DE102013205895B4 - Powder dense phase pump for conveying coating powder, powder spray coating device and corresponding process - Google Patents

Abstract

Powder dense phase pump (1) for conveying coating powder from a first powder reservoir (101) to a second powder reservoir arranged downstream or a powder spray coating gun (102) arranged downstream, wherein the powder dense phase pump (1) is designed as a single-chamber powder dense phase pump and has only a single powder conveying chamber (4) for conveying coating powder, wherein the powder dense phase pump (1) has a powder inlet (2) connected or connectable to the first powder reservoir (101) and a powder outlet (3) connected or connectable to the second powder reservoir or to the powder spray coating gun (102), wherein the single powder conveying chamber (4) has a powder passage at one end region which serves both as a powder inlet and as a powder outlet, and wherein the powder dense phase pump (1) further has a powder inlet valve (7) via which the powder passage of the single powder conveying chamber (4) is connected to the Powder inlet (2) of the dense phase powder pump (1) is fluidly connected or connectable, and has a powder outlet valve (8) via which the powder passage of the single powder feed chamber (4) is fluidly connected or connectable to the powder outlet (3) of the dense phase powder pump (1), characterized in that at least one additional compressed air inlet device (9) opens into the powder path after the powder outlet valve (8) at at least one point for supplying additional compressed air as additional transport compressed air as required, wherein the pulse frequency of the additional compressed air is at least as high as the frequency of the powder feed chamber (4) with which powder portions are delivered from the powder feed chamber (4), and/or wherein the pulse frequency of the additional compressed air is as high as the frequency of the powder feed chamber (4) with which powder portions are delivered from the powder feed chamber (4), and wherein the device is designed to supply pulsating additional compressed air to the at least one additional compressed air inlet device (9), to supply the additional compressed air to the at least one additional compressed air inlet device in antiphase with respect to the powder discharge cycle of the powder feed chamber.

Description

The present invention relates to a dense phase powder pump for conveying coating powder.

In particular, the invention relates to a dense phase powder pump for conveying coating powder from a first powder reservoir to a second powder reservoir arranged downstream of the dense phase powder pump or to a powder spray coating gun arranged downstream of the dense phase powder pump for spraying coating powder.

The invention further relates to a method for conveying coating powder from a first powder reservoir to a second powder reservoir arranged downstream of the first powder reservoir or to a powder spray coating gun arranged downstream of the first powder reservoir for spraying coating powder.

The publication US 2007 0092380 A1 concerns a dense phase powder pump with two powder feed chambers operated in antiphase.

The publication EN 103 00 280 A1 relates to a pump device for powder, whereby a volume change of a powder dosing chamber is measured. Depending on a certain volume change, a time delay is started. After this time delay, the amount of powder stored in the dosing chamber when the time delay expires is pneumatically ejected.

The publication EN 10 2007 005 313 A1 relates to a coating powder conveying device, containing a powder pump which sucks coating powder into a powder chamber in a suction phase and expels coating powder from the powder chamber by means of compressed air in a pressure phase. A pressure measuring device is provided for measuring the pressure of the compressed air and for generating a measuring signal depending on the measured pressure of the compressed air.

The publication EN 10 2007 041 551 A1 relates to a powder spray coating device and a coating powder conveying device. A pump unit contains two powder push pumps, each with a powder chamber, whereby coating powder can be alternately sucked into one powder chamber, while coating powder can be expelled from the other powder chamber by means of compressed air.

The publication US 6 447 216 B1 concerns another pump for conveying powdered material.

The publication US 2007 0095945 A1 also concerns a dense phase pump for conveying coating powder.

The publication US 2001 0003568 A1 relates to a device for pneumatically conveying powdered material.

The printed publications US 7 163 359 B2 and US 2005 0207901 A1 also affect feed pumps.

The publication DE 103 53 968 A1 relates to a coating powder conveying device, containing at least one hose diaphragm pump, which has a powder inlet valve at a powder inlet and a powder outlet valve at a powder outlet of a conveying chamber. A suction line is connected to the powder outlet. A fluidizing compressed air line conveys fluidizing compressed air into a powder container in the suction area of the suction line.

The publication EN 10 2005 006 522 B3 relates to a device for conveying coating powder with an inlet valve, an outlet valve and a powder conveying chamber formed from an elastic conveying chamber hose.

The powder feed chamber is arranged between the inlet valve and the outlet valve and has a feed air inlet. In addition, the volume of the powder feed chamber can be changed by deforming the feed chamber hose.

Dense phase powder pumps of the type mentioned above are known in principle from the state of the art.

For example, the publication EP 1 551 558 A1 a dense phase powder 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 dense phase powder pump known from this prior art are each delimited on both the intake side and the feed side by a mechanically operated pinch valve arrangement.

In detail, it is intended that in the suction-side or delivery-side area of the dense phase powder pump, the in which powder hoses can be deformed with a mechanically operated stamp in order to squeeze or open the hose section if necessary. Each powder feed chamber of the dense phase powder pump known from this prior art is assigned a filter tube which delimits the circumference of the corresponding powder feed chamber. The filter tube is permeable to air, but not to coating powder, and is surrounded by an annular chamber to which negative pressure or compressed air can be alternately connected. This means that coating powder can be alternately sucked into each powder feed chamber or expelled from the corresponding powder feed chamber by means of compressed air. The two powder feed chambers arranged parallel to one another are operated in alternating phases, which means that one of the two powder feed chambers sucks in coating powder through the powder inlet of the dense phase powder pump, while the other of the two powder feed chambers discharges a portion of coating powder previously sucked into the powder feed chamber via the powder outlet of the dense phase powder pump.

Powder dense phase pumps with several, in particular two parallel connected powder feed chambers are also known from the publication WO 2005 005060 A2 ( US 2006 0193704 A1 ), the publication DE 199 59 473 A1 ( US 2001 0003568 A1 ) and the publication EP 1 752 399 A1 known.

The use of dense phase powder pumps for conveying coating powder to corresponding devices for spraying coating powder, such as in particular powder spray coating guns, is known from the publication DE 196 11 533 B4 , the WO 2004/087331 A1 and the EP 1 566 352 A2 known.

Before the use of dense phase powder pumps of the type mentioned above became known for conveying coating powder, powder pumps designed as injectors were used, which are still used today to convey coating powder. In contrast to dense phase powder pumps of the type mentioned above, however, powder pumps designed as injectors have the disadvantage that the powder pumps designed as injectors can usually only convey a smaller amount of coating powder per unit of time.

In this respect, dense phase powder pumps of the type mentioned above have become established in practice, particularly for applications in which a relatively large amount of coating powder has to be pumped per unit of time.

In practical use, however, it has been shown that a powder dense phase pump, such as that described in the publication EP 1 551 558 A1 known, has several disadvantages, particularly with regard to its maintenance and the operating costs incurred during operation of the dense phase powder pump. This is due to the fact that - in contrast to powder pumps designed as injectors - a dense phase powder pump of the type described above has a relatively large number of components that must be continuously operated during operation of the dense phase powder pump. For example, a conventional dense phase powder pump uses at least four valves that must be operated alternately, whereby the maintenance of a single valve inevitably results in the failure of the dense phase powder pump for a certain maintenance period.

Because conventional dense phase powder pumps use at least two powder inlet valves on the input side and at least two powder outlet valves on the output side, the maintenance-free running time of the dense phase powder pump is inevitably reduced accordingly.

In addition, conventional dense phase powder pumps require a relatively complex circuit diagram in order to be able to control the individual, alternately controlled components of the pump in a coordinated manner.

Based on this problem, the present invention is based on the object of developing a dense phase powder pump of the type mentioned at the beginning in such a way that it requires fewer maintenance-prone components, while at the same time the powder conveying capacity of the pump remains as unchanged as possible.

Furthermore, it is an object of the invention to construct a dense phase powder pump of the type mentioned at the outset in a structurally simpler manner and, in particular, to simplify or reduce its size.

Furthermore, a correspondingly simplified method for conveying coating powder is to be specified.

With regard to the device, the object underlying the invention is achieved according to the invention by the subject matter of independent patent claim 1.

With regard to the method, the object underlying the invention is solved by the subject matter of patent claim 31.

Advantageous further developments of the powder dense phase pump according to the invention are specified in the dependent patent claims 2 to 30.

Accordingly, according to the invention, in particular a powder dense phase pump is specified for conveying coating powder from a first powder reservoir to a second powder reservoir arranged downstream (with respect to the first powder reservoir) or a powder spray coating gun arranged downstream for spraying coating powder, wherein the powder dense phase pump is designed as a single-chamber powder dense phase pump and in particular has only a single powder conveying chamber for conveying the coating powder.

The solution according to the invention is based on the surprising finding that even with a single-chamber dense phase powder pump, i.e. a dense phase powder pump which has only a single powder conveying chamber for conveying the coating powder, a continuous conveying of coating powder sufficient for practical use is possible.

The prejudice that has existed up to now among experts, namely that at least two powder conveying chambers arranged in parallel and operated alternately must be used for the continuous conveying of coating powder, has been overcome with the present invention in that a powder dense phase pump designed as a single-chamber powder dense phase pump can certainly ensure continuous conveying of coating powder, in particular if the pumping frequency, i.e. the frequency with which coating powder is sucked in by the single powder conveying chamber and then released again, is increased accordingly in the powder dense phase pump designed as a single-chamber powder dense phase pump, and/or if additional compressed air is introduced into the powder path as additional transport compressed air at the powder outlet of the single powder conveying chamber at suitable times before or after the powder outlet of the powder dense phase pump.

By introducing additional compressed air into the powder path, the powder concentration in the powder path can be homogenized.

By specifically introducing additional compressed air into the powder path at the powder outlet of the powder feed chamber, it is possible in particular to ensure that the flow rate of the powder being fed in the powder line downstream of the powder outlet of the dense phase powder pump assumes a constant value and that the powder can flow homogeneously through the powder line. It is particularly advantageous if the amount of additional compressed air fed into the powder path per pump cycle is the same or at least essentially the same as the amount of transport compressed air fed into the powder feed chamber per pump cycle, which is used to pneumatically eject powder portions from the powder feed chamber.

By increasing the pumping frequency of the dense phase powder pump designed as a single-chamber dense phase powder pump, i.e. the frequency with which coating powder is sucked into the only powder feed chamber of the dense phase powder pump designed as a single-chamber dense phase powder pump and then released again, and/or by introducing additional compressed air into the powder path downstream of the powder outlet of the powder feed chamber, in particular in pulses and in coordination with the pumping frequency of the dense phase powder pump designed as a single-chamber dense phase powder pump, the flowability of the coating powder fed by the dense phase powder pump downstream of the dense phase powder pump can be improved. In particular, at least one of these measures enables uniform powder feed from the dense phase powder pump to a powder reservoir downstream of the dense phase powder pump or to a powder spray coating gun downstream of the dense phase powder pump for spraying coating powder.

In comparison to conventional dense phase powder pumps, which are designed as multi-chamber dense phase powder pumps and have several, in particular at least two powder conveying chambers arranged parallel to one another and operated in antiphase to one another, the dense phase powder pump according to the present invention can achieve powder conveyance with a comparable uniformity without flow pulsations in the powder path downstream of the powder outlet of the dense phase powder pump, while on the other hand the number of components to be actuated during operation of the dense phase powder pump is significantly reduced and the structural design of the dense phase powder pump is significantly simplified.

The present invention thus provides a particularly easy-to-implement but nevertheless effective alternative to conventional dense phase powder pumps designed as multi-chamber dense phase powder pumps, while simultaneously reducing the structural components and simplifying the circuit diagram required to operate the dense phase powder pump.

According to the present invention, the dense phase powder pump has a powder inlet connected or connectable to the (upstream) first powder reservoir and a powder outlet connected or connectable to the (downstream) second powder reservoir or to the (downstream) powder spray coating gun for spraying coating powder. The powder inlet of the dense phase powder pump can be arranged at a first end region of the dense phase powder pump and the powder outlet of the dense phase powder pump can be arranged at an opposite second end region of the dense phase powder pump, wherein the (only) powder feed chamber of the dense phase powder pump is arranged between the powder inlet and the powder outlet of the dense phase powder pump.

According to the present invention, the single powder feed chamber of the dense phase powder pump according to the invention has a powder inlet at a first end region and a powder outlet at an opposite second end region, wherein the dense phase powder pump according to the invention also has a powder inlet valve and a powder outlet valve. The powder inlet of the (single) powder feed chamber is or can be connected in terms of flow to the powder inlet of the dense phase powder pump via the powder inlet valve. On the other hand, the powder outlet of the single powder feed chamber of the dense phase powder pump is or can be connected to the powder outlet of the dense phase powder pump via the powder outlet valve.

According to the present invention, the dense phase powder pump has a powder inlet that is or can be connected to the first powder reservoir and a powder outlet that is or can be connected to the second powder reservoir or to the powder spray coating gun for spraying coating powder, wherein the single powder feed chamber of the dense phase powder pump according to the invention has a powder passage at one end region that serves both as a powder inlet and as a powder outlet for the powder feed chamber. According to the present invention, it is advantageous if the dense phase powder pump also has a powder inlet valve and a powder outlet valve, wherein the powder passage of the single powder feed chamber is or can be connected in terms of flow to the powder inlet of the dense phase powder pump via the powder inlet valve, and wherein the powder passage of the single powder feed chamber is or can be connected in terms of flow to the powder outlet of the dense phase powder pump via the powder outlet valve.

According to a preferred implementation, the powder dense phase pump also has a distributor in order to fluidically connect the powder passage of the powder feed chamber to the powder inlet valve on the one hand and the powder outlet valve on the other. It is particularly conceivable to use a Y-piece as a distributor. Of course, other embodiments are also possible.

In preferred embodiments of the solution according to the invention, a control device is also provided which is designed to alternately control the powder inlet valve and/or the powder outlet valve of the dense phase powder pump. The control device is preferably also designed to alternately apply an overpressure and a negative pressure in the (single) powder feed chamber of the dense phase powder pump.

The (single) powder feed chamber of the dense phase powder pump is preferably assigned a gas path through which the powder feed chamber can be alternately connected to a vacuum line or vacuum source for sucking coating powder into the powder feed chamber through the open powder inlet valve while the powder outlet valve is closed, or to a compressed air line or compressed air source for pneumatically ejecting a portion of powder present in the powder feed chamber through the open powder outlet valve while the powder inlet valve is closed. The control device is designed to alternately switch the single powder feed chamber between sucking in and ejecting powder.

In advantageous implementations of the dense phase powder pump according to the invention, the aforementioned gas path has a suction air opening and a compressed air opening in a housing peripheral wall of the powder feed chamber, wherein preferably a microporous filter element, preferably in the form of a filter tube, is also provided, which forms the peripheral wall of the powder feed chamber at least over a partial length or preferably the entire length of the powder feed chamber and separates the powder chamber from an annular chamber. The annular chamber is formed between the outer circumference of the filter element, which is preferably designed as a filter tube, and the inner circumference of the housing peripheral wall and surrounds the filter element, which is preferably designed as a filter tube.

The filter element, preferably designed as a filter tube, is permeable to air but not to coating powder due to its small pore size. It is preferably made of a sintered material.

In embodiments in which the powder inlet and powder outlet of the single powder feed chamber are located at opposite end regions of the powder feed chamber, it is advantageous if the suction air opening opens into the annular chamber close to the powder outlet and the compressed air opening opens into the annular chamber close to the powder inlet.

Of course, it is also conceivable to choose a single (common) opening for both the suction air opening and the compressed air opening.

The powder inlet valve and the powder outlet valve of the (single) powder conveying chamber present in the dense phase powder pump according to the invention are preferably each designed as a pinch valve, in particular of the type which has a flexible elastic hose as a valve channel, wherein this flexible elastic hose can be squeezed together in order to close the corresponding valve with the aid of actuating compressed air in a pressure chamber surrounding the hose.

In particular, it is advantageous in this context if the powder inlet valve designed as a pinch valve and the powder outlet valve designed as a pinch valve each have a pinch valve housing with a powder inlet and a powder outlet and with an elastically deformable valve element, preferably in the form of a hose section. In particular, the valve element should be arranged inside the pinch valve housing in such a way that the powder inlet of the pinch valve can be brought into fluid communication with the powder outlet of the pinch valve via the valve element designed as a hose section.

It is advantageous if the pinch valve housing has at least one connection for the supply of compressed air (actuating compressed air) as required into the space formed between the inner wall of the pinch valve housing and the valve element arranged inside the pinch valve housing. When actuating compressed air is supplied, an overpressure is formed in the space between the inner wall of the pinch valve housing and the valve element, as a result of which the valve element is compressed in the radial direction and the pinch valve is closed. When pressure is then relieved in the pinch valve housing, the valve element returns to its original state, so that a fluid connection is established between the powder inlet of the pinch valve and the outlet of the pinch valve via the valve element.

In this context, it is also conceivable that the pinch valve housing has at least one connection for applying a negative pressure inside the pinch valve housing as required in order to reduce the opening time of the pinch valve.

The amount of powder that can be conveyed per unit of time by the dense phase powder pump according to the invention depends on several parameters, in particular on the size (volume) of the powder conveying chamber, the frequency with which coating powder is sucked into the powder conveying chamber and then released again, the strength (height) of the vacuum applied to suck the coating powder into the powder conveying chamber, the opening time of the powder inlet valve during the suction phase and the flow resistances in the powder lines upstream and in particular downstream of the dense phase powder pump. The flow resistances in the powder lines upstream and in particular downstream of the dense phase powder pump depend in particular on the length and the internal cross-section of the powder lines, usually powder hoses.

The conveying frequency of the dense phase powder pump depends primarily on the frequency with which coating powder is sucked into the powder conveying chamber and then released again or can be released.

In order to avoid or at least reduce pulsations in the delivered powder stream at the powder outlet of the dense phase powder pump according to the invention and designed as a single-chamber dense phase powder pump, which has only a single powder feed chamber, the dense phase powder pump is structurally designed in such a way that the reaction time for switching from a suction phase, during which the powder feed chamber of the single-chamber dense phase powder pump is connected to a vacuum source, and a discharge phase, during which the powder feed chamber of the single-chamber dense phase powder pump is connected to a compressed air source or transport compressed air source, can be shortened accordingly, so that ultimately the feed frequency of the dense phase powder pump can be increased.

For this purpose, according to one aspect of the invention, during the suction phase of the powder feed chamber, a negative pressure is applied in the powder feed chamber at the earliest at the same time as, or preferably a certain delay time later than, a control signal for opening the powder inlet valve arranged at the powder inlet of the powder feed chamber, so that the The build-up of the negative pressure in the powder feed chamber begins at the earliest at the same time as the opening of the powder inlet valve, but preferably later than the opening of the powder inlet valve by the predetermined delay time mentioned. The predetermined delay time is preferably in a range between 0 ms and 50 ms with a feed cycle of the feed chamber (= pump cycle of the dense phase powder pump) of approximately 200 ms. However, this example does not exclude the use of other delay times and cycle times for the dense phase powder pump.

Because, in advantageous implementations of the solution according to the invention, a negative pressure is only applied in the powder feed chamber during the suction phase of the dense phase powder pump when the powder inlet valve is already open or at the earliest at the same time as the powder inlet valve is opened, it can be achieved that the negative pressure in the powder feed chamber counteracts an opening movement of the powder inlet valve, in particular if this is designed as a pinch valve, 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 and designed as multi-chamber dense phase powder pumps.

In order to shorten the reaction time of the dense phase powder pump according to the invention and thus to increase the conveying frequency of the same, in addition to or as an alternative to the aforementioned measure, it is preferably provided that the powder inlet valve provided at the powder inlet of the powder conveying chamber and the powder outlet valve provided at the powder outlet of the powder conveying chamber are each designed as a pneumatically controllable pinch valve. To control these pinch valves, appropriate control valves are used, with which actuating compressed air is supplied to the pinch valves in a coordinated manner.

According to preferred embodiments of the powder dense phase pump according to the invention, it is provided that the length of the pneumatic control lines to the pinch valves is as short as possible in order to ensure that reaction delay times can be minimized when actuating the corresponding pinch valves, i.e. when supplying actuating compressed air or when applying a negative pressure or when venting the corresponding pinch valve housing.

For this purpose, in preferred embodiments of the dense phase powder pump according to the invention, for example, a material block preferably composed of several modules is provided in which the only powder feed chamber of the dense phase powder pump is formed or on which the only powder feed chamber of the dense phase powder pump is arranged, wherein the powder inlet valve and the powder outlet valve of the (only) powder feed chamber of the dense phase powder pump are also advantageously arranged on this material block. In particular, the corresponding control valves, which serve to pneumatically control the powder inlet and powder outlet valve, which are preferably each designed as a pinch valve, are directly connected in terms of flow to the powder inlet valve and the powder outlet valve via compressed air channels formed in the material block in such a way as to ensure the supply and discharge of actuating air to the powder inlet and powder outlet valve designed as a pinch valve.

In this context, it is also advantageous if all control valves which are fluidically connected to the (single) powder feed chamber of the dense phase powder pump according to the invention for the supply of transport compressed air (during the discharge phase of the dense phase powder pump) and of vacuum (during the suction phase of the dense phase powder pump) are arranged on the material block and are fluidically connected directly to the single powder feed chamber by means of channels which are formed in the material block.

With these measures, it can be achieved that the length of the pneumatic control lines to the pinch valves and the length of the air lines to the powder feed chamber are shortened as much as possible in order to ensure that reaction delay times can be minimized when operating the corresponding pinch valves, i.e. when supplying actuating compressed air or when applying a negative pressure or when venting the corresponding pinch valve housing.

As already explained, the reaction time of the dense phase powder pump according to the invention can be shortened and thus the conveying frequency increased by ensuring that during the suction phase of the dense phase powder pump, i.e. when a negative pressure is applied in the powder conveying chamber, this begins at the earliest at the same time as the opening of the powder inlet valve arranged at the powder inlet of the powder conveying chamber. Alternatively or in addition to this, the pumping frequency can be increased by shortening as much as possible the channels provided for the pneumatic actuation of the powder inlet valve designed as a pinch valve or the outlet valve designed as a pinch valve for supplying or discharging actuating compressed air to the pinch valves.

In addition, it is advantageous if the path length of the channels or the channel for supplying the transport compressed air to the single powder feed chamber or the path length of the channels or the channel for applying a vacuum in the powder feed chamber is shortened. In this way, reaction delay times can be reduced when the powder inlet valve or the powder outlet valve is controlled and when a vacuum is applied in the single powder feed chamber during the suction phase or an overpressure is applied during the discharge phase.

By increasing the feed frequency of the dense phase powder pump accordingly, sufficient homogeneity in the powder flow delivered at the powder outlet of the dense phase powder pump is ensured.

In order to further increase the homogeneity of the powder flow at the powder outlet of the dense phase powder pump and in particular to avoid the occurrence of disruptive pulsations in the powder flow downstream of the powder outlet of the dense phase powder pump, according to preferred implementations of the solution according to the invention, an additional compressed air inlet device is used in addition to or as an alternative to the measures mentioned above. This additional compressed air inlet device opens at least one point into the powder path between the powder outlet valve assigned to the only powder feed chamber and the powder outlet of the dense phase powder pump or preferably immediately downstream of the powder outlet of the dense phase powder pump and serves to supply additional compressed air as required, which serves as additional transport compressed air. In other words, in addition to the transport compressed air introduced into the powder feed chamber during the discharge phase of the dense phase powder pump, additional transport compressed air is fed in with the aid of the additional compressed air inlet device immediately before or after the powder outlet of the dense phase powder pump at suitable times or events.

To implement the at least one additional compressed air inlet device, a filter tube is preferably provided through which the powder path runs at least in part between the powder outlet valve and the powder outlet of the dense phase powder pump. The powder path downstream of the powder outlet valve of the dense phase powder pump is preferably guided through the filter tube over part of its length. The filter tube is permeable to compressed air, but not to the particles of the coating powder. In this case, it is advisable to form the filter tube from microporous material, such as sintered material. The filter tube forms a peripheral wall around the powder path and thus a relatively large area through which even small amounts of additional compressed air can flow homogeneously through the filter tube into the powder path and influence powder particles in the sense of equalizing the powder concentration.

In this context, it is particularly advantageous if the filter tube has a circumference of at least 180° and forms a channel wall inner surface of at least 180° of the powder path circumference.

Of course, it is also possible to design the additional compressed air inlet device without a filter element, in particular a filter tube. The filter element or filter tube only serves to prevent powder particles from penetrating an additional compressed air line connected to the additional compressed air inlet device.

In order to be able to reduce or avoid flow pulsations in the powder path downstream of the powder outlet of the dense phase powder pump particularly effectively, it is advantageous if additional compressed air is introduced in a pulsating manner into the powder path after the powder outlet valve of the dense phase powder pump via the additional compressed air inlet device. The pulse frequency of the additional compressed air should be at least as high as the frequency of the powder feed chamber with which powder portions are released from the powder feed chamber.

According to preferred implementations of the dense phase powder pump according to the invention, the pulse frequency of the additional compressed air is the same as the frequency of the powder feed chamber, i.e. the frequency with which powder portions are released from the powder feed chamber. In this context, it is advisable to provide a device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device, wherein this device for supplying pulsating additional compressed air is advantageously designed such that the additional compressed air is supplied to the at least one additional compressed air inlet device in antiphase with respect to the powder delivery cycle of the powder feed chamber. In this way, it can be achieved that the additional compressed air is always fed into the powder path after the powder outlet valve when the powder outlet valve is closed. With this measure, in particular, the flow velocity in the powder line downstream of the powder outlet of the dense phase powder pump can assume a constant value without fluctuations occurring.

According to preferred embodiments of the solution according to the invention, it is provided that the only powder feed chamber of the dense phase powder pump has at least one air exchange opening, via which the powder feed chamber can be temporarily supplied with transport compressed air for ejecting powder portions from the powder feed chamber during the dispensing phase. In a particularly easy to implement but nevertheless effective manner, it is further provided that the device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device has a switching element, in particular a three/two-way valve or similar switching valve, via which compressed air from a common compressed air source can be alternately supplied to the at least one air exchange opening of the powder feed chamber or to the at least one additional compressed air inlet device. By providing such a switching element, via which the powder feed chamber and the additional compressed air inlet device can be alternately connected in terms of flow to a common compressed air source, it can be effectively ensured in a particularly easy to implement manner that either transport compressed air or additional compressed air is supplied to the dense phase powder pump and fed into the powder path at all times.

In this context, it is conceivable that the device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device is designed such that the amount of additional compressed air supplied to the at least one additional compressed air inlet device per pump cycle can be adjusted in particular as a function of the amount of transport compressed air supplied to the at least one air exchange opening of the powder conveying chamber per pump cycle. In particular, it is advantageous here if the device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device is designed to adjust the amount of additional compressed air supplied to the at least one additional compressed air inlet device per pump cycle such that the amount of additional compressed air fed into the powder path via the at least one additional compressed air inlet device per pump cycle is essentially the same as the amount of transport compressed air fed into the powder conveying chamber via the at least one air exchange opening per pump cycle.

In this context, "essentially the same" means that the amount of additional compressed air fed in per pump cycle deviates by no more than 15% from the amount of transport compressed air fed into the powder path or powder feed chamber per pump cycle. The smaller the deviation, the more evenly the flow rate of the powder-air mixture can be set in the powder line downstream of the powder outlet of the dense phase powder pump.

The present invention is based in particular on the finding that in a dense phase powder pump designed as a single-chamber dense phase powder pump, it is advantageous to feed additional compressed air as additional transport compressed air at the powder outlet of the dense phase powder pump, whereby downstream of the powder outlet of the dense phase powder pump the powder-air mixture flows through the powder line all the more homogeneously if the amount of additional compressed air fed into the powder path downstream of the powder outlet valve during the suction phase of the powder feed chamber is essentially the same as the amount of transport compressed air fed into the powder feed chamber during the powder discharge phase, which serves to pneumatically eject the powder portion previously sucked into the powder feed chamber.

In order to implement this finding in the powder dense phase pump according to the invention, it is conceivable, on the one hand, to provide a device for supplying pulsating additional compressed air to the at least one additional pressure inlet device, wherein this device adapts the amount of additional compressed air fed into the powder path to the amount of transport compressed air fed into the powder feed chamber.

However, a complex compressed air quantity control can be dispensed with if it is achieved that the pneumatic resistances occurring when feeding the transport compressed air into the powder feed chamber and when feeding the additional compressed air into the powder path assume essentially the same value. In order to achieve this, it is advantageous if at least the essential components of the additional compressed air inlet device, i.e. the components that are required to feed the additional compressed air into the powder path, have the same structure as the essential components of the powder feed chamber, i.e. the components of the powder feed chamber that are required to feed the transport compressed air during the discharge phase of the powder feed chamber. For example, it is conceivable in this context that the additional compressed air inlet device has a chamber wall which is formed at least over part of its length by a filter which surrounds the powder path and separates it from an intermediate chamber which surrounds the filter and is formed between the filter and a housing of the additional compressed air inlet device. At least the filter of the additional compressed air inlet device should be identical in construction to the filter of the powder feed chamber.

On the other hand, it is also conceivable if a control device is provided by which the additional compressed air frequency can be set, preferably automatically controlled or regulated depending on the powder discharge frequency of the powder feed chamber. In particular, by adapting the pulse frequency of the additional compressed air to the frequency of the powder feed chamber, whereby the additional compressed air is advantageously always fed into the powder path after the powder outlet valve of the dense phase powder pump when the dense phase powder pump is in its suction phase in which the powder inlet valve is open and the powder outlet valve is closed, it is ensured that a sufficient amount of transport compressed air is always used, which is necessary for transporting the coating powder.

Of course, it is also conceivable that during the discharge phase of the dense phase powder pump, additional compressed air is introduced into the powder path after the powder outlet valve of the dense phase powder pump via the additional compressed air inlet device.

However, by only feeding additional compressed air into the powder path using the additional compressed air inlet device when the dense phase powder pump is in its suction phase, resources (compressed air and thus energy) for operating the dense phase powder pump can be reduced. In particular, this also prevents too much transport compressed air from being present in the powder path downstream of the powder outlet of the dense phase powder pump, thus preventing powder particles from being expelled from the spray jet at the consumer arranged downstream of the dense phase powder pump (powder spray coating gun for spraying coating powder).

In this context, it is particularly advantageous if, with the aid of a control device, the amount of additional compressed air flowing through the additional compressed air inlet device per unit of time, which is introduced into the powder path after the powder outlet valve of the dense phase powder pump, can be adjusted, preferably automatically controlled or regulated, depending on the total amount of powder conveyed per unit of time.

The invention is not only directed to a dense phase powder pump, which is designed as a single-chamber dense phase powder pump and has only a single powder feed chamber for conveying the coating powder, but also to a powder spray coating device for spray coating objects with coating powder, wherein the powder spray coating device has a dense phase powder pump of the type described above and at least one preferably automatic and manual spray coating gun. The spray coating gun has a coating powder inlet, which is connected or can be connected to the powder outlet of the dense phase powder pump via a powder line.

1. a) Erzeugen eines Unterdruckes in der einzigen Pulverförderkammer der Pulverdichtstrompumpe zum Einsaugen von Beschichtungspulver in die Pulverförderkammer durch ein geöffnetes Pulvereinlassventil der Pulverdichtstrompumpe, während das Pulverauslassventil der Pulverdichtstrompumpe geschlossen ist;
2. b) Verschließen des Pulvereinlassventils und Öffnen des Pulverauslassventils;
3. c) Einleiten von Druckgas in die Pulverförderkammer zum Abgeben des Beschichtungspulvers aus der Pulverförderkammer durch das offene Pulverauslassventil, während das Pulvereinlassventil geschlossen ist; und
4. d) Verschließen des Pulverauslassventils und Öffnen des Pulvereinlassventils.

With regard to the method for conveying coating powder from a first powder reservoir to a second powder reservoir arranged downstream of the first powder reservoir or to a powder spray coating gun arranged downstream of the first powder reservoir for spraying coating powder, the invention provides that the method comprises the method step of providing a powder spray coating device of the aforementioned type, which thus has the powder dense phase pump according to the invention and at least one spray coating gun, and the method step of carrying out a specific operating cycle, wherein this specific operating cycle comprises the following cycle steps:

1. a) generating a negative pressure in the single powder feed chamber of the dense phase powder pump for sucking coating powder into the powder feed chamber through an open powder inlet valve of the dense phase powder pump, while the powder outlet valve of the dense phase powder pump is closed;
2. b) closing the powder inlet valve and opening the powder outlet valve;
3. c) introducing pressurised gas into the powder feed chamber to discharge the coating powder from the powder feed chamber through the open powder outlet valve while the powder inlet valve is closed; and
4. d) Close the powder outlet valve and open the powder inlet valve.

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

In the method according to the invention, the additional compressed air is preferably fed into the powder path in a manner previously described in connection with the dense phase powder pump.

The invention will be explained below with reference to the accompanying drawings. exemplary embodiments of the dense phase powder pump according to the invention are described in more detail.

• 1: eine Längsschnittdarstellung entlang des Pulverweges durch eine erste exemplarische Ausführungsform der erfindungsgemäßen Pulverdichtstrompumpe;
• 2: eine perspektivische Ansicht auf die erste exemplarische Ausführungsform der erfindungsgemäßen Pulverdichtstrompumpe gemäß 1;
• 3: eine perspektivische Ansicht auf eine zweite exemplarische Ausführungsform der erfindungsgemäßen Pulverdichtstrompumpe;
• 4: eine schematische Darstellung einer ersten exemplarischen Ausführungsform einer Pulversprühbeschichtungsvorrichtung, bei welcher eine Pulverdichtstrompumpe gemäß der vorliegenden Erfindung zum Einsatz kommt;
• 5: eine schematische Darstellung einer zweiten exemplarischen Ausführungsform einer Pulversprühbeschichtungsvorrichtung, bei welcher eine Pulverdichtstrompumpe gemäß der vorliegenden Erfindung zum Einsatz kommt;
• 6: eine schematische Darstellung einer dritten exemplarischen Ausführungsform der erfindungsgemäßen Pulverdichtstrompumpe; und
• 7: eine schematische Darstellung einer vierten exemplarischen Ausführungsform der erfindungsgemäßen Pulverdichtstrompumpe.

The drawings show:

• 1 : a longitudinal sectional view along the powder path through a first exemplary embodiment of the dense phase powder pump according to the invention;
• 2 : a perspective view of the first exemplary embodiment of the powder dense phase pump according to the invention according to 1 ;
• 3 : a perspective view of a second exemplary embodiment of the dense phase powder pump according to the invention;
• 4 : a schematic representation of a first exemplary embodiment of a powder spray coating device in which a powder dense phase pump according to the present invention is used;
• 5 : a schematic representation of a second exemplary embodiment of a powder spray coating device in which a dense phase powder pump according to the present invention is used;
• 6 : a schematic representation of a third exemplary embodiment of the powder dense phase pump according to the invention; and
• 7 : a schematic representation of a fourth exemplary embodiment of the dense phase powder pump according to the invention.

The following are based on the illustrations in the 1 to 3, 6 and 7 exemplary embodiments of the dense phase powder pump 1 according to the invention are described.

In the 4 and 5 Powder spray coating devices 100 are shown schematically, in which embodiments of the dense phase powder pump 1 according to the invention are used for conveying coating powder from a first powder reservoir 101 to a powder spray coating gun 102 arranged downstream of the dense phase powder pump 1. Instead of the powder spray coating gun 102, another device for spraying coating powder onto an object to be coated or onto a second powder reservoir can also be used.

As in 4 As shown, the exemplary embodiment of the dense phase powder pump 1 according to the invention used there has a powder inlet 2 which is or can be connected in terms of flow to the first powder reservoir 101 by means of a powder line 103, in particular by means of an intake pipe or the like. A powder outlet 3 is provided at the opposite end region of the dense phase powder pump 1, which is or can be connected to a coating powder inlet 105 of the powder spray coating gun 102 by means of a powder line 104, in particular by means of a powder hose.

In detail, and as can be seen in particular from the representations in the 1 to 3 can be seen, in the first and second exemplary embodiments both the powder inlet 2 and the powder outlet 3 of the dense phase powder pump 1 are each designed as a hose connection piece to which the corresponding powder line 103 or 104 can be plugged and fixed with a hose clamp. Of course, other embodiments for the powder inlet 2 or the powder outlet 3 are also possible.

The dense phase powder pump 1 according to the invention is characterized in that it is designed as a single-chamber dense phase powder pump, wherein only a single powder conveying chamber 4 is provided for conveying coating powder from the first powder reservoir 101 to the powder spray coating gun 102 or to another device for spray coating objects or to another powder reservoir.

In the exemplary embodiments of the powder dense phase pump 1 according to the invention according to 1 to 5 the (only) powder feed chamber 4 has a powder inlet 5 at a first end region, which points in the direction of the powder inlet 2 of the dense phase powder pump 1. The powder feed chamber 4 also has a powder outlet 6 pointing in the direction of the powder outlet 3 of the dense phase powder pump 1. A powder inlet valve 7 is arranged directly adjacent to the powder inlet 5 of the powder feed chamber 4, in such a way that this powder inlet valve 7 is located between the powder inlet 5 of the powder feed chamber 4 and the powder inlet 2 of the dense phase powder pump 1. In the same way, a powder outlet valve 8 is arranged directly adjacent to the powder outlet 6 of the powder feed chamber 4.

In contrast to the powder inlet area of the dense phase powder pump 1, the powder outlet valve 8 is not arranged directly between the powder outlet 6 of the powder feed chamber and the powder outlet 3 of the dense phase powder pump 1 at the powder outlet area of the dense phase powder pump 1; rather, an additional compressed air inlet is arranged between the powder outlet valve 8 and the powder outlet 3 of the dense phase powder pump 1. inlet device 9. As will be described in more detail below, this additional compressed air inlet device 9 serves to feed additional transport compressed air into the powder path between the powder outlet valve 8 and the powder outlet 3 of the dense phase powder pump 1 as required.

At this point, it should be noted that it is not absolutely necessary to arrange the additional compressed air inlet device 9 between the powder outlet valve 8 and the powder outlet 3 of the dense phase powder pump 1. The effects that can be achieved with the additional compressed air inlet device 9, which are described in more detail below, can also be achieved if the additional compressed air inlet device 9 is arranged behind the powder outlet 3 of the dense phase powder pump 1.

Although not shown in the drawings, in advantageous implementations of the dense phase powder pump 1 according to the invention, a further valve, in particular a pinch valve, is provided between the additional compressed air inlet device 9 and the powder outlet 3 of the dense phase powder pump 1, which then takes over the function of the powder outlet valve since it is arranged directly at the powder outlet 3 of the dense phase powder pump 1.

As is particularly evident from the presentation in 1 can be seen, the powder inlet 2 of the dense phase powder 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 additional compressed air inlet device 9 and the powder outlet 3 of the dense phase powder pump 1 are located along a common longitudinal axis L. In other words, the powder inlet 2 of the dense phase powder pump 1 is provided at the opposite end of the powder outlet 3 of the dense phase powder pump 1.

The structure and the functioning in particular of the single powder feed chamber 4 of the exemplary embodiment of the powder dense phase pump 1 shown in the drawings are described in more detail below.

As the longitudinal section in 1 or the schematic representation in 3 can be removed, the powder feed chamber 4 is formed between its powder inlet 5 and its powder outlet 6 by the cylindrical wall of a tube-like filter 10, which is permeable to air but not to coating powder and can be made of sintered material, for example. The filter 10, designed as a filter tube, is surrounded by an intermediate chamber 11, which is delimited on its outside by a housing 12 of the powder feed chamber 4.

An air exchange opening 13 opens through the housing 12 and is connected in terms of flow to a control valve V1 (cf. 3 ). Via the control valve V1, the powder conveying chamber 4 can be alternately supplied with transport compressed air from a compressed air supply line 50 or with vacuum or negative pressure from a vacuum source 52.

In the 4 and 5 In the schematically illustrated embodiments of the powder spray coating device 100 according to the invention, the vacuum source 52 has an injector 55, to which injector compressed air is supplied from a compressed air supply line 54 or a compressed air source 58, for example via a pressure regulator 53 and a further control valve V2.

In order to be able to suck coating powder from the first powder reservoir 101 into the powder feed chamber 4 via the powder inlet 2 of the powder dense phase pump 1 during a suction phase of the powder dense phase pump 1, the powder outlet valve 8 arranged at the powder outlet 6 of the powder feed chamber 4 is closed and the powder inlet valve 7 arranged between the powder inlet 2 of the powder dense phase pump 1 and the powder inlet 5 of the powder feed chamber 4 is opened. At the same time as the powder outlet valve 8 and the powder inlet valve 7 are actuated or immediately thereafter, the powder feed chamber 4 is connected to the vacuum source 52 via the control valve V1 and the associated air exchange opening 13, so that a negative pressure is present in the powder feed chamber 4 and coating powder can be sucked in from the first powder reservoir 101.

After coating powder has been sucked into the powder conveying chamber 4, there is a change from the suction phase to the ejection phase of coating powder from the conveying chamber 4. For this purpose, the powder inlet valve 7 is closed and the powder outlet valve 8 is opened, while the control valve V1 provides a flow connection between the air exchange opening 13 and the compressed air supply line 50, so that the coating powder portion previously sucked into the powder conveying chamber 4 during the suction phase is ejected through the open powder outlet valve 8 by means of the transport compressed air supplied via the air exchange opening 13.

Subsequently, the operating phase of sucking in coating powder takes place again via the powder inlet 2 of the dense phase powder pump 1 and via the opened powder inlet valve 7. This alternation of the operating phases is repeated continuously.

Here, the term “pump cycle” refers to a cycle consisting of a suction phase and an exhaust phase.

The valves arranged on the inlet and outlet sides of the powder feed chamber 4 (powder inlet valve 7, powder outlet valve 8) are preferably each designed as pinch valves, although other valve types are also possible in principle.

The powder inlet and powder outlet valves 7, 8, each designed as a pinch valve in the exemplary embodiment shown in the drawings, each have a flexible elastic hose 14.1, 14.2 that serves as a valve channel. The flexible elastic hose 14.1, 14.2 can be squeezed together by means of actuating compressed air in a pressure chamber 15.1, 15.2 surrounding the flexible elastic hose 14.1, 14.2 in order to close the corresponding valve (powder inlet valve 7, powder outlet valve 8).

For this purpose, an air exchange opening 16 is provided in each pressure chamber 15.1, 15.2, which is connected to a corresponding control valve V3, V4. The control valves V3, V4 serve to alternately apply excess pressure from a compressed air supply line 56 to the pressure chambers 15.1, 15.2 of the two powder inlet and powder outlet valves 7, 8, each designed as a pinch valve.

As shown, the compressed air supply line 56 is connected to a pressure accumulator 57, wherein the pressure accumulator 57 is in turn connected to a compressed air source 58. Of course, it is also conceivable that the compressed air supply line 56 is connected directly to the compressed air source 58 (i.e. without the interposition of a pressure accumulator 57).

The flexible elastic hose 14.1, 14.2 of the powder inlet valve 7 or powder outlet valve 8 designed as a pinch valve preferably has such elasticity or inherent tension that it automatically stretches again after the pressure of the actuating compressed air in the pressure chamber 15.1, 15.2 has been removed and thereby opens the corresponding valve channel. In order to support the opening of the pinch valves and thus increase the achievable switching frequency of the powder dense phase pump 1, it is conceivable that a negative pressure is applied via the corresponding air exchange openings 16.

In order to achieve a homogeneous powder flow without disturbing pulsations in the single-chamber powder dense phase pump according to the invention downstream of the powder outlet 3 of the powder dense phase pump 1, various measures are provided in the solution according to the invention.

For example, the dense phase powder pump 1 is structurally designed and constructed in such a way that the pumping frequency that can be achieved with the dense phase powder pump 1 can be increased compared to the pumping frequency that can be achieved with conventional multi-chamber dense phase powder pumps. For this purpose, the solution according to the invention uses a material block 60 to which, in advantageous implementations of the dense phase powder pump 1 according to the invention, the powder inlet valve 7 required for conveying coating powder and the powder outlet valve 8 also required for conveying coating powder, including the control valves V3, V4 required to actuate these valves 7, 8, can be attached (not explicitly shown in the drawings). Both the powder inlet valve 7 and the powder outlet valve 8 and the control valves V3, V4 required to actuate them are preferably connected to channels that are formed in the material block 60 (not shown in the figures). The same applies to the control valve V1, which is fluidly connected to the air exchange opening 13 of the powder feed chamber 4 via at least one channel formed in the one-piece material block 60.

Because in exemplary embodiments of the dense phase powder pump 1 according to the invention the corresponding control valves V1, V3 and V4 as well as the powder inlet and powder outlet valve 7, 8 are arranged as close as possible to the components of the dense phase powder pump 1 to be switched, it is avoided that in the corresponding pressure lines to the pneumatically operated valves 7, 8 or in the corresponding pressure line to the air exchange opening 13 of the powder feed chamber 4 there are large volumes which have to be either evacuated or filled with compressed air when the dense phase powder pump 1 is operated alternately. This can prevent excessive reaction delay times from occurring, which would ultimately also limit the frequency with which the dense phase powder pump 1 can feed coating powder.

As can be seen in particular from the depictions in the 1 to 2 can be seen, the powder dense phase pump 1 according to the invention advantageously has a modular structure in which the components “powder inlet 2 of the powder dense phase pump 1”, “powder inlet valve 7”, “powder conveying chamber 4”, “powder outlet valve 8” and “additional compressed air inlet device 9” together with “powder outlet 3 of the powder dense phase pump 1” are each designed as a modular component. The The module which forms the powder inlet 2 of the dense phase powder pump 1 is designated in the drawings with the reference number “61”, while the module 62 arranged downstream thereof forms the powder inlet valve 7. The modules 63 and 64 form the powder feed chamber 4 and the powder outlet valve 8, while the module 65 forms the combination of the additional compressed air inlet device 9 and the powder outlet 3 of the dense phase powder pump 1. The individual modules 61, 62, 63, 64 and 65 are axially aligned with respect to the common longitudinal axis L and mounted one behind the other on the material block 60.

The modular design of the dense phase powder pump 1 simplifies the maintenance of the pump considerably, since if necessary, for example in the event of a defect or for the purpose of maintenance and/or cleaning, the individual modules 61, 62, 63, 64 and 65 of the pump with the corresponding components can be replaced particularly easily and, in particular, quickly.

Because the dense phase powder pump 1 according to the invention uses only two powder valves (powder inlet valve 7 and powder outlet valve 8), which are preferably designed as pinch valves, the pump's susceptibility to failure is significantly reduced compared to conventional multi-chamber dense phase powder pumps, in which at least four powder valves and a correspondingly higher number of control valves must be used to control the powder valves. In particular, the number of wearing parts in the dense phase powder pump 1 according to the invention is reduced to a minimum, so that corrections to the settings of the dense phase powder pump 1 due to wearing parts are carried out much less frequently and a high level of reproducibility of the pump settings is guaranteed.

In addition, the single-chamber design used in the dense phase powder pump 1 according to the invention allows a particularly compact design of the pump. For example, with a dense phase powder pump 1 with a pump length of approx. 250 mm, a powder feed of up to 400 g of coating powder per minute is possible (pump width: 40 mm).

In the exemplary embodiments of the dense phase powder pump 1 according to the invention shown in the drawings, in order to reduce or avoid pulsations downstream of the powder outlet 3 of the dense phase powder pump 1, in particular the additional compressed air inlet device 9 already mentioned is provided, which is provided at the outlet of the powder outlet valve 8 or at the powder outlet 3 of the dense phase powder pump 1 in order to be able to feed additional transport compressed air into the powder path if required.

In the exemplary embodiments of the dense phase powder pump 1 according to the invention shown in the drawings, the additional compressed air inlet device 9 used has a filter tube 17 which has a circumference of at least 180° (in the embodiments shown a circumference of 360°) and forms, at least over a partial length of the corresponding powder path, a channel wall inner surface of at least 180° (in the embodiments shown in the drawings a channel wall inner surface of 360°) of the powder path circumference.

In other words, in the illustrated embodiments of the dense phase powder pump 1 according to the invention, the additional compressed air inlet device 9 has a filter tube 17 which surrounds the corresponding powder path at least over a partial length by 360°, so that the powder portion ejected from the powder feed chamber 4 of the dense phase powder pump 1 during a powder ejection phase can flow homogeneously through the filter tube channel 18 formed by the filter tube 17.

A compressed air chamber 19, designed as a compressed air ring chamber in the embodiment shown in the drawings, surrounds the filter tube 17 on its outer circumference. The compressed air chamber 19, designed here as a compressed air ring chamber, is surrounded on its radially inner circumference by the filter tube 17 and, at a distance from the filter tube 17, on its radially outer circumference by a housing 20. An air exchange opening 21 is introduced into the housing 20, through which compressed air can flow as required from a compressed air line 59 via a control valve V5 into the compressed air chamber 19 and from there through the filter tube 17 into the filter tube channel 18.

Depending on the amount of additional transport compressed air to be fed into the powder path per unit of time, the compressed air chamber 19 and the filter tube channel 18 formed by the filter tube 17 must be designed with a correspondingly larger volume.

As already explained, the filter tube 17 of the additional compressed air inlet device 9 consists of microporous material such that it is permeable to air but not to coating powder. The filter tube 17 preferably consists of a sintered body, for example of metal or plastic, or of a material mixture containing metal or plastic. Furthermore, it can consist of another material and/or be formed by a filter membrane.

The filter pores of the filter tube 17 are preferably designed in such a way that compressed air is guided into the powder path over a powder path area that is large both in the circumferential direction and in the longitudinal direction of the powder path. These micropores of the powder tube 17 can be inclined radially or in the axial direction to the powder path and/or open out of the filter tube 17 into the filter tube channel 18 tangentially to the powder path circumference and direct the compressed air accordingly. Due to the large surface area of the filter tube 17 on its inner circumference, the axial powder distribution in the filter tube channel 18 and thus also in the powder path downstream of the powder outlet 3 of the dense phase powder pump 1 can be homogenized with a small amount of compressed air. This makes it possible to avoid or at least reduce pulsations in the powder flow in the powder path. Furthermore, a homogenization of the powder density in the longitudinal direction and across the cross section of the powder path can be achieved.

The amount of transport compressed air fed into the powder path per unit of time can be kept so low that it has no or only a slight influence on the flow rate of the coating powder in the flow path. In addition, it is possible to increase the flow rate by increasing the pressure of the transport compressed air additionally fed in with the aid of the additional compressed air inlet device 9 in order to influence the flow rate of the coating powder.

The compressed air additionally fed into the powder path of the dense phase powder pump 1 as required by the additional compressed air inlet device 9 can flow in the form of jets or in the form of small air bubbles from the filter tube 17 into the filter tube channel 18, depending on the type of filter pores and the air pressure.

The filter tube 17 of the additional compressed air inlet device 9 should extend around the powder path over at least 180° of the powder path circumference, preferably over the full 360° of the powder path circumference.

The filter tube 17 of the additional compressed air inlet device 9 is preferably a rigid body. However, it could also be a flexible body.

According to a preferred embodiment of the invention, the additional compressed air is supplied to the additional compressed air inlet device 9 in a pulsating manner with a pulse frequency which is equal to or preferably greater than the frequency of the powder feed chamber 4, with which the powder feed chamber 4 delivers powder portions. For this purpose, a pulsating compressed air source or a compressed air pulse generator can be provided for the additional compressed air inlet device 9.

According to a further advantageous embodiment of the invention, a control device 90 is provided which is designed such that the pulse frequency of the additional compressed air supplied to the additional compressed air inlet device 9 can be adjusted depending on the powder discharge frequency of the powder feed chamber 4 in at least one of the following ways: for example, it can be adjusted manually and/or preferably automatically controllable or preferably adjustable. In an advantageous manner, the additional compressed air pulse frequency can thereby be increased with increasing powder discharge frequency and reduced with decreasing powder discharge frequency.

According to a further preferred embodiment of the invention, the control device 90 can advantageously be designed such that by means of it the amount of additional compressed air flowing through the additional compressed air inlet device 9 per unit of time can be adjusted as a function of the amount of powder conveyed in at least one of the following ways: for example, it can be adjusted manually and/or preferably can be controlled automatically or preferably can be regulated.

The control device 90 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 control device 90 can contain all control elements or two or more control devices can be provided. If it is desired to manually set the additional compressed air pulse frequency or the additional compressed air flow rate, a manual setting 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 dense phase 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 types of valves, and because powder deposits can be easily cleaned by the air flow in them. Pinch valves are valves that can be controlled by compressed air or by negative pressure. In principle, however, other controllable valves can also be used. Furthermore, it is also possible to use automatic valves instead of controllable valves, for example ball valves or flap valves, which are controlled by the differential pressure between the valve inlet side and the valve outlet side and thus automatically by the overpressure and underpressure. pressure prevailing in the powder feed chamber 4.

To control the operation of the powder dense phase pump 1, the already mentioned control device 90 is used, which is 3 is indicated schematically. The control device 90 is designed to suitably control the individual controllable components of the powder dense phase pump 1, in particular the control valves V1, V2, V3, V4 and V5, and to coordinate their actuation.

In the 4 and 5 In the schematically illustrated embodiments of the powder spray coating device 100 according to the invention, a further control valve V6 is provided, via which the powder feed chamber 4 can be subjected to high pressure in a cleaning cycle of the powder dense phase pump 1.

The control device 90 is preferably designed such that it opens the control valve V4 in preparation for the suction phase of the powder feed chamber 4, so that the compressed air provided in the pressure accumulator 57 or by the compressed air source 58 is guided via the compressed air supply line 56 and the air exchange opening 16 into the pressure chamber 15.2 of the powder outlet valve 8 designed as a pinch valve. As a result of this, the flexible elastic hose 14.2 of the powder outlet valve 8 designed as a pinch valve is squeezed together, as a result of which the powder path provided by the flexible elastic hose 14.2 is closed by the powder outlet valve 8.

When the powder outlet valve 8 is closed, the air exchange opening 13 provided in the housing 12 of the powder feed chamber 4 is fluidly connected to the vacuum source 52 with the aid of the control device 90 in order to generate a negative pressure in the interior of the powder feed chamber 4, so that coating powder can be sucked into the powder feed chamber 4 via the powder inlet 2 of the dense phase powder pump 1 and the (open) powder inlet valve 7 as well as the powder inlet 5 of the powder feed chamber 4.

According to preferred embodiments of the invention, in order to initiate the suction phase of the dense phase powder pump 1, the control device 90 generates a control signal for generating the negative pressure in the powder feed chamber 4 at the earliest at the same time as, or preferably a predetermined delay time later than, a control signal for opening the powder inlet valve 7, so that the build-up of the negative pressure in the powder feed chamber 4 begins at the earliest at the same time as the opening of the powder inlet valve 7, preferably 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 with a feed cycle of the powder feed chamber 4 of approximately 200 ms.

This ensures that the negative pressure in the powder feed chamber 4 counteracts an opening movement of the powder inlet valve 7, in particular 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 strongly than in the prior art, where a pressure reduction usually takes place in the corresponding powder feed chamber even before the powder inlet valve opens.

The control valve V3 is then fluidically connected to the compressed air supply line 56, as a result of which an overpressure is created in the pressure chamber 15.1 of the powder inlet valve 7 designed as a pinch valve, which causes the flexible elastic hose 14.1 of the powder inlet valve 7 designed as a pinch valve to be squeezed together. In this way, the powder inlet valve 7 is closed. The control valve V4 depressurizes the air exchange opening 17 of the pressure chamber 15.2 of the powder outlet valve 8 designed as a pinch valve or vents the pressure chamber 15.2. Due to the elasticity of the hose 14.2 of the powder outlet valve 8 designed as a pinch valve, this then immediately changes to its open state.

At this moment or immediately thereafter, the control valve V1 is switched with the aid of the control device 90 in such a way that the air exchange opening 13 formed in the housing 12 of the powder feed 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 V1, the intermediate chamber 11 and the filter element 10 into the powder feed chamber 4 and expels 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 conveying 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 additional compressed air inlet device 9 and the powder outlet 3 of the dense phase powder pump 1.

The control device 90 is designed in particular to pulse additional transport compressed air into the powder path between the powder outlet valve 8 and the powder outlet 3 of the powder dense stream via the additional compressed air inlet device 9. pump 1. In this case, it has proven to be advantageous if the additional transport compressed air fed into the powder path in pulses via the additional compressed air inlet device 9 is always fed into the powder feed chamber 4 during the entire or during a predetermined or predeterminable partial period of the suction phase in order to effectively avoid or minimize pulsations in the powder flow delivered by the dense phase powder pump 1.

In detail, for this purpose, the control device 90 is designed to fluidically connect the air exchange opening 21 of the compressed air chamber 19 of the additional compressed air inlet device 9 to the compressed air source 58 whenever the powder outlet valve 8 is closed.

In the 4 and 5 In the embodiments of the powder spray coating device 100 according to the invention shown, the individual compressed air supply lines 50, 54, 56 and 59 run into a control unit 91 in which the compressed air supply of the individual components of the powder spray coating device 100 is coordinated and controlled. In particular, the control unit 91 can also be used to set the amount of additional compressed air supplied to the powder spray coating gun 102 per unit of time via the compressed air inlet 106 of the powder spray coating gun 102, which serves to atomize, shape and/or otherwise influence the coating powder to be sprayed by the powder spray coating gun 102, and/or the amount of electrode flushing air supplied to the powder spray coating gun 102 per unit of time via the compressed air inlet 107 of the powder spray coating gun 102.

As can be seen from the schematic representation in 5 can be taken, it is advantageous if components are used to feed the additional compressed air into the powder path that are identical in construction to the components of the powder feed chamber here, which feed transport compressed air into the powder feed chamber 4 during the dispensing phase. The term “identical in construction” as used here refers in particular to the size and structure of the filter tube 17 used in the additional compressed air inlet device 9 and the filter 10 used in the powder feed chamber 4. In this way, it is ensured that the transport compressed air introduced into the powder feed chamber 4 during the dispensing phase experiences the same pneumatic resistance as the additional compressed air that is fed into the powder path downstream of the powder outlet valve 8 via the additional compressed air inlet device 9 during the powder suction phase.

The solution according to the invention is not limited to a powder dense phase pump 1, which has a powder inlet 2 at a first end region and a powder outlet 3 at an opposite second end region, which are shown in the illustrations according to the 1 to 5 Rather, the solution according to the invention is also suitable for embodiments in which - as in the 6 and 7 shown schematically - the single powder feed chamber 4 of the powder dense phase pump 1 has a powder passage 30 at one end region, which serves both as a powder inlet and as a powder outlet for the powder feed chamber 4. In the 6 and 7 In the embodiments shown, the powder inlet 2 of the dense phase powder pump 1 is connected to the powder passage 30 of the powder feed chamber 4 via the powder inlet valve 7 and the powder outlet 3 of the dense phase powder pump 1 is connected to the powder passage 30 of the powder feed chamber 4 via the powder outlet valve 8. In particular, a distributor 31 is used here, which in the 6 and 7 illustrated embodiments is designed as a Y-piece. Via this distributor 31, the powder passage 30 of the powder feed chamber 4 is fluidly connected to the powder inlet valve 7 on the one hand and the powder outlet valve 8 on the other hand.

In the 7 The schematically illustrated embodiment of the powder dense phase pump 1 differs from that in 6 shown embodiment in that the additional compressed air inlet device 9 is designed to be identical to the transport compressed air inlet device of the powder conveying chamber 4 in order to equalize the pneumatic resistances occurring when introducing the transport compressed air and when introducing the additional compressed air.

The structure and functionality of the other components of the 7 and 8th The embodiments shown correspond to the components of the embodiments according to the 1 to 5 , in which context reference is made to the previous statements.

The invention is not limited to the embodiments of the dense phase powder pump according to the invention shown in the drawings, but results from a combination of all the features disclosed herein.

Claims (31)

Powder dense phase pump (1) for conveying coating powder from a first powder reservoir (101) to a second downstream powder reservoir or a downstream powder spray coating gun (102), wherein the powder dense phase pump (1) is designed as a single-chamber powder dense phase pump and has only a single powder feed chamber (4) for feeding coating powder, wherein the dense phase powder pump (1) has a powder inlet (2) connected or connectable to the first powder reservoir (101) and a powder outlet (3) connected or connectable to the second powder reservoir or to the powder spray coating gun (102), wherein the single powder feed chamber (4) has a powder passage at one end region which serves both as a powder inlet and as a powder outlet, and wherein the dense phase powder pump (1) further has a powder inlet valve (7) via which the powder passage of the single powder feed chamber (4) is or can be connected to the powder inlet (2) of the dense phase powder pump (1) in terms of flow, and a powder outlet valve (8) via which the powder passage of the single powder feed chamber (4) is or can be connected to the powder outlet (3) of the dense phase powder pump (1), characterized in that that at least one additional compressed air inlet device (9) opens into the powder path after the powder outlet valve (8) at at least one point for supplying additional compressed air as additional transport compressed air as required, wherein the pulse frequency of the additional compressed air is at least as great as the frequency of the powder feed chamber (4) with which powder portions are dispensed from the powder feed chamber (4), and/or wherein the pulse frequency of the additional compressed air is as great as the frequency of the powder feed chamber (4) with which powder portions are dispensed from the powder feed chamber (4), and wherein the device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device (9) is designed to supply the additional compressed air to the at least one additional compressed air inlet device in antiphase with respect to the powder dispensing cycle of the powder feed chamber. Powder dense phase pump (1) according to Claim 1 , wherein a distributor (31), in particular in the form of a Y-piece, is further provided for fluidly connecting the powder passage of the powder feed chamber (4) with the powder inlet valve (7) on the one hand and the powder outlet valve (8) on the other hand. Powder dense phase pump (1) according to Claim 1 or 2 , wherein the additional compressed air inlet device (9) opens at least one point into the powder path between the powder outlet valve (8) and the powder outlet (3) of the dense phase powder pump (1). Powder dense phase pump (1) according to one of the Claims 1 until 3 , wherein the additional compressed air inlet device (9) has a filter tube (17) which has a circumference of at least 180° and forms a channel wall inner surface on at least 180° of the powder path circumference on a partial length of the powder path between the powder outlet valve (8) and the powder outlet (3) of the dense phase powder pump (1). Powder dense phase pump (1) according to Claim 4 , wherein the filter tube (17) consists of microporous material and is permeable to compressed air but not to coating powder. Powder dense phase pump (1) according to Claim 4 or 5 , wherein the filter tube (17) is surrounded by a compressed air chamber (19) which can be connected to a compressed air supply line (59) or a compressed air source (58). Powder dense phase pump (1) according to one of the Claims 4 until 6 , wherein the filter tube (17) and the channel wall inner surface formed by it extend over 360° of the powder path circumference. Powder dense phase pump (1) according to Claim 5 , wherein the micropores in the inner peripheral surface of the filter tube (17) open into the filter tube channel (18) of the filter tube (17) in a plurality of at least four different directions, of which at least two are different oblique longitudinal tube directions, in order to guide the additional compressed air in a corresponding plurality of different directions in the form of micro-thin streams into the filter tube channel (18). Powder dense phase pump (1) according to one of the Claims 4 until 8th , wherein the filter tube (17) is a sintered body, preferably made of metal or plastic or of a material mixture containing metal or plastic. Powder dense phase pump (1) according to one of the Claims 4 until 9 , wherein the filter tube (17) is a rigid body. Powder dense phase pump (1) according to one of the Claims 1 until 10 , wherein the additional compressed air inlet device (9) is designed to introduce additional compressed air in a pulsating manner into the powder path after the powder outlet valve (8). Powder dense phase pump (1) according to one of the Claims 1 until 11 , wherein the single powder feed chamber (4) has at least one air exchange opening (13) via which the powder feed chamber (4) can be temporarily supplied with transport compressed air for ejecting powder portions from the powder feed chamber (4), wherein the device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device (9) comprises a switching element element, in particular a 3/2-way valve, via which compressed air from a common compressed air source is alternately supplied to the at least one air exchange opening (13) of the powder conveying chamber (4) or to the at least one additional compressed air inlet device (9). Powder dense phase pump (1) according to one of the Claims 10 until 12 , wherein the single powder feed chamber (4) has at least one air exchange opening (13) via which the powder feed chamber (4) can be temporarily supplied with transport compressed air for the expulsion of powder portions from the powder feed chamber (4), wherein the amount of additional compressed air supplied to the at least one additional compressed air inlet device (9) per pump cycle is substantially equal to the amount of transport compressed air fed into the powder feed chamber (4) per pump cycle via the at least one air exchange opening (13). Powder dense phase pump (1) according to one of the Claims 1 until 13 , wherein the single powder feed chamber (4) has at least one air exchange opening (13) via which the powder feed chamber (4) can be temporarily supplied with transport compressed air for the expulsion of powder portions from the powder feed chamber (4), wherein the at least one additional compressed air inlet device (9) is designed such that the pneumatic resistance occurring when additional compressed air is fed into the powder path is substantially equal to the pneumatic resistance which occurs when the transport compressed air is introduced into the powder feed chamber (4). Powder dense phase pump (1) according to one of the Claims 1 until 14 , wherein a control device (90) is further provided for controlling the powder inlet valve (7) and/or the powder outlet valve (8) and for alternately applying an overpressure and a negative pressure in the single powder feed chamber (4). Powder dense phase pump (1) according to one of the Claims 1 until 15 , wherein the powder inlet valve (7) and the powder outlet valve (8) can be controlled separately from one another. Powder dense phase pump (1) according to one of the Claims 1 until 16 , wherein the powder inlet valve (7) and the powder outlet valve (8) are each designed as a pinch valve, preferably of the type which has a flexible elastic hose (14.1, 14.2) as a valve channel, which can be squeezed together in order to close the corresponding valve by means of actuating compressed air in a pressure chamber (15.1, 15.2) surrounding the hose (14.1, 14.2). Powder dense phase pump (1) according to Claim 17 , wherein a negative pressure can be applied in the pressure chamber (15.1, 15.2) of the corresponding valve to open the powder inlet valve (7) and/or the powder outlet valve (8). Powder dense phase pump (1) according to one of the Claims 1 until 18 , wherein the single powder feed chamber (4) has at least one air exchange opening (13) in order to alternately subject the single powder feed chamber (4) to overpressure or negative pressure. Powder dense phase pump (1) according to Claim 19 in combination with Claim 15 , wherein the control device (90) is designed to alternately connect the at least one air exchange opening (13) of the single powder feed chamber (4) to a vacuum line or vacuum source (52) for sucking coating powder into the single powder feed chamber (4) through the open powder inlet valve (7) while the powder outlet valve (8) is closed, or to connect it to a compressed air supply line (50) or compressed air source (58) for pneumatically ejecting a powder portion present in the single powder feed chamber (4) through the open powder outlet valve (8) while the powder inlet valve (7) is closed. Powder dense phase pump (1) according to Claim 19 or 20 , wherein the powder dense phase pump (1) has a compressed air/vacuum source (58, 52), and wherein the at least one air exchange opening (13) of the single powder conveying chamber (4) is connected or connectable to the compressed air/vacuum source (58, 52). Powder dense phase pump (1) according to one of the Claims 1 until 21 , wherein the single powder feed chamber (4) has a chamber wall, wherein the chamber wall of the single powder feed chamber (4) is formed over at least part of its length by a filter (10) which surrounds the powder feed chamber (4) and separates it from an intermediate chamber (11) which surrounds the filter (10) and is formed between the filter (10) and a powder feed chamber housing (12), wherein the filter (10) is permeable to gas but not to coating powder. Powder dense phase pump (1) according to Claim 22 combined with Claim 20 or 21 , wherein the at least one air exchange opening (13) of the single powder feed chamber (4) opens into the intermediate chamber (11), wherein the overpressure and the negative pressure can be transferred through the filter (10) into the powder feed chamber (4). Powder dense phase pump (1) according to Claim 14 in combination with Claim 22 , whereby the Additional compressed air inlet device (9) has a chamber wall which is formed over at least part of its length by a filter (17) which surrounds the powder path and separates it from an intermediate chamber (19) which surrounds the filter (17) and is formed between the filter (17) and a housing (20), wherein the filter (17) of the additional compressed air inlet device (9) is structurally identical to the filter (17) of the powder feed chamber (4). Powder dense phase pump (1) according to one of the Claims 1 until 24 , wherein a control device (90) is provided, by which the additional compressed air frequency can be adjusted, preferably automatically, depending on the powder discharge frequency of the powder conveying chamber (4), preferably automatically controllable or regulated. Powder dense phase pump (1) according to one of the Claims 1 until 25 , wherein a control device (90) is provided, by means of which the amount of additional compressed air flowing through the additional compressed air inlet device (9) per unit of time can be adjusted, preferably automatically controlled or regulated, depending on the amount of powder conveyed. Powder dense phase pump (1) according to one of the Claims 1 until 26 , wherein a control device (90) is provided, by means of which the additional compressed air is always fed in when the powder outlet valve (8) is closed. Powder dense phase pump (1) according to one of the Claims 1 until 27 , wherein a preferably one-piece material block (60) is provided, in or on which the single powder feed chamber (4) is formed or arranged, and wherein all control valves (V1, V3, V4, V5) which are fluidically connected to the single powder feed chamber (4) for the supply of transport compressed air and vacuum are arranged on the material block (60) and are directly fluidically connected to the single powder feed chamber (4) by means of channels which are formed in the material block (60). Powder dense phase pump (1) according to Claim 28 , wherein the powder inlet valve (7) and the powder outlet valve (8) are arranged on the material block (60), and wherein control valves (V3, V4) are provided which are directly connected in terms of flow to the powder inlet valve (7) and the powder outlet valve (8) by means of channels formed in the material block (60) for the supply and discharge of actuating compressed air. Powder spray coating device (100) for spray coating objects with coating powder, the powder spray coating device (100) comprising: - a powder dense phase pump (1) according to one of the Claims 1 until 29 ; and - at least one preferably automatic or manual spray coating gun (102) with a coating powder inlet (105), wherein the coating powder inlet (105) of the spray coating gun (102) is connected or connectable to the powder outlet (3) of the dense phase powder pump (1) via a powder line (104). Method for conveying coating powder from a first powder reservoir (101) to a second powder reservoir arranged downstream of the first powder reservoir (101) or to a spray coating gun (102) arranged downstream of the first powder reservoir (101), the method comprising the following method steps: - providing a powder spray coating device (100) according to Claim 30 ; and - carrying out the following operating cycle at least once: a) generating a negative pressure in the single powder feed chamber (4) of the dense phase powder pump (1) for sucking coating powder into the powder feed chamber (4) through the open powder inlet valve (7) of the dense phase powder pump (1), while the powder outlet valve (8) of the dense phase powder pump (1) is closed; b) closing the powder inlet valve (7) and opening the powder outlet valve (8); c) introducing compressed gas into the powder feed chamber (4) for discharging the coating powder from the powder feed chamber (4) through the open powder outlet valve (8), while the powder inlet valve (7) is closed; d) closing the powder outlet valve (8) and opening the powder inlet valve (7); characterized in that during cycle step a) or when changing from cycle step d) to cycle step a), additional compressed air is fed into the powder path after the powder outlet valve (8) at least at one point.

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