Powder conveying chamber for a powder-density current pump and powder-density current pump with a powder conveying chamber

Description

[0001] The present invention relates to a powder conveying chamber for a powder dense-phase pump according to the preamble of independent claim 1.

[0002] Accordingly, the invention relates to a powder conveying chamber for a powder dense-phase pump for conveying powder, in particular coating powder, wherein the powder conveying chamber has at least one air exchange opening, which is designed and configured to be alternately connected to a vacuum line or vacuum source or to a compressed air supply line or compressed air source for drawing powder into the powder conveying chamber.For the pneumatic ejection of a powder portion present in the powder conveying chamber, wherein the powder conveying chamber has an end region via which the powder conveying chamber is or can be connected to a powder line, wherein the end region of the powder conveying chamber is designed and configured as a transition region to reduce an effective flow cross-section of the powder conveying chamber to an effective flow cross-section of the powder line and / or to an effective flow cross-section of a valve, in particular a pinch valve, arranged between the powder conveying chamber and the powder line, wherein a flushing system is assigned to the end region via which flushing air, in particular in the form of compressed air, can be supplied to the end region as required in order to keep the end region free of powder deposits or to remove powder deposits at the end region.

[0003] The invention further relates to a powder dense-phase pump with at least one such powder conveying chamber.

[0004] The powder dense-phase pump according to the invention is used in particular for conveying coating powder from a first powder reservoir to a second powder reservoir arranged downstream of the powder dense-phase pump, or to a powder spray gun or similar device arranged downstream of the powder dense-phase pump for spraying coating powder. Powder dense-phase pumps (English: dense phase power pumps The aforementioned types are known in principle from the prior art. For example, EP 1 551 558 A1 relates to a dense-phase powder pump which has a first powder conveying chamber and a second powder conveying chamber arranged parallel to the first powder conveying chamber. The two powder conveying chambers of the dense-phase powder pump known from this prior art are each delimited on the suction side and the conveying side by a mechanically actuated pinch valve arrangement.

[0005] Specifically, the design provides that, in the intake and delivery sides of the powder dense-phase pump, the powder hoses connected to the respective powder delivery chambers of the pump are deformable by a mechanically actuated plunger in order to pinch off or open the hose section as needed. The two parallel powder delivery chambers operate in alternating phases, meaning that one chamber draws in coating powder through the powder inlet of the pump, while the other discharges a portion of coating powder previously drawn into the chamber through the pump's outlet.

[0006] Powder dense-phase pumps with several, in particular two, powder conveying chambers connected in parallel are also known from DE 10 2013 211550 A1, WO 2005 / 005060 A2 (US 2006 / 0193704 A1), DE 199 59 473 A1 (US 2001 / 0003568 A1) and EP 1 752 399 A1.

[0007] The use of dense-phase powder pumps for conveying coating powder to suitable devices for spraying coating powder, such as powder spray guns, is known from DE 196 11 533 B4, WO 2004 / 087331 A1, and EP 1 566 352 A2. Before the use of dense-phase powder pumps for conveying coating powder became known, powder pumps designed as injectors were used, and these are still used today for conveying coating powder. However, unlike dense-phase powder pumps, powder pumps designed as injectors, which are also referred to as "thin-phase powder pumps," have the disadvantage that these powder pumps can typically only convey a relatively small quantity of coating powder per unit of time.

[0008] Therefore, in practice, powder dense-phase pumps have become particularly prevalent for applications where a relatively large quantity of coating powder needs to be conveyed per unit of time.

[0009] In practical use, however, it has been shown that a powder dense-phase pump, such as that known from EP 1 551 558 A1, exhibits problems with the continuous conveying of certain types of powder, or requires relatively frequent maintenance.

[0010] The invention aims to solve the problem of preventing or at least reducing powder accumulation and blockages, particularly at the powder inlet side and / or outlet side of the powder conveying chamber of a dense-phase powder pump of the aforementioned type, in a simple manner. This is intended to apply especially to powder types that tend to clump and / or adhere during conveying.

[0011] In particular, a powder dense-phase pump of the aforementioned type is to be further developed in such a way that it is less prone to maintenance during operation and, in particular, ensures continuous and uniform powder conveying regardless of the type of powder.

[0012] This problem is solved according to the invention by the subject matter of independent claim 1.

[0013] Accordingly, the invention relates in particular to a powder conveying chamber for a powder dense-phase pump for conveying powder, especially coating powder, wherein the powder conveying chamber has an end region via which the powder conveying chamber is or can be connected to a powder line, optionally via a valve, in particular a pinch valve. The end region of the powder conveying chamber is designed as a transition region and configured to reduce the effective flow cross-section of the powder conveying chamber to the effective flow cross-section of the valve in the open state or to the effective flow cross-section of the powder line.

[0014] According to the invention, it is provided that a wall region forming the end region of the powder conveying chamber is designed, at least in part, as a porous wall region permeable to compressed air but impermeable to powder.

[0015] By providing such an end-area rinsing system, disruptive and therefore undesirable powder accumulations (powder aggregation) and a potentially associated powder blockage in the powder conveying mode of the dense-phase powder pump at the powder inlet and / or powder outlet of the powder conveying chamber can be effectively prevented.

[0016] Specifically, the flushing system can be used during the discharge phase of the powder dense-phase pump, and especially at the end of the discharge phase, or during a cleaning cycle of the powder dense-phase pump, to clean the corresponding end area and especially the intake and discharge area of ​​the powder conveying chamber.

[0017] For example, if, during the discharge cycle of the powder dense-phase pump, in addition to the transport compressed air introduced into the powder conveying chamber (by applying a corresponding overpressure to the powder conveying chamber), purging air is introduced into the end regions of the powder conveying chamber, effective purging of these end regions occurs. This optimally prevents or at least reduces powder aggregation and the associated clogging.

[0018] Several approaches are possible for implementing end-area flushing.

[0019] In preferred embodiments, the end region of the powder conveying chamber, which is at least partially conical, is designed as a filter that limits the circumference of the end region accordingly. The filter is permeable to air but not to coating powder and is surrounded by an annular chamber to which compressed air can be connected as needed.

[0020] In particular, according to implementations of the solution according to the invention, a control device is assigned to the rinsing system, which is configured to connect at least one rinsing air outlet of the end region of the powder conveying chamber to a compressed air supply line or a compressed air source as required. The control device is specifically configured to connect the at least one rinsing air outlet of the end region of the powder conveying chamber to the compressed air supply line or the compressed air source during cleaning operation.

[0021] Alternatively or additionally, the control device is designed to connect the at least one purge air outlet of the end area of ​​the powder conveying chamber to the compressed air supply line or the compressed air source in a flow-wise manner during a powder ejection cycle of the powder conveying chamber.

[0022] According to further developments of the aforementioned embodiments, the control device is designed to adjust the quantity of compressed air to be supplied to the at least one purge air outlet of the end region of the powder conveying chamber per unit of time, particularly depending on an operating state and / or an operating cycle of the powder conveying chamber. It is advantageous for the control device to supply a higher quantity of compressed air per unit of time to the at least one purge air outlet of the end region of the powder conveying chamber during cleaning operation compared to the quantity of compressed air supplied to the at least one purge air outlet per unit of time during powder discharge operation.

[0023] According to embodiments of the powder conveying chamber according to the invention, the end region of the powder conveying chamber is or can be connected to the powder line via a valve, in particular a pinch valve, wherein the valve, in particular a pinch valve, has an effective flow cross-section in its open state. It is advantageous for the end region of the powder conveying chamber to be designed in such a way as to reduce the effective flow cross-section of the powder conveying chamber to the effective flow cross-section of the valve, in particular a pinch valve, in its open state.

[0024] Like the end section of the powder conveying chamber, the powder conveying chamber itself or a main body section of the powder conveying chamber should have at least one air exchange opening, which is designed and constructed separately from a purge air outlet of the end section, and is alternately connected to a vacuum line or vacuum source or to a compressed air supply line or compressed air source for drawing powder into the powder conveying chamber or for pneumatically ejecting a portion of powder present in the powder conveying chamber and previously drawn in.

[0025] According to embodiments of the present invention, the powder conveying chamber has a first end region and an opposing second end region, wherein the powder conveying chamber is fluidically connected or connectable to a first powder line via the first end region and to a second powder line via the second end region. The first and / or second end region of the powder conveying chamber is each designed and configured as a transition region to reduce the effective flow cross-section of the powder conveying chamber to the effective flow cross-section of the corresponding powder line.In particular, this training course provides that both the first and the second end area are each assigned a rinsing system, via which rinsing air in the form of compressed air can be supplied to the respective end area as needed, in order to keep the corresponding end area free of powder deposits or to remove powder deposits from the end area.

[0026] Preferably, the diameter decreases at both ends of the powder conveying chamber, resulting in a reduction of the cross-sectional area and consequently, due to changing material velocities, turbulence and increased impact forces, which can ultimately lead to powder deposits on the conical surfaces. These deposits are more frequently observed at the inlet of the powder conveying chamber. To counteract this, the ends of the powder conveying chamber are equipped with a suitable flushing system. The ends of the powder conveying chamber can, in particular, be designed as separate, i.e., replaceable, end pieces, which consist at least partially of porous material and can be pressurized with compressed air, so that air flushing occurs on the inner conical surface of the end pieces.

[0027] According to embodiments of the invention, the rinsing system comprises a filter element that tapers, at least in part, and is permeable to air but not to powder. The conical filter element limits the circumference of the powder conveying chamber at its end region. The filter element is surrounded by an annular chamber formed by a filter housing, to which compressed air can be connected as needed.

[0028] The filter element is preferably detachably connected or connectable with its larger diameter end region to an end region of a main body region of the powder conveying chamber, particularly a cylindrical one. Conversely, the filter element is preferably detachably connected or connectable with its smaller diameter end region to an end region of the powder line or to an end region of a valve, particularly a pinch valve, arranged between the powder conveying chamber and the powder conveying line.

[0029] The invention further relates to a rinsing system for the end region of a powder conveying chamber, in particular a powder conveying chamber of the aforementioned type according to the invention. The rinsing system is designed, in particular, to supply rinsing air in the form of compressed air to the end region of the powder conveying chamber as required, in order to keep the end region free of powder deposits or to remove powder deposits at the end region.

[0030] The invention further relates to a dense-phase powder pump for conveying coating powder from a first powder reservoir to a second, downstream powder reservoir or a downstream powder spray gun or similar device for spraying coating powder. The dense-phase powder pump has at least one powder conveying chamber of the aforementioned type according to the invention, which is fluidically connected or connectable to the first powder reservoir via a powder inlet and to the second powder reservoir or to the powder spray gun or similar device for spraying coating powder via a powder outlet. An inlet valve and an outlet valve are provided at the powder inlet and outlet of the dense-phase powder pump, respectively.

[0031] In preferred embodiments of the powder dense-phase pump according to the invention, the powder inlet valve is designed to be correspondingly oversized compared to the powder outlet valve. This embodiment is based on the understanding that the powder inlet valve of the powder dense-phase pump is crucial for regulating the actual powder flow rate that the pump can deliver per unit of time. Therefore, according to embodiments of the powder dense-phase pump according to the invention, the at least one powder inlet valve has an effective flow cross-section in its open state that is larger than the effective flow cross-section of the powder outlet valve in its open state.

[0032] Alternatively, in embodiments of the powder dense-phase pump according to the invention, the at least one powder inlet valve and the at least one powder outlet valve have at least substantially the same effective flow cross-section in their respective open states. This embodiment has the advantage that identical valves can be used for the at least one powder inlet valve and the at least one powder outlet valve, which offers advantages with regard to maintenance and spare parts inventory.

[0033] According to the invention, the powder dense-phase 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 gun or similar device for spraying coating powder. The powder inlet of the powder dense-phase pump can be located at a first end region of the pump, and the powder outlet can be located at an opposite second end region of the pump, with the at least one powder conveying chamber of the pump being arranged between the powder inlet and the powder outlet.

[0034] In an advantageous embodiment of the present invention, the at least one powder conveying chamber of the powder dense-phase pump according to the invention has a powder inlet with at least one powder inlet valve at a first end region and a powder outlet with at least one powder outlet valve at an opposite second end region. The powder inlet of the at least one powder conveying chamber is fluidically connected or connectable to the powder inlet of the powder dense-phase pump via the at least one powder inlet valve. Conversely, the powder outlet of the at least one powder conveying chamber of the powder dense-phase pump is fluidly connected or connectable to the powder outlet of the powder dense-phase pump via the at least one powder outlet valve.

[0035] According to another aspect of the present invention, the powder dense-phase pump has a powder inlet connected or connectable to the first powder reservoir and a powder outlet connected or connectable to the second powder reservoir or to the powder spray coating gun or the like device for spraying coating powder, wherein the at least one powder conveying chamber of the powder dense-phase pump according to the invention has a powder passage at an end region which serves both as a powder inlet and as a powder outlet for the at least one powder conveying chamber.According to this aspect of the present invention, it is advantageous if the powder passage of the at least one powder conveying chamber is fluidly connected or connectable to the powder inlet of the powder dense-phase pump via the at least one powder inlet valve of the powder dense-phase pump, wherein the powder passage of the at least one powder conveying chamber is fluidly connected or connectable to the powder outlet of the powder dense-phase pump via the at least one powder outlet valve.

[0036] According to a preferred embodiment, the powder dense-phase pump further comprises a distributor to connect the powder flow path of the powder conveying chamber to the powder inlet valve on the one hand and the powder outlet valve on the other. A Y-piece is particularly suitable for use as the distributor. Of course, other embodiments are also possible.

[0037] In preferred embodiments of the solution according to the invention, a control device is further provided which is configured to alternately control the at least one powder inlet valve and / or the at least one powder outlet valve of the dense-phase powder pump. The control device is preferably further configured to alternately apply an overpressure and a vacuum in the at least one powder conveying chamber of the dense-phase powder pump.

[0038] The at least one powder conveying chamber of the dense-phase powder pump is preferably associated with a gas path through which the corresponding powder conveying chamber can be connected alternately to a vacuum line or vacuum source for drawing coating powder into the powder conveying 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 conveying chamber through the open powder outlet valve while the powder inlet valve is closed. The control device is designed to switch the single powder conveying chamber alternately between drawing in and ejecting powder.

[0039] In advantageous embodiments of the powder dense-phase pump according to the invention, the aforementioned gas path has a suction air opening and a compressed air opening in a housing circumferential wall of the powder conveying chamber. Preferably, a microporous filter element, preferably in the form of a filter tube, is also provided, which forms the circumferential wall of the powder conveying chamber for at least a partial length or preferably the entire length of the 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 circumferential wall and surrounds the filter element, which is preferably designed as a filter tube. The filter element, which is preferably designed as a filter tube, is permeable to air but not to coating powder due to its small pore size. It preferably consists of a sintered material.

[0040] The at least one powder inlet valve and the at least one powder outlet valve of the powder dense-phase pump according to the invention are preferably each designed as a pinch valve, in particular of the design which has a flexible elastic hose as a valve channel, wherein this flexible elastic hose can be squeezed together in a pressure chamber surrounding the hose to close the corresponding valve with the aid of actuating compressed air.

[0041] In this context, it is particularly advantageous if the at least one powder inlet valve and the at least one powder outlet valve, both designed as pinch valves, each have a pinch valve housing with a powder inlet and a powder outlet, as well as 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 such that the powder inlet and powder outlet of the pinch valve can be brought into fluid contact via the valve element formed as a hose section.

[0042] It is advantageous if the pinch valve housing has at least one connection for supplying compressed air (actuating compressed air) as needed into the space formed between the inner wall of the pinch valve housing and the valve element located inside the pinch valve housing. When actuating compressed air is supplied, an overpressure is created in the space between the inner wall of the pinch valve housing and the valve element, causing the valve element to be compressed radially and the pinch valve to close. If pressure is subsequently released in the pinch valve housing, the valve element returns to its initial state, so that a fluid connection exists between the powder inlet and outlet of the pinch valve via the valve element.

[0043] According to one aspect of the invention, it is further provided that during the suction phase of the powder conveying chamber, a vacuum is applied in the powder conveying chamber at the earliest simultaneously with, or preferably after a certain delay time, a control signal for opening the powder inlet valve located at the powder inlet of the powder conveying chamber. This ensures that the build-up of the vacuum in the powder conveying chamber begins at the earliest simultaneously with the opening of the powder inlet valve, but preferably after the aforementioned predetermined delay time. The predetermined delay time is preferably in a range between 0 ms and 50 ms, with a conveying chamber cycle (= pump cycle of the powder dense-phase pump) of approximately 200 ms. However, this example does not preclude the use of other delay times and cycle times for the powder dense-phase pump.

[0044] In advantageous implementations of the solution according to the invention, a vacuum is only applied in the powder conveying chamber during the suction phase of the powder dense-phase pump when the powder inlet valve is already open, or at the earliest simultaneously with the opening of the powder inlet valve. This ensures that the vacuum in the powder conveying chamber does not oppose the opening movement of the powder inlet valve, particularly when it is designed as a pinch valve, as strongly as in solutions known from the prior art and designed as multi-chamber powder dense-phase pumps, at least at the time of the beginning of the opening movement of the powder inlet valve.

[0045] To shorten the reaction time of the powder dense-phase pump according to the invention and thus to increase its delivery frequency, it is preferably provided, in addition to or as an alternative to the aforementioned measure, 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 pneumatically actuated pinch valves. Appropriate control valves are used to actuate these pinch valves, supplying actuating compressed air to the pinch valves in a coordinated manner.

[0046] According to preferred embodiments of the powder dense-phase pump according to the invention, the length of the pneumatic control lines to the pinch valves is shortened as much as possible in order to minimize reaction delay times when actuating the corresponding pinch valves, i.e., when supplying actuating compressed air, applying a vacuum, or venting the corresponding pinch valve housings.

[0047] For this purpose, in preferred embodiments of the powder dense-phase pump according to the invention, for example, a material block, preferably composed of several modules, is provided in which the at least one powder conveying chamber of the powder dense-phase pump is formed or on which the at least one powder conveying chamber of the powder dense-phase pump is arranged, wherein, advantageously, the powder inlet valve and the powder outlet valve of the at least one powder conveying chamber of the powder dense-phase pump are also arranged on this material block. In particular, the corresponding control valves, which serve for the pneumatic actuation of the powder inlet and powder outlet valves, preferably each designed as pinch valves, are connected to the powder inlet valve and the powder outlet valve, respectively.The powder outlet valve is directly connected via compressed air channels formed in the material block in such a way as to ensure the supply and removal of actuating air to the powder inlet and powder outlet valve designed as a pinch valve.

[0048] In this context, it is further advantageous if all control valves, which are fluidically connected to the at least one powder conveying chamber of the powder dense-phase pump according to the invention for the supply of transport compressed air (during the discharge phase of the powder dense-phase pump) and of vacuum (during the suction phase of the powder dense-phase pump), are arranged on the material block and are fluidically directly connected to the single powder conveying chamber by means of channels formed in the material block.

[0049] These measures make it possible to shorten the length of the pneumatic control lines to the pinch valves and the length of the air lines to the at least one powder conveying chamber as much as possible, in order to minimize reaction delay times when actuating the corresponding pinch valves, i.e. when supplying actuating compressed air or applying a vacuum or venting the corresponding pinch valve housings.

[0050] As already explained, the reaction time of the powder dense-phase pump according to the invention can be shortened, and thus the delivery frequency increased, by ensuring that during the suction phase of the powder dense-phase pump, i.e., when a vacuum is applied in the powder conveying chamber, this vacuum begins at the earliest simultaneously with the opening of the powder inlet valve located at the powder inlet of the powder conveying chamber. Alternatively or additionally, the pump frequency can be increased by shortening as much as possible the channels provided for the pneumatic actuation of the powder inlet valve and the outlet valve, which are designed as pinch valves, for supplying and removing actuating compressed air to the pinch valves.

[0051] In addition, it is advantageous if the path length of the channels or channels supplying the transport compressed air to the at least one powder conveying chamber, or the path length of the channels or channels for creating a vacuum in the powder conveying chamber, is shortened. This allows for a reduction in reaction delay times when the powder inlet valve or powder outlet valve is actuated, and when a vacuum is applied in the at least one powder conveying chamber during the suction phase or an overpressure during the discharge phase.

[0052] By increasing the delivery frequency of the powder dense-phase pump accordingly, sufficient homogeneity is ensured in the powder flow delivered at the powder outlet of the powder dense-phase pump.

[0053] 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, a supplementary compressed air inlet device is used in preferred implementations of the solution according to the invention, either additionally or alternatively to the measures mentioned above. This supplementary compressed air inlet device opens into the powder path at at least one point between the powder outlet valve associated with the at least one powder conveying chamber and the powder outlet of the dense-phase powder pump, or preferably directly downstream of the powder outlet of the dense-phase powder pump, and serves to supply supplementary compressed air as needed, which serves as additional transport compressed air.In other words, in addition to the transport compressed air introduced into the powder conveying chamber during the discharge phase of the powder dense-phase pump, additional transport compressed air is fed in at suitable times or events immediately before or after the powder outlet of the powder dense-phase pump by means of the additional compressed air inlet device.

[0054] To implement the at least one additional compressed air inlet device, a filter tube is preferably provided through which the powder path between the powder outlet valve and the powder outlet of the dense-phase powder pump runs, at least partially. Preferably, the powder path downstream of the powder outlet valve of the dense-phase powder pump is guided through the filter tube for a portion of its length. The filter tube is permeable to compressed air but not to the particles of the coating powder. It is advantageous to make the filter tube from a microporous material, such as sintered material. The filter tube forms a circumferential wall around the powder path and thus a relatively large surface area through which even small amounts of additional compressed air can flow homogeneously into the powder path and influence the powder particles in a way that homogenizes the powder concentration.

[0055] Of course, it is also possible to design the auxiliary compressed air inlet device without a filter element, in particular a filter tube. The filter element or filter tube merely serves to prevent powder particles from entering an auxiliary compressed air line connected to the auxiliary compressed air inlet device.

[0056] To effectively reduce or prevent flow pulsations in the powder path downstream of the powder outlet of the dense-phase powder pump, it is advantageous to introduce pulsating additional compressed air 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 equal to the frequency at which powder portions are dispensed from the powder feed chamber.

[0057] In preferred embodiments of the powder dense-phase pump according to the invention, the pulse frequency of the additional compressed air is equal to the frequency of the powder conveying chamber, i.e., the frequency at which powder portions are dispensed from the powder conveying chamber. In this context, it is advantageous to provide a device for supplying pulsating additional compressed air to the at least one additional compressed air inlet device. This device is advantageously configured such that the additional compressed air is supplied to the at least one additional compressed air inlet device in opposite phase with respect to the powder dispensing cycle of the powder conveying chamber. In this way, it can be ensured that the additional compressed air is always fed into the powder path downstream of the powder outlet valve when the powder outlet valve is closed.This measure allows the flow velocity in the powder line downstream of the powder outlet of the dense-phase powder pump to assume a constant value without fluctuations occurring.

[0058] The present invention is based in particular on the finding that, especially in the case of a single-chamber powder dense-phase pump, it is advantageous to supply additional compressed air as additional transport compressed air at the powder outlet of the powder dense-phase pump, wherein the powder-air mixture flows more homogeneously through the powder line downstream of the powder outlet of the powder dense-phase pump if the amount of additional compressed air supplied into the powder path downstream of the powder outlet valve during the intake phase of the powder conveying chamber is essentially the same as the amount of transport compressed air supplied into the powder conveying chamber during the powder discharge phase, which serves to pneumatically eject the powder portion previously drawn into the powder conveying chamber.

[0059] In order to realize this insight 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 conveying chamber.

[0060] A complex compressed air flow control system can be dispensed with, in particular, if the pneumatic resistances occurring when supplying the transport compressed air to the powder conveying chamber and when supplying the supplementary compressed air to the powder path are essentially the same. To achieve this, it is advantageous if at least the essential components of the supplementary compressed air inlet device—i.e., the components required for supplying the supplementary compressed air to the powder path—have the same design as the essential components of the powder conveying chamber—i.e., the components of the powder conveying chamber required for supplying the transport compressed air during the discharge phase of the powder conveying chamber.For example, in this context, it is conceivable that the auxiliary compressed air inlet device has a chamber wall which, at least along part of its length, is formed by a filter surrounding the powder path and separating it from an intermediate chamber that surrounds the filter and is located between the filter and a housing of the auxiliary compressed air inlet device. At least the filter of the auxiliary compressed air inlet device should be identical in design to the filter of the powder conveying chamber.

[0061] On the other hand, it is also conceivable that a control device is provided by which the additional compressed air frequency can be adjusted, preferably automatically, depending on the powder delivery frequency of the powder conveying chamber. In particular, by adapting the pulse frequency of the additional compressed air to the frequency of the powder conveying chamber, and advantageously by always feeding the additional compressed air into the powder path after the powder outlet valve of the dense-phase powder pump when the powder 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 quantity of transport compressed air is always used, which is necessary for transporting the coating powder.

[0062] Of course, it is also conceivable that additional compressed air is introduced into the powder path after the powder outlet valve of the powder dense-phase pump via the additional compressed air inlet device during the delivery phase of the powder dense-phase pump.

[0063] However, by only introducing additional compressed air into the powder path via the auxiliary compressed air inlet device when the powder dense-phase pump is in its suction phase, resources (compressed air and thus energy) for operating the powder dense-phase pump can be reduced. In particular, this also prevents an excess of transport compressed air from being present in the powder path downstream of the powder outlet of the powder dense-phase pump, thus preventing powder particles from being forced out of the spray jet at the consumer located downstream of the powder dense-phase pump (powder spray gun or similar device for spraying coating powder).

[0064] 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 powder dense-phase pump, can be adjusted, preferably automatically controlled or regulated, depending on the total amount of powder conveyed per unit of time.

[0065] With regard 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 or similar device for spraying coating powder arranged downstream of the first powder reservoir, the invention provides that the method comprises the process step of providing a powder spray coating device, which includes the powder dense-phase pump according to the invention and at least one spray coating gun, and the process step of performing a specific operating cycle, wherein this specific operating cycle comprises the following cycle steps: a) Creating a vacuum in the at least one powder conveying chamber of the dense-phase powder pump to draw coating powder into the powder conveying 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; b) Closing the powder inlet valve and opening the powder outlet valve; c) Introducing pressurized gas into the powder conveying chamber to discharge the coating powder from the powder conveying chamber through the open powder outlet valve while the powder inlet valve is closed; and d) Closing the powder outlet valve and opening the powder inlet valve.

[0066] According to one aspect of the inventive method, it is provided that, during cycle step c), purge air is injected into the powder path at at least one point at the powder outlet area of ​​the powder conveying chamber. Alternatively or additionally, it is provided that, during cycle step d), purge air is injected into the powder path at at least one point at the powder inlet area of ​​the dense-phase powder pump.

[0067] An exemplary embodiment of the invention is described in more detail below with reference to the accompanying drawings.

[0068] They show: FIG. 1 schematically and in an isometric view an exemplary embodiment of the powder dense-phase pump according to the invention with two powder conveying chambers arranged parallel to each other; FIG. 2 schematically and in an exploded view the in FIG. 1 The exemplary embodiment of the powder dense-phase pump according to the invention is shown; FIG. 3 schematically represents the operating principle of the exemplary embodiment of the powder dense-phase pump according to the invention. FIG. 1 ; and FIG. 4 schematically a pneumatic diagram for the exemplary embodiment of the powder dense-phase pump according to the invention. FIG. 1 .

[0069] The following section will first refer to the presentation in FIG. 3 The functioning of a powder dense-phase pump 1 according to an exemplary embodiment of the present invention is described, in which two powder conveying chambers 2, 2' arranged parallel to each other are used.

[0070] As schematically in FIG. 3 As shown, each of the two powder conveying chambers 2, 2' arranged parallel to each other has a main body section 3, in particular cylindrical, with an effective flow cross-section that is at least substantially uniform. Each main body section 3 of the two powder conveying chambers 2, 2' has a cylindrical, in particular circular cylindrical, jacket tube 4 and a filter element 5 located inside the jacket tube 4. The filter element 5 of the main body section 3 of the powder conveying chamber 2, 2' is in particular a cylindrical filter element 5.

[0071] Each powder feed chamber 2, 2' has a powder inlet with a powder inlet valve 6 and a powder outlet with a powder outlet valve 7. The respective powder inlet valves 6 are hereinafter also referred to as "first valves" or "intake-side valves". The powder outlet valves 7 are also referred to as "second valves" or "feed-side valves".

[0072] At the respective intake-side and conveying-side end regions of the main body sections of the powder conveying chambers 2, 2', these chambers have a transition region 8 designed to reduce the effective flow cross-section of the powder conveying chamber 2, 2' to the effective flow cross-section of the correspondingly connected powder line 9 or to the effective flow cross-section of the valve 6, 7 arranged between the powder conveying chamber 2, 2' and the powder line 9. The transition region 8 is, in particular, designed at least partially as a conical region.

[0073] The respective transition areas 8 arranged at the intake-side end region of the main body region 3 of the powder conveying chamber 2, 2' and at the conveying-side end region of the main body region 3 of the powder conveying chamber 2, 2' are designed as components separate from the main body region 3, which are detachably connected or connectable to the main body region 3 of the powder conveying chamber 2, 2'.

[0074] The transition areas 8 serve to adapt / reduce the nominal diameter of the main body area 3 of the powder conveying chamber 2, 2', i.e. the inner diameter of the main body area 3 of the powder conveying chamber 2, 2', to the nominal diameter of the correspondingly connected powder line 9 or to the nominal diameter of the intermediate valve 6, 7.

[0075] The transition areas 8 have a filter element 10, which is in particular cone-shaped and is housed in a filter housing 11.

[0076] During a suction process, a vacuum (negative pressure) is generated in one of the powder conveying chambers 2, 2' of the powder dense-phase pump 1. The negative pressure draws the powder to be conveyed, in particular coating powder, into the powder conveying chamber 2, 2' via the corresponding powder inlet. The fine-pored filter element 5 in the main body area 3 of the powder conveying chamber 2, 2' separates the powder. The powder conveying chamber 2, 2' is closed on the suction side and / or conveying side during the suction process by the corresponding conveying-side valve.

[0077] During the conveying process, the intake-side valve 6 on the powder inlet side of the powder conveying chamber 2, 2' is closed, while the conveying-side valve 7 is opened. The coating powder previously drawn into the powder conveying chamber 2, 2' during the intake process is then forced out of the powder conveying chamber 2, 2' and conveyed further by means of overpressure, which is built up with compressed air through the fine-pored filter element 5 of the main body area 3 of the powder conveying chamber 2, 2'.

[0078] As the depiction in FIG. 3 The intake and conveying process alternates between the two parallel powder conveying chambers 2, 2'. In other words, the two parallel powder conveying chambers 2, 2' are operated in opposite phases.

[0079] The schematic representation in FIG. 3 Furthermore, the functioning of the cone-shaped filter elements 10 in the transition area 8 at the powder outlet-side end area and at the powder inlet-side or conveying-side end area of ​​the main body area 3 of the powder conveying chamber 2, 2' is indicated.

[0080] In detail, according to implementations of the present invention, during the conveying process, i.e., when the intake-side valve 6 on the powder inlet side of the powder conveying chamber 2, 2' is closed and the conveying-side valve 7 is open, an overpressure is applied not only in an annular space between the cylindrical filter element 5 of the main body region 3 and the cylindrical shell region 4 of the main body region 3, but also at the respective conical filter element 10 of the transition regions 8. In this way, during the conveying process, purge air in the form of compressed air is supplied via the conical filter elements 10 to the two end regions of the powder conveying chamber 2, 2' in order to keep the end regions free of powder deposits or to remove powder deposits at the end regions.

[0081] The following refers to the representations in FIG. 1 and FIG. 2 An exemplary embodiment of a powder dense-phase pump 1 is described, in which two powder conveying chambers 2, 2' arranged parallel to each other are used according to an embodiment of the present invention.

[0082] In detail, it shows FIG. 1 Figure 1 shows an isometric view of the structure of a dense-phase powder pump 1 with two powder conveying chambers 2, 2' arranged parallel to each other, according to an exemplary embodiment of the present invention. The dense-phase powder pump 1 has two powder conveying chambers 2, 2', each of which has a cylindrical main body section 3 with a cylindrical, and in particular circular-cylindrical, jacket tube 4 and a gas-permeable filter element 5 arranged inside the jacket tube 4. The filter element 5 is preferably a rigid body made of sintered material, preferably sintered metal, for example bronze or aluminum, or sintered plastic or a sintered material mixture.

[0083] As is particularly evident in the FIG. 2 As can be seen from the exploded view shown, the main body section 3 of each powder conveying chamber 2, 2' has a transition section 8 on both the intake and conveying sides, which is detachably connected or connectable to the main body section 3 and is part of the powder conveying chamber 2, 2'. The transition section 8 serves to adapt / reduce the nominal diameter of the main body section 3 of the powder conveying chamber 2, 2' to the nominal diameter of an intake or conveying-side valve 6, 7.

[0084] In order to reduce the nominal diameter, i.e. the inner diameter of the cylindrical main body area 3 of the powder conveying chamber 2, 2', accordingly to the (reduced) nominal diameter of the corresponding valve 6, 7 or the corresponding powder line 9, each transition area 8 has a filter element 10 which tapers in particular conically towards the valve 6, 7 or towards the conveying line.

[0085] The filter element 10 – like the filter element 5 of the main body region 3 – is preferably a rigid body, in particular made of sintered material, preferably sintered metal, for example bronze or aluminum, or sintered plastic or a sintered material mixture. Of course, other embodiments are also possible for the filter element 10 of the transition region 8, which tapers conically towards the respective valve 6, 7.

[0086] The filter element 10, which tapers conically towards the corresponding valve 6, 7, defines the effective flow cross-section of the transition area 8 in order to adapt the nominal diameter of the main body area 3 of the powder conveying chamber 2, 2' to the nominal diameter of the valve 6, 7 connected to the respective end area of ​​the powder conveying chamber 2, 2'.

[0087] As shown in the exploded view in FIG. 2 The respective conically tapered filter element 10 of the transition area 8 can be removed and is detachably connected to the corresponding end area of ​​the main body area 3 of the powder conveying chamber 2, 2', in particular via a plug connection that can be fixed by means of a screw connection or by means of another detachable connection, for example by means of a bayonet fitting.

[0088] Each transition area 8 further comprises a corresponding filter housing 11 in which the conically tapered filter element 10 can be accommodated. An air space is formed between the inner area of ​​the filter housing 11 and the outer area of ​​the conically tapered filter element 10, which can be pressurized as required via a corresponding air duct.

[0089] At the powder inlet of each powder feed chamber 2, 2' of the in FIG. 1 and FIG. 2 In the schematically shown powder dense-phase pump 1, a first pinch valve 6 is provided at the suction-side end region of the powder conveying chamber 2, 2'. A second pinch valve 7 is connected at the respective conveying-side end region of the powder conveying chamber 2, 2', i.e., at the conveying-side end region of the transition region 8 of the powder conveying chamber 2, 2'.

[0090] Although in the exemplary embodiment, pinch valves (English: ) are used as powder inlet and powder outlet valves 6, 7. pinch valves) They can, of course, be of any type when used.

[0091] In the illustrated embodiment, the powder inlet side of the two first (suction-side) valves 6 is connected via supply line branches of a Y-connector 12 to a powder supply line 9, which leads, for example, to a powder container (not shown in the drawings). Hose connectors are used to connect the powder inlet side of the two first valves 6 (pinch valves) to the supply line branches of the Y-connector 12.

[0092] However, it is also conceivable that instead of a Y-connecting piece 12, the respective powder inlet sides of the first (suction-side) valves / pinch valves 6 are flow-connected to one or two different powder containers via separate powder supply lines.

[0093] In the illustrated embodiment, the powder outlets of the two second (conveyor-side) valve / pinch valves 7 are connected by dispensing line branches, for example also a Y-shaped line connector 12, to one end of a powder dispensing hose 9, the other end of which opens into a further (not shown) powder container. The powder dispensing line can be a rigid pipe, but is preferably a flexible hose.

[0094] At the in FIG. 1 and FIG. 2 In the illustrated embodiment, the powder feed chambers 2, 2' are each received in a holder 13 and locked therein. The powder feed chambers 2, 2' are connected to the holder 13, in particular by means of a detachable screw or bayonet connection.

[0095] The following refers to the exploded view according to FIG. 2 The construction of each powder conveying chamber 2, 2' used in the powder dense phase pump 1 is described in more detail.

[0096] Accordingly, each powder conveying chamber 2, 2' is divided into a main body area 3 with an at least essentially uniform effective flow cross-section and two transition areas 8 arranged at the respective end areas of the main body area 3 with a conical flow cross-section.

[0097] Each of the main body section 3 of a powder conveying chamber 2, 2', which is particularly cylindrical, is associated with a jacket tube 4, inside which a gas-permeable and at least substantially cylindrical filter element 5 is located. The jacket tube 4 with the filter element 5 contained within it forms the main body section 3 of each powder conveying chamber 2, 2'.

[0098] At the intake-side end region of the main body section 3 of the powder conveying chamber 2, 2', an intake-side transition region 8 of the aforementioned type is provided. In other words, a conically tapered filter element 10 with a corresponding jacket section 11 associated with the conically tapered filter element 10 is assigned to the intake-side end region of the main body section 3. The same applies, figuratively speaking, to the transition region 8 arranged accordingly at the conveying-side end region of the main body section 3 of the powder conveying chamber 2, 2'.

[0099] In the exemplary embodiment of the powder dense-phase pump 1 according to the invention shown in the drawings, the first (intake-side) valves 6 and the second (delivery-side) valves 7 are preferably each designed as pinch valves.

[0100] Each pinch valve 6, 7 has a pinch valve housing 15 with an inlet-side flange and an outlet-side flange. An elastically deformable valve element 14 is accommodated in the pinch valve housing 15. The elastically deformable valve element 14 is, in particular, an elastically deformable hose section. Each flange has a powder line connection (hose connection) to which a powder line 9 (powder hose) can be connected.

[0101] As shown, for example, in the pneumatic diagram FIG. 4 In each transition area 8, the conically tapered filter element 10 is arranged inside a corresponding filter housing 11 such that an inlet of the conically tapered filter element 10 can be brought into fluid contact with the outlet of the main body area 3 of the powder conveying chamber 2, 2'.

[0102] The filter housing 11 of the transition area 8 has a connection 16 to supply compressed air, if required, into the space formed between the inner wall of the filter housing 11 and the conically tapered filter element 10 located inside the filter housing 11. When compressed air is supplied, the area of ​​the conveying chamber 2, 2' formed by the transition area 8 is rinsed accordingly, and powder deposits are removed or prevented from accumulating there.

[0103] In the exemplary embodiment of the powder dense-phase pump 1 according to the invention shown in the drawings, each first and second valve 6, 7 is designed in particular as a pinch valve, wherein each pinch valve 6, 7 is assigned an elastically deformable valve element 14, which is arranged inside a corresponding pinch valve housing 15 in such a way that the inlet of the pinch valve 6, 7 can be brought into fluid contact with the outlet of the pinch valve 6, 7 via the valve element formed as an elastically deformable valve element 14.

[0104] The pinch valve housing 15 has a connection 17 to supply compressed air, as needed, into the space formed between the inner wall of the pinch valve housing 15 and the valve element 14 located inside the pinch valve housing 15. When compressed air is supplied, the valve element 14 is elastically deformed, thus interrupting the fluid connection between the inlet and outlet of the pinch valve 6, 7. Conversely, if no compressed air is present in the space between the inner wall of the pinch valve housing 15 and the valve element 14 located inside the pinch valve housing 15, the previously elastically deformed valve element 14 returns to its original state, in which a fluid connection exists between the inlet and outlet of the pinch valve housing 15.

[0105] A vacuum connection can also be connected via at least one connection of the pinch valve 6, 7 in order to evacuate the compressed air previously introduced into the space in order to quickly open the pinch valve.

[0106] The conically tapered filter element 10 of the transition region 8 is preferably designed as a gas-permeable filter element 10 over a circumference of at least 180° and preferably over a circumference of 360°. The filter element 10 preferably consists of a microporous material such that it is permeable to air but not to coating powder. The filter element 10 can, for example, consist 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.

[0107] The filter pores of the filter element 10 are preferably configured such that compressed air is guided over a relatively large powder path area, both circumferentially and longitudinally, of the filter element 10 into the powder path formed / defined by the transition area 8. The micropores of the filter element 10 can be inclined radially or axially to the powder path.

[0108] In FIG. 4 is an exemplary embodiment of a pneumatic scheme for the in FIG. 1 or FIG. 2 Powder dense-phase pump 1 shown schematically.

[0109] As in FIG. 4 As shown schematically, a control unit 100 is used to operate the powder dense-phase pump 1, which is located in FIG. 4 The control unit 100 is designed to control the individual controllable components of the powder dense-phase pump 1, in particular the control valves S1 to S8, and to coordinate their actuation.

[0110] This involves, firstly, the coordinated control of the pinch valves 6, 7 via the control valves S5, S6 and S7. Secondly, it involves the appropriate control of the control valves S1, S2 and S4 to supply compressed air or create a corresponding vacuum to the respective main body section 3 of the two powder conveying chambers 2, 2' in a coordinated manner. Furthermore, it involves the coordinated control of control valve S1 to supply compressed air as purge air to the respective transition sections 8 of the main body sections of the two powder conveying chambers 2, 2' in a coordinated manner.

[0111] The pneumatic diagram according to FIG. 4 This is characterized in particular by the fact that compressed air is supplied to the respective transition areas 8 at the intake-side and conveying-side end regions of the powder conveying chamber 2, 2'. Specifically, this preferably occurs simultaneously with the supply of compressed air to the main body region 3 of the corresponding powder conveying chamber 2, 2'.

[0112] Accordingly, the so-called cone flushing, i.e. the flushing in the respective transition areas of the powder conveying chamber 2, 2', is only activated during a cleaning cycle.

[0113] Alternatively or additionally, it is also conceivable that this cone cleaning is activated during powder transport operation. In particular, it is conceivable that the cone cleaning is operated at a lower intensity during powder transport and at a higher intensity during the cleaning operation itself. The additional volume of air introduced during cleaning also results in increased cleaning efficiency.

[0114] The invention is not limited to the embodiments shown in the drawings, but is defined by the respective subject matter of the following claims. Bezugszeichenliste

[0115] 1 Powder compaction pump 2, 2' Powder conveying chamber 3 Main body area 4 Jacket pipe 5 Filter element 6 Powder inlet valve 7 Powder outlet valve 8 Transition area 9 Powder line 10 Conical filter element 11 Filter housing 12 Y-connector 13 Bracket 14 Valve element (pinch valve) 15 Pinch valve housing 16 Connection on filter housing 17 Connection on pinch valve housing 100 Control unit S1 - S8 Control valve

Claims

1. A powder conveying chamber (2, 2') for a dense phase powder pump (1) for conveying powder, in particular coating powder, wherein the powder conveying chamber (2, 2') comprises at least one air exchange opening which is in particular designed and formed separately from a cleaning air outlet of the end region for alternately connecting fluidly to a vacuum line or vacuum source, respectively, or to a compressed air supply line or compressed air source, respectively for drawing powder into the powder conveying chamber (2, 2'), or, respectively, pneumatically expelling a portion of powder present within the powder conveying chamber (2, 2'), wherein the powder conveying chamber (2, 2') comprises an end region via which the powder conveying chamber (2, 2') is fluidly connected or connectable to a powder line (9), wherein the end region of the powder conveying chamber (2, 2') is configured as a transition region (8) and designed to reduce an effective sectional area of flow of the powder conveying chamber (2, 2') to an effective sectional area of flow of the powder line (9) and / or to an effective sectional area of flow of a valve (6, 7), in particular a pinch valve, arranged between the powder conveying chamber (2, 2') and the powder line (9), wherein the end region is allocated a cleaning system via which cleaning air in the form of compressed air can be supplied to the end region, particularly as necessary, in order to keep the end region free of powder deposits or to remove powder deposits at the end region, characterized in that a wall area of the end region forming the end region of the powder conveying chamber (2, 2') is designed at least partly as a porous wall area permeable to compressed air but not permeable to powder.

2. The powder conveying chamber (2, 2') according to claim 1, wherein the end region of the powder conveying chamber (2, 2') has at least one cleaning air outlet for blowing out the cleaning air as needed in a powder conveying path defined by the powder conveying chamber (2, 2') and in particular by the transition region (8).

3. The powder conveying chamber (2, 2') according to claim 1 or 2, wherein the cleaning system has a filter element (10) at least in part tapering in particular conically which is permeable to air but not to powder, wherein the filter element (10) is or can be accommodated in a filter housing (11) able to be supplied with cleaning air in the form of compressed air, particularly as necessary, wherein the filter element (10) is or can be preferably releasably connected to an end region of an in particular cylindrical main body region of the powder conveying chamber (2, 2') by its larger end region in terms of diameter, and wherein the filter element (10) is or can be preferably releasably connected to an end region of the powder line (9) or to an end region of a valve (6, 7), in particular a pinch valve, arranged between the powder conveying chamber (2, 2') and the powder line (9) by its smaller end region in terms of diameter.

4. The powder conveying chamber (2, 2') according to one of claims 1 to 3, wherein a control device (100) is assigned to the cleaning system which is designed to fluidly connect at least one cleaning air outlet of the end region of the powder conveying chamber (2, 2') to a compressed air supply line or a compressed air source when needed, wherein the control device (100) is in particular designed to fluidly connect the at least one cleaning air outlet of the end region of the powder conveying chamber (2, 2') to the compressed air supply line or the compressed air source during a cleaning operation; and / or wherein the control device (100) is in particular designed to fluidly connect the at least one cleaning air outlet of the end region of the powder conveying chamber (2, 2') to the compressed air supply line or compressed air source during a powder output cycle of the powder conveying chamber (2, 2').

5. The powder conveying chamber (2, 2') according to claim 4, wherein the control device (100) is designed to regulate - particularly as a function of an operating state and / or operating cycle of the powder conveying pump - the volume of compressed air to be supplied to the at least one cleaning air outlet of the end region of the powder conveying chamber (2, 2') per unit of time, wherein the control device (100) is in particular designed to supply a higher volume of compressed air per unit of time to the at least one cleaning air outlet of the end region of the powder conveying chamber (2, 2') during a cleaning operation compared to the volume of compressed air to be supplied to the at least one cleaning air outlet per unit of time during the powder output mode.

6. The powder conveying chamber (2, 2') according to one of claims 1 to 5, wherein the end region of the powder conveying chamber (2, 2') is fluidly connected or connectable to the powder line (9) by means of a valve (6, 7), in particular a pinch valve, wherein the valve (6, 7), particularly pinch valve, exhibits an effective sectional area of flow in its open state, and wherein the end region of the powder conveying chamber (2, 2') is designed to reduce an effective sectional area of flow of the powder conveying chamber (2, 2') to the effective sectional area of flow of the valve (6, 7), particularly pinch valve, in its open state; and / or wherein the powder conveying chamber (2, 2') comprises an in particular cylindrical main body region (3) having an at least substantially uniform effective sectional area of flow; and / or wherein the powder conveying chamber (2, 2') has a first end region and an oppositely disposed second end region, wherein the powder conveying chamber (2, 2') is or can be fluidly connected to a first powder line (9) via the first end region and is or can be fluidly connected to a second powder line (9) via the second end region, wherein the first and / or second end region of the powder conveying chamber (2, 2') is / are implemented as a transition region (8) and designed to reduce an effective sectional area of flow of the powder conveying chamber (2, 2') to an effective sectional area of flow of the corresponding powder line (9), and wherein a cleaning system is in each case allocated to the first and / or second end region via which cleaning air in the form of compressed air can be supplied to the respective end region, particularly as necessary, in order to keep the respective end region free of powder deposits or to remove powder deposits at the end region.

7. A dense phase powder pump (1) for conveying coating powder from a first powder reservoir to a second downstream powder reservoir or to a downstream powder spray coating gun or similar device for spraying coating powder, wherein the dense phase powder pump (1) has at least one powder conveying chamber (2, 2') according to one of claims 1 to 6 which is fluidly connected or connectable to the first powder reservoir via a powder inlet and to the second powder reservoir, or to the powder spray coating gun or similar device for spraying coating powder respectively, via a powder outlet, wherein at least one powder inlet valve (6) is provided at the powder inlet and at least one powder outlet valve (7) is provided at the powder outlet.

8. The dense phase powder pump (1) according to claim 7, wherein the at least one powder inlet valve (6) and the at least one powder outlet valve (7) have at least substantially the same effective sectional area of flow in their respective open state; or wherein the powder inlet valve (6) exhibits a larger effective sectional area of flow in the open state than an effective sectional area of flow of the powder outlet valve (7) in its open state.

9. The dense phase powder pump (1) according to claim 7 or 8, wherein the dense phase powder pump (1) is designed as a single-chamber dense phase powder pump (1) and only has a single powder conveying chamber (2, 2') for the conveyance of coating powder; or wherein the dense phase powder pump (1) is designed as a multi-chamber dense phase powder pump (1) and has a plurality of powder conveying chambers connected in parallel to each other for the conveyance of coating powder.

10. The dense phase powder pump (1) according to one of claims 7 to 9, wherein the at least one powder conveying chamber (2, 2') has the powder inlet at a first end region and the powder outlet at an oppositely disposed second end region, wherein the at least one powder inlet valve (6) and at least one powder outlet valve (7) are arranged at respectively opposite end regions of the at least one powder conveying chamber (2, 2'); or wherein the at least one powder conveying chamber (2, 2') has a powder duct at one end region which serves both as a powder inlet as well as a powder outlet, wherein the at least one powder inlet valve (6) and at least one powder outlet valve (7) are in each case provided in the powder duct, wherein preferably a distributor, particularly in the form of a Y-piece, is furthermore provided for fluidly connecting the powder duct of the at least one powder conveying chamber (2, 2') to the at least one powder inlet valve (6) on one side and the at least one powder outlet valve (7) on the other.

11. The dense phase powder pump (1) according to one of claims 7 to 10, wherein a control device (100) is furthermore provided to control the at least one powder inlet valve (6) and / or the at least one powder outlet valve (7) as well as to alternately apply positive pressure and negative pressure in the at least one powder conveying chamber (2, 2'), wherein preferably the at least one powder inlet valve (6) and the at least one powder outlet valve (7) are separately controllable; and / or wherein the at least one powder inlet valve (6) and the at least one powder outlet valve (7) are each designed as a pinch valve, preferably of the style having a flexible elastic hose (14) as a valve channel which is able to be squeezed together in a pressure chamber (15) surrounding the hose (14) by means of actuating compressed air in order to close the corresponding valve (6, 7); and / or wherein a control device (100) is provided which is designed to alternately connect at least one air exchange opening of the at least one powder conveying chamber (2, 2') to a vacuum line or vacuum source for drawing coating powder into the at least one powder conveying chamber (2, 2') through the at least one open powder inlet valve (6) while the at least one powder outlet valve (7) is closed or to a compressed air supply line or compressed air source for pneumatically expelling a portion of powder present within the at least one powder conveying chamber (2, 2') through the at least one open powder outlet valve (7) while the at least one powder inlet valve (6) is closed.

12. The dense phase powder pump (1) according to one of claims 7 to 11, wherein at least one auxiliary compressed air inlet device furthermore empties into the powder path at least at a location after the at least one powder outlet valve (7) for supplying auxiliary compressed air as supplementary conveying compressed air when needed, wherein the auxiliary compressed air inlet device in particular empties into the powder path at least at a location between the powder outlet valve (7) and the powder outlet of the dense phase powder pump (1).

13. The dense phase powder pump (1) according to claim 12, wherein the auxiliary compressed air inlet device is designed to introduce auxiliary compressed air into the powder path in a pulsating flow.

14. The dense phase powder pump (1) according to claim 12 or 13, wherein a device for supplying pulsating auxiliary compressed air to the at least one auxiliary compressed air inlet device is further provided, wherein the pulse frequency of the auxiliary compressed air is at least the same as the frequency of the at least one powder conveying chamber (2, 2') at which portions of powder are dispensed from the at least one powder conveying chamber (2, 2').

15. The dense phase powder pump (1) according to claim 14, wherein the pulse frequency of the auxiliary compressed air is the same as the frequency of the at least one powder conveying chamber (2, 2') at which portions of powder are dispensed from the powder conveying chamber (2, 2'), and wherein the device for supplying pulsating auxiliary compressed to the at least one auxiliary compressed air inlet device is designed such that the auxiliary compressed air is supplied to the at least one auxiliary compressed air inlet device in phase opposition with respect to the powder dispensing cycle of the at least one powder conveying chamber (2, 2').