EP0631823A1 - High pressure spraying apparatus for solid wax - Google Patents

Abstract

An apparatus and a method for airless spraying of solid wax envisage that the solid wax is heated in a filling container (2), which is connected directly to a high-pressure pump (1), and is thus liquefied. From the pump (1), the solid wax passes through a single compression-proof line (3) to a spray gun (4). Prewarming lines (3) and wax circulation, which prevents cooling of the wax in the line (3), can be forgone. Critical for the functional reliability of the spraying apparatus is essentially only the liquefaction of the wax in the lower region of the filling container (2) and in the suction region (21) of the pump (1). <IMAGE>

Description

The invention relates to a device according to claim 1.

Hard wax is increasingly being used to impregnate wooden surfaces, especially in furniture. The waxes used are solvent-free and their composition is adapted to the function of the surface being treated. It has been shown that even with natural components such as linseed oil, wood oil, natural resin, beeswax and carnauba wax, optimal impregnation can be achieved without harmful solvents. In order to prevent the labor-intensive manual application with cotton towels and the sometimes uneven distribution of the wax, the wax is applied to the surface using a hot spray process.

The known devices for hot spraying hard wax heat the wax to approximately 60 ° C. The wax is liquefied by the heating. The liquid hard wax is continuously circulated between the pump and the spray gun in a preheated circulation loop and heated in a continuous-flow heater so that the wax and the lines of the circulation loop are kept at a temperature at which the wax is liquid. The circulation loop comprises two pressure-resistant lines, one leading from the pressure side of the pump to a connector at the spray gun and the other from the connector to a container from which a suction line leads to the pump. The connecting piece is essentially arranged as a T-piece in such a way that a portion of the circulation of the wax flowing in via the first line always flows back to the pump via the second line. The amount of wax that emerges from the spray gun is significantly smaller than the amount of circulation, so that most of the funding is used to circulate the wax.

Both hard wax sprayers with low pressure and those with high pressure pumps are known. At low pressure, the wax is atomized using compressed air that is injected into the wax at the nozzle. For this purpose, a compressed air line must be run parallel to the two lines for the wax and a compressed air connection or a compressor must be available. The handling of the spraying device is made difficult by the three hoses and the necessary proximity to the compressed air source. The investment costs are also high due to the many components. A large amount of overspray is created during air dusting, i.e. a considerable part of the sprayed wax does not reach the surface but is sprayed into the ambient air.

In spray devices with high pressure pumps, the wax can be sprayed airless. The requirements for the tightness of the piping system with its connections are increased due to the high pressure. In particular, the effort for the continuous-flow heater inserted into the wax line on the high-pressure side becomes very great. Since solvent-containing substances may also be sprayed, the safety regulations for the preferably electric heater of the instantaneous water heater are extremely strict, so that correspondingly high production costs also arise.

It has now been shown that the known spraying devices require complex process steps during commissioning and at the end of operation. The line system must be preheated during commissioning. Various procedures are known for this. The lines are, for example, wrapped around a heat source and heated by contact heat, or a heated heating medium, preferably linseed oil, is circulated through the lines until they have the required temperature. The heat medium is returned from a separate heatable container through the pump and the circulation lines to this container. To do this, the suction and return lines from linseed oil must be changed to the wax container and vice versa. If necessary, the heat medium is filled into the wax container so that it is before filling the wax must be derived again. To prevent the lines and the pump from becoming blocked, the entire system must be flushed, preferably with linseed oil, at the end of a work cycle.

For waxes that, due to chemical reactions such as oxidation, undergo chemical changes and thus loss of quality, at least during long warming times at high temperatures, the wax circulation with sometimes very long residence times of circulating wax components is not suitable. The circulation is also not a good solution in terms of energy technology, because the majority of the promotion only serves the circulation and because heat is emitted along the entire circulation path, which must be continuously introduced by the instantaneous water heater. The heat input required to compensate for the heat losses depends on the temperature of the ambient air, so that when working in cold outside air, the heating output has to be adjusted, otherwise hardening problems can be expected. In order to maintain the circulation, the delivery rate of the pump must be significantly greater than the desired spray rate or the spray rate of the spray gun. Such an oversized pump leads to an increase in device costs.

The object of the invention is now to describe a spraying device which is simple in construction and is user-friendly, which optimally converts the energy used into spraying power and can be produced at low cost.

The inventive solution for a hard wax spraying device is that a heatable filling container is connected directly to a high-pressure pump and a single pressure-resistant line leads from the pump to a spray nozzle device.

In a first inventive step, it had to be recognized that the prejudice that had long been widespread in the field of hard wax spraying that the wax in the pipe system between the pump and the spray nozzle was always liquid was not correct. In In a second inventive step, it was recognized that cold and thus solid, or at least viscous, hard wax can be conveyed through an unheated, cold delivery line at a sufficiently high delivery pressure and that even when it emerges from an airless nozzle due to the large pressure drop above the nozzle Spray jet is created. The minimum pressures required for delivery and spraying are, depending on the desired delivery rate, on the required nozzle opening and on the line cross-section, at least 30 bar, optionally at least 50 bar, but preferably at least 70 to 80 bar.

The necessary pressures can be easily reached when using high pressure pumps. A diaphragm pump, in particular a pump with an electrically driven hydraulic piston, which drives the pump diaphragm via the hydraulic oil, is preferably used. If necessary, a piston pump can also be used advantageously. The tests carried out have shown that it is possible to pump solid hard wax as long as there is liquid hard wax on the suction side of the pump. In order to meet this requirement with little effort, an inlet container that can be heated, at least in its lower outlet area, is provided, which is connected to the pump at the shortest possible distance to the suction and pump element, preferably to the membrane, that is to say without a hose connection. If necessary, the liquefaction of the wax in the area between the filling tank and the pump element is stimulated in the connection area between the pump and the filling tank, at least via heat conduction, possibly also by a heating device arranged in this area.

Placing the filling container above the suction chamber of the pump ensures that the wax liquefied in the container runs into the pump due to gravity. As soon as liquid wax is on the suction side of the moving pump element, the pump can begin to build up pressure. The spraying process can begin when the pressure required to convey the hard wax on the pressure side of the pump is minimal.

The filling device attached to the pump and the use of only one line from the pump to the spray nozzle device give the spray device a simple structure. Since the heating device is arranged in the filling container and no longer on the high-pressure side of the pump, it can be made much simpler and cheaper. The airless spraying process used does not require expensive compressed air and, without overspray, brings essentially all wax onto the surface to be processed.

In addition to simplifying the device, the spraying process is also significantly simplified by the invention. Lines must not be cleaned and / or heated before or after spraying. The device can simply be switched off so that the wax in the pump, in the lines and in the filling container becomes hard. When starting up again after the heating device of the filling container has been switched on, it is only necessary to wait until the hard wax has melted at least between the lower region of the container and the pump element. Then the spraying process can begin. By omitting cleaning and heating rinses, no mixed products, such as linseed oil with wax, are required. Since no circulation has to be maintained, the entire energy is optimally converted into spraying power.

In addition to the advantages of the inventive solution already mentioned, it should be noted that by correctly arranging a heatable filling container on a commercially available high-pressure pump, a high-pressure spraying device according to the invention can be put together for hard wax with minimal effort. If the heater remains off, the same device can also be used to spray paints and varnishes. So it is a universal spraying device. Thanks to the solution according to the invention, two devices, one for paints and lacquers and one for hard wax, can be dispensed with. All necessary spraying work can thus be made possible with the investment costs for just one device.

The inventive solution can also be expanded for use in automated production processes. If necessary, a nozzle system with several point and / or line nozzles is used instead of a point nozzle, which must be guided over the entire area to be sprayed. A moving device can be used to move the pieces to be sprayed or to move the nozzle system. In order to control the spray sequence, a central control device can be used, which is also connected to the movement device and to the nozzle system, in particular to a closing and opening device of the same. The heating device essentially comprises a heating device with a heating control which controls the respective heating power by means of at least one temperature value detected by at least one temperature sensor. The heating control can be connected to the central control device so that, for example, the spraying process only begins when the required temperature has been reached.

In order to have direct information as to whether the wax is liquid in the inlet area, the use of at least one liquid sensor, preferably an optical, possibly also an acoustic measuring system, can also be provided, these measuring systems also being connected to the central control device. On the basis of the information from a level sensor in the filling container, the control device can start up a wax feed device if the level is too low. To control the pump, the central control device is connected to the pump motor and on the high pressure side of the pump to a pressure sensor and an adjustable pressure control valve.

Fig. 1:

Perspektivische Darstellung einer Spritzvorrichtung beim Spritzen einer Oberfläche

Fig. 2:

Schnitt durch einen Einfüllbehälter

Fig. 1 zeigt eine Pumpe 1 mit einem Einfüllbehälter 2 und einer druckfesten Wachsleitung, bzw. einem druckfesten Schlauch 3, der von der Pumpe 1 zu einer Spritzpistole 4 führt. Eine Bedienungsperson 5 richtet die Spritzpistole 4 gegen eine zubehandelnde Oberfläche 6. Durch das Verwenden des luftlosen Hochdruck-Spritzverfahrens entsteht ein Spritzstrahl 7, der das austretende Wachs im wesentlichen verlustfrei auf die Oberfläche 6 bringt. Die Pumpe 1 sieht vorzugsweise auf der Hochdruckseite ein Umstellventil 8 so vor, dass das Wachs von der Pumpe entweder in die Wachsleitung 3 gelangt oder über eine Kurzschlussleitung 9 wieder in den Einfüllbehälter 2. Der Hochdruck wird durch einen von einem Pumpenmotor 1a in einem Pumpenteil 1b direkt unter dem Einfüllbehälter 2 erzeugt. An einem Manometer 10 kann der aktuelle Druck abgelesen werden. Eingestellt wird der Druck über ein Druckregelventil, bzw. über einen daran befestigten Regler 11.The drawings explain the invention on the basis of schematically represented embodiments.

Fig. 1:

Perspective view of a sprayer spraying a surface

Fig. 2:

Cut through a filling container

1 shows a pump 1 with a filling container 2 and a pressure-resistant wax line, or a pressure-resistant hose 3, which leads from the pump 1 to a spray gun 4. An operator 5 directs the spray gun 4 against a surface 6 to be treated. By using the airless high-pressure spraying method, a spray jet 7 is created which brings the emerging wax onto the surface 6 essentially without loss. The pump 1 preferably provides a changeover valve 8 on the high-pressure side such that the wax either comes from the pump into the wax line 3 or via a short-circuit line 9 back into the filling container 2. The high pressure is generated by a pump motor 1a in a pump part 1b generated directly under the filling container 2. The current pressure can be read on a manometer 10. The pressure is set via a pressure regulating valve or a regulator 11 attached to it.

On the upper side of the pump part 1b there is a suction flange 12, to which the outlet opening of the filling container is attached. The outlet opening is attached to the lower end of the filling container 2. Also in the area of the lower end of the filling container 2 is a supply and control unit 13 for at least one heating device with at least one temperature sensor 14, which measures the temperature of the wax or a heating medium or a contact surface. The heating power is selected via the control device 13, depending on the current temperature, so that the wax reaches the desired temperature. At least one setting element 13a is optionally provided for preselecting a desired temperature or a temperature range. When using an electric pump motor 1a, it is preferably fed together with the heating device via a common connecting cable 15.

2 shows a filling container 2 according to the invention in section and schematically the adjoining device parts. Inside the container 2 is a receiving space 16 into which the hard wax is filled. The container 2 is at least partially constructed with double walls, so that an intermediate space 19 is formed between an outer 17 and an inner container wall 18, into which a heating medium, preferably thermal oil, can be filled. For heating the thermal oil, a heating device 20 is preferably provided, which is arranged in particular in the lower end region of the container 2 in the intermediate space 19 and is fed by the feed and control device 13. In order to control the supply, a temperature sensor 14 is preferably provided in the hissing space 19 in such a way that it detects the current temperature of the thermal oil. If necessary, the temperature sensor 14 is also fastened in the receiving space 16 or on the inner container wall 18. The temperatures required to achieve the liquefaction depend on the composition of the hard wax and are between 40 ° C and 100 ° C, but preferably between 60 ° C and 80 ° C. In order to prevent the desired temperature from being exceeded, the heating power is optionally set by the control device 13 as a function of the difference between the desired and the current temperature.

The heating device 20, 13, 14 must ensure that the wax can be liquefied at least in the lower end region of the filling container 2 and in a suction region 21 of the pump 1 adjoining it. If necessary, a second heater, or a continuous-flow heater 22, which at least partially adjoins the suction area 21, is provided for this purpose. However, the suction area 21 is preferably selected to be so short that the heating device 20 can also liquefy the wax in the suction area. If necessary, this can be better achieved in that a pipe surrounding the suction area has good thermal conductivity properties. The embodiment according to FIG. 2 provides that an outlet opening 16a of the filling container 2 coincides with a suction opening 23a of the pump 1. When using a commercially available pump, make sure that the suction area 21 is as short as possible and that the wax is accessible from above. The liquid wax must be able to enter from above due to gravity.

At the end of the suction space 21, a first check valve 24 is preferably arranged such that liquid is drawn in during suction Wax can flow from the suction area through the valve 24 against a movable pump element 25. When the pump element 25 moves against the first check valve 24, the latter is closed and the wax must escape through a pressure line 26 adjoining the suction area 21. In the pressure line 26, a second check valve 27 ensures that the wax can only enter the pressure line 26, but cannot flow back out of it. In order to be able to set a desired pressure, an adjustable pressure control valve 28 is provided in the pressure line 26. The current pressure in the pressure line 26 is measured by a pressure gauge 29 connected to the pressure line 26.

In order to guide the high-pressure wax, either through the pressure-resistant hose 3 to the spray gun 4, or through a short-circuit line 9 back into the filling container 2 or another container, an adjustable line switch is made between the pressure line 26 and the lines 3 and 9 30 installed. The short-circuit line 9 can be used, for example, for emptying the filling container into another container.

So that there is no risk of explosion even when spraying waxes containing solvents, all electrical switches and plug connections must work without sparks when the heating device 20 and high-pressure pump 1 are operated electrically.

Since, as already mentioned, the inventive spraying device can also be expanded to an automatic spraying system, a central control device 31 is also shown in FIG. 2. If necessary, this is connected to a part of the elements listed below. To control the spraying power, the control device 31 is connected to the pump motor 1a, optionally with the adjustable pressure control valve 28 and with the pressure sensor 29, as well as with the spray gun 4 or a nozzle device. The feed and control device 13 is connected to the central controller 31 so that, for example, the pump is only switched on when the desired temperature and the liquid state of the wax have been reached is. If necessary, to check the wax consistency, a liquid sensor with an optical or acoustic measurement method is provided in the suction area 21 and connected to the controller 31.

In order to control the amount of wax in the filling container, or at least to achieve a minimum wax level, at least one level sensor, preferably a light barrier, could be provided, which would switch a wax feed device on and off via the controller 31, for example. In a large-scale system, the movement device for the nozzle device or the pieces to be sprayed would also be connected to the central control. In order to automatically empty the filling container 2 after the spraying process, the controller 31 could also switch the adjustable line switch 30.

Claims (9)

High-pressure spraying device, for the airless spraying of hard wax, with a storage container, a high-pressure pump, a heating device, a line system and an actuatable spray nozzle device, characterized in that a) the storage container as a filling container (2) connects directly to the pump (1), b) the heating device (20) is assigned to the filling container (2), so that the hard wax can run directly into the pump (1) due to the heating in the liquid state and c) the line system comprises a single pressure-resistant line (3) from the pump (1) to the nozzle device (4). High-pressure spraying device according to claim 1, characterized in that at least one of the following features is provided a) the filling container (2) is at least partially funnel-shaped and has a narrower end region at the bottom, b) the filling container (2) has an outlet opening (16a) in its lower end region and is arranged directly above the suction opening (23a) of the pump (1), so that the outlet opening (16a) preferably connects directly to the suction opening (23a) and thus the distance from the outlet opening (16a) to the movable suction element (25) of the pump (1) becomes minimal, and c) the heating device (20) is arranged at least in a partial area of the filling container (2), preferably close to an outlet opening (16a), and optionally also heats the connecting area (21, 23) between the outlet opening (16a) and the movable suction element (25 ) of the pump (1). High-pressure spraying device according to claim 1 or according to claim 2, characterized in that the filling container (2) is at least partially constructed with double walls, so that An intermediate space (19), which at least partially surrounds the container (2), is created, which receives a heating medium, in particular thermal oil, and preferably also a heating device (20). High-pressure spraying device according to one of claims 1 to 3, characterized in that the heating device (20) at least one heating element (20) and preferably also a control device (13) with an adjusting element (13a), at least one temperature sensor (14) and a feed control (13) for the at least one heating element (20) in such a way that the heating element (20) essentially only generates heat if the measured temperature is below a temperature selected on the setting element (13a), in particular below a set temperature range, the Heating device (20) must be designed so that the temperatures necessary to achieve the liquefaction, which are between 40 ° C and 100 ° C, but preferably between 60 ° C and 80 ° C, depending on the composition of the hard wax. High-pressure spraying device according to claim 4, characterized in that the at least one temperature sensor (14) optionally inside (16) of the filling container (2) and thus in the wax, but preferably in a heating medium, the heat through at least one separating surface to the wax in Fills container (2), or in particular is arranged on a heat-emitting contact surface. High-pressure spray device according to one of claims 1 to 5, characterized in that at least one of the following features is provided a) on the high-pressure side of the pump (1) is connected to an adjustable pressure control valve (28), only a pressure-resistant line (3) leading to the spray nozzle device (4), the pressure required for airless spraying of the wax being at least 30 bar, optionally at least 50 bar, but preferably at least 70 to 80 bar, b) the pump (1) is preferably designed as a diaphragm pump, but possibly as a piston pump, the distance from the suction opening to the movable suction element (25) of the pump being preferably minimal and optionally the line (23) being heatable in this area, and c) the heating device (20) and preferably also the high-pressure pump (1) are operated electrically and all electrical switches and plug connections work without sparking, so that there is no risk of explosion even when spraying solvent-containing waxes. Method for airless high pressure spraying of hard wax, with a spray system consisting of a reservoir, a high pressure pump, a heating device, a line system and an actuatable spray nozzle device, characterized in that a) the hard wax is heated in a storage container designed as a filling container (2) and thereby liquefied, b) the liquid hard wax passes directly from the filling container (2) through a suction opening (23a) into a suction area (21) of the pump, c) hard wax is pressed by the pump (1) under high pressure through a line (3) to the spray nozzle device (4), as long as there is liquid hard wax in the suction area (21), d) when spraying everything through the line (3) to the nozzle device (4) wax coming through it and atomized into fine particles due to the large pressure drop and the formation of the nozzle device and in the form of a widened jet (7) to be processed Surface (6) is applied, e) in the event of spray interruptions, the wax located in the line (3) remains between the pump and the closed nozzle device and thereby cools down and becomes at least partially hard and when spraying again hard form is pressed through the line (3) and the nozzle device (4). A method according to claim 7, characterized in that at least one of the following features is provided a) the temperatures required to achieve the liquefaction, depending on the composition of the hard wax, are between 40 ° C and 100 ° C, but preferably between 60 ° C and 80 ° C, b) the high pressure required for airless spraying of the wax is at least 30 bar, optionally at least 50 bar, but preferably at least 70 to 80 bar, and c) the optimum pressure for spraying is set as a function of the desired hard wax throughput, the design of the nozzle device (4) and the line cross section. A method according to claim 7, characterized in that at least one of the following features is provided a) before the spraying, a warm-up phase is provided for the hard hard wax present in the filling container (2) in order to liquefy at least the wax in the lower region of the filling container and in the suction region (21) of the pump, b) at the end of a spraying cycle, the pump (1) and the heating device (20) are switched off, so that the wax remains hard in the filling container (2), in the pump (1) and in the line (3) to the nozzle device (4) can be, and c) before using the spraying device for spraying another wax or a paint or lacquer, the liquid wax is drained from the filling container (2) and the wax remaining in the pump (1) and in the line (3) a cleaning liquid, preferably linseed oil, filled into the filling container (2).

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