WO2008141754A1

WO2008141754A1 - Device and method for supplying a core sand magazine for a core shooter with humidified gas

Info

Publication number: WO2008141754A1
Application number: PCT/EP2008/003832
Authority: WO
Inventors: Andreas Eichelberger; Werner Pichler
Original assignee: Hottinger Maschinenbau Gmbh
Priority date: 2007-05-23
Filing date: 2008-05-13
Publication date: 2008-11-27
Also published as: DE102007023883A1

Abstract

The invention relates to a gas supply device (10) for supplying a core sand magazine of a core shooter with a humidified gas that is under pressure, comprising a compressed gas reservoir (12) for the humidified gas, the reservoir having a gas outlet (18) for supplying the core sand magazine, and a gas inlet (16) for filling the compressed gas reservoir. The gas supply device (10) further comprises a gas humidification device (14), which is arranged in a gas supply line to the gas inlet (16) and humidifies a gas up to a predetermined humidity in order to form the humidified gas.

Description

Apparatus and method for supplying a core sand hopper to the core shooter with moistened shot gas

description

The present invention relates to a shot-gas supply apparatus, and more particularly to a shot-gas supply apparatus which makes it possible to provide a pressurized gas of predetermined adjustable humidity to a core shooting facility.

More recently, it has become necessary to intentionally and precisely humidify core sands used to produce metal cores to ensure the safe and reliable operation of the entire core shooting process, that is, the process of creating a sand core. This is due to the fact that, for reasons of environmental protection, there is currently a shift from sand cores bound by organic binders to sand cores bound with inorganic binders.

Regardless of the type of binder used, in core making a molding material, a so-called "core sand", is filled into a mold having a cavity having the shape of the sand core to be formed. The core sand is usually introduced via a plurality of distributed openings arranged, so-called "shot openings" in the mold. When filling in each of the firing openings, a nozzle ("firing nozzle") is introduced, through which the core sand is introduced into the cavity, which is usually carried by compressed air or pressurized gas at high speed, so that the core sand is also injected. The core sand itself is normally stored within a closed volume on the side of the shot nozzle facing away from the mold, the so-called "shot hood." For introducing the core sand, the core sand volume is suddenly and briefly recorded (within about 500 ms to 800 ms) By pressurizing the core sand is introduced into the mold, wherein the core sand is completely penetrated by the gas, so that the majority of the introduced gas through the core sand and through the weft nozzles flows into the mold, from which the shot gas can escape via vents.

In processes with organic binding materials, dry air is usually used as a shot gas, since these binders are hardened after introduction of the core sand into the mold by adding an activating gas.

However, the use of this activating gas as well as the use of organic binders leads to a non-negligible burden on the workplace or the environment, so that the development of core sands with inorganic binders, such as water glass, have been promoted. The inorganic binders cure under the influence of supplied heat so that an activating, polluting gas can be dispensed with.

For curing, therefore, the filled with the core sand mold is heated, or the core sand is introduced into an already preheated mold. Therefore, a heat effect on the core sand before the actual introduction into the molded part must be avoided in order to prevent premature curing of the core sand. Such premature curing, for example in the firing nozzles, leads inevitable that the core shooter is clogged and thus the core manufacturing process is interrupted.

This problem can be observed especially in the firing nozzles, which are located in the vicinity of the preheated molds, ie indirectly heated by them. However, the core binder with inorganic binder cures slowly even at normal ambient temperature, so that curing was observed even within the located in the firing hood sand volume.

Curing can be prevented by moistening the sand, whereby the amount of moisture supplied must be precisely metered to allow the production of high quality sand cores. If too little moisture is supplied per unit of time or per volume of sand, premature hardening and thus clogging of the apparatus still occurs at the points which are particularly exposed to temperature. However, if too much moisture is added, condensation of the moisture may occur, leading to the formation of drops of the liquid supplied, which are introduced by the shot nozzles into the mold and lead to voids in the sand core. This inevitably leads to a deterioration in the quality of the sand cores and thus an increase in rejects in the foundry.

In order to ensure suitable moistening, attempts have been made inter alia to apply enough moisture to the core sand mixture even before it is brought into the core shooter. In such a process, however, one relies on the fact that there must be no production interruptions, since in these waiting times the core sand mixture on the transport route to Kernschießma- machine or silo could lose so much moisture that it again to the above-mentioned premature Sandaushärten can come in shotguns and shot nozzles. In the event of such an interruption, the waiting time, the finished sand mixture would have to be removed from the core shooter and the transport routes to the core shooting machine consequently. Alternatively, it would have to be re-moistened exactly controlled, ie be humidified again depending on the respective, possibly even seasonally changing, environmental conditions, so that subsequently in the continuation of the core production reproducible high-quality sand cores can be produced. However, both approaches are not feasible with a reasonable cost / benefit ratio.

Since a completely trouble-free operation in industrial production also does not correspond to reality, the use of pre-moistened sand is of little promise, or inevitably leads to disruptions in the production process.

The German utility model 202006010504 Ul proposes to carry out a compressed air humidification within a compressed air tank, in which the firing air of the core shooting machine is stored, that there is liquid water within the compressed air tank. The compressed air is introduced either above the water level in the compressed air tank or below the water level, so that the newly introduced compressed air is first passed through the water to be moistened during the introduction. In both cases, the moisture or water taken up by the compressed air is to be returned to the core sand mixture (sand, binder and possibly also activators or promoters) during the firing process.

Both alternatives of humidification have disadvantages. If the compressed air is only passed through the water reservoir, this leads to an uncontrolled and inadequate water absorption of the gas or the air, since the time between two firing operations in industrial core production not sufficient to allow the adjustment of a thermal equilibrium between the water and the gas, so that a reproducible amount of liquid water could go into the gaseous phase to moisten the shot air. As a result of this, inadequate moistening, in particular during the core formation of core sands bonded with inorganic binders, as already described, results in the core sand at exposed points in the core shooter (in particular within the weft hood and the weft nozzles) as a result of the hardening process of the sand in the tool required heat input into the mold or the molding and the resulting heat radiation in the firing hood / shot nozzles hardens too quickly. That is, it too quickly evaporates too much from the existing sand moisture and the sand hardens too quickly. This has the input described consequences of production disruption or production interruption.

When the compressed air is passed through the water reservoir, there is also no thermal equilibrium between the gas and the liquid. Rather, it can lead to the uncontrolled entrainment of too much water. As a result, portions of the weft hood, the weft nozzles and also the mold are washed out when the moisture condenses from a supersaturated compressed air. The result is the mis-production of sand cores.

The entrainment of water is also favored, among other things, when trying to moisten the air in the highly dynamic range of the system. As already mentioned, a shot process, within which the core sand is transported into the mold, lasts only between 500 ms to 800 ms. In this short period of time, the compressed air tank is thus partially emptied and its content is transported via the firing nozzles into the molded part. As a result, high gas velocities also occur within the evacuated pressure vessel, which in addition result in considerably more water being transported by the compressed air than would be the case with a thermodynamic equilibrium at the dew point, since the water can be carried along by the rapidly flowing gas.

When the liquid within the air tank is heated to increase the rate of evaporation, there is the problem that a temperature gradient forms within the air tank, i. At the bottom of the compressed air tank with the liquid prevails a higher temperature than at the other end of the compressed air tank. As a result, parts of the liquid evaporating in the warm area of the compressed air tank condense again at the other end of the tank, so that no uniform air humidity is established inside the tank. Thereby, the moisture supplied to the core sand, i. the amount of moisture per volume of air, can not be controlled accurately. Since it is attempted to humidify the air in the high dynamic range of the system even when using the heater, it comes in addition to the problems described above.

The present invention has for its object to provide a shot gas supply device, which makes it possible to provide shot gas with a predetermined humidity to use this within a core shooter.

This object is achieved by a device according to one of the claims 1 or 7 and by a method according to claim 9.

Some exemplary embodiments of the invention are based on the finding that a core sand hopper can be supplied with a moistened gas of predetermined humidity if a shot gas supply device is used which has a compressed gas reservoir and a gas humidification system. has device. The compressed gas reservoir has a gas outlet for supplying the core sand magazine and a gas inlet for filling the compressed gas reservoir. The gas humidifying device for humidifying the gas is arranged in a gas feed to the gas inlet of the compressed gas reservoir. That is, the gas is moistened before it is stored in the compressed gas reservoir.

The moistening therefore takes place at a point in the gas guide in which no discontinuous states prevail. The location of humidification is therefore not in the high-dynamic range of the system, there are no abrupt changes in the flow rate of the gas or gas pressure instead.

This makes it possible to apply the gas with high accuracy and completely reproducible with an adjustable amount of moisture.

In one embodiment of the invention, for this purpose, the gas is completely saturated with the moisture, ie, the gas is moistened until at the temperature of the gas, the thermodynamic equilibrium between the liquid and the gaseous phase of the liquid used for moistening, established.

In some embodiments of the invention, an already pressurized gas is humidified. This means that a gas which is under pressure above the ambient pressure is moistened.

In a further embodiment of the present invention, therefore, a gas humidifier comprises temperature control means for varying the temperature of the gas to precisely adjust the dew point and thus the amount of moisture that can be taken up and transported by the gas according to the laws of thermodynamics. Before discussing further exemplary embodiments of the invention, it should be pointed out that, in the context of this application and the description of the invention, the term gas is to be understood as meaning any gas mixture which can be used to supply core shooting machines. It does not have to be a monoatomic gas, but also any gas mixtures, such as air, in question and should be understood by the term gas. In a similar way, the term moisture is to be understood, which should not be understood as limited to water. Rather, the term moisture should be understood to mean the gaseous phase of any liquid which is suitable for mixing with core sands. This can be, for example, water or an activator / moderator that can be added to core sands in order, depending on its concentration, to accelerate or possibly also to prevent hardening of the core sand.

Importantly, in some embodiments of the invention, it is possible to produce humidified gas of a predetermined humidity that can be adjusted and accurately reproduced to supply a shotgun device.

In a further embodiment of the invention, the temperature control device of the gas humidifier has a heating element in the form of a microwave radiator. This has the great advantage that the entire volume within the gas humidification device can be uniformly heated by means of the microwaves, so that it is ensured that no temperature gradients can occur within the gas humidification device. As a result, a uniform humidification of the gas can be ensured.

In a further embodiment of the present invention, both the temperature of the compressed gas reservoir as well as the temperature of the gas supply between the gas humidifier and the compressed gas reservoir regulated at a temperature or heated to a temperature which is above the temperature which is set within the gas humidifier (dew point temperature). Thus it can be prevented that the exact humidification of the gas or the exact amount of moisture transported by the gas is reduced by the fact that parts of the liquid condense again before the humidified gas is supplied to the core sand hopper.

Preferred embodiments of the present invention will be explained below with reference to the accompanying figures. Show it:

1 shows a schematic representation of a shot gas supply device;

FIG. 2 shows a schematic representation of a core shooter; FIG.

3 shows a further schematic representation of a core shooter; and

Fig. 4 is a schematic representation of a method for supplying a core sand magazine with humidified gas.

1 schematically shows a shot gas supply device 10 for supplying a core sand hopper of a core shooter with a pressurized humidified gas of predetermined humidity. The shotgas supply device 10 comprises a compressed gas reservoir 12 for the humidified gas and a gas humidification device 14, which is arranged in a gas duct to a gas inlet 16 of the compressed gas reservoir 12. The compressed gas reservoir 12 has a remote gas outlet 18 for supplying the core sand magazine. According to some embodiments of the invention, the humidification of the gas prior to the storage of the humidified gas in the compressed gas reservoir 12 is carried out in order to make it possible to precisely adjust the humidification, ie the amount of liquid transported by the gas.

1 thus shows the concept of the arrangement of apparatus and methods for controlled humidification and tempering (heating and / or cooling, depending on the requirements of the respective ambient conditions) of the compressed air or a gas or gas mixture required for the subsequent core production process.

The compressed air or gas humidification system is installed in the supply line to the compressed gas tank (or compressed air reservoir, boiler, buffer, reservoir) required for the core production process. The compressed air, or the gas or gas mixture, is regulated and tempered (ie heated or cooled) in the supply line to the compressed air tank 12 by means of suitable apparatuses and moistened with a liquid such as, for example, softened / demineralized / demineralised water, that the air or the gas is always saturated. The humidification of the gas in the gas humidifying device 14 is thus carried out in some embodiments so that the volume of the gas humidifier 14 and the gas located within this volume are at a temperature corresponding to the desired humidification of the gas, if this is up to its (temperature-dependent) saturation is laden with moisture.

For example, since high gas temperatures result in more moisture being transported, a heater may be mounted within the gas humidifier 14 to increase the amount of water taken up or the liquid received. Should it require the process, cooling can alternatively be used be provided to transport a smaller amount of moisture than would be the case because of the ambient temperatures or the temperature of the supplied gas without cooling. Thus, the moisture transported by the gas can be adjusted precisely by means of a simple temperature control, without falsifying the amount of moisture transported by the highly dynamic processes taking place within the compressed gas reservoir 12.

In order to prevent that a part of the moisture of the gas in the gas supply to the compressed gas reservoir 12 or on the walls of the compressed gas reservoir 12 itself condenses again and thus distorts the desired amount of moisture transport, the gas supply to the gas inlet 16 and the compressed gas reservoir 12 optionally with a temperature control device 20 may be coupled to keep the temperature of the gas supply and the compressed gas reservoir 12 above the dew point temperature of the humidified gas.

At largely constant ambient conditions can be dispensed with such a trace heating, as long as the process result is not compromised. This is especially not the case if the ambient temperature is reliably higher than the dew point set in the gas humidifier 14 or the temperature set there.

In other words, the purpose of such a heat tracing is to keep the respective required saturation temperature of the compressed air / gas / gas mixture and thus the moisture content of the compressed air / gas / gas mixture largely constant and to prevent the humidity from condensing.

FIG. 2 shows an embodiment of a core shooter including a shot gas supply device 10 as shown in FIG. The core shooter further includes a core sand hopper 24 within which the core sand is located and which is connected to the gas outlet 18 of the compressed gas reservoir 12. The core sand hopper 24 includes the core sand, which can be introduced via the located on the bottom of the core sand hopper 24 shot nozzles 26 a to 26 c in a mold, not shown. If the ambient conditions make it necessary to provide additional heat tracing and thermal insulation which supports the desired process result, a gas connection 28 between the compressed gas reservoir 12 and the core sand hopper 24 can also be connected to a temperature control in order to keep the temperature of the gas connection 28 above the dew point temperature ,

In the core shooting machine shown schematically in FIG. 2, therefore, the pipelines between the humidifying unit and the compressed air tank and between the compressed air tank and the shooting device and the compressed air tank itself are insulated and provided with a heater to ensure that the moisture content of the gas which is exactly in the gas humidifying device 14 is not falsified by condensation of moisture on the way to the core sand magazine 24.

3 shows a detailed representation of a core shooting machine, based on the schematic representation of FIG. 2. Therefore, functionally identical elements are provided with the same reference character, so that the descriptions of similar or functionally identical elements can also be mutually applied to one another. This applies in the above for all functionally similar or identical components in different figures.

In Fig. 3, a core shooting machine is shown, which uses air as a shot gas and demineralized water as a liquid for humidification.

In the embodiment shown in FIG. 3, the gas humidifier 14 includes a water softener 40 to to generate the demineralised water used for humidification on site.

The wetting air to be moistened is supplied to the gas moistening device 14 via a valve 42 from an external compressed air supply. The moistened shot air is conducted via a gas feed 44 to the gas inlet 16 of the compressed gas reservoir 12. The sand magazine 24 shown in FIG. 3 has two separately controllable partial magazines, so that by means of the sand magazine 24 at the same time two different molding tools can be filled with molding sand. In order to exploit the possibility of separate control, two gas feeds 46a and 46b are provided in FIG. 3 between the compressed gas reservoir 12 and the sand hopper 24, these firing valves 48a and 48b associated with the gas connections each having a chamber of the sand hopper 24 are connected. Gas supply 44 and the gas connections 46a and 46b and the compressed gas reservoir 12 are connected in the embodiment shown in Fig. 3 with a schematically illustrated temperature control device 20 to maintain the temperature of these components at a temperature above the dew point of the humidified gas.

In order to allow venting of the sand hopper 24 and the separate chambers of the sand hopper 24, two vent valves 50a and 50b are further provided, which are connected to their respective associated chambers of the sand hopper 24.

Further, a shot vent cleaning valve 52 is connected to the sand hopper 24 and an external pressurized gas source. Via the line between the Schussentlüftung- cleaning valve 52 and the sand hopper 24 also a pressure switch 54 is also connected to the sand hopper, which monitors the pressure in the sand hopper 24 during the vent after the shot. By means of the pressure switch 54 so the venting process is monitored, so for example from a pressure level in the sand hopper 24 of about 0.1 bar overpressure, the vent can be considered complete, whereupon then the sand hopper 24 with firing hood is driven up and to the side. At the same time, a possible gasification device can be moved over the tool in order to be braced with it and, for example, to conduct hot air into the tool for hardening the cores (possibly also in addition to tool heating).

The shot vent cleaning valve 52 is triggered synchronously with the shot, i. Through a port Ll additional compressed air is blown into the sand hopper 24 during the firing process and by time delay also something in the venting time. As a result, the lines and the pressure switch 54 sand magazine remain free of contamination.

Further, Fig. 3 shows in dashed line pneumatic control lines 56, which serve to control the individual valves or to provide a required for their operation operating pressure. The operating pressure is adjusted by means of a pressure regulator 58. The control may be purely pneumatic, but other control mechanisms may be used, such as electrical signals or messages transmitted on a data bus.

In the embodiment shown in FIG. 3, the gas humidifying device 14 has a closed volume 60 through which the gas to be humidified or the air to be humidified is passed. Within this volume 60, an evaporation body 62 is arranged, which is wetted with the water of the water softening system 40 and preferably has a large surface, so that the evaporation of the water is promoted. Furthermore, the gas humidifying device 14 has a schematically illustrated temperature control device 64 for varying the temperature of the air or the humidified air. The temperature Geleinrichtung 64 can be implemented in various ways, such as by a resistance wire heater or a microwave.

In the case shown in FIG. 3, the supply of softened water is controlled by the volume 60 containing a sensor that is sensitive to the liquid collecting at a bottom of the volume 60. If no liquid is detected, additional water is added. This has the further advantage that the presence of a liquid phase is also an indication that the gas in the volume 60 at the set temperature is saturated with moisture. The presence of the liquid within the volume 60 may thus be used in another embodiment to regulate the flow rate of the gas to ensure that the gas within the residence time in the volume 60 is saturated.

The entire system shown in Fig. 3, which adjoins the gas humidifier 14, i. that is, the gas supply 44, the compressed gas reservoir 12, and the gas connections 46a and 46b are provided with a heater connected to a temperature control to prevent condensation of liquid from the gas. Both the heating and the temperature control are shown in Fig. 3 only schematically.

The humidified air is transported via the gas supply 44 into the compressed gas reservoir 12, wherein the pressure in the gas feed 44 is controlled by a pressure regulator 66 and kept constant.

A further pressure regulator 68 controls the pressure of the gas within the compressed gas reservoir 12. This allows the pressure to be adjusted to the required conditions, such as the core sand used or the desired speed of filling the molding tools. len. In addition, by means of the pressure regulator, for example, an excessively high pressure can be prevented by opening a venting valve when a permissible maximum pressure is exceeded. Pressures in which a transfer of the sand reliably succeeds, for example, between 3 bar and 8 bar.

For the filling or shooting of the core sand, the shot valves 48a and 48b are opened, so that the humidified gas from the compressed gas reservoir 12 flows into the sand hopper 24 and shoots the core sand into the molds by the sudden overpressure.

Thus, due to the embodiments described with reference to FIGS. 1 to 3 and the method and apparatus arrangements shown therein, sufficient or exactly the required amount of moisture into the core sand will always be exactly at the right time (that is to say exactly at the time the sand is fired) -Binder mixture (which may optionally also contain additional promoters or activators) introduced. As a result, both washing out and premature curing of the core sand can be reliably avoided in order to obtain sand cores of the desired reproducible quality.

4 shows a schematic representation of an example of a method for supplying a core sand magazine of a core shooter with a moistened gas of predetermined moisture.

At first, in a humidifying step 70, the gas is humidified to the predetermined humidity to form humidified gas. The humidified gas is stored in a storage step to make it available to a core sand hopper. The fact that the gas is first moistened before it is stored with precisely set humidity in a reservoir in which highly dynamic conditions prevail makes it possible to reproduce zierbar and precisely metered to adjust that amount of moisture that requires the subsequent process, or can prevent premature curing of a fed with the humidified gas core sand mixture.

Although in the preceding embodiments, the humidification of the gas was mainly represented by using an evaporative body, it is not absolutely necessary to use an evaporative body in the context of the invention. Rather, the gas can be humidified in any other way that allows reproducible humidification or saturation of the gas used. It is conceivable, for example, fine mist of liquid to be used for moistening, through which the gas can be passed. Furthermore, the gas can be passed over a liquid level, for example, if sufficient time is available for the thermodynamic equilibrium to form above the surface of the liquid level, so that the gas is saturated at a set temperature.

As already mentioned, to set the dew point or the adjustment of the temperature of the gas to be humidified within the gas humidifier any heating or cooling device can be used, which allows the gas to be heated to an adjustable temperature or to cool over the Temperature set the recorded moisture content. In particular, both cooling and heating may be provided within the gas humidifier to provide a system that can flexibly respond to any possible environmental condition.

The geometric arrangement of the individual components, which is shown in Figures 1 to 3, is to be understood only as an example. In particular, it is not necessary that the gas humidification device is arranged spatially separated from the compressed gas reservoir. Rather, it is for example It is also possible to carry out the gas moistening device as an integrated element of the compressed gas reservoir, as long as it is ensured that the moistening is not carried out in the dynamic range of the system in which pressure conditions or flow velocities change rapidly. This can be achieved for example by a valve between the gas humidifier and the compressed gas reservoir.

Claims

claims

A shot gas supply apparatus (10) for supplying a core sand hopper (24) of a core shooter with a humidified predetermined humidity gas, comprising:

a compressed gas reservoir (12) for the humidified gas, which has a gas outlet (18) for supplying the core sand magazine (24) and a gas inlet (16) for filling the compressed gas reservoir (12), and

a gas humidifier (14) disposed in a gas supply to the gas inlet (16) for humidifying a gas to predetermined humidity to form the humidified gas.

2. Shot gas supply device (10) according to claim 1, wherein the gas humidifying device (14) is adapted to moisten the gas to a temperature of the gas corresponding saturation moisture.

A shotgas supply device (10) according to any one of claims 1 or 2, wherein the gas humidifying means (14) comprises temperature control means (64) for changing a temperature of the humidified gas.

4. shotgas supply device (10) according to claim 3, wherein the temperature control device (64) has a microwave radiant heater for heating the humidified gas.

5. shotgas supply device (10) according to one of the preceding claims, which has a further temperature control device (20) to a temperature of the Gas supply between the gas humidifier (14) and the gas inlet (16) and / or a temperature of the compressed gas reservoir (12) to be regulated so that it is above the dew point of the humidified gas.

6. shot gas supply device (10) according to any one of the preceding claims, wherein the gas humidifying means (14) having a wetted with a liquid for moistening evaporation body (62), which in a gas-flowed volume (60) of the gas humidifying device (14) is arranged.

7. shot gas supply device (10) according to one of the preceding claims, wherein the gas humidifying device (14) is adapted to moisten a standing at a pressure above the ambient pressure gas.

8. shot gas supply device (10) according to claim 7, wherein the gas humidifying device (14) is adapted to moisten a standing under a pressure between 3 bar and 8 bar gas.

9. shot gas supply device (10) according to any one of the preceding claims, with the following additional feature:

a pressure regulating device connected to the compressed gas reservoir (12) for adjusting a predetermined pressure of the humidified gas in the compressed gas reservoir (12).

10. Core shooter with the following features:

a shot gas supply device (10) according to any one of claims 1 to 9; and a core sand hopper (24) connected to the gas outlet (18).

11. Core shooter according to claim 10, wherein a gas connection (28) between the gas outlet (18) and the core sand hopper (24) with a temperature control device (20) is connected to the temperature of the gas connection (28) to regulate that above the dew point of the humidified gas is.

A method of supplying a core sand hopper (24) of a core shooter (10) with a humidified predetermined moisture gas, comprising the steps of:

Humidifying a gas to the predetermined humidity to form the humidified gas; and

Save the humidified gas to provide the humidified ^'gas for supplying the core sand magazine ready.