Controlled powder flow rate regulator

0001The present invention relates to a method according to the Preamble of claim 1 and a device for carrying out the process.

0002From DE-44 09 493 a metering device is known to the to regulate amount of powder a powder coating device, and specifically such that the conveying speed of the to administered powder even with varying amount of powder at least remains almost the same. The method proposed in DE-44 09 493 Air splitter member, by means of which the air supply in Dosing and conveying air is divided, it is before a adjusted coating campaign and constant during the campaign leave. Allfällig during a coating campaign occurring influences and changing the coating parameters, as climate variability, composition of the powder and the like, are not taken into account and can be different Coating results lead.

0003It is therefore an object of the present invention, a solution of the problems suggest. According to the invention a method according to the wording of claim 1 proposed.

0004The inventive method is based on DE-44 09 493, in which a powder coater, an air part organ has for the allocation of an air supply in dosing and conveying air, such that for different settings the air division differently funded amount of powder be applied at a constant conveying speed can. According to the invention it is now proposed that for regulating the layer thickness of powder by means of a coater coated objects in the field of coating organ, such as a powder gun, and / or to be coated in the area of ​​and / or the coated objects measured at least one coating of relevant parameters is and because of the measurement, the adjustment of the air divider organ is affected.

0005According to a first embodiment, it is proposed for certain objects to optimize coating parameters relevant and then store this data. With are these stored parameters to be coated objects then, for example, with a field relevant to these objects in code what code before coating is detected by a sensor, followed by retrieving the stored data, the air divider organ optimally adjusted becomes.

0006According to a further embodiment, it is proposed that the layer thickness of an already coated object by is determined a sensor, the measured value with a Set value is compared, and then the actuator of will air splitter organ such controlled or changed, that the layer thickness subsequently to be coated objects at least almost the standard value. Assigns example Thickness of flat coated object too small Value, so the air splitter member is to be driven such that split the air supply into more feed air and dosage air less is, thereby promoting a greater amount of powder and is applied.

0007Of course it would be possible per se, at any coater more coating powder to promote, without an upstream division of the air supply in carried conveying air and dosage air. The consequence would be that the conveying speed is also increased, whereby a Control the coater more difficult is. Also it is expected that much in this case more powder is to promote, as to be expected with larger losses is. it is advantageous according to the invention that the scheme or checking the layer thickness in combination with the Air part organ takes place, which described in DE-44 09 493 is.

0008However, this optimization of the coating is also combinable by the aforementioned detection of a code for certain Objects by first air splitter member according to the stored Data is set and then a Fine optimization of the coating takes place by means of the values, which are determined on the initially coated objects. Whether this conclusively so newly determined, optimal parameters are stored, or the originally stored Data for the coating further object campaigns be used, can be made dependent on each, have led to what external influences that not originally stored data optimized for desired led success.

0009According to a further embodiment, it is proposed the height or longitudinal extent of the objects to be coated to determine before the coating process and the measured height forwarded to a lifting device by means of which the Coating organ, such as a coating gun, out in its height during the coating process or is changed. By the measured object height, the Lifting the lifting device to be coated effectively Height of the object to be limited, which in turn to administered amount of powder can be optimized. simultaneously it is possible to occur in objects with great height extension To avoid different coating thicknesses, as usually in the amount more powder is to be applied as in the depth since, due to the gravity to be applied, a portion of the falling powder down. Experience has shown that when an object with height extension per meter above about 3 to 6% more powder to be applied as at depth. The different powder to be administered amount can now turn by different Setting the air divider organ be effected, which is controlled by the measuring device, by means of which measuring device the height of the object to be coated is determined.

0010According to still another embodiment is the fact taken into account that, for example, when using Tribo guns, the charging of the powder on frictional charging based, with the charge depending on the composition of the powder and depending on the climatic conditions during a coating operation Is subject to fluctuations. The coating result thus depends largely on the friction charging of the powder from where for the same charge and the layer thickness remains substantially constant. Thus, it is proposed that the charge to measure the powder to be applied and fluctuations the charges again to drive the air splitter member, such that the conveyor air is changed so as to maintain a constant To ensure the charge of the powder. Thus, in declining increase charge corresponding to the promotional amount of powder respectively at an elevated charge to reduce the amount of powder.

0011The control of the air divider organ or of a related Actuator can both analog as well be digital, and also the control by comparing a measured actual value with a set value set in advance can be analog or done electronically.

0012The invention will now by example and Referring explained in more detail to the accompanying figures.

0013They show:<dl tsize="8"><dt>Fig. 1</dt><dd>schematically a powder coating apparatus comprising an air splitter element according to DE-44 09 493 and a measuring sensor and a control circuit for assuring a constant layer thickness,</dd><dt>FIG. 2</dt><dd>shows schematically a measuring device as well as a associated lifting device for coating objects with different height expansion,</dd><dt>Fig. 3</dt><dd>schematically shows a coating device, wherein the charging of the powder takes place by friction and in which means influencing the to be applied layer thickness by measuring the charge of Powder is and</dd><dt>Fig. 3a</dt><dd>the charging or the sensor of Fig. 3, in section, in enlargement.</dd></dl>

0014In FIG. 1, objects 1 are arranged on a conveyor belt 2, which are to be coated or have been coated. The Coating takes place by means of a coating organ as For example, a powder gun 3, by means of which the powder 5 is applied to the object. The feed example the gun 3 by means of a powder coating device, described in DE-44 09 493. For a better understanding is at this point briefly this coater described as well as their functioning. The Air supply for example, via an inlet pressure regulator 9, by means of which set the air zugespiesene can be. The air is supplied to an air divider member 11, in which a double valve 13 is provided, which by means of For example, a knob 17 is adjustable. By means of Display 15 can be read as the division of the Inlet pressure regulator 9 air fed in conveying air 19 and dosage 21 is divided. By means of the conveying air 19 is in an injector 22, for example by arranging a venturi-like Zone 15 is sucked from a powder supply 25 powder and a second Venturi tube-like zone 27 supplied. In the latter zone is also fed to the dosing and 21 mixed with the conveying air and the powder. will then the powder via the connecting line of the coating gun 3, respectively.

0015By means of the metering device described in DE-44 09 493 is now ensured that the powder even at different is to be applied quantity of powder always at constant fed conveying speed of the gun and the object is applied. This is advantageous for achieving a uniform and high-quality coating.

0016Following the scheme in Fig. 1 is now subsequently to the coating zone a measuring sensor 31 is arranged, by means of which the layer thickness measured at the already coated object 1 or can be determined. The measured thickness is a Recording 33 is supplied in which the measured value is compared to a setpoint 35, which by means of a setting can be set or changed 37. by virtue of the deviation of the actual value from the setpoint is now a control 39 so influenced that the knob 17 is actuated becomes. This of course only when the actual value of Setpoint deviates. If the layer thickness is too small, the Knob so set in motion that the conveying air increased 19 is and is promoted accordingly more powder. Is the Layer thickness is too large, the knob 17 is operated in such a way that the double valve 13 is moved in the direction of conveying air 19, respectively more dosing the venturi-like device 27 is supplied and promoted accordingly less powder becomes.

0017Due to this control loop can now be ensured that after a few coated objects a constant Layer thickness is applied, and that occurring should existing Variations of influences, such as temperature, Humidity, composition of the powder, etc., Layer thickness is at any time automatically corrected.

0018In FIG. 2 is again represented schematically as in objects with different extent in the direction of their height or in Longitudinally optimize the consumed amount of powder in the coating can be. Again, objects 1 which over Suspension means 43 connected to a conveyor 41 or are attached to this coated, initially before a coating device by means of a measuring device 45 whose height or longitudinal extension detected or determined becomes. The measured by the measuring device 45 signal 47 is via a control device to the coating assembly passed which mobile for example on a Device 51 is arranged. This coating comprises arrangement on the one hand the coating gun 3, which on the other hand is arranged on a lifting device 49 to the height adjustable to be operated. is by the measurement signal 47 Now, the stroke of the powder gun is controlled so that the detected Object 1 in its entire height or longitudinal extension is sprayed, but the stroke movement is limited such that the pistol on the limitation of the object in the longitudinal or Height direction also moves or operates. Thereby ensures that there is no unnecessary sprayed powder, which is not deposited on the surface of the object.

0019However, practical experience has shown that the the upper end of an object more powder to spray than at lower end, as a part of the powder to be applied according falling down and therefore at the bottom of the powder density in the spray cloud is higher than the upper end of the object. correspondingly it is proposed according to the invention that the measured Signal 47 is also used, the air splitter member 11 to drive from FIG. 1 and the amount of powder, which means the gun is applied 3 to control accordingly. The control is effected such that in the upper region of the object 1 more powder is sprayed than in the lower region, Experience shows per altitude upwardly about 3 to 6% more powder to be applied than at the lower end to a to achieve the coating of the object uniform layer thickness. Thus, it is necessary, for example in an object with a longitudinal extension of approximately 4m and with a height extension of 4 m at the upper end is about 10 to 20%, more powder to applied as at the lower end of the property. Of course does not allow for all of the objects and for all compositions the coating powder specify an exact value, but the different quantities of powder in the upper and in the lower Range are to be determined by practical experience. Again, it has been shown that it is not advantageous, just the powder to be administered amount along the vertical movement the powder gun vary, but that it is important is that the conveying speed of the powder to be applied at least is almost constant, which only by means of a Air organ part 11 shown in FIG. 1 and described in DE-44 09 493, can be obtained.

0020Yet another example is shown in scheme 3 of Fig. which shown with the scheme in Fig. 1 largely is identical. The exception is that in the Arrangement according to FIG. 3 is not primarily the film thickness on a is measured or determined already coated object but, that here the charge of powder to be applied in a is sensor 51 measured or detected. According to experience it has been found that for the same charge at least virtually identical layers are obtained on objects 1 may, more or less independent of the amount of the applied Powder. For example, the use of more new Powder or more recycled powder leads to different Charges in the powder to be applied so that different Coatings are obtained. This particularly when using of so-called tribo guns, where the charging of the powder by means of friction. The charge is usually about 1 - 5 uA or 1-2 Coulomb / g. FIGS. 3 now shows in longitudinal section and increases the charge route or the sensor 51, in which the charge for the use of generated or detected by the so-called tribo guns becomes. The powder is conveyed in the arrow direction, rubs against a Teflon coating 55 and is loaded. The the Teflon coating surrounding metal tube 53 is a Measuring element 57 is connected to ground. The measured or flowing Current is a parameter for the amount of charge in the powder / air mixture.

0021The respectively in the sensor or detector 51st 57 measured charge signal is again compared with an actual value, and is carried out according to the the control of the control dial 17 by a circuit . 39

0022It is of course possible that in the three schemes to combine detectors shown, so that, for example, not only the charge is measured in the powder, but also the layer thickness on already coated objects and the Control of the control dial 17 by combining two or multiple detected signals occurs.

0023The coatings or illustrated in the three schemes Measuring systems are of course only examples, to the present invention to provide details. That's the way it is of course, possible other parameters in the field of Coating, before or after the coating of objects to measure and use it to control the air splitter member, adjust the amount of powder to be administered. That's the way it is for example, also possible by means of optical sensors, to measure density of the cloud of powder 5 and detected by the Signal to drive the control dial on the air divider organ. can also Temperature measurements, humidity measurements, voltage fluctuations etc. can be used to be administered to the controlling amount of powder. It is also possible, as already beginning of the description given in advance for certain to be coated Objects to optimize coating parameters, and save it. By means of a detector or sensor at the beginning the coating line are to be coated respectively Objects detected, and is carried on the air divider organ the optimized adjustment means of the previously determined, optimized Parameter. Of course, it is possible to advance these optimized to optimize values ​​during coating and continue to ajustieren, for example, using one of the three advance and in Figures 1 embodiments shown up. 3

0024is essential to the invention that the measured signal is not only is used, regardless of the selected conveyor speed the powder during application, the amount of powder to vary, but that the variation in the amount of powder at least substantially constant delivery rate of Powder is what, for example, by means of a coater, described in DE-44 09 493, permits becomes.