Patent Grant
9815074
The present invention relates to a powder supply device for a powder coating system.
The device according to the invention is particularly suitable for supplying powder to a powder coating system used to electrostatically spray coat objects in which fresh coating powder (hereinafter also called “fresh powder”) and, as applicable, reclaimed coating powder (hereinafter also called “recovered powder”) is situated in the powder container and is supplied to a powder dispensing mechanism of a spraying device. The spraying device can be designed for example as a manual spray gun or an automatic spray gun.
A powder injector is normally used as the powder dispensing mechanism. It is thereby provided for compressed air from the feed air connection of the powder injector to be pushed through a venturi nozzle into the collector nozzle. On its way through the powder injector, the feed air passes across a powder suction tube connected to the powder container at which point coating powder is sucked out of the powder container due to the negative pressure.
The powder container is thereby fed fresh powder as needed via a fresh powder line from a supplier's container with which the powder supplier supplied the fresh powder to the powder user. The powder forms a compact mass in the supplier's container. By contrast, the coating powder should be in a fluidized state in the powder container so that it can be for example pumped out by the suction effect of the powder dispensing mechanism (powder injector) and be fed to the spraying device as a flow of powder. A powder supply device therefore in particular comprises a powder container serving as a powder chamber for storing coating powder, wherein the coating powder is normally fluidized in the powder container so that it can be more easily conveyed pneumatically to either another powder container or to a powder spraying device.
As already indicated, the powder spraying device can be a manual or automatic powder spraying device which can have a spray nozzle or a rotary atomizer.
The powder supply device disclosed herein is based on the problem of known powder supply devices generally having a high compressed air requirement. In addition, only with difficulty can conventional powder supply devices generate a precisely adjustable continuous flow of powder.
Accordingly, a powder supply device is disclosed having a reduced compressed air need during operation and additionally achieving a maximum of precision as regards the powder flow rate.
In particular, a powder supply device for a powder coating system is disclosed having at least one powder container comprising a powder chamber for coating powder. Unlike with the known prior art powder supply devices, the inventive solution does not use a powder injector as a powder dispensing mechanism; instead at least one dense phase powder pump is provided which is connected or connectable to a powder dispensing channel emptying into the powder chamber via a powder discharge opening so as to suck coating powder out of the powder chamber during the powder coating operation of the powder coating system.
According to one aspect of the invention, the at least one dense phase powder pump of the powder supply device is designed in particular as a single-chamber dense phase powder pump comprising just one powder feed chamber for drawing the coating powder.
A plurality of advantages are achieved with the powder supply device according to embodiments of the invention. For instance, using a dense phase powder pump, particularly a single-chamber dense phase powder pump, can achieve a maximum of precision with respect to the powder feed rate. Additionally, the powder supply device consumes considerably less air with the dense phase powder pump than with powder injectors.
The powder pump is in particular directly connected or connectable to the powder dispensing channel emptying into the powder chamber via the powder discharge opening. This results in a particularly short suction distance to the benefit of the adjustability and reproducibility of the powder flow rate. Lastly, the inventive powder supply device requires considerably less space.
One preferred further development of the powder supply device provides for the powder dispensing channel to be formed in a side wall of the powder container and the dense phase powder pump be connected or connectable to the powder dispensing channel via a suction tube connector. Providing the powder dispensing channel in the side wall of the powder container can allow the powder pump to be fixed particularly close to the powder container. The powder pump is hereby fixed at a particularly close distance from the powder discharge opening configured as a suction pump. Accordingly, the lifting effort required to convey the coating powder through the powder dispensing channel is fundamentally reduced. The short suction distance also has a positive effect on the adjustability and reproducibility of the powder flow rate. The dense phase powder pump can thereby be connected or connectable to the powder dispensing channel via a separate suction tube connector. By means of the suction tube connector, it is conceivable for previously known powder containers to be retrofit with the dense phase powder pumps designed as single-chamber pumps.
The powder supply device can additionally comprise a suction tube fluidly connected or connectable to a through-hole of the suction tube connector. The suction tube is thereby in particular configured so as to be insertable into the powder dispensing channel. The suction tube, which is connected or connectable to the suction tube connector, enables the inner diameter of the powder dispensing channel to be easily varied. For example, the suction tube can thereby have an inner diameter of 3 mm to 10 mm, preferably an inner diameter of 5 mm to 8 mm, and more preferably an inner diameter of 4 mm. Reducing the diameter of the powder dispensing channel by means of the suction tube can improve the suction performance of the powder pump. This is due in particular to the reduced quantity of powder within the powder dispensing channel as well as the slower venting of the powder.
According to one embodiment of the inventive powder supply device, the suction tube comprises a hopper region of expanded inner diameter at an end section opposite the suction connector. The hopper region effectively prevents deposits of coating powder at the inlet of the suction tube. This is thus particularly the case due to the hopper region creating a gradual transition between the inner diameter of the powder dispensing channel and the inner diameter of the suction tube.
It is lastly noted that the suction tube can exhibit a length which substantially corresponds to the length of the powder channel. This thereby allows easily reducing the inner diameter of the powder channel along its entire length. As will be described in greater detail particularly in conjunction with the figures, the length of the suction tube is thereby dimensioned specifically such that the suction tube does not enter into the interior of the powder chamber.
According to a further realization of the inventive powder supply device, the powder dispensing channel comprises a lower end section via which the powder dispensing channel empties into the powder chamber through a powder discharge opening. An upper end section to which the suction tube connector is fixed or fixable is additionally provided, wherein the upper end section of the powder dispensing channel is situated at an upper end section of the powder container. In other words, the suction tube connector, and thus the dense phase powder pump, is fixed to an upper end section of the powder container. Doing so thereby prevents the coating powder from rising out of the powder chamber into the powder pump when it is switched off.
The upper end section of the powder dispensing channel can thereby comprise a preferably cylindrical recess designed to receive the preferably cylindrical suction tube connector. The suction tube connector can accordingly be easily force-fit connected to the upper end section of the powder dispensing channel. Alternatively or additionally hereto, it is of course also conceivable to use fixing means to mount the suction tube connector to the upper end of the powder dispensing channel. To this end, engaging means (e.g. retaining screws) can for example be driven into the powder container housing. It is particularly preferential for the suction tube connector to be configured and accommodated in the recess such that it projects over the upper end section of the powder container. In other words, the suction tube connector of this implementation forms an extension, whereby the at least one powder pump can be fixed to the powder container of the inventive powder supply device. It is hereby for example conceivable to fit the at least one powder pump onto the extension formed by the suction tube connector.
According to a further aspect of the inventive powder supply device, the dense phase powder pump comprises a connecting element detachably affixed to a first end section of the dense phase powder pump facing the suction tube connector. The connecting element is in particular designed so as to create a force-fit connection between the suction tube connector and the dense phase powder pump. As will be described in greater detail below, the connecting element is thereby particularly used to realize a connection between a feed channel in the powder pump and the powder dispensing channel.
Particularly in the case of the suction tube connector—as noted above—being configured as an extension, the connecting element can preferably comprise a recess formed on the end section facing the suction tube connector. The recess is in particular designed so as to receive the projecting section (extension) of the suction tube connector. Alternatively or additionally hereto, the connecting element can of course also be connected to the suction tube connector via fixing means (e.g. retaining screws).
According to a further aspect of the present invention, the dense phase powder pump comprises a powder inlet connected or connectable to the (upstream) powder dispensing channel and a powder outlet connected or connectable to the (downstream) powder reservoir on the output side or to a device for spraying the coating powder. The powder inlet can thereby be arranged on a first end section of the dense phase powder pump and the powder outlet arranged on second end section of the dense phase powder pump opposite thereto, whereby the (single) powder feed chamber is arranged between the powder inlet and the powder outlet of the dense phase powder pump. According to this embodiment, the above-cited connecting element can be designed so as to be connected or connectable to the powder inlet such that the powder inlet of the dense phase powder pump is substantially flush with an outer surface of the side wall. In other words, the powder inlet is fit as close as possible to the upper end section of the powder dispensing channel. This again reduces the suction distance, whereby the lifting effort required to convey the powder is reduced.
According to one advantageous realization of the present invention, the (preferably one) powder feed chamber of the dense phase powder pump comprises a chamber intake at a first end section and a chamber exit at an opposite second end section.
The dense phase powder pump furthermore accordingly comprises a powder inlet valve by means of which the chamber intake of the powder feed chamber can be fluidly connected or connectable to the powder inlet and a powder outlet valve by means of which the chamber exit of the single powder feed chamber can be fluidly connected or connectable to the powder outlet of the dense phase powder pump. This thus particularly allows the powder pump to operate in two different pump phases. Specifically, there is thereby an intake phase as well as a feed phase, the principle of which is known from the prior art relative to dense phase powder pumps. Hence, the inventive powder supply device achieves a particularly continuous powder supply. The powder inlet valve also prevents coating powder from infiltrating into the powder feed chamber through the powder discharge line in the deactivated state of the powder pump.
According to a further preferred embodiment of the inventive solution, a control device is further 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 particularly designed to alternately generate a positive pressure and a negative pressure in the (single) powder feed chamber of the dense phase powder pump. As noted above, doing so thus enables two-phase operation of the powder pump. In particular, generating a negative pressure initiates an intake phase and generating a positive pressure initiates a feed phase. It is thereby of particular advantage when the control device can control the powder inlet valve and the powder outlet valve separately from each other.
The powder inlet valve and the powder outlet valve of the inventive powder supply device are each respectively designed as a pinch valve, particularly of the design having a flexible, elastic tube as the valve channel, wherein this flexible, elastic tube can be squeezed by means of actuating compressed air in a pressure chamber surrounding the tube to close the respective valve.
In conjunction hereto, it is particularly advantageous for the powder inlet valve designed as a pinch valve and the powder outlet valve designed as a pinch valve respectively to have a pinch valve housing with a powder inlet and a powder outlet as well as an elastically pliable valve, preferably in the form of a tube section. In detail, the valve element should thereby be arranged in the interior of the pinch valve housing such that the powder inlet of the pinch valve can be brought into fluid connection with the powder outlet of the pinch valve by means of the valve element formed as a tube.
It is thereby particularly advantageous for the pinch valve housing to comprise at least one connection for supplying compressed air (actuating compressed air) as needed to the space (pressure chamber) formed between the inner wall of the pinch valve housing and the valve element arranged in the interior of the pinch valve housing. Positive pressure is generated in this pressure chamber between the inner wall of the pinch valve housing and the valve element upon actuating compressed air being supplied, in consequence of which the valve element is radially squeezed and the pinch valve closed. When a release of pressure follows in the pinch valve housing (for example by negative pressure being generated), the valve element returns to its initial state such that the valve element creates a fluid connection between the powder inlet of the pinch valve and the outlet of the pinch valve.
As already indicated, it is further conceivable in this regard for the pinch valve housing to comprise a connection to generate a negative pressure in the interior of the pinch valve housing as needed so as to thereby considerably reduce the time the pinch valve remains open.
To further increase the homogeneity of the powder flow at the powder outlet of the dense phase powder pump, and particularly to prevent the occurrence of disruptive pulsations in the dense phase powder pump's powder flow (downstream of the powder outlet), one preferential realization of the inventive solution makes use of an auxiliary pressure inlet device additionally or alternatively to the measures specified above. Said auxiliary pressure inlet device feeds into at least one point in the powder path between the powder outlet valve associated with the single powder feed 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 additional compressed air serving as auxiliary compressed conveyor air as needed. In other words, in addition to the compressed conveyor air introduced into the powder feed chamber during the feed phase of the dense phase powder pump, the auxiliary compressed air inlet device supplies additional conveyor air directly ahead or behind of the powder outlet of the dense phase powder pump at applicable times or upon applicable events.
In accordance with a further aspect of the invention, the powder supply device comprises a plurality of dense phase powder pumps, particularly single-chamber dense phase powder pumps, each connected or connectable to a powder discharge channel of the powder chamber. The powder discharge channels of the plurality of dense phase powder pumps are thereby configured in two opposite side walls of the powder chamber. Particularly the design of the powder pump as a single-chamber dense phase powder pump enables maximizing the number of powder pumps used. This thereby achieves a particularly high pumping capacity. Of course, alternatively or additionally to fixing the powder discharge channels in the side walls of the powder chamber, it is also conceivable for them to be configured in the third and fourth side walls of the powder chamber.
According to a further embodiment, the at least one dense phase powder pump is arranged next to the powder chamber such that a side surface of the dense phase powder pump facing the powder chamber abuts an outer surface of the powder chamber side wall. Particularly in combination with the suction connector designed as an extension, this can thereby achieve the simple fitting of the dense phase powder pump on the powder chamber. The dense phase powder pump is accordingly particularly horizontally aligned and supported by the side wall of the powder chamber.
Lastly, in accordance with a further realization, it can be provided for the at least one dense phase powder pump to be arranged at a height relative to the powder chamber which substantially corresponds to the adjustable powder level in the powder chamber. As already indicated above, doing so can achieve keeping the lift required to convey the coating powder as low as possible.
The powder chamber of the powder supply device can exhibit any form, wherein preferential however is a cube-shaped, cylindrical, conical or frustoconical configuration. It is particularly conceivable in this regard for the powder chamber to be configured beneath or within a cyclone separator.
The following will reference the embodiment examples depicted in the drawings in describing the inventive powder supply device in greater detail.
Shown are:
For reasons of clarity, analogous components will be provided with the same reference numerals in the following detailed description of the figures.
Powder pumps 4 are provided to pneumatically pump the coating powder. These can be dense phase powder pumps in which coating powder is suctioned out of a powder container by means of negative pressure, wherein the powder is then expelled from a powder feed chamber under positive pressure and flows to a spraying device.
To generate the compressed air for the pneumatic pumping of the coating powder and the fluidizing of the coating powder, a compressed air source 6 is provided which is connected to the various devices by means of the appropriate pressure setting elements 8, for example pressure regulators and/or valves.
Fresh powder from a powder supplier is dispensed from a supplier's container, which for example can be a small container 12 e.g. in the form of a dimensionally stable container or a bag containing a powder quantity of for example between 10 and 50 kg, e.g. 25 kg, or for example a large container 14, e.g. likewise in a dimensionally stable container or a bag containing a powder quantity of for example between 100 kg and 1000 kg, into a fresh powder line 16 or 18 of a screening device 10 by means of a powder pump 4. The screening device 10 can be provided with a vibrator 11. In the following description, the terms “small container” and “large container” respectively refer both to “dimensionally stable containers” as well as “non-dimensionally stable, flexible bags” unless explicit reference is made to one or the other container type.
The coating powder screened through the screening device 10 is conveyed via one or more powder feed lines 20, 20′ by gravity or preferably by a respective powder pump 4 through powder inlet openings 26, 26′ into a powder chamber 22 of a dimensionally stable powder container 24. The volume of the powder chamber 22 is preferably substantially smaller than the volume of the small fresh powder container 12. According to one conceivable realization of the inventive solution, the powder pump 4 of the at least one powder feed line 20, 20′ to the powder container 24 is a compressed air thrust pump. The first section of the powder feed line 20 can hereby serve as a pump chamber in which screened powder from the screening device 10 falls through a valve, for example a pinch valve. After this pump chamber holds a certain portion of powder, the powder feed line 20 is fluidly isolated from the screening device 10 by closing the valve. The portion of powder is thereafter pushed through the powder feed line 20, 20′ into the powder chamber 22 by compressed air.
Powder pumps 4, e.g. dense phase powder pumps 200, are connected to one or preferably a plurality of powder outlet openings 36 in the powder container 24 to pump coating powder through the powder lines 38 to spraying devices 40. The spraying devices 40 can comprise spray nozzles or rotary atomizers to spray the coating powder 42 onto the object 2 to be coated, which is preferably situated in a coating booth 43. The powder outlet openings 36 can be—as shown in
In the embodiment of the powder container 24 depicted in
The powder chamber 22 can be provided with a fluidizing device 30 for fluidizing the coating powder taken into the powder container 24. The fluidizing device 30 comprises at least one fluidizing wall of an open-pored or narrow-holed material which is permeable to compressed air but not to coating powder. Although not shown in
Coating powder 42 which does not adhere to the object 2 to be coated will be sucked into a cyclone separator 48 as excess powder through an excess powder line 44 by a flow of suction air from a blower 46. The cyclone separator 48 separates as much excess powder from the suction air flow as possible. The separated portion of powder is then fed as reclaimed powder or recovered powder through a reclaimed powder line 50 from the cyclone separator 48 to the screening device 10 where it passes through the screening device 10, either alone or mixed with fresh powder via powder feed lines 20, 20′, to re-enter the powder chamber 22.
Depending on the type of powder and/or how dirty the powder is, the option can also be provided of separating the reclaimed powder line 50 from the screening device 10 and routing the reclaimed (recovered) powder into a waste receptacle as is schematically depicted in
The powder container 24 can be provided with one or more, for example two, sensors S1 and/or S2 to control the supply of coating powder in the powder feed lines 20, 20′ to the powder chamber 22 by means of the control device 3 and the powder pumps 4. For example, the lower sensor S1 detects a lower powder level limit and the upper sensor S2 an upper powder level limit.
The lower end section 48-2 of the cyclone separator 48 can be designed and used as a storage container for reclaimed powder and provided with one or more, preferably two, sensors S3 and/or S4 operatively coupled to the control device 3 for that purpose. Doing so allows for example automatically stopping the fresh powder feed through the fresh powder feed lines 16 and 18 as long as the cyclone separator 48 contains enough reclaimed powder to supply a sufficient amount of reclaimed powder to the powder chamber 22 through the screening device 10 as required by the spraying devices 40 for the spray coating operation. When there is no longer enough reclaimed powder in the cyclone separator 48 for that purpose, there can be an automatic switching to a supply of fresh powder through the fresh powder feed lines 16 or 18. There is also the further possibility of supplying fresh powder and reclaimed powder to the screening device 10 simultaneously so that they are mixed together.
The exhaust air of the cyclone separator 48 is routed via an exhaust line 54 to an afterfilter device 56 where it runs through one or more filter elements 58 to the blower 46 and from there into the external atmosphere. The filter elements 58 can be filter bags, filter cartridges, filter plates or other similar filter elements. The powder which the filter elements 58 separate from the airflow is normally waste powder and falls into a waste receptacle under the force of gravity or it can be pumped, as shown in
Multi-color operation, in which different colors are each only sprayed for a short time, normally uses the cyclone separator 48 and the afterfilter device 56, the waste powder of the afterfilter device 56 ending up in the waste receptacle 62. While the powder separating efficiency of the cyclone separator 48 is usually less than that of the afterfilter device 56, it can be cleaned faster than the afterfilter device 56. In single-color operation, in which the same powder is used for a long time, it is possible to dispense with the cyclone separator 48 and connect the excess powder line 44 instead of the exhaust air line 54 to the afterfilter device 56 and connect the waste lines 60, which in this case contain reclaimed powder, to the screening device 10 as reclaimed powder lines. The cyclone separator 48 is normally only used in combination with the afterfilter device 56 in single-color operation in cases of problematic coating powder. In such cases, only the reclaimed powder of the cyclone separator 48 will be supplied via the powder reclaimed line 50 of the screening device 10 while the waste powder of the afterfilter device 56 will end up as waste in the waste receptacle 62 or another waste receptacle which can be positioned directly below an outlet opening of the afterfilter device 56 without waste lines 60.
The lower end of the cyclone separator 48 can comprise an outlet valve 64, for example a pinch valve. A fluidizing device 66 for fluidizing the coating powder can further be provided above said outlet valve 64 in or on the lower end of the lower end section 48-2 of the cyclone separator 48 designed as a storage container. The fluidizing device 66 comprises at least one fluidizing wall 80 of an open-pored or narrow-holed material which is permeable to compressed air but not to coating powder. The fluidizing wall 80 is arranged between the powder path and a fluidizing pressure chamber 81. The fluidizing pressure chamber 81 is connectable to the compressed air source 6 by means of a pressure setting element 8. The fresh powder line 16 and/or 18 can be fluidly connected at its upstream end, either directly or by means of powder pump 4, to a powder feed line 70 able to be dipped into the supplier container 12 or 14 to draw up fresh coating powder. The powder pump 4 can be arranged in the fresh powder line 16/18 at its start, end or therebetween or at the upper or lower end of the powder feed line 70.
As a small fresh powder container, a fresh powder bag 12 is shown in
Although not depicted in
The powder inlet openings 26, 26′ are arranged in a side wall of the powder container 24, preferably close to the bottom of the powder chamber 22. In the example embodiments of the powder container 24 depicted in
In order to be able to initiate purifying compressed air into the powder chamber 22 in the cleaning operation, the powder container 24 comprises at least one purifying compressed air inlet 32-1, 32-2 in a side wall. In cleaning operation of the powder coating system 1, the purifying compressed air inlet 32-1, 32-2 is fluidly connected to a compressed air source 6 via purifying compressed air feed lines 101-1, 101-2, 101-3 in order to supply purifying compressed air to the powder chamber 22. Preferably each purifying compressed air inlet 32-1, 32-2 comprises an inlet opening in the side wall of the powder container 24 which is identical to a powder inlet opening 26, 26′ through which coating powder is fed as needed into the powder chamber 22 in the powder coating operation of the powder coating system 1. The process of cleaning the powder chamber 22 will be described in greater detail below with reference to the powder container 24 depicted in
In the side wall of the powder container 24 in which the inlet openings of the purifying compressed air inlets 32-1, 32-2 are provided, at least one outlet opening of a residual powder outlet 33 can be further provided through which the residual powder can be driven out of the powder chamber 22 in the cleaning operation of the powder coating system 1 by means of the purifying compressed air introduced into said powder chamber 22.
As noted above, the powder container 24 is equipped with a fluidizing device 30 in order to introduce fluidizing compressed air into the powder chamber 22 during the powder coating operation of the powder coating system 1. The powder container 24 further comprises at least one fluidizing compressed air outlet 31 having an outlet opening through which the fluidizing compressed air introduced into the powder chamber 22 can be discharged again for the purpose of pressure equalization. The outlet opening of the fluidizing compressed air outlet 31 is preferably identical to the outlet opening of the residual powder outlet 33.
The following will reference the depictions provided in
As shown in
As can be particularly noted from the depiction provided in
In detail, and as can be particularly noted from the
On the other hand, as indicated in
The embodiment depicted in
A fluidizing device 30 for introducing fluidizing compressed air into the powder chamber 22 is preferably provided in the embodiment depicted in
In the embodiment depicted in
As can be noted particularly from the
In the exemplary embodiment depicted in
It is hereby conceivable for a further level sensor to be provided which is arranged relative to the powder container 24 so as to detect a minimum powder level and, as soon as this minimum powder level is reached and/or fallen short of, correspondingly signals a control device 3 to preferably automatically supply fresh powder or recovered powder to the powder chamber 22 via the inlet opening of the at least one powder inlet 20-1, 20-2. The level sensor S1, S2 for detecting the powder level in the powder chamber 22 is preferably a non-contact level sensor and arranged separately from the powder chamber 22 externally of same. Doing so prevents fouling of the level sensor S1, S2. The level sensor S1, S2 generates a signal when the powder level reaches a certain height. A plurality of such powder level sensors S1, S2 can also be arranged at different heights, to detect for example predetermined maximum levels and to detect a predetermined minimum level.
The signals of the least one level sensor S1, S2 are used, for example, to control an automatic powder supply of coating powder into the powder chamber 22 through the powder inlets 20-1, 20-2 in order to also maintain a predetermined level or predetermined level range therein during the period when the powder pumps 4 configured here as single-chamber dense phase powder pumps 200 suck coating powder out of the powder chamber 22 and pneumatically pump it to the spraying devices 40 (or into other containers). During such a powder spray coating operation, purifying compressed air is not channeled into the powder chamber 22, or only done so at reduced pressure. To clean the powder chamber 22 during coating breaks, for example when changing from one type of powder to another type of powder, purifying compressed air is fed through the at least one purifying compressed air inlet 32-1, 32-2 of the powder chamber 22. The purifying compressed air creates an air roller 35 within the powder container 24 which dislodges any residual powder which may be adhering to the inner wall of the powder container 24 and drives it out of the powder chamber 22 through the residual powder outlet 34.
Although not explicitly depicted in the drawings, it is further conceivable to provide a device for measuring the air pressure prevailing in the powder chamber 22. This is important to the extent of how much care needs to be taken to ensure that too much excess pressure cannot build up inside the powder container 24 from the introduction of fluidizing compressed air during the powder coating operation of the powder coating system 1 or from the introduction of purifying compressed air during the cleaning operation of the powder coating system 1 respectively since the powder container 24 is not as a rule designed as a high-pressure storage container. It is preferential in this respect for the maximally allowable positive pressure in the powder chamber 22 not to exceed 0.5 bar.
It is particularly conceivable with the above-cited embodiment for the air pressure measured in the powder chamber 22 continuously or at prespecified times or upon prespecified events to be supplied to a control device 3, wherein the amount of fluidizing compressed air to be supplied to the powder chamber 22 per unit of time and/or the amount discharged out of the powder chamber 22 via the at least one fluidizing compressed air outlet 31 per unit of time is preferably automatically adjusted as a function of the air pressure prevailing in the powder chamber 22. During the cleaning operation of the powder coating system 1, however, it is preferential for the control device 3 to preferably automatically set the amount of the purifying compressed air supplied to the powder chamber 22 per unit of time and/or the amount of the purifying compressed air discharged per unit of time via the at least one residual powder outlet 33 as a function of the air pressure prevailing in the powder chamber 22.
As can be noted from the
It is particularly preferential for the powder chamber 22 to exhibit an angular inner configuration in which the bottom surface and the side surfaces of the powder chamber 22 are connected together by the edges, particularly right-angled edges. This angular inner configuration to the powder chamber 22 ensures that the air roller 35 forming inside the powder chamber 22 during the cleaning operation of the powder coating system 1 does not develop a laminar but instead a turbulent boundary layer, which facilitates the removal of the residual powder adhering to the inner wall of the powder container 24. In order to be able to form the most ideal air roller 35 possible inside the powder container 24 during the cleaning operation of the powder coating system 1, it has been shown in practice that it is preferable for the powder chamber 22 to have a height of 180 mm to 260 mm, preferably 200 mm to 240 mm, and further preferably 220 mm, whereby the powder chamber 22 has a width of 140 mm to 220 mm, preferably 160 mm to 200 mm, and further preferably 180 mm, and whereby the powder chamber 22 has a length of 510 mm to 590 mm, preferably 530 mm to 570 mm, and further preferably 550 mm. With these given dimensions of the powder chamber 22, the at least one purifying compressed air inlet 32-1, 32-2 and the at least one residual powder outlet 33 are further to be provided in a common front wall 24-3 of the powder container 24.
The powder supply device shown in
The powder discharge openings 36 preferably have an elliptical form such that the effective area for drawing in fluidized coating powder is increased. The powder discharge openings 36 are disposed as low as possible within the powder chamber 22 in order for the powder pumps 4 configured here as single-chamber dense phase powder pumps 200 to be able to extract the absolute most possible coating powder from the powder chamber 22. The powder pumps 4 are preferably situated at a higher point than the highest powder level and are each connected to one of the powder discharge openings 36 via a powder dispensing channel 13 (depicted with dotted lines in
The powder dispensing channel 13 can be formed for example in a dip tube extending into the powder chamber 22 or—as provided for in the embodiment as per
As depicted in
The powder pump 4 configured as a single-chamber dense phase powder pump 200 is fixed at the upper end section of the powder container 24 and detachably connected to the powder dispensing channel 13. As already stated above, the powder dispensing channel 13 thereby extends particularly through the side wall 24-5 of the powder container 24 and leads into the powder chamber 22 via a preferably elliptical powder discharge opening 36.
An enlarged partly sectional view of the powder supply device depicted in
The powder supply device according to an embodiment of the invention further comprises a suction tube 100 shown in
The inserting of the suction tube 100 reduces the inner diameter of the powder dispensing channel 13. This can reduce the lift needed to suck the coating powder out of the powder chamber 22. The inner diameter of the suction tube 100 is particularly in a range of from 3 mm to 10 mm, preferably in a range of from 5 mm to 8 mm, and particularly preferably approximately 4 mm.
A hopper region 103 of widened inner diameter is provided at an end section 102 of the suction tube 100 opposite from the suction tube connector 90. The hopper region 103 prevents powder residue from the coating powder located in the powder chamber 22 from settling in the lower end section of the suction tube 100. The suction tube 100 furthermore has a length which substantially corresponds to the length of the powder channel.
It is thereby to be noted that the powder channel 13 leads particularly diagonally into the powder chamber 22 so that the suction tube 100 reaches just to the upper end of the powder discharge opening 36 such that the suction tube 100 will not enter into the powder chamber 22.
As indicated above, the powder dispensing channel 13 comprises a lower end section via which the powder dispensing channel 13 empties into the powder chamber 22 through a powder discharge opening 36 and an upper end section to which the suction tube connector 90 is fixed and fixable. The upper end section of the powder dispensing channel 13 is particularly situated at an upper end section of the powder container 24, whereby the suction tube connector 90 as well as the recess 13-1 are configured such that the suction tube connector 90 projects over the upper end section of the powder container 24. Accordingly, the suction tube connector 90 forms an extension 92 via which the dense phase powder pump 200 can be fixed to the side wall 24-5 of the powder container 24.
The dense phase powder pump 200 preferably comprises a connecting element 110 for this purpose which is detachably fixed to a first end region of the dense phase powder pump 200 facing the suction tube connector 90.
As can be learned for example from the frontal view of the powder pump 4 depicted in
The connecting element 110 serves to establish a force-fit connection between the suction tube connector 90 and the dense phase powder pump 200. To this end, the connecting element 110 can comprise a recess 112 at an end section facing the suction tube connector 90, same being particularly evident in
The powder pump 4 configured as dense phase powder pump 200 comprises a powder inlet 201 connected or connectable to the powder dispensing channel 13 which at the same time forms a front end region of the powder channel of the dense phase powder pump 200. A powder outlet 202 connected or connectable to an output-side powder reservoir (not shown), or a mechanism for spraying coating powder (not shown) respectively, is additionally provided. The powder inlet 201 is arranged on a first end region of the dense phase powder pump 200, wherein the powder outlet 202 is arranged on an oppositely disposed second end region of the dense phase powder pump 200. Situated between the powder inlet 201 and the powder outlet 202 is the previously cited single powder feed chamber 204 of the dense phase powder pump 200 designed to alternately draw powder out of the powder chamber 22 and pump it in the direction of the powder outlet 202.
The powder feed chamber 204 comprises a chamber inlet 205 at a first end section and a chamber outlet 206 at an oppositely disposed second end section. Specifically, a powder inlet valve 208 is further provided at the chamber inlet 205 by means of which the chamber inlet 205 of the powder feed chamber 204 is fluidly connected or connectable to the powder outlet 201 of the dense phase powder pump 200. A powder outlet valve 210 is provided at the chamber outlet 206 of the powder feed chamber 204 by means of which the single powder feed chamber 204 can be fluidly connected or connectable to the powder outlet 202 of the dense phase powder pump 200.
However, in contrast to the powder inlet region of the dense phase powder pump 200, the powder outlet valve 210 at the powder outlet region of the dense phase powder pump 200 is not disposed directly between the chamber outlet 206 of the powder feed chamber 204 and the powder outlet 202 of the dense phase powder pump 200; instead, an auxiliary compressed air inlet device 220 is additionally arranged between the powder outlet valve 210 and the powder outlet 202 of the dense phase powder pump 200. As will be described in greater detail in the following, this auxiliary compressed air inlet device 220 serves to feed additional compressed conveyor air as needed into the powder path between the powder outlet valve 210 and the powder outlet 202 of the dense phase powder pump 200.
It is to be pointed out at this point that it is not absolutely necessary for the auxiliary compressed air inlet device 220 to be arranged between the powder outlet valve 210 and the powder outlet 202 of the dense phase powder pump 200. The effect which can be realized with the auxiliary compressed air inlet device 220 can also be realized when the auxiliary compressed air inlet device 220 is arranged behind the powder outlet 202 of the dense phase powder pump 200.
Although not shown in the drawings, a further valve can be provided between the auxiliary compressed air inlet device 220 and the powder outlet 202 of the dense phase powder pump 200 in the dense phase powder pump 200 of the present invention which then assumes the function of the powder outlet valve.
The powder inlet and powder outlet valves 208, 210 shown in
To this end, an air exchange opening 216 is provided in each pressure chamber 214 which is connected to a corresponding control valve of a control device 300. The control device serves to alternately subject the pressure chambers 214 of both powder inlet and powder outlet valves 208, 210 respectively configured as pinch valves to positive pressure from a compressed air feed line.
The flexible, elastic tube 212 of the powder inlet valve 208 or powder outlet valve 210 respectively configured as pinch valves preferably has such elasticity or residual stress so as to independently stretch back out when the pressure of the actuating compressed air in the pressure chamber 214 ceases and thereby open the respective valve channel. Yet to support the opening of the pinch valve and thereby increase the switching frequency realizable with the dense phase powder pump 200, it is additionally also conceivable to subject the pressure chamber 214 to a negative pressure by means of the respective air exchange openings 216.
As already indicated above, to reduce or prevent pulsations downstream of the powder outlet 202 of the dense phase powder pump 200, an auxiliary compressed air inlet device 220 is provided at the outlet of the powder outlet valve 210 or powder outlet 202 of the dense phase powder pump 200 respectively in the exemplary embodiment of the dense phase powder pump 200 depicted in the drawings so as to be able to feed additional compressed conveyor air as needed into the powder path there.
Preferably the additional compressed air of the auxiliary compressed air inlet device 220 is supplied at an intermittent pulse frequency which is the same or preferably greater than the frequency of the powder feed chamber 204 at which the powder feed chamber 204 dispenses portions of powder. A pulsed compressed air or compressed air pulse generator can be provided for the auxiliary compressed air inlet device 220 for this purpose, same being connected via an air exchange opening 222 of the auxiliary compressed air inlet device 220.
It is clear from
Although not shown in the drawings for the sake of clarity, it is nonetheless particularly preferential for the powder supply device 1 to comprise a plurality of single-chamber dense phase powder pumps 200 each connected or connectable to a respective powder dispensing channel 13 of the powder chamber 22. The powder dispensing channels 13 of the plurality of dense phase powder pumps 200 are thereby preferably configured in the two oppositely disposed side walls 24-4 and 24-5 of the powder chamber 22. In accordance with the concrete
This is also particularly enabled by the single-chamber design used for the dense phase powder pump 200 of the inventive powder supply device 1 being of particularly compact construction. Hence, the single-chamber dense phase powder pump 200 can have a width of for example just 40 mm, whereby a plurality of dense phase powder pumps 200 can be fixed to the side walls 24-4 and 24-5 of the powder container.
Returning to the representation according to
Lastly, it is noted that the at least one dense phase powder pump 200 according to the inventive powder supply device is disposed at a height relative to the powder chamber 22 which substantially corresponds to the adjustable powder level in the powder chamber 22. In other words, the dense phase powder pump 200 is preferably disposed at the height of the powder level inside powder chamber 22 in the inventive powder supply device. Doing so thus minimizes the lift required to convey the powder out of the powder chamber 22.
The present invention is not limited to the embodiments depicted in the drawings but rather yields from a synopsis of all the features disclosed herein together.
| Number | Date | Country | Kind |
|---|---|---|---|
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| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/067649 | 8/19/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/036205 | 3/19/2015 | WO | A |
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