EP1393816A1 - Coating apparatus comprising a rotary spray device and method for controlling its operation - Google Patents

Abstract

The coating device which has an atomiser and drive turbine (101) includes a heating device (115) for heating the gas flowing through the atomiser or parts of the atomiser and/or coating machine which are in heat-conductive connection with the gas flowing through the atomiser. The heating device which warms up the air flowing into the atomiser can have a heat exchanger (116) through which air from the turbine motor can pass. Independent claim describes method for controlling operation of coating device where gas flowing through atomiser or parts of the atomiser are heated by a heater.

Description

The invention relates to a coating device with a rotary atomizer mounted on a coating machine for series coating of workpieces and a process to control the operation of such a coating device according to the preamble of the independent claims.

As is well known, the bell plate is used for electrostatic Series coating of workpieces such as vehicle bodies usual rotary atomizer with compressed air turbines driven at extremely high speeds (DE 34 29 075, DE 43 06 800, EP 0 796 663, EP 0 801 991 etc.). The one flowing through the turbine Air has about the temperature when it enters the atomizer the environment and is due to the relaxation in the turbine Cooled temperatures that depend on the turbine power and, for example, in the coating systems used up to now were on the order of up to -20 ° C. If, among other things because of the in recent times, the desire for even higher ones has increased rapidly Speeds and paint flow rates the performance of the Turbine should be further increased, the cooling can Air at the turbine outlet is below -40 ° C.

Even with turbines of relatively low power occur as a result of Cooling problems caused by condensation when the water content (Pressure dew point) of the compressed air supplied to the turbine does not correspond to the values specified for the coating system. Problems caused by wrong pressure dew point can be caused by Release heating of the turbine supply air. In particular arises but due to the strong cooling in performance-enhanced turbine engines for higher speeds and paint flow rates of condensation water by condensing the air at the with the exhaust gas in heat-conducting Related components of the atomizer and the coating machine, which with the ambient air in the Spray booth with a humidity of usually more than 50% come into contact. As the turbine exhaust air the coating process could interfere if they are directly on the atomizer in the Would exit, it is usually by the Sprayer-carrying arm of the coating machine, e.g. one Paint robot derived through, so that for example also the surfaces of the flange connection between the atomizer and the wrist of the machine and the adjacent areas of the machine arm are cooled down with the consequence corresponding Condensation. The resulting water drops can cause paint defects.

The object of the invention is to provide a coating device or a process, especially in electrostatic Rotation atomizers with high drive power condensation the ambient air on components of the atomizer and / or the Prevent coating machine as much as possible.

This object is solved by the features of the claims.

A first measure to prevent the formation of condensation is heating the turbine drive gas which is in usually compressed air. With the warming of the drive air can cause excessive cooling in some coating systems should be avoided, but above all an immediate one Heating the exhaust air of the turbine is expedient while if only the supply air is heated, part of the thermal energy by conduction on condensation less affected air supply side of the atomizer is lost and / or undesirable heating of components there Atomizer. Generally the possibility of warming by the permissible maximum temperatures of the affected Components or conduit hoses etc. limited, for example, from plastic.

The heating of the exhaust air from the turbine can be particularly expedient be on a heat exchanger that on the one hand from the exhaust air and on the other hand separately from the supply air to the turbine or from one supplied liquid or gaseous medium such as e.g. heated air is flowed through. When the heated supply air through a single heating device is sufficient for the heat exchanger for heating the supply air and as an additional measure of the exhaust air without having to rely on two different types of heating Make additional air consumption. It is advantageous this also means that undesirably strong heating of supply air ducts and adjacent components can be avoided.

The exhaust air from the turbine can also be warmer by adding it Air can be heated. For example, directly on the Exhaust opening of the bearing unit of the turbine compressed air from the existing compressed air network of the coating system or from one Fan-conveyed air can be directed into the exhaust air flow. The The amount and temperature of this additional air can be used to avoid the undesirable condensation depending on the exhaust air temperature and set to relatively low values by the air humidity become.

The cooling of the components through expansion of the drive air the turbine depends on its load and is the stronger, the higher the speed, the amount of paint sprayed per unit of time, the diameter or the mass of the bell plate and the temporal utilization rate of the atomizer during a painting cycle are. In addition, there are higher air consumption quantities for increasing loads required, which in turn intensify the cooling. As a result, atomizers with high load can in addition to or instead of heating the drive air the turbine other measures may be advantageous.

A suitable option for this is i.a. the warming of the Internal clearance of the turbine, the shaft of which in a manner known per se an air bearing rotates. The warming of the internal clearance has the The advantage that the internal clearance flows through a large part of the turbine and can thereby heat it more evenly.

However, the air volumes and thus the heat capacity of the Warehouse clearance relatively low. It may therefore be appropriate to use larger ones warmed air volumes (e.g. in the order of magnitude of 100 rpm) by additional, separate from the path of the drive air, i.e. in known atomizers and coating machines channels of the storage unit and / or others not provided Components of the atomizer or the coating machine to lead.

Another option is to heat the steering air, which in a manner known per se, if necessary, in various ways flows past the bearing unit of the turbine and / or through the Turbine flows through (DE 102 33 198). The steering air temperature is set so that the one formed by the steering air Spray cone is not affected and not an undesirable Influence on the painting process.

With gaseous or liquid heating media supplied from the outside components at risk from condensation in the cabin air of the atomizer and / or the coating machine also directly be warmed. For example, besides the atomizer even the flange construction on the robot wrist, the Wrist and / or the robot arm corresponding channels for the heated media included.

The temperature of the supplied to reduce cooling Air or other media can preferably be dependent on one or more temperature sensors are controlled which e.g. the temperature of the supply air and / or exhaust air of the turbine, the Engine bearing air, possibly the steering air and / or from to the inlet and Exhaust air routes of the turbine air adjacent components of the atomizer or measure the coating machine and with an associated one Controls the preheating temperature in a closed control loop can control. Instead of regulation via temperature sensors or independently of this, the preheating temperature can also based on predefined diagrams or saved program data depending on the speed and amount of paint, i.e. depending on the load to be controlled.

The arrangement of an electric heater for the atomizer supplied for the purpose described here, preferably has electrically insulating heating media outside the atomizer especially with electrostatic atomizers with direct charging of the coating material the advantage that problems regarding the required electrical isolation between the heater and the components at high voltage potential of the atomizer can be avoided.

With suitable electrical isolation and with atomizers with external charging can cause the condensation of the cabin air on cold components of the atomizer or the coating machine also directly by installing a heating device in the concerned Components can be prevented. Also an electrically conductive one Heating fluid such as Water or an electric heating coil can be used in this case.

According to another feature of the invention, the usual outer housing of the atomizer to avoid the formation of condensate surrounded by an insulating sleeve on the outside of the atomizer be, preferably at a distance to form an insulating Air layer.

All the ways described above to avoid one too strong cooling can be used individually or in any combination may be meaningful and thus lead depending on Construction and operation of the coating system reliably to avoid the annoying condensation. A special advantage The invention consists in the fact that strong temperature differences can be avoided within the atomizer, due to the different expansion coefficients Malfunctions or damage to components could result. The measures described here do not allow selective, but very even heating of the components.

Fig. 1

eine Querschnittsansicht eines elektrostatischen Rotationszerstäubers;

Fig. 2

ein zweckmäßiges Beispiel für die Luftversorgung des Turbinenmotors des Rotationszerstäubers in schematischer Darstellung; und

Fig. 3

in teilweise vereinfachter Darstellung ein weiteres Ausführungsbeispiel eines Rotationszerstäubers, dessen Gehäuse von einer Isolierhülse umschlossen ist.

The invention is explained in more detail using the exemplary embodiment shown in the drawing. Show it

Fig. 1

a cross-sectional view of an electrostatic rotary atomizer;

Fig. 2

an expedient example of the air supply to the turbine motor of the rotary atomizer in a schematic representation; and

Fig. 3

in a partially simplified representation, another embodiment of a rotary atomizer, the housing of which is enclosed by an insulating sleeve.

The rotary atomizer 1 shown in Fig. 1 has the in the structure described in DE 102 33 198 and can with its mounting flange 2 e.g. on the wrist of a painting robot be mounted. To drive its rotating bell plate 4 it contains a compressed air turbine 5, the drive air of which Painting robot is fed via the mounting flange 2, the supply of the drive air here for simplification is not shown.

For shaping the spray jet emitted by the bell cup 4 is a steering air ring 6 is provided in the bell-side End face of a housing 7 of the rotary atomizer 1 is arranged. In the steering air ring 6 are several axially aligned Steering air nozzles 8, 9 arranged, via which in the operation of the Rotary atomizer 1 a steering air flow axially outside on the conical Shell surface of the bell plate 4 are blown can. Depending on the amount and speed of the from the steering air nozzles 8, 9 blown out steering air Spray jet shaped and the desired jet width set.

The supply of the steering air for the two steering air nozzles 8, 9 takes place each through a flange opening 10, 11, which in the mounting flange 2 of the rotary atomizer 1 is arranged are. The position of the flange opening 10, 11 within the End face of the mounting flange 2 is here by the Position of the corresponding connections on the associated mounting flange of the painting robot.

The external steering air nozzle 8 is used in a conventional manner powered by a steering air line 12 on the outside the compressed air turbine 5 between the housing 6 and the compressed air turbine 5 is guided along. For this, the flange opening opens 10 first in an axially extending bore 13, which is then in a radial bore 14 merges, which eventually the outside of a valve housing 15 into a space opens between the housing 7 and the valve housing 15. The Steering air is then past the compressed air turbine 5 into a so-called Airspace 16, from where they finally passed through Branch bores 17 in the steering air ring 6 to the steering air nozzle 8 arrives.

The supply of the steering air for the steering air nozzle 9, however, takes place through a steering air line 18 which extends from the flange opening 11 in the mounting flange 2 starting axially and preferably goes through the valve housing 15 without kinks. Furthermore the steering air line 18 also passes axially through a bearing unit 19 of the compressed air turbine 5. The radial distance of the steering air line 18 of the axis of rotation of the bell plate 4 is here larger than the outside diameter of the to simplify not Turbine wheel shown, so that the steering air line 18 the outside of the turbine wheel. The steering air line 18 then opens into another air space on the bell plate side 20 between a substantially cylindrical portion 21 of the compressed air turbine 5 and a cover surrounding it 22 is arranged.

There are several bores in the lateral surface of section 21 23, which in the bell-side face of the Compressed air turbine and finally into the steering air nozzles 9 lead. The bores 23 in the section 21 of the compressed air turbine 5 consist of one of the lateral surface of the section 21 outgoing radial tap hole and one from the bell face end face of section 21 outgoing axial tap hole, which is a simple Assembly enables.

The air supply to the compressed air turbine 5 of the atomizer according to Fig. 1 can, for example, the scheme shown in Fig. 2 correspond. As described in EP 1 245 292, this is when there is an increased need for drive energy in the basic supply line the air turbine via a switchable separate channel Additional air supplied at a higher pressure.

The compressed air turbine has a bearing unit 101 for the bell cup 102 supporting, for example, air-bearing hollow shaft 103 with the turbine wheel 104. The bearing unit 101 is located in the atomizer housing 105. The turbine wheel 104 is driven by a external speed controller via a leading into the atomizer Hose 107 and one serving as an internal basic supply line Feed channel 108 of the atomizer is supplied with drive air A. The turbine wheel receives from another output of the speed controller 104 via a valve VB and a separate line LB Brake air B. The basic supply line 108 can also consist of several end in parallel at different locations on the turbine wheel Channels exist. As far as it has been described so far it is a conventional electrostatic rotary atomizer act. The mode of operation of the speed controller, the one, for example opto-electronically recorded actual value compares the turbine speed with a target value and at Deviations actuates the ventilation valves of an actuator and can also control a brake valve is known per se.

As shown, it contains through the hose 107 and the channel 108 formed air supply path of the turbine e.g. pneumatically or electrically controlled valve arrangement 110 which locks off a separate duct 111 for connecting air, which also drives the turbine wheel 104 on this empties. A plurality of additional channels 111 with a plurality of nozzles can also be used be provided on the turbine wheel.

The exhaust air from the turbine is on the way indicated at 113 out of the atomizer through the atomizer flange and e.g. in the arm of the painting robot.

In operation, when the drive energy requirement is low, that in the separate Channel 111 leading branch of the valve arrangement 110 closed, so that the turbine in the already usual Is driven only via the channel 108.

Increases, for example, due to increased paint application or when using a larger bell cup 102, etc. the drive energy requirement over one for normal air supply through channel 108, the limit in branching of valve arrangement 110 leading channel 111 is opened, so that through the connected channel 111 the turbine with a larger amount of air with higher pressure, i.e. with the required Additional energy is supplied. The outside in the atomizer leading air hose 107 has such a large size Cross section that all the air required is provided can be. In contrast, it is sufficient for channel 108 a relatively small diameter. With decreasing energy requirements or if when starting the atomizer with increased Air performance the nominal speed is reached, the way in the Channel 11 closed again, so that the air consumption on the for the amount of torque required now decreases.

Instead of a simple on / off function, the valve arrangement 110 also the way in channel 111 (or the ways in both channels 108 and 11) for the respective operating and control conditions throttle best values. This throttling can are automatically set and changed.

One of the options for heating of through the exhaust air of the atomizer according to FIG. 1 undesirably strong cooled components e.g. in with an outside arranged by the atomizer e.g. electric heater to heat the steering air through the line 18, through the Valve housing 15 and through the bearing unit 19 of the compressed air turbine 5 goes through. The same applies to those through the holes 13 and 14 flowing steering air. Similar channels could also for one that does not serve as steering air, but on others Because of gaseous or escaped from the atomizer again liquid heating medium may be provided.

If, on the other hand, the drive air of the turbine is to be heated, after heating, it is shown schematically in FIG e.g. electric heater 115 preferably by passed a heat exchanger 116 through which the path 113 of the Exhaust air leads, which in the case of such facilities known way is heated by the supply air. The heat exchanger 116 should be placed as close as possible to the atomizer when it is not built into the atomizer.

As is also shown in FIG. 2, the temperature of the drive air A is regulated by a temperature controller 118 which compares the actual value signal t _i coming from at least one temperature sensor (not shown) in the atomizer with a setpoint signal t _s and, depending on this, the Heater 115 controls. As has already been mentioned, the control signal st of the heating device could also be predetermined without a control circuit by program data stored as setpoints.

3 is a further exemplary embodiment of the invention electrostatic rotary atomizer shown, the largely e.g. the atomizer of FIG. 2 or a conventional Rotary atomizers correspond approximately to DE-A 43 06 800 can. Accordingly, it contains a bell cup 34 driving Compressed air turbine 35 with the associated bearing unit 31 and a valve housing 36 within the usual conical-cylindrical Outer housing 37, which is suitably made of plastic can exist. For example, from the valve housing 36 through a bore, as shown in Fig. 1 at 13 and 14 is, steering air into the space on the inside of the outer case 37 exit. With one on the mounting flange 32 of the Atomizer and / or attached to the valve housing 36 mounting pin 33 can the atomizer in the DE-A 43 06 800 known manner on an external flange 40 for example on the wrist of a painting robot or on another painting machine be attached.

The atomizer described so far could do anything with high humidity in operation on the outside of the outer housing 37 form condensate water, especially from the area where the steering air exits into the outer housing 37, up to the steering air ring (6 in Fig. 1). To solve this problem is the outer housing 37 of a similarly shaped, so here on the conical side facing the bell plate 34 and on the opposite side cylindrical insulating sleeve 42 enclosed. The inside diameter of the insulating sleeve 42 is preferably 42 greater than the outside diameter over most of its length of the atomizer housing, i.e. of the outer housing 37 so that a heat-insulating air space 43 is formed between them. According to the illustration, the insulating sleeve 42 on the bell-side front end of the outer housing 37 or on the provided there Steering air ring sit on it while on its opposite End up to the machine flange 40 and at the Scope may apply. Through an O-ring 44 or 45 between the ends of the insulating sleeve 42 and the steering air ring or outer housing 37 or the machine flange 40 is the air space 43 sealed outside.

The insulating sleeve 42 can be made of heat insulating material such as e.g. consist of a foam plastic and composed of half shells or be formed in one piece so that they on the Atomizer can be placed on the machine flange 40 is mounted.

Another possibility, not shown, for avoiding Condensation on the surface of the outer casing consists of moving the housing to one above the dew point of the environment to heat lying temperature, for example with a installed in the outer housing or arranged on the inside thereof Heating device.

To avoid undesirable consequences of the condensation on inside of the atomizer or external surfaces also possible in the area in question in a known manner Way to prevent the formation of water drops by absorption Embed (hydrophilic) particles.

Claims (15)

Coating device with a rotary atomizer mounted or mountable on a coating machine for the serial coating of workpieces
with a turbine motor (5) of the atomizer driven by air or another gas, in whose bearing unit (101) the shaft (103) of the rotating atomizing element (4) driven by the motor is mounted,
with an inlet path (107) through which the gas is supplied under pressure to the turbine wheel (104) of the engine,
and with an exit path (113) through which the relaxed exhaust gas is led out of the bearing unit (101) and out of the rotary atomizer,
characterized in that a heating device (115) is provided, with which the gas flowing through the rotary atomizer or with its inlet and / or outlet paths (107, 113) in heat-conducting components of the atomizer and / or the coating machine can be heated. Coating machine according to claim 1, characterized in that the heating device (115) heats air (A) flowing into the atomizer. Coating device according to claim 1 or 2, characterized in that the heating element of the heating device (115) is located outside the atomizer. Coating device according to one of the preceding claims, characterized in that the heating device has a heat exchanger (116) which is flowed through by the supply air (A) of the turbine motor or by another warm fluid and by the exhaust air of the turbine motor. Coating device or storage unit for a coating device according to one of the preceding claims, characterized in that the storage unit and / or other components of the atomizer or the coating machine separate channels (13, 14) from the inlet and outlet paths (107, 113) of the gas driving the turbine engine , 18), through which the medium heated by the heating device (115) flows or through which it can flow. Coating device according to one of the preceding claims, characterized in that the atomizer and / or the coating machine have at least one temperature sensor which controls the heating device (115). Coating device according to one of the preceding claims, characterized in that at least one component of the atomizer and / or the coating machine which is thermally conductive to the input and / or output path (107, 113) of the gas driving the turbine motor contains an electrical heating element, for example. Coating device according to one of the preceding claims, characterized in that the outer housing (37) of the atomizer is surrounded by a heat-insulating shell (42). Coating device according to claim 8, characterized in that a heat-insulating air space (43) is formed between the outer housing and the inside of the insulating sleeve (42). Method for controlling the operation of a coating device with a rotary atomizer, in which a gas driving a turbine motor (5) of the rotary atomizer, in particular air, is supplied under pressure to the turbine wheel (104) of the turbine motor through an inlet path (107) and as relaxed exhaust gas through an outlet path (113) is led out of the bearing unit (101) of the turbine engine and out of the atomizer,
characterized in that the gas flowing through the rotary atomizer or with its inlet and / or outlet paths (107, 113) which are in thermally conductive connection to the atomizer and / or the coating machine are heated by a heating device (115). A method according to claim 10, characterized in that the drive gas is heated in front of and / or behind the turbine engine. A method according to claim 10 or 11, characterized in that the bearing air of the bearing unit of the turbine engine containing an air bearing for the shaft is heated. Method according to one of claims 10 to 12, characterized in that the steering air is heated, which is passed through the rotary atomizer and directed to the sprayed coating material for setting the spray jet. Method according to one of claims 10 to 13, characterized in that warm air is passed into the exhaust air of the turbine engine. Method according to one of claims 10 to 14, characterized in that the temperature of the gas flowing through the rotary atomizer or with its inlet and / or outlet paths (107, 113) in thermally conductive components of the atomizer and / or the coating machine in a closed Control loop regulated or controlled depending on predetermined setpoints.

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