EP3302819A1

EP3302819A1 - Method for operating a dense phase powder pump and dense phase powder pump

Info

Publication number: EP3302819A1
Application number: EP16723962.3A
Authority: EP
Inventors: Felix Mauchle; Hanspeter Vieli
Original assignee: Gema Switzerland GmbH
Current assignee: Gema Switzerland GmbH
Priority date: 2015-05-29
Filing date: 2016-05-03
Publication date: 2018-04-11
Anticipated expiration: 2036-05-03
Also published as: US10835907B2; DE102015108492A1; BR112017025101B1; BR112017025101A2; EP3302819B1; US20180147585A1; WO2016192915A1; CN107683178A

Abstract

The invention relates to a dense phase powder pump (1) and a method for operating a dense phase powder pump (1) in a powder-conveying mode. In order, in a simple manner, to prevent or at least reduce powder accumulations and clogging with powder, in particular on the powder inlet side of the powder conveying chamber (4) of the dense phase powder pump (1), and thus in the region of the powder inlet valves (7), according to the invention, during a predefined or specified time period in at least one output phase and preferably at the end time of the output phase of a powder cycle, at least one of the following conditions exists: i) the powder inlet valve (7) of the dense phase powder pump (1) is open; ii) the powder outlet valve (8) of the dense phase powder pump (1) is closed; and/or iii) the application of an overpressure to the powder conveying chamber (4) of the dense phase powder pump (1) is interrupted.

Description

PROCEDURE FOR OPERATING AN ER POWDER DENSITY PUMP

AS WELL AS POWDER DENSITY PUM PE

description

The present invention relates to a method for operating a powder seal pump in the powder delivery mode and to a corresponding powder seal pump. In the powder conveying mode, the powder sealant pump is particularly designed to convey powder, in particular coating powder, from a first powder reservoir to a second powder reservoir located downstream of the powder seal pump or to a powder spray gun or powder coating device downstream of the powder seal pump or the like.

For this purpose, the powder sealant pump has at least one and preferably exactly one powder feed chamber with a powder inlet and a powder outlet, wherein the powder inlet is assigned a powder inlet valve and the powder outlet is assigned a powder outlet valve, and the powder feed chamber has at least one air exchange opening for alternately pressurizing the powder feed chamber ( for supplying transport compressed air) or negative pressure (for sucking in powder). In the powder conveying mode of the powder sealant pump, during a suction phase, powder, in particular coating powder, is sucked into the powder feed chamber from a first powder reservoir, and during a subsequent ejection phase, the powder previously sucked into the powder feed chamber to a second, downstream Powder seal pump arranged powder reservoir or a device arranged downstream of the powder seal pump for spraying powder is ejected. During the suction phase, the powder inlet valve is at least temporarily opened and the powder outlet valve is at least temporarily closed, while the powder conveying chamber is at least temporarily subjected to negative pressure. During the ejection phase, the powder inlet valve is at least temporarily closed and the powder outlet valve is at least temporarily opened, while the powder conveying chamber is at least temporarily exposed to overpressure in order to feed at least part of the transport compressed air required for conveying the powder via the powder feed chamber into the powder path.

Powder dense phase pumps (dense phase powder pumps) with this mode of operation are at least known in principle from the prior art.

For example, EP 1 551 558 A1 relates to a powder sealant pump which has a first powder feed chamber and a second powder feed chamber arranged parallel to the first powder feed chamber. The two powder feed chambers of the known from this prior art Pulverdicht- current pump are bounded both the upstream side and on the conveyor side in each case by a mechanically operated pinch valve.

In detail, it is provided that in the suction-side or conveyor-side region of the powder seal pump, the powder hoses connected to the powder feed chambers of the powder sealing pump can be deformed with a mechanically actuated piston in order to squeeze or open the hose section as required. Each powder feed chamber, the known from this prior art powder seal pump is associated with a filter tube which limits the circumference of the corresponding powder feed chamber. The filter tube is permeable to air but not to coating powder and surrounded by an annular chamber to which alternate negative pressure or compressed air can be connected.

As a result, coating powder can be alternately sucked into each powder feed chamber or ejected by means of compressed air from the corresponding powder feed chamber. The two mutually parallel Pulverförder- ammers are operated in alternating phase, which means that one of the two powder feed chambers sucks coating powder through the powder inlet of the powder seal, while the other of the two powder feed chambers a coating powder portion sucked into the powder feed chamber beforehand via the powder outlet of the powder seal pump.

Pulverdichtstrompumpen with several, in particular two parallel powder feed chambers are also from the document

WO 2005/005060 A2, the document DE 199 59 473 AI and EP 1 752 399 AI known.

The use of powder sealant pumps for conveying coating powder to corresponding devices for spraying coating powders, in particular spray-coating guns, is known from the publication DE 196 11 533 B4, the document WO 2004/087331 A1 and the document EP 1 566 352 A2 , Before the use of powder sealant pumps for conveying coating powder became known, powder pumps designed as injectors were used, which are still used today to convey coating powder. In contrast to the powder sealant pump of the type initially mentioned, however, powder pumps designed as injectors have the disadvantage that the powder pumps designed as injectors can usually only convey a relatively small amount of coating powder per unit of time.

In this respect, powder seal pumps of the type mentioned in practice have prevailed in particular for those applications in which a relatively large amount of coating powder per unit time is to promote.

The amount of powder delivered by a powder sealant pump per unit of time depends in particular on the size (volume) of the delivery chamber, on the frequency with which coating powder is sucked in the delivery chamber and then released again, on the amount of vacuum applied to the powder delivery chamber. to suck powder from a powder reservoir into the powder feed chamber in an intake phase, the opening period of the powder inlet valve during the suction phase (intake subcycle), and the flow resistances in the powder lines upstream and, in particular, downstream of the powder seal pump. The flow resistance are particularly dependent on the length and the inner cross section of the powder lines, mostly powder hoses.

The transport compressed air introduced into the powder conveying path, in particular during the ejection phase via the powder feed chamber of the powder sealant pump, mixes only slightly with the powder to be conveyed, in particular coating powder, and pushes the powder out of the powder feed chamber through the powder outlet valve. In practical use, it has been found that a powder sealant pump, as is known, for example, from the publication EP 1 551 558 A1, tends to blockage in the powder delivery mode. This applies in particular to the powder inlet side of the powder seal flow pump and here the powder inlet valve provided there.

The object of the invention is to solve the problem in the powder conveying mode of a powder sealant pump of the type mentioned in a simple manner to avoid or at least reduce powder accumulations and powder clogging, in particular on the powder inlet side of the powder feed chamber of the powder sealant pump, and here in the region of the powder inlet valve. This should apply in particular to those types of powders which are prone to clumping and / or buildup during production.

This object is achieved by a method for operating a powder seal pump according to the independent claim 1 or by a powder seal pump according to the independent claim 13.

Accordingly, in particular a method for operating a Pulverdichtstrom- pump in the powder delivery mode is proposed, the powder sealant pump having at least one and preferably exactly one powder feed chamber with a powder inlet and a powder outlet, wherein the powder inlet a powder inlet valve and the powder outlet is associated with a powder outlet. The powder delivery chamber has at least one air exchange opening for alternately pressurizing the powder delivery chamber (during a discharge phase) or negative pressure (during a suction phase). In the powder delivery mode, powder, in particular coating, is added during the suction phase. suction powder, sucked from a first powder reservoir in the powder conveying chamber and ejected during a preferably immediately after the suction phase discharge phase, the previously sucked powder to a second, downstream of the powder seal pump powder reservoir or a downstream of the powder seal pump means arranged for spraying powder.

During the suction phase, the powder inlet valve at the powder inlet of the powder feed chamber is at least temporarily open and the powder outlet valve at the powder outlet of the powder feed chamber at least temporarily closed, while the powder feed chamber is at least temporarily subjected to negative pressure, so as to be able to suck the powder from the first powder reservoir. During the ejection phase, on the other hand, the powder inlet valve at the powder inlet of the powder feed chamber is at least temporarily closed and the powder outlet valve at the powder outlet of the powder feed chamber at least temporarily opened, while the powder feed chamber is at least temporarily subjected to overpressure so as to eject the previously sucked into the powder feed chamber powder through the powder outlet of the powder feed chamber , In order to effectively prevent a disturbing and thus unwanted accumulation of powder (powder aggregation) and a potentially associated powder clogging in the powder delivery mode of the powder seal pump, in particular the powder inlet valve of the powder delivery chamber, the invention provides that during a predetermined or definable period of at least one ejection phase of a plurality of Pump cycles, and preferably at the end of each ejection phase at least one of the following conditions:

i) the powder inlet valve is open;

ii) the powder outlet valve is closed; and or

iii) the application of pressure to the powder delivery chamber is interrupted.

In this way it is achieved that takes place during the ejection phase, and in particular at the end of the ejection phase, a cleaning and / or backwashing of the suction of the powder seal. In particular, the actuation of the powder inlet valve and / or the powder outlet valve causes it to no or only a very small amount of powder in the intake of the powder seal current pump can settle, as given by the valve actuation and a pulse to the powder and thus an accumulation of powder particles is prevented.

If, in addition to a valve actuation, transport compressed air is also introduced into the powder feed chamber (by applying a corresponding overpressure to the powder feed chamber), it is possible to flush back any powder particles present in the powder feed line (powder suction line) on the powder inlet side of the powder inlet valve. In order for a powder aggregation and congestion, in particular the powder inlet valve is even better avoided or at least reduced. If during the pre-set or determinable time period of the ejection phase, which is preferably at the end of the ejection phase, only the powder inlet valve is open (condition i), a "gentle" backwash occurs due to the system back pressure of powder particles.

If, in addition to this, the powder outlet valve is at least temporarily closed during the predetermined or determinable time period, the transport compressed air introduced during the ejection phase into the powder feed chamber due to the application of overpressure is diverted. This reinforces the backwashing and thus leads to an improved cleaning effect.

Preferably, the period of time during which at least one of said conditions i) to iii) is present, in particular individually and independently for all conditions i) to iii). As a result, the intensity of the influence of the corresponding conditions can be increased by appropriate variation of the time periods assigned to conditions i) to iii). This allows an individual adaptation of the powder delivery process to different powder types. Advantageous developments of the method according to the invention for operating a powder seal current pump in the powder delivery mode are specified in the dependent claims. The invention further relates to a powder sealant pump for conveying coating powder from a first powder reservoir to a second downstream powder reservoir or a downstream powder spray coating gun or the like device for spraying coating powder. The powder sealant pump has at least one and preferably exactly one single powder feed chamber with a powder inlet and a powder outlet, wherein the powder inlet is assigned a powder inlet valve and the powder outlet is assigned a powder outlet valve. The powder feed chamber of the powder seal current pump according to the invention has at least one air exchange opening, via which the powder feed chamber can be alternately pressurized with negative pressure or reduced pressure. In addition, a control device is provided, which is designed to control the powder inlet valve, the powder outlet valve and / or a device for applying a negative pressure or overpressure to the powder feed chamber such that the powder feed method according to the invention is realized or feasible.

Preferably, in the powder seal pump according to the invention, the powder outlet and the powder outlet valve and the powder inlet valve are arranged by the single powder conveying chamber or by each powder conveying chamber such that its powder passageway extends in the chamber longitudinal direction, preferably axially to the chamber centerline.

The powder inlet valve and the powder outlet valve used according to the invention are preferably pinch valves. With them, the valve channel is formed by a flexible, elastic tube which is radially compressible to close the valve, either by a mechanical element or by the pressure of compressed air in a pneumatic chamber surrounding the tube on its outside.

According to an additional aspect of the invention, it is provided that the method according to the invention comprises the method step of providing a powder sealant pump of the aforementioned type, and the method step of the method according to the invention. a) generating a negative pressure in the preferably single powder feed chamber of the powder sealant pump for sucking coating powder into the powder feed chamber through an opened powder inlet valve of the powder seal pump while the powder outlet valve of the powder seal current pump is closed is;

b) closing the powder inlet valve and opening the powder outlet valve; c) introducing pressurized gas into the powder feed chamber for discharging the coating powder from the powder feed chamber through the open powder discharge valve while the powder inlet valve is closed; and d) closing the powder outlet valve and opening the powder inlet valve.

According to the invention, it is provided in the method that during the cycle step a) or when changing from the cycle step d) to the cycle step a) additional compressed air is fed as additional transport compressed air at least one point in the powder path after the powder outlet.

The invention also relates to a powder spray coating apparatus comprising a powder seal pump of the invention.

According to a further inventive idea, at least one flow resistance is arranged in the powder flow path upstream or downstream of the powder seal current pump, preferably a flow resistance. the flow resistance variable flow restrictor. This inventive concept has the advantage that even small amounts of powder flow per unit time can be promoted by the powder sealant pump with relatively good adherence to a desired value. The reason is that the flow resistance reduces the amount of powder flow per unit time, thereby maintaining the transporting compressed air flow rate per unit time at such a high level as to ensure powder delivery in and downstream of the powder sealant pump without being disadvantageously disadvantageous Powder deposits occur in the powder path. The invention will be described below with reference to the accompanying drawings with reference to a preferred exemplary embodiment.

In the drawings show:

FIG. 1 is a longitudinal sectional view along the powder path through a

exemplary embodiment of the powder sealant pump according to the invention; and FIG. 2 is a timing diagram to illustrate an exemplary

Embodiment of the powder conveying method according to the invention.

Hereinafter, with reference to the illustrations in FIGS. 1 and 2, exemplary embodiments of the powder-sealing current pump according to the invention and of the powder-conveying method according to the invention will be described.

In detail, in FIG. 1 shows schematically an exemplary embodiment of a powder spray coating apparatus 100, in which an embodiment of the powder seal current pump 1 according to the invention for conveying powder (here: coating powder) from a first powder reservoir 101 to a powder spray coating gun 102 arranged downstream of the powder seal current pump 1 is used. Instead of the powder spray coating gun 102, another device for spraying coating powder onto an object to be coated or a second powder reservoir can also be used.

As shown in FIG. 1, the exemplary embodiment of powder sealant pump 1 according to the invention used therein has a powder inlet 2, which is connected or connectable to a first powder reservoir 101 by means of a powder line 103, in particular by means of an intake pipe or the like. At the opposite end region of the powder seal current pump 1, a Pu lverauslass 3 is provided which is connected or connectable by means of a powder line 104, in particular by means of a powder hose, with a coating powder 105 of a powder spray coating gun 102. In particular, in the case of FIG. 1 schematically illustrated, exemplary embodiment, both the powder inlet 2 and the powder outlet 3 of the powder sealant pump 1 each designed as a hose connection piece to which the corresponding powder line 103 and 104 attachable and can be fixed with a hose clamp. Of course, other embodiments for the powder inlet 2 and the powder outlet 3 come into question.

The in FIG. 1 is shown as a single-chamber Pulverdichtstrompumpe, wherein for the promotion of Beschichtungspul- ver from the first powder reservoir 101 to the powder spray coating gun 102 or to another means for spray coating of objects or to another powder reservoir only a single powder feed chamber 4th is provided. However, the invention is not limited to such a one-chamber

Pulverdichtstrompumpe trained powder seal pump limited. Rather, the teachings of the invention are also applicable to a multi-chamber powder sealant pump, such as a powder sealant pump, such as known from EP 1 551 558 A1

In the exemplary embodiment of the powder seal current pump 1 according to the invention according to FIG. 1, the (only) powder delivery chamber 4 has at a first end region a powder inlet 5 which points in the direction of the powder inlet 2 of the powder sealant flow pump 1. Furthermore, the powder delivery chamber 4 has a powder outlet 6 pointing in the direction of the powder outlet 3 of the powder sealant flow pump 1. A powder inlet valve 7 is disposed immediately adjacent the powder inlet 5 of the powder delivery chamber 4, in such a way that this powder inlet valve 7 lies between the powder inlet 5 of the powder delivery chamber 4 and the powder inlet 2 of the powder sealant pump 1. In the same way, a powder outlet valve 8 is arranged immediately adjacent to the powder outlet 6 of the powder conveying chamber 4.

Unlike the powder inlet portion of the powder sealant flow pump 1, however, at the powder outlet portion of the powder sealant pump 1, the powder outlet valve 8 is not disposed directly between the powder outlet 6 of the powder delivery chamber and the powder outlet 3 of the powder sealant flow pump 1; rather is between the Pulverauslassventil 8 and the powder outlet 3 of the powder seal current pump 1 nor an additional compressed air inlet device 9 is arranged.

As will be described in more detail below, this auxiliary compressed air inlet device 9 is used to feed additional transport compressed air as needed into the powder path between the powder outlet valve 8 and the powder outlet 3 of the powder seal current pump 1.

It should be pointed out at this point that it is not absolutely necessary to provide an auxiliary compressed air inlet device 9 at all or to arrange the optionally provided additional compressed air inlet device 9 between the powder outlet valve 8 and the powder outlet 3 of the powder seal current pump 1.

However, should be provided an additional compressed air inlet device 9, it should be noted that the achievable with this additional compressed air inlet device 9 effects, which are described in more detail below, even if let the additional compressed air inlet device 9 behind the powder outlet 3 of the powder seal 1 is arranged. Although in FIG. 1, in advantageous embodiments of the powder sealant pump 1 according to the invention between the additional compressed air inlet device 9 and the powder outlet 3 of the powder sealant pump 1, a further valve, in particular pinch valve is provided, which then takes over the function of the powder outlet valve, since it is directly at the powder outlet 3 of the powder seal 1 is arranged.

As in particular but the representation in FIG. 1, the powder inlet 2 of the powder seal stream pump 1, the powder inlet valve 7, the powder inlet 5 of the powder feed chamber 4, the powder feed chamber 4, the powder outlet 6 of the powder feed chamber 4, the auxiliary compressed air inlet device 9 (provided in this exemplary embodiment) and the powder outlet 3 of the powder sealant pump 1 along a common longitudinal axis. In other words, in the case of FIG. 1 schematically shown, exemplary embodiment of the powder seal current pump 1 according to the invention is the pulse 2 of the powder sealant pump 1 is provided at the opposite end of the powder outlet 3 of the powder sealant pump 1.

Hereinafter, the construction and operation of the particular powder conveying chamber 4 of FIG. 1 exemplary embodiment of the powder sealant pump 1 described in more detail.

As shown in the longitudinal section in FIG. 1, the powder conveying chamber 4 between its powder inlet 5 and its powder outlet 6 is formed by the cylindrical wall of a tubular filter 10, which is permeable to air, but not to coating powder and may for example consist of sintered material. The filter 10 designed as a filter tube is surrounded by an intermediate chamber 11, which is bounded on its outer side by a housing 12 of the powder delivery chamber 4.

Through the housing 12 opens an air exchange opening 13, which is connected in terms of flow to a control valve VI. The powder feed chamber 4 can be supplied alternately with transport compressed air from a compressed air supply line 50 via the control valve VI or can be supplied with vacuum or negative pressure from a vacuum source 52.

In the in FIG. 1 schematically illustrated embodiment of the powder spray coating device 100 according to the invention, the vacuum source 52 an injector 55, which injector compressed air from a compressed air supply line 54 and a compressed air source 58, for example via a pressure regulator 53 and another control valve V2, are supplied.

In order to be able to suck powder, in particular coating powder, into the powder delivery chamber 4 during a suction phase of the powder sealant pump 1 via the powder inlet 2 of the powder sealant pump 1, the powder outlet valve 8 arranged at the powder outlet 6 of the powder delivery chamber 4 is closed and that between the powder inlet 2 the powder seal pump 1 and the powder inlet 5 of the powder conveying chamber 4 arranged powder inlet valve 7 is opened.

Simultaneously with the actuation of the Pulverauslassventils 8 and the powder inlet valve 7 or immediately thereafter is via the control valve VI and the associated air exchange port 13, the powder delivery chamber 4 connected to the vacuum source 52, so that in the powder delivery chamber 4, a negative pressure is applied and coating powder from the first powder reservoir 101 can be sucked.

After the suction of coating powder into the powder conveying chamber 4, there is a change from the suction phase to the ejection phase of powder, in particular coating powder, from the delivery chamber 4. For this purpose, the powder inlet valve 7 is closed and the powder outlet valve 8 is opened while the control valve VI is a fluid connection of the air exchange opening 13 with the compressed air supply line 50, so that the powder portion previously sucked into the powder feed chamber 4 during the suction phase is discharged through the open powder discharge valve 8 by means of the compressed air supplied through the air exchange port 13.

According to the invention, a control device 90 is provided, which is formed, for example, in FIG. 1, the valve V3 associated with the powder inlet valve 7, the valve V4 associated with the powder outlet valve 8, the valves VI and V6 associated with the powder conveying chamber 4, the valve V5 associated with the positive pressure air inlet device 9 and / or the injector 55 To control valve V2 according to a predefined or definable program sequence.

An exemplary embodiment for such a program flow will be described later in connection with FIG. 2 described flowchart.

According to a further advantageous aspect of the invention, the control device 90 is configured such that the pulse frequency of the additional compressed air inlet device 9 supplied additional compressed air in dependence on the powder dispensing frequency of the powder delivery chamber 4 is adjustable in at least one of the following ways: for example, manually adjustable and / or preferably automatically controllable or preferably controllable. Advantageously, thereby the additional compressed air pulse frequency can be increased with increasing Pulverabgabefrequenz and reduced with decreasing Pulverabgabefrequenz.

According to a further preferred embodiment of the invention, the control device 90 may be formed in an advantageous manner such that means the additional compressed air quantity flowing through the additional compressed air inlet device 9 per unit of time can be set in at least one of the following ways depending on the delivered powder quantity: for example manually adjustable and / or preferably automatically controllable or preferably controllable.

The control device 90 of the powder seal current pump 1 or of the powder spray coating device 100 can be designed for the aforementioned setting of the additional compressed air pulse frequency or for the aforementioned setting of the additional compressed air quantity or for both settings. The controller 90 may include all controls, or two or more controllers may be provided. If it is desired to set the additional compressed air pulse frequency or the additional compressed air flow rate manually, a manual adjusting element can be provided for each of these.

As already indicated, the powder inlet valve 7 and the powder outlet valve 8 of the powder seal current pump 1 according to the invention are each preferably designed as pinch valves, since less coating powder can be deposited in pinch valves than in other valve types, and because powder deposits due to the air flow in let them clean easily.

Pinch valves are controllable by means of compressed air or by means of negative pressure valves. In principle, however, other controllable valves are used. Furthermore, it is also possible to use instead of controllable valves automatic valves, such as ball valves or flap valves, which are controlled by the differential pressure between the valve inlet side and the Ventilauslassseite and thus automatically by the pressure and negative pressure, which prevails in the powder feed chamber 4. For controlling the operation of the powder seal current pump 1, the already mentioned control device 90 is used, which is shown in FIG. 1 is indicated schematically. The control device 90 is in particular designed to control the individual controllable components of the powder seal current pump 1, in particular the control valves VI, V2, V3, V4 and V5, suitably and to coordinate their actuation. In the in FIG. 1 schematically illustrated embodiments of the invention Pulverdichtstrompumpe 1 and Pulversprühbeschichtungsvorrichtung 100 is still another control valve V6 provided, via which in a cleaning cycle of the powder sealant pump 1, the powder delivery chamber 4 can be acted upon by high pressure.

The control device 90 is preferably designed such that it opens the control valve V4 in preparation for the suction phase of the powder delivery chamber 4, so that the compressed air provided in the pressure accumulator 57 and the compressed air source 58 via the compressed air supply line 56 and the air exchange opening 16 in the pressure chamber of the Pinch valve trained powder outlet valve 8 is passed. As a result, the flexible elastic hose of the powder discharge valve 8 formed as a pinch valve is squeezed, as a result of which the powder path provided by the flexible elastic hose is closed by the powder discharge valve 8.

With the closing of the powder outlet valve 8, the air exchange opening 13 provided in the housing 12 of the powder delivery chamber 4 is fluidly connected to the vacuum source 52 by means of the control device 90 to generate a negative pressure in the interior of the powder delivery chamber 4, so that coating powder via the powder inlet 2 the powder seal current pump 1 and the (opened) powder inlet valve 7 and the powder inlet 5 of the powder feed chamber 4 can be sucked into the powder feed chamber 4. According to preferred embodiments of the invention, to initiate the suction phase of the powder sealant pump 1 from the control means 90, a control signal for generating the negative pressure in the powder delivery chamber 4 at the same time as, or preferably by a predetermined delay time later than a control signal for opening the powder inlet valve 7, so that the construction of the negative pressure in the powder delivery chamber 4 starts at the same time as the opening of the powder inlet valve 7, preferably by the said predetermined delay time later than the opening of the powder inlet valve 7. The predetermined delay time is preferably in the range between 0 ms and 50 ms for a delivery cycle of the powder delivery chamber 4 of about 200 ms. This ensures that the negative pressure in the powder delivery chamber 4, an opening movement of the powder inlet valve 7, especially if this is a pinch valve, at least at the time of the beginning of the opening movement of the powder inlet valve 7, less counteracted than in the prior art, where usually already before the opening of the powder inlet valve in the corresponding powder feed chamber, a pressure reduction takes place.

Thereafter, the control valve V3 is fluidly connected to the compressed air supply line 56, as a result of which an overpressure is applied in the pressure chamber 15.1 of the pinch valve formed powder inlet valve 7, which causes a squeezing of the flexible elastic tube of the pinch valve formed as Pullaßlassventils 7. In this way, the powder intake valve 7 is closed. The control valve V4 switches the air exchange opening 17 of the pressure chamber of the powder outlet valve 8 designed as a pinch valve without pressure or venting the pressure chamber. Due to the elasticity of the hose of the powder outlet valve 8 designed as a pinch valve, this then passes directly into its open state.

At this moment or immediately thereafter, by means of the control device 90, the control valve VI is switched such that the air exchange opening 13 formed in the housing 12 of the powder delivery chamber 4 is fluidly connected to the compressed air source 58. The compressed air then flows via the compressed air supply line 50, the control valve VI, the intermediate chamber 11 and the filter element 10 into the powder feed chamber 4 and drives the previously sucked-in powder portion from the powder outlet 6 of the powder feed chamber 4.

With the aid of the transport compressed air fed into the powder feed chamber 4 via the compressed air supply line 50, the powder portion is transported further through the opened powder outlet valve 8, the filter tube channel 18 of the auxiliary compressed air inlet device 9 and the powder outlet 3 of the powder seal current pump 1. In particular, the control device 90 is also designed in order to introduce, via the additional compressed air inlet device 9, pulsed additional transport compressed air into the powder path between the powder outlet valve 8 and the powder outlet 3 of the powder feed in the dense-flow pump 1. In this case, it has proven to be advantageous if the fed via the additional compressed air inlet device 9 pulse manner in the powder path additional transport compressed air is always fed during the entire or during a predetermined or predeterminable period of the suction phase of the powder feed chamber 4, in order to effectively pulsations in to avoid or minimize the powder flow discharged from the powder seal current pump 1.

Specifically, for this purpose, the control device 90 is designed to always connect the air exchange opening 21 of the compressed air chamber 19 of the auxiliary compressed air inlet device 9 with the compressed air source 58 when the powder outlet valve 8 is closed.

In order to prevent powder agglomeration and possibly congestion of the powder inlet valve 7, or at least the risk of clogging, during powder production (in the powder conveying mode of the powder seal flow pump 1), in particular also in powder types which tend to clump or blockages In the exemplary embodiment of the powder sealant pump 1 according to the invention, it is provided that at least one of the following conditions is present during at least one ejection phase of a plurality of pump cycles, and preferably at the end of each ejection phase, during a predefined or definable time period:

i) the powder intake valve 7 is open;

ii) the powder outlet valve 8 is closed; and or

iii) the pressurization of the powder feed chamber 4 with overpressure is interrupted.

In this way it is achieved that, during the ejection phase, and in particular at the end of the ejection phase, a cleaning and / or backwashing of the suction region of the powder seal current pump 1 takes place. In particular, the effect of the actuation of the powder inlet valve 7 and / or the powder outlet valve 8 is that no or only a very small amount of powder can settle in the intake region of the powder seal current pump 1, since a pulse is also given off to the powder by the actuation of the valve and so on an accumulation of powder particles is prevented. If, in addition to a valve actuation, for example, transport compressed air is also introduced into the powder feed chamber 4 (by applying a corresponding overpressure to the powder feed chamber 4), it is possible that any powder particles present on the powder inlet side of the powder inlet valve are backwashed into the powder feed line (powder suction line) become. In order for a powder aggregation and congestion, in particular the powder inlet valve is even better avoided or at least reduced.

If during the predetermined or definable time period of the ejection phase, which is preferably at the end of the ejection phase, only the powder inlet valve is opened (condition i), a "gentle" backwash occurs due to the system back pressure and aggregation of powder particles.

This backwashing preferably takes place at the end of each discharge phase of coating powder from the powder delivery chamber 4. Conceivable in this context, it is also that the backwashing is not at each ejection phase, but only if necessary or cyclically, in particular manually initiated takes place. Hereinafter, with reference to the timing diagram of FIG. 2 describes an exemplary embodiment of the conveying method according to the invention, which is described, for example, with the aid of the control device 90 in the conveying method shown in FIG. 1 schematically illustrated embodiment of the powder seal current pump 1 according to the invention can be realized.

Specifically, in the flowchart of FIG. 2 schematically illustrated as in an exemplary embodiment of the solution according to the invention by means of a control device 90 in, for example, the in FIG. 1, the valve V3 assigned to the powder inlet valve 7, the valve V4 associated with the powder outlet valve 8, the valves VI and V6 associated with the powder conveying chamber 4, the valve V5 associated with the positive pressure air inlet device 9 and the valve V2 associated with the injector 55 are actuated ,

The flowchart shows a pump cycle consisting of a suction phase (intake half cycle) and a subsequent ejection phase (ejection half cycle).

In the exemplary embodiment, the duration of the suction phase and the duration of the ejection phase are the same. Of course, it is also conceivable to choose different periods of time for the intake phase and the discharge phase.

In order also in a powder sealant pump 1, which - as shown in FIG. 1 schematically indicated - only a single powder delivery chamber 4, pulsations in the dispensed powder stream to avoid or at least reduce, the suction and the ejection phase should preferably each be no longer than 250 ms. In particular, according to developments of the invention, it is provided that the suction phase or the ejection phase amounts to a total of 100 to 250 ms, preferably a total of 120 to 200 ms, and more preferably a total of 160 to 180 ms.

In order to shorten the reaction time of the powder sealant pump 1 according to the invention and thus to increase the delivery frequency thereof, it is provided according to one aspect of the invention that during the suction phase of the powder delivery chamber a negative pressure in the powder delivery chamber 4 at the same time as, or preferably by a certain delay time later than Control signal for opening the arranged on the powder inlet of the powder feed chamber powder inlet valve is applied, so that the build-up of the negative pressure in the powder delivery chamber 4 at the earliest commences simultaneously with the opening of the powder inlet valve, but preferably by said predetermined delay time later than the opening of the powder inlet valve. The predetermined delay time is preferably in a range between 0 ms and 50 ms for a delivery cycle of the powder delivery chamber (= pump cycle of the powder seal flow). pump) of about 200 ms. However, this example does not exclude the use of other delay times and cycle times for the powder sealant pump. Due to the fact that in advantageous realizations of the solution according to the invention during the suction phase of the powder seal in the powder conveying chamber only a negative pressure is applied when the powder inlet valve is already open or at the same time with the opening of the powder inlet valve, can be achieved that the negative pressure in the powder delivery chamber an opening movement of the powder inlet valve, in particular when it is designed as a pinch valve, counteracts less strongly at least at the time of the beginning of the opening movement of the powder inlet valve than in solutions known from the prior art powder sealant pumps. This delayed application of a negative pressure in the powder delivery chamber is shown in the timing diagram of FIG. 2 in the first intake half cycle (left side) indicated.

The right side of the timing diagram according to FIG. Figure 2 shows the ejection half-cycle in an exemplary embodiment of the solution according to the invention.

As shown in FIG. 2 exemplarily shown, during the ejection half-cycle (ejection phase), the powder inlet valve 7 is closed until time tl and the powder outlet valve 8 is opened, while the powder feed chamber 4 is pressurized and transport compressed air is fed into the powder feed chamber 4.

At time t 1, for example, at the time shown in FIG. 1, the powder inlet valve 7 is opened, the powder outlet valve 8 is closed and the pressurization of the powder conveying chamber 4 is interrupted (the supply of transport compressed air). In this way, it is achieved that, at the end of the ejection phase, a cleaning of the suction region of the powder sealant body takes place. In particular, the actuation of the powder inlet valve 7 and the powder outlet valve 8 causes no or only a very small amount of powder to settle in the suction region of the powder sealant flow pump 1 can, as given by the valve actuation and a pulse to the powder and thus an accumulation and aggregation of powder particles is effectively prevented. If, in addition to a valve actuation, for example, transport compressed air is also introduced into the powder feed chamber (by applying a corresponding overpressure to the powder feed chamber), it is possible to flush back any powder particles present in the powder feed line (powder suction line) on the powder inlet side of the powder inlet valve. In order for a powder aggregation and consequent blockage in particular of the powder inlet valve is even better avoided or at least reduced.

Although in the case of FIG. 2, the powder inlet valve 7 is opened at the same time, the powder outlet valve 8 is closed and the pressurization of the powder delivery chamber 4 is interrupted with overpressure, this is not to be understood as a restriction. Of course, it is conceivable to choose the respective times for opening the powder inlet valve 7, for closing the powder outlet valve 8 and / or for interrupting the loading of the powder conveying chamber 4 with overpressure different at the end of the ejection phase.

It is also not absolutely necessary for all of the conditions mentioned to be present at the end of the ejection phase (powder inlet valve 7 is open, powder outlet valve 8 is closed, pressurized powder feed chamber 4 is interrupted).

According to preferred implementations of the solution according to the invention, at least one of said conditions is initiated with a maximum of 50 ms and preferably not more than 30 ms before the end of the ejection half-cycle.

The invention is not limited to the exemplary embodiments shown schematically in the figures, but results from a synopsis of all the features disclosed herein.

Claims

claims

A method of operating a powder sealant pump (1) in a powder delivery mode, wherein the powder sealant pump (1) comprises at least one and preferably exactly one powder delivery chamber (4) having a powder inlet and a powder outlet, the powder inlet having a powder inlet valve (7) and the Powder outlet is associated with a powder outlet valve (8), and wherein the powder delivery chamber (4) has at least one air exchange opening (13) for alternately pressurizing the powder delivery chamber (4) with overpressure or negative pressure,

wherein in the powder delivery mode of the powder sealant pump (1) is alternately sucked during a suction phase powder, in particular coating powder from a first powder reservoir (101) in the powder delivery chamber (4), and during a subsequent ejection phase, the previously aspirated powder to a second, downstream of the Powder Dust Pump (1) arranged powder reservoir or a downstream of the powder sealant pump (1) arranged means for spraying powder is ejected,

wherein, during the intake pase, the powder inlet valve (7) is at least temporarily opened and the powder outlet valve (8) is at least temporarily closed, while the powder delivery chamber (4) is subjected at least temporarily to negative pressure,

wherein during the ejection phase, the powder inlet valve (7) at least temporarily closed and the powder outlet valve (8) at least temporarily is open while the powder feed chamber (4) is at least temporarily subjected to overpressure,

d a d u r c h e c e n c i n e s that

during at least one ejection phase of a plurality of pump cycles, and preferably at the end of time of each ejection phase, at least one of the following conditions exists during a predetermined time period:

i) the powder inlet valve (7) is open;

ii) the powder outlet valve (8) is closed; and or

iii) the pressurization of the powder conveying chamber (4) is interrupted.

2. The method according to claim 1,

wherein all the conditions i) to iii) are present during the predeterminable or fixed time period at the end of the ejection phase.

3. The method according to claim 1 or 2,

wherein the suction phase and / or the ejection phase in each case takes a total of 100 to 250 ms, preferably in each case a total of 120 to 200 ms and even more preferably in each case a total of 160 to 180 ms.

4. The method according to any one of claims 1 to 3,

wherein the duration of the suction phase and the duration of the ejection phase are the same.

5. The method according to any one of claims 1 to 4,

wherein the duration of the suction phase and / or the duration of the ejection phase is / is adjustable.

6. The method according to any one of claims 1 to 5,

wherein the period of time during which at least one of the conditions i) to iii) is present is a maximum of 50 ms and preferably a maximum of 30 ms.

7. The method according to any one of claims 1 to 6,

wherein the time period during which at least one of the conditions i) to iii) is present is adjustable, preferably individually for all conditions i) to iii).

8. The method according to any one of claims 1 to 7,

wherein, during the suction phase, the powder inlet valve (7) is closed for a first time period, opened for a second time period subsequent to the first time period, and closed again for a third time period subsequent to the second time period.

9. The method according to claim 8,

wherein the first and / or third time period lasts 10 to 50 ms, preferably 20 to 40 ms and more preferably about 30 ms / lasts; and / or wherein the second time period lasts 80 to 150 ms, preferably 100 to 130 ms, and more preferably about 120 ms.

10. The method according to claim 8 or 9,

wherein the duration of the first, second and / or third time period of the suction phase is adjustable / is.

11. The method according to any one of claims 1 to 10,

wherein the powder outlet valve (8) is closed during the entire intake phase; and or

wherein during the entire intake phase, the powder delivery chamber (4) is subjected to negative pressure.

12. The method according to any one of claims 1 to 11,

the powder sealant pump (1) further comprising an auxiliary compressed air inlet device (9) opening at at least one location in the powder path downstream of the powder outlet valve (8) for supplying supplemental compressed air as additional transport compressed air as required, the method further comprising the steps of: during the intake phase of the additional compressed air inlet device (9) at least temporarily additional compressed air is fed as additional transport compressed air in the powder path; and During preferably the entire ejection phase, no additional compressed air is fed from the auxiliary compressed air inlet device (9) as additional transport compressed air into the powder path.

A powder sealant pump (1) for conveying powder, in particular coating powder, from a first powder reservoir (101) to a second downstream powder reservoir or a downstream powder spray coating gun (102) or the like powder spraying device, wherein the powder seal current pump (1) is at least a powder feed chamber (4) and preferably exactly one single powder feed chamber (4) with a powder inlet and a powder outlet, the powder inlet being associated with a powder inlet valve (7) and the powder outlet with a powder outlet valve (8), and the powder feed chamber (4) has at least one air exchange opening for mutual pressurization of the powder delivery chamber (4) with overpressure or negative pressure,

d a d u r c h e c e n c i n e s that

the powder sealant pump (1) further comprises a control device (90) which is designed to carry out the method according to one of claims 1 to 12.