Feed pump for powder

0001The invention relates to a powder conveying pump for use in a powder coating plant.

0002In powder coating systems has been promoting as a coating material serving powder before the so-called Dilute phase method is used, in which the powder in the fluidized State in a flow of air through tubular conveying lines to the application device (eg spray gun or Rotary atomizer) was promoted. The term thin-flow process is because the powder content in the produced Powder-air mixture is relatively low, so that the tubular conveyor lines a correspondingly large had to have cross-section to the desired amount of powder to promote.

0003For this reason, the so-called dense phase powder promotion has already been (PDF) proposed that a larger amount of powder has in the produced powder-air mixture. The actual powder feed may in this case by a well PDF pump Marked done powder conveying pump, a Feed chamber having an inlet and an outlet, said sucked in via the inlet in the powder delivery chamber and is subsequently ejected through the outlet to a Application equipment (eg spray gun or rotary atomizer) to get. To fill the feed chamber is first the outlet of the feed chamber is closed while the opens inlet of the feed chamber to powder of a to suck powder container. Subsequently, then in the delivery chamber a vacuum is produced by blowing air on the Förderkammerwandung is sucked, the Förderkammerwandung is permeable to air but pulverundurchlässig so that not sucked the powder contained in the feed chamber becomes. After a sufficient filling of the pumping chamber the extraction is then ended and the intake valve closed. For ejection of contained in the feed chamber Powder of the outlet is then opened and the air-permeable Förderkammerwandung pressure air into the feed chamber blown, whereby the powder discharged from the pumping chamber becomes. By a cyclic operation of the above described intake and discharge phases of the powder Powder containers conveyed to the application device. The feed chamber can consist of a tube or pipe section consist whose hollow cylindrical wall permeable to gas, but is pulverundurchlässig and thus forms a filter element, wherein the inlet to the feed chamber through an inlet valve is closed, while the outlet from the feed chamber can be closed by an exhaust valve.

0004Disadvantage known on the above PDF-pump is the fact that the Förderkammerwandung from a porous material which gradually during operation the powder may be added, whereby the air permeability the Förderkammerwandung and thus decreases the flow rate.

0005The invention is therefore based on the object in the described known PDF pump clogging of air-permeable Förderkammerwandung prevent.

0006This object is, starting from the above-described known PDF pump according to the preamble of claim 1, solved by the characterizing features of claim 1.

0007The invention comprises the general technical teaching that Förderkammerwandung in departure from the design principle the described known PDF pump substantially gas- or air-tight and perform the extraction of the feed chamber for vacuum generation instead in other perform way. In this way it is prevented, that constitute the powder in the Förderkammerwandung can. This is particularly advantageous, because the powder within the feed chamber mostly along the Förderkammerwandung flows and therefore accumulate there very easy can.

0008Preferably, the negative pressure generating is carried out in the feed chamber in the inventive powder conveying pump by that the negative pressure connection in the interior of the feed chamber to the Förderkammerwandung spaced opens. This is advantageous, because the powder density wandungsnah is particularly large, while the powder density in the center of the conveying chamber substantially is lower, so that the risk of clogging is the powder substantially lower if to Förderkammerwandung is sucked spaced.

0009In a preferred embodiment, is in the feed chamber arranged a membrane body which at least partially gas-permeable, but pulverundurchlässig, said vacuum port for extracting from the feed chamber in the Membrane body opens. The exhaust from the pumping chamber So this is not done directly from the feed chamber, but on the membrane body according to the porous Wall in the known PDF-pump described at the outset a filter element forms.

0010The membrane body is preferably added to the Förderkammerwandung spaced and can be for example within the feed chamber located centrally. This makes sense because the Powder density within the feed chamber in the middle of significantly is less than in the area of ​​Förderkammerwandung, so that the risk of clogging of the membrane body with the Powder is correspondingly lower.

0011In addition, the membrane body is preferably streamlined and between the inlet and the outlet of the feed chamber oriented in the direction of flow, wherein the inlet and the outlet of the feed chamber each preferably opposite.

0012In a variant of the invention, the membrane body is at least gas-permeable over a large part of its surface, but pulverundurchlässig, resulting in a lower Stömungswiderstand of the membrane body may be achieved during suctioning.

0013In another variant of the invention, the membrane body on the other hand on the inlet side facing substantially impermeable to gas and pulverundurchlässig and on the outlet the feed chamber side facing gas-permeable, but pulverundurchlässig. The gas and the Pulverundurchlässigkeit Membrane body more difficult on the inlet side facing advantageously assessing the powder in the Menbrankörper. On the outlet-facing side of Membrane body, the risk of assessing powder steeply flow conditions significantly less, so that the membrane body be carried out to check gas permeable can to suck air out of the feed chamber.

0014The emptying of the feed chamber after a previous Filling takes place as in the known initially described PDF pump by the powder located in the feed chamber is ejected by compressed air. To this end the invention preferably powder conveying pump an overpressure connection on the inside of the feed chamber in the diaphragm body opens. The supply of compressed air for ejecting the powder from the feed chamber takes place here so indirectly via the membrane body, which acts as a filter element.

0015Here, it is possible that the vacuum connection to the suction from the feed chamber and the positive pressure port to Discharge of the powder from the feed chamber via a common Line in the membrane body open. This is advantageous, as so on a separate line for the vacuum port or the overpressure connection can be dispensed.

0016However, it is alternatively also possible that the overpressure connection for discharging the powder from the feed chamber directly, that is, outside of the membrane body, in the feed chamber opens. This is advantageous because the pressure buildup in the Feed chamber during discharge of the powder from the feed chamber thus not impeded by the flow resistance of the membrane body is what a more rapid emptying of the feed chamber allows.

0017The invention comprises the general technical Teaching, the vacuum in the feed chamber at least partially build before the inlet of the feed chamber is opened. The inlet into the feed chamber is thus open only when already built up in the feed chamber, a vacuum Has. This offers the advantage that fluctuations in the pressure build-up in the feed chamber less influence have on the metering accuracy. The powder conveying pump according to the invention Therefore, a intake valve and an exhaust valve which are independently controllable from each other in order before first open the intake valve opening the purge valve to be able to allow a negative pressure built up in the feed chamber becomes.

0018Preferably, the generating of the negative pressure in the feed chamber is even terminates before the inlet of the delivery chamber opens. The phase of vacuum generation and So Einsaugphase preferably have no overlap in time on. This offers the advantage that during suctioning of Air from the pumping chamber due to the then closed Inlet no powder can be sucked what undesirable would. For this reason, even on a filter element for Air extraction are omitted from the feed chamber, thereby with a given equipment expenses, a higher vacuum can be produced in the feed chamber. preferably takes place but also in the context of the invention the extraction of the feed chamber through a filter element, to the suction to prevent residual powder that may still be in the feed chamber.

0019The inlet of the feed chamber is preferably only opened when in the feed chamber, a predetermined vacuum has built. This offers the advantage that at the beginning the Einsaugphase rule defined pressure conditions, so that calculate the amount of powder sucked easily and control or regulate leaves.

0020For this purpose, the negative pressure in the conveying chamber through a Pressure sensor to be measured, wherein a control unit the purge closes and simultaneously or with a delay time the inlet valve opens when the measured vacuum reaches a predetermined limit value in the feed chamber Has.

0021However, it is alternatively also possible that in the feed chamber before opening of the intake valve, a predetermined vacuum is constructed by the purge valve in accordance with the open desired vacuum for a predetermined period is to give the functional relationship between the opening period of the suction valve and the resulting can be determined by vacuum tests.

0022The delivery of the present in the feed chamber through powder the outlet is preferably carried out by the powder from the Feed chamber is ejected. These preferably opens a Via pressure port in the delivery chamber through which a fluid initiated at the discharge of the powder into the feed chamber can be wherein the positive pressure port by a discharge valve is closable. Preferably, the discharge valve regardless of the intake valve, the exhaust valve and / or the purge controllable. This offers the advantage that the Vacuum generating phase Einsaugphase, the exhaust phase and the ejection phase are controllable independently of one another, In order to achieve an optimal promotion behavior.

0023Moreover, in the context of the invention a cleaning the delivery chamber carried by a cleaning fluid (for example, Compressed air) is introduced into the feed chamber. In contrast to the known PDF-pump described above is the Cleaning fluid here preferably on the membrane body and not directly introduced into the feed chamber. This provides the advantage of a slower pressure build-up in the feed chamber during the cleaning operation, whereby the risk of an Bursting of the delivery hose is reduced. However, there is in the context of the invention also the alternative possibility, that the cleaning fluid directly, bypassing the membrane body is introduced into the feed chamber.

0024Preferably, the duration of a complete working cycle is including vacuum generating phase, Einsaugphase and ejection phase in the range of 200 ms to 1 s, wherein any Intermediate values ​​are also possible and a value of the clock period is 500 ms particularly advantageous.

0025The vacuum generating phase Einsaugphase and the ejection phase may have different lengths or be of equal length, with values ​​between 50 ms and 200 ms or any intermediate values ​​within this interval possible are. Here, has a time duration of 150 ms for the negative pressure generating phase, the Einsaugphase and / or the ejection phase has proved advantageous. The invention is, however, not limited to the above-mentioned values ​​for the duration of the Vacuum generating phase, the Einsaugphase and the ejection phase limited, but in principle with other values realizable.

0026Furthermore, it should be mentioned that between the vacuum generating phase, the Einsaugphase and / or the ejection phase preferably Delay times are, for example, in can be range from 20 ms to 200 ms. These delay times to ensure that the respective valves after a corresponding triggering the desired valve position achieved. However, the invention is with respect to the duration of the delay times not limited to the above- Values ​​described limited, but in principle with other values ​​for the delay time realized.

0027Finally it should be mentioned that the invention is not limited to a Powder conveying pump is limited as a single part, but Rather, a powder coating plant with such a comprising powder feed pump.

0028Other advantageous developments of the invention are in the are in dependent claims or together hereinafter with the description of the preferred embodiment the invention based on the figures explained. Show it:<dl tsize="11" compact="compact"><dt>figure 1</dt><dd>a Fluidikdiagramm a preferred embodiment a powder coating plant with an inventive powder conveying pump,</dd><dt>figure 2</dt><dd>several time diagrams to illustrate the Opening and closing behavior of the individual Valves of the powder conveying pump according to the invention of Figure 1, and</dd><dt>figures 3-6</dt><dd>Various embodiments of the pumping chambers the powder feed pump from FIG. 1</dd></dl>

0029The Fluidikdiagramm in Figure 1 shows a powder coating plant a powder conveying pump 1 according to the invention powder supplying a rotary atomizer 2, wherein the Rotary atomizer 2 may be of conventional and will therefore not be further described in the following. instead However, the rotary atomizer 2 can also another powder application device be used, such as a spray gun.

0030To pick up a serving as a coating agent powder 3, the powder conveying pump 1 on the input side with a powder container 4, wherein the powder container 4 also may be conventionally constructed and therefore hereinafter is not described in detail.

0031In addition, the powder feed pump 1 is the input side to a compressed air container 5 is connected, which from a compressed air pump 6 is fed.

0032For powder delivery, the powder conveying pump 1 two parallel connected conveyor branches, each with a feed chamber 7, 8.

0033The two pumping chambers 7, 8 each have an inlet , wherein the two inlets of the pumping chambers 7, 8 via in each case an inlet valve 9, 10 is connected to the powder container 4 are. When intake valve 9, 10 open so can the 3 powder from the powder container 4 into the pumping chambers 7, 8 be sucked in, as will be described in detail.

0034Furthermore, the pumping chambers 7, 8 each have an outlet on, whereby the two outlets of the pumping chambers 7, 8 via each exhaust valve 11, 12 with the rotary atomizer 2 are connected. When can open exhaust valve 11, 12 So the left in the conveying chambers 7, 8 powder 3 from the pumping chambers 7, 8 ejected, as also still is described in detail.

0035The inlet valves 9, 10 and the exhaust valves 11, 12 can be designed here as pinch valves, the pneumatic, can be hydraulically or electrically powered.

0036For sucking the powder 3 via the inlet valves 9, 10 in the pumping chambers 7, 8, the powder conveying pump 1 a Vacuum generator 13, which conventionally constructed se is. The vacuum generator 13 has an injector nozzle, which is fed from the compressed air tank 5 with compressed air and according to the Venturi principle a vacuum at a vacuum port generated.

0037The vacuum connection of the vacuum generator 13 is connected via a purge valve 14 with an inside of the pumping chamber 7 arranged membrane body 15, and a purge valve located 16 to an inside of the pumping chamber 8 connected membrane body 17th The membrane body 15, 17 are each gas-permeable, but pulverundurchlässig so on the membrane body 15, 17 air from the pumping chambers 7, 8 can be sucked, whereas the powder 3 in the delivery chambers 7, 8 remains. When the purge valve 14 is opened is sucking the vacuum generator 13 through the membrane body 15 air from the feed chamber 7 and generates there a Vacuum for sucking the powder from the powder container 3 4. According to the vacuum generator 13 creates a vacuum in the delivery chamber 8, when the purge valve 16 is open.

0038The compressed air tank 5 is, however, not only with the vacuum generator 13 connected to a vacuum in the pumping chambers 7, 8 to produce, but also serves for ejecting the powder 3 from the pumping chambers 7, 8. To this end, the Compressed air tank 5 via a discharge valve 18 with the feed chamber 7 and another discharge valve 19 with the feed chamber 8. In the open state of the exhaust valves 18, 19 so pressurized air from the compressed air container 5 blown into the conveying chambers 7, 8, whereby in the Conveying chambers 7, 8 located powder 3 from feed chambers 7, 8 is discharged, if the exhaust valves 11, 12 open are. Of importance here is that the exhaust valves 18, 19, bypassing the membrane body 15, 17 directly in the pumping chambers 7, 8 open. This provides the advantage that the pressure build-up during the ejection of the pumping chambers 7, 8 Powder 3 from feed chambers 7, 8 not by the flow resistance the membrane body 15 is slowed 17th

0039The direct supply of the pressurized air into the pumping chambers 7, 8 therefore advantageously allows a faster pressure build-up and by a rapid emptying of the conveying chambers 7. 8

0040The energy stored in the compressed air tank 5 of compressed air is used However, not only for the ejection of the pumping chambers 7, 8 powder contained 3, but also for cleaning the feed chambers 7, 8. To this end, the compressed air tank 5 through a Purge valve 20 with the feed chamber 7 and in appropriate Way through a purge valve 22 with the feed chamber 8. The compressed air tank 5 so blowing compressed air for cleaning purposes in the feed chamber 7 a when the Purge valve 20 is opened. Accordingly, Compressed air for cleaning purposes in the feed chamber 8 blown when the purge valve 22 is opened.

0041The supply of the cleaning air over the membrane body 15, 17 provides the advantage that the pressure build-up in the cleaning operation slower, thereby reducing the risk of a burst a conveyor tube is reduced in the cleaning operation.

0042It will now be based on figure 2 of the invention Operating procedures of the powder conveying pump 1 described. The four upper timing charts in Figure 2 show this from the top Down the temporal behavior of the suction opening 14, the intake valve 9, the exhaust valve 11 and the exhaust valve 18. The bottom four timing diagrams in Figure 2 show contrast from top to bottom, the temporal behavior of opening of the suction valve 17, the intake valve 10, outlet valve 12 and the discharge valve 19th

0043At the beginning of a work cycle, first the purge 14 is opened while the intake valve 9, the exhaust valve 11 and the discharge valve 18 are closed. The opening of the Purge valve 14 takes place here for a period T_SAUGThat in may be the range of 50 ms and 200 ms. During this vacuum generating phase is in the feed chamber 7 a defined generated vacuum, the later for sucking the powder 3 is used in the feed chamber 7, as in more detail will be described.

0044After the vacuum generating phase the purge is 14 is closed, wherein the inlet valve 9, the exhaust valve 11 and the discharge valve 18 during a predetermined Delay time T_PAUSE remain closed. The Delay time T_PAUSE here comes within the range of 10 ms to 200 ms and ensures that no time overlaps the individual phases of a working cycle occur.

0045After the delay time T_PAUSE is then the inlet valve 9 is opened, so that the in the feed chamber 7 before Under pressure built up, the powder from the powder container 3 4 sucks, whereby the feed chamber 7 is filled with powder. The inlet valve 9 is in this case for a period T_ON open, which may range between 50 ms and 200 ms. After Expiry of the intake phase, the inlet valve 9 is closed, wherein the exhaust valve 11, the discharge valve 18 and the Purge valve 14 during a further delay time, first also remain closed.

0046After this delay time are then simultaneously the exhaust valve 11 and the discharge valve 18 is opened, so that compressed air from the compressed air container 5 in the feed chamber 7 is blown, whereby the present in the feed chamber 7 Powder 3 discharged through the exhaust valve 11 becomes. The opening phase of the exhaust valve 11 may in this case a duration T_OUT have, in the range of 50 ms to 200 ms lies. Also, the opening phase of the exhaust valve 18 may include a Take_PUSH have, ranging from 50 ms to 200 ms.

0047After the expiry of the discharge outlet and then the phase Exhaust valve 11 and the discharge valve 18 is closed, whereby the inlet valve 9 and the suction valve 14 for a delay time also remain closed. After this Delay time is the work cycle described above repeated cyclically, a clock, a period T_PERIODhaving that is eg 500 ms.

0048The inlet valve 10, exhaust valve 12, the discharge valve 19 and the purge valve 16 are controlled in the same way, but a phase shift T_PHASE scheduled which may be in the range of 250 ms.

0049An advantage of the lack of temporal overlap of the vacuum generating phase and Einsaugphase is the fact that at the beginning of Einsaugphase already defined Vacuum was created in the feed chamber 7 or 8, so that the flow rate can be determined with accuracy.

0050The direct connection of the exhaust valves 18, 19 with the delivery chambers 7, 8 provides bypassing the membrane body 15, 17 the advantage that the pressure build-up across the membrane body 15, 17 is not hindered, resulting in a more rapid emptying the pumping chambers 7, 8 allows.

0051The detailed view in Figure 3 shows the feed chamber 7, wherein the other feed chamber 8 is constructed similarly and therefore is not further described.

0052For the supply of the powder 3 7, the feed chamber a Inlet 23, the inlet 23 shown in Figure 1 with the Intake valve 9 is connected.

0053Furthermore, the feed chamber 7 has an outlet 24 which connected to the outlet valve 11 shown in Figure 1 is.

0054The diaphragm body 15 is in this case streamlined and within the feed chamber 7 located centrally. This is advantageous, because the powder density in operation within the feed chamber 7 wandungsnah is substantially greater than in the middle, so that the risk of clogging of the membrane body 15 by the powder 3 in the middle of the feed chamber 7 at the lowest is.

0055In addition, the membrane body 15 in the feed chamber 7 parallel to the direction of flow between the inlet 23 and aligned the outlet 24 so that the membrane body 15, the Flow within the feed chamber 7 only minimally impaired.

0056Figure 4 shows an alternative embodiment of the pumping chamber 7, the substantially described with the above- and coincides in Figure 3 illustrated embodiment, so that to avoid repetition largely Reference is made to the preceding description and for corresponding Components the same reference numerals as in Figure 3 be used.

0057A peculiarity of this embodiment is, that both the compressed air supply to the discharge of the powder 3 from the feed chamber 7 and the suction from the pumping chamber 7 to vacuum forming over the membrane body 15 done. The discharge valve 18 and the purge valve 14 are Here, on a common line 25 to the diaphragm body 15. This provides the advantage that within the Feed chamber 7 dispense with an additional line can.

0058The embodiment illustrated in Figure 5 of the feed chamber 7 also largely corresponds to the above-described and illustrated in Figure 3 embodiment consistent, so that to avoid repetition largely Reference is made to the above description of FIG 3 and below for corresponding components the same reference numerals are used as in FIG. 3

0059A peculiarity of this embodiment is, that the membrane body 15 facing to the inlet 23 Page both gas impermeable and pulverundurchlässig is. In this way prevents the powder 3 by the flow within the feed chamber 7 in the membrane body may lay down 15th

0060At the outlet 24 side facing the membrane body 15, however, a gas-permeable, but pulverundurchlässige porous wall 26, via which during the vacuum generating phase, sucked air from the feed chamber 7 becomes. Clogging of the wall 26 through the powder 3 is Here, however, flow conditions largely excluded.

0061Finally, the embodiment according to FIG 6 combined the shape of the membrane body 15 shown in Figure 5 with the common line 25 of FIG. 4

0062The invention is not limited to the above-described preferred Embodiments limited. Rather, it is a Plurality of variants and modifications are possible which likewise make use of the inventive idea and therefore fall within the scope.