Device for dispensing coatings

Abstract

The invention relates to a device for dispensing sizing agents by means of compressed air from a reservoir onto a surface of a mold or the like, wherein the reservoir for the sizing agent is associated with an agitator, and wherein the transport of the sizing agent from the reservoir is carried out by means of a pump device to a spray device with a spray head, wherein a sizing nozzle is located in the spray head, which is designed at a distance from an air blow nozzle with a compressed air connection, wherein the air blow nozzle and the sizing nozzle are arranged at an angle of about 90° or less to each other.

Description

[0001] The invention relates to a device for dispensing coating by means of compressed air from a storage container into a mold or the like, as well as a method for carrying out the dispensing of coating.

[0002] In permanent mold casting, coatings are used to achieve good casting results. A sprayable coating is formulated from any desired material and applied to the interior surfaces of permanent molds or similar castings using compressed air in a conical spray jet. The liquid coating acts as a mold coating that can be applied completely evenly, in either a thin or thick layer. By applying the coating, the surfaces of the permanent molds or similar castings are modified in such a way that demolding is facilitated. This is because the application of coatings allows the surfaces of the permanent molds or similar castings to be aligned, insulated, and heat-dissipating, thus simplifying demolding of the casting.

[0003] DE 20 2005 017 275 U1 describes an atomizer head for a perfume container including an atomizer device.

[0004] DE 1 901 671 A1 describes a method for applying coatings from liquid coating compounds. The coating compounds contain a flammable liquid for coating the surfaces of a casting mold. The coating compound is applied using a spray gun, which has a device near its nozzle for igniting a spray jet of the coating compound.

[0005] In order to prepare the components of a sizing composition for use, DE 10 2018 131 811 A1 describes the use of a high-shear stirrer.

[0006] DE 10 2005 021 688 A1 discloses a method for producing a molded part using gravity die casting. A die is filled with casting materials. Before the die is filled with the casting material, the interior of the die is coated with a release agent, thereby achieving a uniform coating of the inside of the die.

[0007] The object of the invention is to provide a device with which a uniform application of different coatings can be ensured for different applications of molds or the like.

[0008] The object of the invention is achieved by a device according to claim 1. The subclaims following claim 1 represent a further embodiment of the invention.

[0009] In permanent mold casting, many factors determine casting success, including the correct mold design and optimal melt flow during the casting process, as well as the optimal alloy. The use of a coating is one of the quality-relevant processes. Unfortunately, these processes are often given too little attention in the foundry industry. The coating should not only ensure good separation between the mold material and the solidifying alloy or similar, but also optimally influence the flowability of the metal into the mold to avoid cold runs or oxide buildup. Heat control also has a significant influence on solidification, which in turn is strongly influenced by the coating.

[0010] To achieve these goals, coatings are composed of a variety of different components that either conduct heat well or have an insulating effect, and contain particles capable of binding the metal oxide film and thus positively influencing flow during permanent mold casting. Finally, the coating particles are held together with a binder, such as water glass. After spraying onto the mold surface, they should then be firmly fixed. The water in the coating evaporates upon contact with the hot mold wall, leaving behind a structured, glass-like film on the surface that retains its properties over many castings. However, this is only possible if the coating is optimally prepared and processed.

[0011] Coatings for processing in a spray device must therefore have a consistency such that processing is possible at any time to avoid interruptions in the casting process. Since coatings are a mixture of different components, the consistency changes during longer downtimes because the heavy particles separate from the lighter particles. This means that the desired composition of the coating is not present at the time of processing. For this reason, coatings must undergo careful preparation before being sprayed onto the surfaces of the mold or similar. This is due to the composition of the coating itself. The sprayable coating is highly diluted and therefore contains a lot of water.The coating cannot be stored at this consistency, as the coating particles sink to the bottom and thus, when transferred to the spray device, contain fewer or more particles, depending on the condition at the time of removal. Considering that the coarse and heavy particles may not be applied to the spray device and thus not to the mold surfaces, optimal flow behavior and thus good mold filling cannot be expected.

[0012] Therefore, coatings are usually supplied as a concentrate. The coating concentrate is mixed with water before spraying until a sprayable consistency is achieved. This means that the coating user has an important task: choosing the correct dilution ratio and simultaneously creating a homogeneous mixture by mixing the water and concentrate, and then spraying this mixture before any separation occurs.

[0013] To ensure that the coating always maintains the same concentration, even during extended downtimes, the storage tank is equipped with an agitator. This agitator can be used continuously or as needed. Using this agitator prevents the coating composition from de-mixing, even during extended downtimes. This ensures that the coating is available at the required concentration at all times. Connected to the storage tank, a pumping device is integrated into the supply line to the at least one spraying device. This pumping device ensures that the required coating concentration is fed under pressure to a spraying device.

[0014] A peristaltic pump has proven to be a particularly effective pumping device. A peristaltic pump offers low energy consumption and a longer service life, as it requires significantly less lubricant than conventional pumping devices and offers excellent abrasion resistance with extremely high suction power. Likewise, peristaltic pumps can withstand dry running indefinitely if the supply of the provided coating is exhausted. Furthermore, abrasive and corrosive coating compositions can be conveyed through the pumping device's hose compression system.

[0015] The device according to the invention for dispensing coating material can be equipped with one or more spray heads. The spray heads can be arranged, for example, on a bar that sprays the direct width or height of the mold or the like. The device contains a reservoir for the required coating material used for the spraying process. Any unused coating material is pumped back into the storage container by the pump system. The reservoir is also connected to a coating nozzle. The spray head also contains a blow nozzle. The coating nozzle works together with the air blow nozzle. In the idle state, the outlet of the coating nozzle is closed by a nozzle needle. The position of the coating nozzle can be continuously adjusted using a thread.To ensure that the set position of the sizing nozzle is maintained, the sizing nozzle can be loaded with a spring element. The spring element penetrates the reservoir and is positioned against a stationary guide projection at the other end. The spring element is located inside the reservoir. The guide projection simultaneously closes the reservoir from a front pressure chamber containing a pneumatic piston.

[0016] The nozzle needle is in direct contact with the pneumatic piston, the relative position of which can be adjusted by control air within a pneumatic cylinder. Before the pneumatic piston is actuated, compressed air is simultaneously fed as blast air into the spray head to the air blast nozzle in a separate step. This type of compressed air control can be implemented in such a way that the blast air opens first, followed by the pneumatic piston opening the coating nozzle via the nozzle needle. This allows the coating in the reservoir to exit at the coating nozzle, where it is atomized by the blast air in the mold or similar. To achieve uniform atomization of the coating on the mold surface or similar, effective spraying of the coating onto the walls of the mold surface or similar is necessary.For this purpose, the air blast nozzle is positioned at an angle of approximately 90° or less relative to the coating nozzle. This ensures that the air jet hits the emerging coating directly in front of the coating nozzle, resulting in excellent atomization of the coating.

[0017] For larger molds or similar applications, it's also possible to mount several spray heads next to each other or one above the other. Furthermore, the spray heads can also be arranged so they can be moved.

[0018] The unsprayed sizing is fed from the reservoir back to the storage container via a pipe and there evenly mixed with the existing sizing by the agitator.

[0019] The invention is explained in more detail below using two possible embodiments. Fig. 1 shows a first preferred embodiment of a spray head for applying a size; Fig. 2 shows a further preferred embodiment of a spray head.

[0020] One spray head 1 after Fig. 1 essentially consists of a distribution block 6 with a docked nozzle holder 5 and an air adapter 16. The nozzle holder 5 is inserted replaceably into the distribution block 6 and sealed by a seal 7 in the distribution block 6. The nozzle holder 5 is then screwed to the distribution block 6. The distribution block 6 contains a blast air inlet 10, which supplies blast air directly to the air blast nozzle 4 via a channel 28. This air blast nozzle 4 is also replaceable and can be secured in the nozzle holder 5 via a thread 25. Within the nozzle holder 5 there is a sizing nozzle 2, which is also replaceably inserted into the nozzle holder 5 via a thread 26. The position of the air blast nozzle 4 and the sizing nozzle 2 to one another is approximately 90° or less, so that good atomization of the sizing can be achieved by the blast air.

[0021] Within the distribution block 6 is a reservoir 11 for the sizing supplied by a peristaltic pump (not shown). This reservoir 11 is penetrated by a sizing needle shaft 9. This sizing needle shaft 9 has a nozzle needle 3 at one end, which, when closed, closes a nozzle needle bore 33 of the sizing nozzle 2. To ensure secure closure, the closed position of the nozzle needle 3 within the sizing nozzle 2 is sealed by a seal 34. At the other end, the sizing needle shaft 9 merges into a pneumatic piston 13, which can be moved translationally in the air adapter 16 within a pneumatic cylinder 15. The sizing needle shaft 9 is guided from the reservoir 11 to the pneumatic piston 15 via a guide 12 and is simultaneously sealed there via seals 24.

[0022] In a preferred embodiment, the seat of the sizing nozzle 2 can be loaded by a spring element 8 in the form of a compression spring, so that the sizing nozzle 2 remains securely in its operating position within the nozzle holder 5 after adjustment. A nozzle needle chamber 27 is formed within the sizing nozzle 2, through which the sizing is fed from the reservoir 11 to the nozzle needle 3. Furthermore, the distributor block 6 also provides access for a further compressed air inlet, namely a return air inlet 20, to which a channel 22 is connected, leading to a return flow control 21. If this return air inlet 20 is pressurized, a front pressure chamber 23 in front of the pneumatic piston 13 is filled with compressed air via a connection (not shown).Filling the front pressure chamber 23 with compressed air causes the nozzle needle 3 to be pulled out of the seat, namely the closed position, of the sizing nozzle 2, and the sizing can exit the reservoir 11 via the nozzle needle 27 at the sizing nozzle 2. The closed position of the nozzle needle 5 in the sizing nozzle 2 can be additionally secured by the seal 34.

[0023] After a spraying process has been completed, the nozzle needle within the coating nozzle 2 must be closed again. For this purpose, a rear pressure chamber 14 is located behind the pneumatic piston 13 within the pneumatic cylinder 15. This rear pressure chamber 14 can be controlled via the inlet of a feed control air 19 in conjunction with a channel 17 and a feed control 18 so that the nozzle needle 3 closes the coating nozzle 2.

[0024] In the Fig. 2 shows a further preferred embodiment of a spray head 1, in which changes compared to the embodiment according to Fig. 1 were made.

[0025] To ensure that the coating can exit the coating nozzle 2 evenly, the nozzle needle 3 has a groove 30 laterally along part of its length within a coating nozzle shaft 36. The groove 30 ensures that, after the nozzle needle 3 is retracted from the closed position of the coating nozzle 2, the coating can enter the nozzle needle chamber 27 from the reservoir 11 in a targeted manner. The groove 30 prevents pulsations and fluctuations in the amount of coating. The coating needle shaft 9 is additionally sealed in the coating nozzle shaft 36 by a seal 32.

[0026] Since the coatings used have different compositions, it may be necessary to remove any buildup of coating droplets or the like at the coating nozzle 2, as otherwise a uniform application of the coating in the mold or the like cannot be guaranteed. To remove these buildup of coating, the coating nozzle 2 has a circumferential groove 29 at its end. To remove such buildup of coating and simultaneously spray it, the air blast nozzle 4 has two side bores 31 next to the air blast outlet 35. The side bores 31 run horizontally so that the coating accumulated in the groove 29 is atomized with the remaining coating. The side bores 31 run as bypasses approximately parallel to the air blast outlet 35. Reference symbol 1 spray head 2 finishing nozzles 3 nozzle needle 4 Air jet nozzle 5 nozzle holders 6 Distribution block 7 Seal 8 spring element 9 sizing needle shank 10 Blow air inlet 11 Reservoir 12 Guide 13 pneumatic pistons 14 Rear pressure chamber 15 pneumatic cylinders 16 air adapters 17 Channel 18 Flow control 19 Flow control air 20 Reverse air inlet 21 Return flow control 22 channels 23 Front pressure chamber 24 Seal 25 threads 26 threads 27 Nozzle needle chamber 28 channel 29 throat groove 30 Groove 31 side hole 32 Seal 33 Nozzle needle bore 34 Seal 35 Air blow outlet 36 Finishing nozzle shaft

Claims

[1] Device for dispensing coatings by means of compressed air from a storage container onto a surface of a mold or the like, wherein an agitator is arranged in the storage container for the coating, and that the coating is transported from the storage container by means of a pump device to a spraying device with a spray head (1), characterized bythat a sizing nozzle (2) is located in the spray head (1), which is designed at a distance from an air blow nozzle (4) with a compressed air connection, wherein the air blow nozzle (4) and the sizing nozzle (2) are arranged offset from one another at an angle of approximately 90° or less, wherein the spray head (1) essentially consists of a nozzle holder (5) arranged on a distributor block (6), and an air adapter (16), wherein the nozzle holder (5) is arranged in the distributor block (6), wherein the sizing nozzle (2) has a nozzle needle bore (33) penetrated by a nozzle needle (3), wherein the sizing nozzle (2) is closed in the rest position by a seal (34), at the same time the nozzle needle (3) has a sizing needle shaft (9) which is connected at its end to a pneumatic piston (13), the sizing nozzle (2) has a sizing nozzle shaft (36) which is penetrated by the sizing nozzle needle shaft (9) at a distance. [2] Device according to claim 1, characterized by that the sizing nozzle (2) and the air blowing nozzle (4) are arranged interchangeably in the nozzle holder (5). [3] Device according to claim 1, characterized by that the sizing nozzle needle shaft (9) has, in the part which dips into the sizing nozzle shaft (36), a groove (30) running laterally in the direction of the sizing nozzle (2), wherein the amount of sizing entering the nozzle needle chamber (27) can be influenced by the formation of the groove (30). [4] Device according to claim 1, characterized by that the sizing nozzle (2) is positioned against the sizing nozzle shaft (36) by means of a spring element (8) in the form of a compression spring. [5] Device according to one or more of the preceding claims, characterized bythat the pneumatic piston (13) is mounted in a pneumatic cylinder (15) of the air adapter (16), and that a front pressure chamber (23) is formed in front of the pneumatic piston (13) and a rear pressure chamber (14) is formed behind the pneumatic piston (13), wherein the relative position of the nozzle needle (3) can be changed by controlling the front pressure chamber (23) or the rear pressure chamber (14). [6] Device according to one or more of the preceding claims, characterized by that a reservoir (11) for the size to be sprayed is formed in the distributor block (6), the reservoir (11) is penetrated by the size needle shaft (9), at the same time the reservoir (11) is connected to a nozzle needle chamber (27), the nozzle needle chamber (27) being formed within the size nozzle (2). [7] Device according to claim 1, characterized bythat the pumping device is designed as a peristaltic pump and pumps the sizing in a circuit via the reservoir (11) and the storage container, wherein an agitator is assigned to the storage container. [8] Device according to one or more of the preceding claims, characterized by that the spray head (1) can be arranged several times next to or above each other.

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