valve pipe and the attachment sleeve co-act with one another in a
manner which renders it unnecessary to screw down the valve pipe to a
maximum in order to establish sealing engagement with the seat.
Arranged above the screwthreaded section of the valve pipe 7 is a grip
means 11 for accommodating a spanner, wrench or some like tool. It is
also possible, of course, for the grip means per se to have the form of
a permanent spanner means or like turning device.
The valve pipe 7 also incorporates an outlet passage 12, the
longitudinal axis B-B of which is eccentric in relation to the screwing
axis A-A. This passage diverges upwardly in a direction away from the
interior of the die.
The outlet end of the outlet passage 12 is closed by a net disc 13
which is secured by a washer or plate 14, which is urged against the
end of the valve pipe by a lock nut 15 screwed onto an external
screwthread 16 formed above the grip means 11 on the valve pipe. The
net disc 13 has a mesh such as to allow the polymer material present in
the casting mix to pass through the net while preventing silica sand
from passing therethrough, so as to form a sand plug beneath the net.
Subsequent to filling the die sufficiently, the plug obtains a
dimension which enables it to withstand the high curing pressure of
approximately 10 bars.
As an additional safetyguard, in the event of the net disc being
pressed out at the beginning of the curing sequence, a piece of hose
can be connected to the lock nut 15, this piece of hose incorporating
in one end thereof a sinter-metal plug permeable to air but impermeable
to casting material.
When curing of the casting material is complete, the lock nut 15 is
unscrewed and the valve pipe 7 rotated about its longitudinal axis. Due
to the eccentricity between the outlet-passage axis and the axis of
rotation, the flash or stalk in the outlet passage will be knocked-off
at the inlet end of said passage upon rotation of the valve pipe 7. The
removed flash or stalk can then be pressed out through the outlet end
of the outlet passage, this removal being facilitated by the fact that
the outlet passage diverges in said direction.
The described embodiment is not restrictive of the invention, since the
scope of the invention is restricted solely by the following claims.