Method and device which moulding compound to be processed is kept moist during the production of cores

Abstract

To produce molds or cores for foundry purposes from a mixture (M) of molding material or sand and at least one binder, the mixture (M) is mixed by means of a mixing device (20) and fed by means of a feeding device (30) to at least one sand storage unit (40) of a core or mold making device (50), wherein the mixing-free area (21) of the mixing device (20) is moistened or kept moist at least temporarily and / or the feeding device (30) located between the mixing device (20) and the core or mold making device (50) and / or the sand storage unit (40) behind the feeding device (30) and in front of the core or mold making device (50) is moistened or kept moist by means of a liquid (71).wherein the liquid (71) used for moistening is atomized into a suspended aerosol by at least one ultrasonic atomizer (60) and is supplied to the mixing device (20) and / or the feeding device (30) and / or the sand storage unit (40) via pipelines (81, 82, 83).

Description

[0001] The invention relates to a method for producing molds or cores, in particular for foundry purposes, wherein molding material or sand and at least one binder, which is at least predominantly inorganic, water-soluble and / or hygroscopic, are mixed by means of a mixing device and wherein this mixture is supplied to at least one sand storage unit of a core or mold making device by means of a feeding device.

[0002] The invention further relates to a device for the production of molds or cores, in particular for foundry purposes, comprising a mixing device for mixing molding material or sand and a binder which is at least predominantly inorganic, water-soluble and / or hygroscopic, comprising a core or mold making device having a sand storage unit and comprising a feeding device for conveying the mixture to the sand storage unit of the core or mold making device.

[0003] Such a method and a comparable device are known from practice and have proven their worth.

[0004] However, it can happen that moisture originally contained in the binder escapes during and after the mixing process, causing the mixture to dry out and crust over in places. This can hinder the further transport and feeding of the mixture to the core or mold making equipment and can also contaminate the mixing equipment, the downstream feeding system, and the sand storage unit. The mold making equipment itself can also become clogged by lumpy mixture. The consequences can include rejects, production stoppages, and extensive cleaning of the entire system – from the mixing equipment to the mold making equipment.

[0005] Up to now, these problems have been reduced by short cleaning intervals, by cooling the mixture, or, if necessary, by increasing the binder content – ​​i.e., by additional effort.

[0006] From WO 03 / 022487 A1 and WO 2007 / 062706 A1, molding machines are known in which a suspended aerosol or moist air is supplied. From DE 12 03 919 B, DE 10 2007 0276298 A1, DE 199 45 569 A1, DE 198 10 273 A1, DE 195 45 917 A1, DE 195 36 803 A1, DE 31 47 131 A1, DE 29 52 403 A1, DE 26 41 361 A1 and DE 601 11 968 T2, mixing devices are known in which water or steam is supplied to moisten a mixture.

[0007] The task is therefore to create a method and also a device of the type mentioned above, in which premature drying and crusting of the mixture and the associated contamination of the mixing device and / or the feeding device are largely avoided.

[0008] To solve this problem, the method defined at the outset stipulates that the mixing-free area of ​​the mixing device and / or the mixing-free area of ​​the feeding device located between the mixing device and the core or mold making device are moistened or kept moist, at least temporarily. This moistening creates a high humidity level in the aforementioned areas, which can prevent or reduce evaporation or leakage of moisture from the mixture. Thus, the mixture cannot fully or partially harden, dry out, or form crusts. Contamination of the mixing device and / or the feeding device and / or the sand storage unit, as well as the core or mold making device, can therefore be reduced and / or the necessary cleaning intervals extended.This can have a particularly positive impact on the productivity of the core and mold manufacturing process, and in addition, cleaning intervals can be extended and cleaning costs reduced.

[0009] It is particularly advantageous if the non-mixing area of ​​the mixing device is moistened or kept moist, at least temporarily, during the mixing process. Moisture from the mixture could escape into the non-mixing area, especially during the mixing process itself. Moisturizing this area easily prevents moisture from escaping the mixture, drying out, accumulating on parts of the mixing device, and contaminating it.

[0010] Furthermore, it can be advantageous to reduce or prevent evaporation or loss of moisture from the mixture by maintaining a high relative humidity above the mixture by supplying moisture, particularly at approximately 70% to 100%, preferably at approximately 80% to 100%. Such relative humidity levels minimize the humidity gradient between the mixture and the surrounding air, thereby largely preventing moisture from evaporating from the mixture into the air and the associated unwanted hardening of the mixture.

[0011] It is possible to atomize the liquid or water used for humidification into a suspended aerosol using ultrasound and then feed it to the mixing device, the feeding system, and / or the sand storage unit. The suspended aerosol contains such small liquid particles that they evaporate directly, increasing the humidity without condensing or forming condensate within the mixing device, the feeding system, and / or the sand storage unit. The size of the liquid particles generated by ultrasound can be on the order of 0.01 mm or smaller. Simultaneously, a sufficiently high humidity level is achieved to prevent the sand-binder mixture from drying out. Both the mixing process and the feeding and storage of the sand-binder mixture can be carried out reliably.

[0012] The aerosol, or rather the quantity of this suspended aerosol and the size of the volume flow containing the aerosol, can be adjusted by changing the pulse packets emitted by the ultrasonic transducer(s) and / or by changing the voltage of the ultrasonic transducer(s). In this way, the quantity of suspended aerosol used to moisten the mixing device and / or the sand storage unit can be adapted to the prevailing conditions such as atmospheric humidity, the size of the volume to be moistened, and the ambient temperature.

[0013] A particularly advantageous embodiment of the method according to the invention consists in the formation of the airborne aerosol and its conveyance to the mixing device and / or the feeding device and / or the sand storage unit via one or more lines. The aerosol is thus generated outside the mixing, feeding, and / or sand storage unit. Therefore, no additional installation space is required in the mixing, feeding, and / or sand storage unit for aerosol production. Nevertheless, it is possible to provide a sufficiently high humidity level to prevent the sand-binder mixture from drying out, without introducing excessive liquid, which could potentially wash out or dissolve the binder.

[0014] To solve the problem, the device defined above is characterized in that a humidification device is provided on the mixing device and / or the feeding device, either acting on its interior or opening into its interior. With the aid of the humidification device, the desired humidity can be generated and maintained in a particularly simple manner, thus reducing the risk of drying out due to moisture loss in the mixture within the mixing device and / or the feeding device. This can advantageously reduce contamination of the mixing device and / or the feeding device and / or the sand storage unit, as well as of the downstream core or mold-making device.

[0015] The humidification device may include at least one ultrasonic transducer in the form of an ultrasonic atomizer for water or, in particular, for a liquid containing water. The invention thus utilizes the fact or knowledge that ultrasonic atomizers can atomize water or a liquid containing water in such a way that the individual droplets can be smaller than 20 micrometers or even smaller than 10 micrometers, so that they dissipate into atmospheric moisture and do not, or hardly, condense as a film of moisture on parts of the mixing device and / or the feeding device and / or the sand storage unit.

[0016] It is particularly advantageous if the ultrasonic atomizer(s) and an associated liquid reservoir are spatially separated from the mixing device and / or the feeding device and / or the sand storage unit, and are connected to the area(s) to be moistened via at least one pipe or hose. Tests have shown that the suspended aerosol formed by an ultrasonic atomizer from water or a water-containing liquid can easily be transported several meters through such a line to provide sufficiently humid air at the desired location. This prevents the mixture of sand or molding material and binder from drying out, particularly in the mixing device itself, the feeding device, and / or the sand storage unit, without over-wetting the mixture.The liquid reservoir with the ultrasonic transducer(s) can thus be advantageously arranged at a location on or near the molding or core shooting machine where sufficient space is available.

[0017] It is particularly advantageous if the mixing device, the feeding device, and the sand storage unit are each connected to the humidification system via a pipe or hose. Separate pipes or hoses for each section of the system allow humid air to be introduced into the mixing device, the feeding device, and / or the sand storage unit in a manner tailored to the individual process steps. This further ensures that the sand binder mixture does not lose moisture, dry out, or become contaminated in any of the aforementioned areas.

[0018] A further development of the device according to the invention can provide that the number of ultrasonic atomizers corresponds at least to the number of pipes or hoses, and that at least one ultrasonic atomizer is provided for each pipe or hose. With at least one ultrasonic atomizer per pipe, it is possible to atomize and supply a sufficient quantity of liquid to the respective areas, even with different humidity levels in the areas to be humidified, in order to prevent the mixture from drying out and crusting.

[0019] Furthermore, it can be advantageous to have a fan or a pressurized gas connection, particularly above the liquid surface in the liquid reservoir, to transport the moisture or aerosol from the ultrasonic atomizer(s) to the mixing device and / or feeding device and / or sand storage unit. While the aerosol might flow towards the mixing device and / or feeding device and / or sand storage unit due to its own pressure, especially with relatively short lines, a fan or a pressurized gas connection can improve this flow and / or allow for a greater distance between the ultrasonic atomizer and the areas of the device requiring humid air supply. Additionally, a fan and / or a pressurized gas connection can overcome height differences between the ultrasonic atomizer and these areas of the device at the core shooting unit.Above all, the aerosol can also be conveyed upwards, allowing the ultrasonic atomizer and liquid reservoir to be positioned lower down, where there is usually sufficient space. Furthermore, this arrangement is advantageous because any condensation that may form on the inner walls of the pipe or hose transporting the aerosol can flow back down into the liquid reservoir.

[0020] A modified embodiment of the invention may provide that the feeding device is at least one movable transport bucket. With a movable transport bucket as the feeding device, it is possible to transport the sand-binder mixture from the mixing device to the sand storage unit of the core or mold making device, even over greater distances.

[0021] An embodiment of the invention is described in more detail below with reference to the drawing. The single figure shows a schematic representation.

[0022] a longitudinal section of a mixing device, a feeding device and a sand storage unit with attached core or mold making device, as well as a humidification device with two ultrasonic atomizers and liquid reservoir and with three feed lines, one of which leads to the mixing device, one to the feeding device and one to the sand storage unit.

[0023] A device designated as a whole by 1 for the production of molds or cores, in the exemplary embodiment for the production of cores for foundry purposes, comprises a mixing device 20 with a mixing tool 22 for producing a mixture M by mixing molding material or sand and a binder, a feeding device 30 for conveying the mixture M to a sand storage unit 40 with a closing device 42 and a core or mold production device 50.

[0024] A humidification device 2 with two ultrasonic atomizers 60 for water or for a liquid 71, particularly one containing water, and with a liquid reservoir 70, serves to humidify the air in the device 1. With the aid of these ultrasonic atomizers 60, the liquid 71 can be atomized into a fine aerosol. This aerosol is indicated in the figure by the two cloud-like structures 61 inside the liquid reservoir 70.

[0025] However, an embodiment of the device (not shown) can also provide for three ultrasonic atomizers 60, each of which is assigned to one of the three pipes 81, 82, and 83, so that at least one ultrasonic atomizer is available for each pipe 81, 82, and 83 for supplying liquid to the areas to be moistened. In this way, the amount of moisture for each area can be individually measured and supplied.

[0026] The figure also shows that the humidification device 2, with the ultrasonic atomizers 60 and the liquid reservoir 70, is spatially separated from the mixing device 20, the feed device 30, and the sand storage unit 40, but is connected to the areas to be humidified via pipes 81, 82, and 83. These pipes extend directly from the liquid reservoir 70 into the aforementioned areas of the device 1 and supply non-mixing areas 21, 31, and 41 with humid air. In the exemplary embodiment, not only the mixing device 20, but also the feed unit 30 and the sand storage unit 40 each have a non-mixing area 31 and 41, at least temporarily.

[0027] In the liquid-free area of ​​the liquid reservoir 70, a fan 90 and a pressurized gas connection 10 can also be seen. Either the fan 90 or the pressurized gas connection 10, or preferably both, serve to convey and transport the aerosol produced by the ultrasonic atomizers 60 via the pipelines 81, 82 and 83 to the mixing device 20, the feeding device 30 and the sand storage unit 40.

[0028] Sufficiently moist air is blown above the mixture M into the mixing device 20, the feeding device 30 and the sand storage unit 40 via the pipes 81, 82 and 83, so that the mixture M cannot harden and dry out in any of the three areas of the device 1, which prevents contamination of the device 1 and thereby improves the uninterrupted operation of the device 1 and increases the quality of the sand cores produced.

[0029] A modified embodiment of the device 1, not shown in detail, may provide that the feed device 30 is at least one transport bucket which can be moved, for example, by means of a rail system or a crane between the mixing device 20 and the sand storage unit 40. This can be particularly advantageous for bridging larger distances between the mixing device 20 and the sand storage unit 40.

[0030] For the production of molds or cores for foundry purposes from a mixture M of molding material or sand and at least one binder, the mixture M is mixed by means of a mixing device 20 and fed by means of a feeding device 30 to at least one sand storage unit 40 of a core or mold making device 50, wherein the mixing-free area 21 of the mixing device 20 is moistened or kept moist at least temporarily and / or the feeding device 30 located between the mixing device 20 and the core or mold making device 50 and / or the sand storage unit 40 downstream of the feeding device 30 and upstream of the core or mold making device 50 by means of a liquid 71, wherein the liquid 71 used for moistening is atomized into a suspended aerosol by at least one ultrasonic atomizer 60 and is supplied to the mixing device 20 and / or the feeding device 30 and / or the sand storage unit 40 via pipelines 81,82 and 83 are supplied.

Claims

1. Method for producing moulds or cores, wherein a moulding compound or sand and at least one binding agent which at least predominantly is inorganic, water soluble, and / or hygroscopic, are mixed by means of a mixing device (20), and wherein this mixture (M) with the aid of an infeed installation (30) is fed to at least one sand storage unit (40) of a core or mould production device (50), characterized in that the mixture-free region (21) of the mixing device (20) is at least temporarily kept humidified or humid and / or the mixture-free region (31) of the infeed installation (30) that is located between the mixing device (20) and the core or mould production device (50) is kept humidified or humid.

2. Method according to Claim 1, characterized in that the mixture-free region (21) of the mixing device (20) is at least temporarily kept humidified or humid at least during the mixing procedure.

3. Method according to Claim 1 or 2, characterized in that an evaporation or a leakage of humidity from the mixture (M) is suppressed in that the air humidity above the mixture (M) is maintained at 70% to 100% by infeeding humidity.

4. Method according to one of Claims 1 to 3, characterized in that the liquid (71) that serves for the humidification, or the water that serves for the humidification, by means of ultrasound is atomized to an aerosol that is capable of suspension and is infed to the mixing device (20) and / or to the infeed installation (30).

5. Method according to one of Claims 1 to 4, characterized in that the aerosol that is formed from the liquid (71), and the size of the volumetric flow that is provided with the aerosol, are set by modifying the pulse bundles that are dispensed by the ultrasonic transmitter(s) and / or by modifying the voltage of the ultrasonic transmitter(s).

6. Method according to one of Claims 1 to 5, characterized in that the aerosol that is capable of suspension is formed and directed to the mixing device (20) and / or the infeed installation (30) by way of one or a plurality of lines (81, 82, 83).

7. Device for producing moulds or cores, having a mixing device (20) for mixing a moulding compound or sand and a binding agent which at least predominantly is inorganic, water soluble, and / or hygroscopic, having a core or mould production device (50) comprising a sand storage unit (4), and having an infeed installation (30) for directing the mixture (M) onward to the sand storage unit (40) of the core or mould production device (50), characterized in that a humidification installation (2) that impinges the interior, or opens into the interior, of the mixing device (20) and / or the infeed installation (30) is provided on the mixing device (20) and / or on the infeed installation (30), such that the mixture-free region of the mixing device (20) in operation can at least temporarily be kept humidified or humid, and / or the mixture-free region of the infeed installation (30) that is located between the mixing device and the core or mould production device (50) can be kept humidified or humid.

8. Device according to Claim 7, characterized in that the humidification installation (2) has at least one ultrasonic transmitter in the form of an ultrasonic atomizer (60) for water or for a liquid (71).

9. Device according to Claim 7 or 8, characterized in that the ultrasonic atomizer(s) (60) and a liquid reservoir (70) that is associated with said ultrasonic atomizer(s) (60) in spatial terms are disposed so as to be separate from the mixing device (20) and / or from the infeed installation (30) and / or from the sand storage unit (40) and are connected to the region(s) to be humidified by way of at least one pipe line or hose line (81, 82, 83).

10. Device according to one of Claims 7 to 9, characterized in that the mixing device (20), the infeed installation (30), and the sand storage unit (40) are in each case connected to the liquid reservoir (70) by way of a pipe line or a hose line (81, 82, 83).

11. Device according to one of Claims 7 to 10, characterized in that the number of ultrasonic atomizers (60) corresponds to at least the number of pipe lines or hose lines (81, 82, 83), and at least one ultrasonic atomizer (60) is provided for each pipe line or hose line (81, 82, 83).

12. Device according to one of Claims 7 to 11, characterized in that a ventilator (90) or a compressed-gas connector (10) for conveying the humidity or the aerosol from the ultrasonic atomizer(s) (60) to the mixing device (20) and / or the infeed installation (30) and / or the sand storage unit (40) is disposed in the liquid reservoir (70).

13. Device according to one of Claims 7 to 12, characterized in that the infeed installation (30) is at least one movable transportation bucket.

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