Abstract: A sand core structure for die-casting includes a positioning-filling rod and a sand core body configured to encompass the positioning-filling rod. The positioning-filling rod has a compressive strength greater than a compressive strength of the sand core body, and the positioning-filling rod is made of a breathable material.

Abstract: A breathable salt core is provided that is placed in a cavity of a casting mold in order to mold a hollow part of a cast product and that is dissolved and removed after casting, the breathable salt core being formed by powder molding innumerable salt particles into a predetermined shape corresponding to the hollow part, wherein a gap that can retain a gas remaining in the cavity in a casting process is formed between the innumerable salt particles that have been powder molded. The breathable salt core thus manufactured assures that residual gas within the cavity pushed by the molten metal to enter the gap formed between salt particles of the salt core, thereby avoiding any incomplete filling of the molten metal, and which can be formed with a simple production process at a low cost.

Abstract: A core molding method capable of satisfactorily exhausting a gaseous body such as gas or water vapor that is generated inside an outer shell layer when a raw material is cured is provided. A core molding method according to one aspect of the present disclosure is a molding method of a core formed of a raw material including a binder and sand, and includes: filling a cavity of a molding die with the raw material; curing the raw material to form an outer shell layer; inserting a tip end part of an exhaust pipe having an internal pin inserted therein and an exhaust hole closed by the internal pin into a part surrounded by the outer shell layer through an opening provided in the molding die; and moving the internal pin and opening the exhaust hole.

Abstract: Methods, systems, and apparatus for reduction of gas pressure within a core, such as a sand casting core package, during a casting process in order to reduce bubble defects. Some embodiments may comprise a mold configured to receive a molten metal to create a metal casting, such as an engine block casting. The mold may comprise a mold core configured to create a cavity within the metal casting. The system may further comprise a filling device configured for delivering a molten metal into the mold for creating the metal casting. The mold core may comprise a material that is permeable to certain gases known to often result in bubble defects. The system may further comprise a vacuum configured to be coupled with the mold to reduce gas pressure within a permeable portion of the mold in order to reduce the incidence of bubble defects within the casting.

Abstract: There is provided an improved valve mechanism for use with a casting or injection mold which is quick acting and simple to construct. The valve includes an inlet coupled to the mold cavity and an outlet for venting gas from the mold cavity. The valve further includes a closure oriented perpendicularly to the inlet and movable between open and closed positions for closing off the outlet. The closure has a central axis and the valve is configured to move the closure into the closed position by directing the melt passing through the inlet to impinge substantially coaxially upon the closure so as to transfer a majority of the momentum of the melt to the closure.

Abstract: A casting die includes a main cavity, a first reservoir and a first vent. The main cavity has a first interior volume for receiving a first molten volume of metal. The first reservoir is in serial fluid communication with the main cavity for storing a first molten backfill volume of metal to accommodate solidification shrinkage in the main cavity. The first vent is in serial fluid communication with the first reservoir.

Abstract: The patent relates to the field of metallurgical products and comprises a cylindrical body (15) provided with a plurality of slots (16), with a taper “A” designed such that the larger opening (18) is at the outer surface of the breather (15) and the smaller opening (19) is located internally with respect to the breather (15), so that the aluminum component (5), when removed from the mold (6), brings with it the burr (17), leaving the slots (16) of the breather (15) always free, and also a breather (20) comprising a cylindrical body constituted from a plurality of holes (21), with a conicity “A” designed such that the larger opening (22) is at the outer surface of the breather (20) and the smaller opening (23) is located internally with respect to the breather (20).

Abstract: The invention relates to an apparatus for ventilation of a casting mold.

Abstract: The patent relates to the field of metallurgical products and comprises a cylindrical body (15) provided with a plurality of slots (16), with a taper “A” designed such that the larger opening (18) is at the outer surface of the breather (15) and the smaller opening (19) is located internally with respect to the breather (15), so that the aluminium component (5), when removed from the mould (6), brings with it the burr (17), leaving the slots (16) of the breather (15) always free, and also a breather (20) comprising a cylindrical body constituted from a plurality of holes (21), with a conicity “A” designed such that the larger opening (22) is at the outer surface of the breather (20) and the smaller opening (23) is located internally with respect to the breather (20).

Abstract: A valve device has a main body in which an exhaust hole configuring a part of the gas drainage path is formed; a valve element capable of opening and closing the exhaust hole; a cylinder housing a piston coupled to the valve element; and an electromagnetic selector valve for selectively switching a supply route of a driving fluid supplied from a fluid supply source of a die-casting machine to the cylinder either to a front chamber of the cylinder or to a rear chamber of the cylinder. The main body includes a front face configuring a part of a parting face and a fitting portion that tightly adheres to a wall face of a housing hole. The electromagnetic selector valve is positioned on a rear side of the main body, and positioned inwardly of a contour line of the man body formed by the fitting portion.

Abstract: A vacuum/vent passageway for use in injection molding and die casting systems comprises a first-side and a second-side. The first-side comprises a first corrugated cooling face having a series of longitudinally spaced channels, wherein channels of the series of longitudinally spaced channels have non-uniform longitudinal cross-sectional trough shapes across the series of longitudinally spaced channels. The second-side comprises a second corrugated cooling face having a series of longitudinally spaced ribs, wherein ribs of the series of longitudinally spaced ribs have non-uniform longitudinal cross-sectional tip shapes across the series of longitudinally spaced ribs.

Abstract: The present invention is to provide a machine and a method for suctioning and exhausting air from a storage tank for sand in a molding machine that has less on-off valves and prevents sand from adhering to the interior of the valve for exhausting air while the air is being exhausted.

Abstract: The casting device (1) comprises a die (3) consisting of two die halves (3a, 3b) forming in their interior a die cavity (4). In addition, the casting device (1) comprises connected to the die cavity (4) a casting chamber (6), the outlet (9) of which can be closed off at least partially by means of a closure member (18,26). At least the one die half (3a) is provided with a vent passage (13) for evacuating the die cavity (4) and/or the casting chamber (6). The vent passage (13) ports into the die parting (12) of the one die half (3a) such that it can be closed off by the other die half (3b) when locking the die (3).

Abstract: The invention relates to a casting mould for the casting of metals, wherein a layer consisting of a material which absorbs harmful substances on at least sections of gas outlet surfaces of the casting mold, in particular the top side thereof. The invention also relates to a coating composition, to a process for producing the casting mold and to the use thereof for casting of metals.

Abstract: A metal casting system and related method are described that eliminate or at least significantly reduce deposition and buildup of resinous materials in gases vented during a casting operation. One or more heating assemblies are provided in vent passageways in the casting equipment, and particularly in the casting dies. The heating assemblies maintain exposed vent passageway surfaces at relatively high temperatures.

Abstract: A vent assembly (453) for a high pressure die casting system including a pair of opposed chill blocks (450, 452) having corresponding chill surfaces defining a continuous vent chamber therebetween, each of the chill surfaces comprising a plurality of adjoining chill faces (62, 136, 162, 163, 170) extending the length of the vent chamber, each chill face having a corresponding chill face on the paired chill block defining a section of the vent chamber, the plane of each chill face being oriented at an angle to an adjoining chill face on the corresponding block. Preferably the chill face on a chill block is substantially equidistant from the chill face of the corresponding chill block defining the respective section of the vent chamber.

Abstract: A gas purging block for use with injection molding and die casting systems comprises a stationary-side block for connecting to a stationary mold or die half, and a movable-side block for connecting to a movable mold or die half. The stationary-side block comprises a recessed cooling face having a first smooth contour extending between a first side and a second side of the stationary-side block to increase the surface area of the recessed cooling face. The movable-side block comprises a protruding cooling face having a second smooth contour extending between a first side and a second side of the movable-side block to increase the surface area of the protruding cooling face.

Abstract: A die casting mold includes a resistance member (17) disposed in a vent passage (16) to reduce a flow velocity of molten metal as the molten metal advances along the vent passage. The resistant member comprises a plurality of discrete protrusions (24) arranged in staggered relation to one another in both a longitudinal direction and a transverse direction of the vent passage so as to define therebetween a labyrinthine part (34) extending between an inlet side and an outlet side of the vent passage.

Abstract: A method for reducing pollutant emissions from a metal casting case used in foundry practice. The metal casting case includes at least a molding material formed to a metal casting mold. The pollutant emissions are released from material making up the casting cases after pouring molten metal in the metal casting mold. The method includes the steps of adding at least one additional combustible substance to at least one region of the casting mold located outside of a contact region of the casting mold with the casting, and burning the at least one additional combustible substance in one of a gaseous and vaporized state together with the pollutant emissions.

Abstract: The present invention relates to a gas purging block for use with injection molding and die casting systems, which includes a stationary-side block adapted to be removably mounted to a stationary-side mold half of the injection molding or die casting system, and an ejector-side block adapted to be removably mounted to an ejector-side mold half of the injection molding or die casting system. At least one of the stationary-side block and the ejector-side block includes a pair of channels extending through the block adapted to selectively function as conduits for cooling fluid and as mounting bores for mounting the block to the respective mold half.

Abstract: An electromagnetic drive-type die casting decompression valve comprises a drive shaft, provided inside a drive block, driven by electromagnetic force from a solenoid, and a valve shaft, provided inside a valve block separate from the drive shaft, provided with a valve body on one shaft end. Also, a closing spring working jointly to urge the valve body in a closing direction is provided on the valve shaft, while an opening spring working jointly to urge the valve body in the opening direction is provided on the drive shaft. The valve block is also provided in a replaceable manner. According to this type of electromagnetically driven die casting decompression valve, bouncing is not caused at the time of closing a decompression valve, and it is also possible to significantly decrease maintenance time and repair costs even when problems arise, such as molten metal infiltrating into a valve body.

Abstract: The venting valve assembly for casting moulds comprises a venting valve for closing a venting channel. The venting valve comprises a valve housing in which a closure member is received that is movable between an open position and a closed position. The closure member can be frictionally locked in its open position and simultaneously biased in closing direction. For frictionally locking the closure member, a chamber is provided that can be put under a hydraulic overpressure. The chamber has a wall portion that bulges towards the closure member in response to the overpressure. The wall portion is resilient such that it moves back to a position releasing the closure member once the overpressure in the chamber is reduced. For reducing the pressure in the chamber, a release valve is provided which is controlled by a sensor detecting any casting material penetrating into the venting channel. The biasing of the closure member in closing direction is performed pneumatically.

Abstract: An electromagnetic drive-type die casting decompression valve comprises a drive shaft, provided inside a drive block, driven by electromagnetic force from a solenoid, and a valve shaft, provided inside a valve block separate from the drive shaft, provided with a valve body on one shaft end. Also, a closing spring working jointly to urge the valve body in a closing direction is provided on the valve shaft, while an opening spring working jointly to urge the valve body in the opening direction is provided on the drive shaft. The valve block is also provided in a replaceable manner. According to this type of electromagnetically driven die casting decompression valve, bouncing is not caused at the time of closing a decompression valve, and it is also possible to significantly decrease maintenance time and repair costs even when problems arise, such as molten metal infiltrating into a valve body.

Abstract: The venting valve assembly for casting moulds comprises a venting valve for closing a venting channel. The venting valve comprises a valve housing in which a closure member is received that is movable between an open position and a closed position. The closure member can be frictionally locked in its open position and simultaneously biased in closing direction. For frictionally locking the closure member, a chamber is provided that can be put under a hydraulic overpressure. The chamber has a wall portion that bulges towards the closure member in response to the overpressure. The wall portion is resilient such that it moves back to a position releasing the closure member once the overpressure in the chamber is reduced. For reducing the pressure in the chamber, a release valve is provided which is controlled by a sensor detecting any casting material penetrating into the venting channel. The biasing of the closure member in closing direction is performed pneumatically.

Abstract: The valve assembly for venting die casting molds includes a venting channel, a venting valve communicating with the venting channel, as well as an actuating device for closing the venting valve. The actuating device includes a power pick-up member that is axially movable under the influence of the liquid casting material entering the venting channel. The venting valve includes a closure member biased against a stop member and operatively connected to an actuating element. The stop member is pivotable by the power pick-up member such that the closure member of the venting valve is displaced from its open position to its closed position under the influence of the actuating element. Thereby, a reliable closing of the venting valve is ensured, even under unfavorable operating conditions.

Abstract: The removal of bonded sand, either core sand or mold sand, from a metal casting comprises placing the metal casting in a furnace chamber and subjecting the metal casting to the action of a high velocity heated gas stream (preferably above 3000 ft/minute) from hot air generators positioned on opposite sides of the chamber at the approximate level of the metal casting and directed to the metal casting. The heated gas stream is at a temperature and oxygen content sufficient to oxidize the binder in the bonded sand and a velocity sufficient to remove the debonded sand. The sand is removed by gravity from the furnace chamber.

Abstract: A die casting machine capable of reducing the pressure in a die cavity to a lower level such as a substantially perfect vacuum, having a movable die and a fixed die, a vacuum pump for reducing pressure in a cavity formed between the dies, and an injection apparatus for injecting and filling molten metal into the cavity with reduced pressure, at least one of the dies having an evacuation path connected with the vacuum pump and communicated with the cavity, a valve element for opening and shutting the evacuation path, and an electromagnetic driving means for making the valve element move linearly in the opening and shutting direction by electromagnetic force.

Abstract: In order to vent a diecasting mold of a diecasting machine, it is proposed that the mold cavity and/or the pressure chamber are vented during the filling operation by a second venting valve, additionally to a first venting valve. The first venting valve is located in a venting channel portion that communicates with a venting channel leading out of the mold cavity. For operating the first venting valve, an impact transmitter is provided that is operationally connected to the first venting valve and that is exposed to and moved by the casting material advancing from the mold cavity to the venting channel. The second venting valve is operated by separate independent means and is closed before the mold cavity is completely filled. As a criterion for closing the second venting valve, the length of the path can be used along which the casting piston runs during the filling operation.

Abstract: A vent-forming apparatus for use in metal casting comprises a gas-permeable membrane with a lead-in tube attached to one surface and a breather tube attached to the opposite surface. The vent-forming apparatus may be used to create independent vents in the walls of shell-type molds used in the ceramic shell casting process for lost wax casting of ferrous and non-ferrous alloys. These vents exhaust gasses in the mold cavity to the atmosphere. The vent-forming apparatus also may be used in solid mold investment casting methods or in any other casting method in which venting is desirable or necessary.

Abstract: In the venting valve device for die-casting, the evacuation valve which is intended to be closed comprises an evacuation piston and is actuatable by a pneumatic control piston which is in the form of a double-acting differential piston, whereby one of its pressure surfaces is supplied with compressed air by a high response valve in order to open while its other pressure surface is supplied with compressed air by a second control valve in order to close. The high response valve is provided with a vent in order to reduce the pressure maintaining the control piston in the open position within a very short time and thus to ensure a very short closing time of the evacuation piston. While being simple in construction, such a venting valve allows a very short closing time and is therefore particularly suitable also for high-speed die-casting.

Abstract: An ingot plate (10) of cleaveable thermoelectric material has a layered structure having substantially parallel cleavage planes. Substantially all of the cleavage planes are disposed at a less cleavage angle with respect to the upper and lower faces (11, 12) of the plate. The ingot plate can be successfully cut into bars (20) along cutting planes generally perpendicular to the cleavage planes without causing substantial interlayer fracture. Electrodes (25) are formed on the opposite sides of the bar which are defined by the cutting planes. The bar is in use to be cut into a number of discrete chips (30) with one of the electrodes fixed on a substrate. Since the cutting is made along planes again generally perpendicular to the cleavage planes of the bar, the bar can be successfully cut into the corresponding chips without causing any substantial fracture.

Abstract: A porous composite forming material is held in a cavity of a casting mold, and molten light alloy is poured into the cavity of the casting mold through a gate. Then a gas pressure is applied to the cavity in the casting mold with the cavity closed, thereby impregnating the pores of the porous composite forming material with the molten light alloy and forming a composite portion formed of a composite material of the light alloy and the composite forming material.

Abstract: A sealing and guiding device for the injection piston (3) of a hot chamber pump for corrosive alloys made up of a body (1) in which a chamber (6) and an injection cavity (2) therebelow are formed, wherein the piston (3) slides with a vertical reciprocating motion (V), includes a bush (8), having an outer diameter smaller than said chamber (6), interposed between centering members housed in the chamber (6) and made coaxial with the chamber (6) and with the piston (3) by a pair of opposite surfaces of revolution (12, 13) formed on said centering members, the upper surface (13) and the relevant centering member performing a pressure-tight sealing. The outer lateral surface (15) of the bush (8) is in communication with the injection cavity (2) whereas the upper side of the bush (8) is in communication with the crucible and immersed therein at a depth (L), measured from the lowest level (23) reachable by the molten alloy, which is greater than the maximum travel (C) of the piston (3).

Abstract: A chill vent is provided with a cooling pipe around a zigzag-shaped gas exhaust passage, and made of a Be--Cu alloy which is superior in cooling power. An accelerated solidification of non-solidified molten metal entering into the chill vent is achieved, thereby effectively preventing flashing of the molten metal without complicating the construction or increasing the size of the entire facility.

Abstract: A chill vent made of copper or copper alloy has a concave section and a convex section, each being subjected to removal of flat parting portions on both side surfaces, and a gas exhaust passage is formed over the entire width region. These gas exhaust passage portions have side surfaces and back surfaces which are enclosed in hard U-shaped guide frames. It is possible to effectively avoid occurrence of leakage or flashing of molten metal due to a plastic deformation of the chill vent by a mold fastening force applied upon assembly of a die-casting mold, which may occur when a copper or copper alloy having a superior cooling property as the material for chill vent.

Abstract: The vent includes a plurality of passages formed by a plurality of stacked plates. The passages are dimensioned to permit the free flow of air but to prohibit the passage of molten metal. During die casting, air is free to exit the die while molten metal is retained.

Abstract: A valve assembly for venting diecasting moulds comprises a venting channel, a venting valve communicating with the venting channel and having an axially displaceable valve closure member, and an actuating member for operating the venting valve from an open position into a closed position. The actuating member includes a power pick up member exposed to the liquid casting material escaping during the casting operation from a casting chamber provided in the diecasting mould through the venting channel and being axially displaceable under the influence of the kinetic energy transmitted from the liquid casting material to the power pick up member when the liquid casting material hits the power pick up member.

Abstract: The core box vent useful in core making, comprises a porous cylinder of sintered ceramic materials, the pores of such cylinder being less than will allow intrusion of the grain size of sand to be introduced to the core box. A method of making cores using the above vent comprises, first, providing mateable core box sections with blow tubes permitting introduction of an air fluidized sand mixture into the interior of such box sections and providing one or more ceramic core box vents in an exhaust side of the mating core box sections to permit egress of air used to fluidize the sand mixture the vents have a labyrinth of passages or pores smaller in diameter at least than the average grain size of the sand in the mixture sand and resin mixture is blown into the interior of the mated core box sections, with the resin being curable to polyurethane by chemical reaction. Next a catalyst curing gas is blown through the mixture via such blow tubes. Lastly, the mixture is purged with air.

Abstract: A casting mold has a main body provided with a vent hole opened up in a casting space of said main body. The improvement is characterized in that the vent hole is provided with air discharging means and air feeding means which are disposed at the vent hole and the air discharging means and air feeding means are suitably selected so that air within the casting space can be discharged and a pressurized air can be fed toward the casting space through the vent hole.

Abstract: The molding apparatus includes a pattern plate carrier for air-pressurized compaction processes. The carrier is equipped with air venting structure running along the inner contour of the mold box of the sand molding apparatus in the form of elongated slotted bars.

Abstract: An apparatus for producing sand mold employing compressed air comprises a sand molding apparatus for use in making sand molds by employing compressed air. The apparatus includes, in the preferred embodiment, a pattern plate carrier having a top surface for supporting a pattern plate thereon. A molding box is positioned on the top surface of the pattern plate carrier and surrounds the pattern plate so as to define between the pattern plate and the interior surface of the molding box a peripheral area on the top surface of the carrier. Vents are provided on either the peripheral area define above or the pattern plate or both and extend around the pattern plate for allowing compressed air which is injected into the molding box during compression of the molding sand to escape on the pattern side of the molding box. A chamber is defined within the carrier beneath the pattern plate and is communicated with the vent structure by means of bores.

Abstract: In a wear plate (16) with a number of air-escape nozzles, in the example shown consisting of annular gaps (27) formed between bores (17) in the wear plate (16) and nozzle members (21) screwed into the bores (17) to make the mold-chamber faces (26) on the nozzle members (21) align with the mold-chamber surface (20) on the wear plate (16) in order to avoid problems when a finished mold or mold part is moved slidingly along the mold-chamber surface (20), the novel feature consists in that the nozzle members (21) have been screwed tight against an abutment tool (23) held temporarily in close abutment (not with a small gap as shown) against the mold-chamber surface on the wear plate (16), after which the nozzle members (21) have been secured in the position of alignment achieved in a suitable manner, such as by using a settable cement (30) filling the spaces between the thread (18) in the bores (17) and the thread (22 ) on the nozzle members (21) and keeping flanks (31) on the nozzle-member thread (22) in engageme

Abstract: The core box has a drag and a cope forming a mold cavity for forming a sand base core. This sand is injected into the cope and the air in the cavity is vented through vents remote or spaced away from where the sand is inserted. These vents are usually in the drag, but may also be in the cope. In each vent adjacent the cavity is a cylindrical cup-shaped plug having slotted perforations in its bottom narrower than the diameter of the sand grains. The diameter of this perforated vent plug is at least 50% greater and preferably at least twice the width of the cavity, slot, or groove at the vent whereby air can be vented along the cavity. Furthermore, the plug having the perforations may be contoured to the groove or that portion of the cavity in which the vent is located so that air can also be vented from the sides of the cavity or groove.

Abstract: In a process for producing mouldings, into whose interior is introduced a medium, particularly for producing core boxes for core shooting, in the mould cavity are provided ventilating holes or vents which are occupied by nozzles. During the moulding of the moulded part or a core member arranged therein, particularly the core box, at least one insert is inserted, whose shape corresponds to that of the nozzle. After the moulding of the core box the insert is removed and replaced by the nozzle.

Abstract: A degassing apparatus for a mold includes a degassing valve, an acoustic wave detecting unit, and a valve closing unit. The degassing valve is located at an end portion of a degassing passage extending from a mold cavity. The acoustic wave detecting unit is arranged midway along the degassing passage and detects an acoustic wave generated when a molten metal collides against a wall surface of the passage, and thereby detecting passing of the molten metal. The valve closing unit closes the valve when a detection signal level is higher than a reference signal level.

Abstract: A gas venting device for molding operations is disclosed having a valve for closing off a gas evacuation system from a mold when the mold cavity is filled with melt. A positive drive mechanism is provided for closing the valve, and a mechanism is provided for allowing the valve body to close more rapidly by action of the melt itself against the valve body in the event the melt advances more rapidly.

Abstract: A gas vent system of a mold improves timing of closing the gas vent passageway, in particular in die castings or in moldings. The gas vent passageway is formed on mating surfaces of a pair of mold halves and communicating a mold cavity with the outside of a mold when the mold is closed. The gas vent valve is mounted on one of the mold halves and disposed intersecting perpendicularly to the gas vent passageway and is provided with a concave portion on its end surface receiving the pressure from the molten pressure charged. The other mold half is provided with a projection which can be fitted tightly in the concave portion of the gas vent valve, and the projection is provided with part of the gas vent passageway so as to direct a flow of the molten material passed through the gas vent passageway from the mold cavity toward the concave portion of the gas vent valve. The gas vent valve is operated to close the gas vent passageway in response to a pressure from the molten material forced into the mold cavity.

Abstract: A gas venting device for molding operations is disclosed having a valve for closing off a gas evacuation system from a mold when the mold cavity is filled with melt. A positive drive mechanism is provided for closing the valve, and a mechanism is provided for allowing the valve body to close more rapidly by action of the melt itself against the valve body in the event the melt advances more rapidly.

Abstract: An improved gas venting valve is provided for use with a material-forming mold or die cavity to control venting of gas through a gas conduit communicating with the cavity. The gas venting valve includes a hollow piston axially movable in a housing and having a valve head connected thereto for movement between open and closed positions relative to a valve seat. The valve seat is disposed in a portal of the housing communicating with the gas conduit. In the open position, a gas venting passage internal of the piston is communicated to the portal by the open valve for venting gas from the cavity as material is introduced therein. In the closed position, the valve head is sealed against the valve seat to prevent material introduced into the mold cavity from escaping. The piston is axially moved in the housing by application of pressurized fluid to respective pressure responsive surfaces on the piston.

Abstract: A gas venting arrangement in a high speed injection molding apparatus such as a high speed die casting machine. The gas venting arrangement includes a gas vent control valve which is closable at an optimum timing and at high speed. This valve closure is achievable by providing an improved combination of a control circuit and a valve driving mechanism. The control circuit is connected to a molten metal sensor and sends a high voltage output drive signal to the valve driving mechanism when the sensor detects a first molten metal or a metal splash. The valve driving mechanism includes an electromagnetic valve connected to a pneumatic source and a pneumatically operated valve connected between the electromagnetic valve and the gas vent control valve. The pneumatically operated valve is also connected to the pneumatic source. The electromagnetic valve performs prompt change-over operation upon receiving the drive signal, and supplies driving pneumatic pressure to the pneumatically operated valve.