Powder conveying injector for conveying coating powder and Venturi nozzle assembly

Disclosed are a Venturi nozzle arrangement for powder conveying injectors and corresponding powder conveying injectors. The Venturi nozzle arrangement has a first region, which serves as a drive nozzle, and a second region, which serves as a collecting nozzle, wherein the second region has a channel that serves as a stream collecting channel with a longitudinal axis, and wherein the first region has a nozzle opening which lies axially opposite the stream collecting channel, the first and second regions of the nozzle arrangement being inseparably connected to one another as a combined component.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is the national phase of PCT Application No. PCT/EP2017/079815 filed on Nov. 20, 2017, which in turn claims priority to German Application No. 102017103316.5 filed on Feb. 17, 2017, the disclosures of which are incorporated by reference herein in their entireties.

BACKGROUND

The present disclosure relates to a powder conveying injector with a Venturi nozzle assembly as well as a Venturi nozzle assembly for powder conveying injectors.

In particular, the disclosure relates to powder conveying injectors for conveying coating powder having a drive nozzle and a collecting nozzle, wherein the collecting nozzle has a stream collecting channel disposed axially opposite from the drive nozzle at a distance. This arrangement of drive and collecting nozzle is also referred to herein as “Venturi nozzle assembly.”

Nozzle assemblies of this type are used in powder conveying injectors which take advantage of the so-called Venturi effect in using conveying air to convey in particular fluidized coating powder from a powder reservoir and feed it through the collecting nozzle via for example a powder supply tube of a coating gun or similar mechanism for spraying coating powder. The collecting nozzle, usually configured as an elongated hollow body, forms a so-called stream collecting channel in its interior to that end into which the powder/air mixture to be conveyed is introduced.

The stream collecting channel of the collecting nozzle is disposed axially upstream of a drive or stream collecting nozzle through which propellant or conveying air is forced into the collecting nozzle. Due to the relatively small diameter of the drive or stream collecting nozzle, a high velocity airflow is formed, whereby a negative pressure is formed in a directly adjacent powder supply channel connected to the powder container. Due to the negative pressure, fluidized coating powder is conveyed in the powder supply channel from the powder reservoir to the collecting nozzle and conducted through same to the powder feed hose.

A powder conveying injector of this type having a corresponding Venturi nozzle assembly is known for example from the German DE 198 24 802 A1 published application.

Known prior art powder conveying injectors have the disadvantage of the drive nozzle and the collecting nozzle and in particular the stream collecting channel of the collecting nozzle being worn away by the airflow and the powder particles. Due to the abrasive effect of the coating powder, which is channeled through the collecting nozzle at high velocity, in particular the stream collecting channel of the collecting nozzle is subject to comparatively high wear, which generally becomes apparent from the abraded material leading to a widening of the stream collecting channel, which results in a decrease in pressure. Thus, over time, continually more propellant or conveying air is required to convey the coating powder which on the one hand is uneconomical and on the other hand can also lead to unsatisfactory coating results due to uneven coating powder flaws or to the conveyed volume of powder decreasing over time respectively.

For this reason, regularly replacing the collecting nozzles becomes necessary in powder conveying injectors. Alternatively or additionally known thereto, for example from DE 198 24 802 A1, is forming the collecting channel of the collecting nozzle from a relatively hard material, in particular glass.

Although regularly replacing collecting nozzles can counteract the disproportionate widening of the stream collecting channel cross section during operation of the powder conveying injector, this measure not does prevent the powder conveyance effected with the powder conveying injector from becoming increasingly more inefficient or poorer. This is because the drive nozzle of the powder conveying injector is also subject to at least creeping wear since the effective flow cross section or effective nozzle opening of the drive nozzle respectively cannot be prevented from changing during the operation of the powder conveying injector and thus no longer corresponding to the originally selected initial value optimized in terms of the powder conveying injector's operation and conveying efficiency.

Particularly when the drive nozzle is made of a plastic material, there is the risk of the nozzle opening of the drive nozzle widening over time due to the conveying air forced through the drive nozzle. If, however, the nozzle opening of the drive nozzle is made of metal, which is “harder” compared to plastic and thus subject to less wear, accumulation and sintering of powder particles onto the nozzle tip generally cannot be prevented since metal has the disadvantage of powder particles tending to adhere to and sinter onto it.

There is thus the generally unavoidable risk in the prior art of changes occurring to the effective nozzle cross section, or effective nozzle opening respectively, of the drive nozzle, and thus also the conveying flow of air, during operation of the powder conveying injector.

SUMMARY

The task to be solved is that of creating the opportunity of ensuring that the powder conveying injector will assure particularly efficient and optimized conveyance of coating powder after a routine or defect-related replacing of the collecting nozzle.

Accordingly, it is in particular provided by the present disclosure for the collecting nozzle and the drive nozzle to be inseparably connected together as one consolidated component. The term of “consolidated as one component” or respectively “inseparably connected together” as used herein is to be understood as a connection of the two “collecting nozzle” and “drive nozzle” components which can no longer be disengaged without destruction.

By the collecting nozzle and the drive nozzle of the powder conveying injector being connected together inseparably as one consolidated component, it is particularly easy for the user of the powder conveying injector to replace the drive nozzle at the same time as replacing the collecting nozzle, whether as a routine or defect-related measure, so that the powder conveying injector, or the mutually adapted nozzle assembly cross sections respectively, thereafter reflect the originally selected factory design. It should be considered here that in conventional powder conveying injectors, the drive nozzle was in fact only replaceable—if at all—with relatively great effort, which hence did not regularly occur in practice.

The disclosed solution, according to which the collecting nozzle and the drive nozzle are inseparably connected together as one consolidated component, moreover enables the powder conveying injector to be implemented as a so-called “inline injector” with which the coating powder to be conveyed by the powder conveying injector is fed axially to the powder conveying injector with respect to the longitudinal axis of the stream collecting channel.

This embodiment as “inline injector” has the decisive advantage that the coating powder to be conveyed in the powder conveying injector no longer needs to be deflected, or only barely, so that only minor turbulence—if any—and in particular less flow resistance results. This increases the conveying capacity of the powder conveying injector at the same conveying air volume, whereby the powder output can at the same time be further homogenized compared to conventional powder conveying injectors not configured as inline injectors. Moreover, the nozzle assembly's susceptibility to wear is significantly reduced since the degree of turbulence in the coating powder to be conveyed in the powder conveying injector is considerably reduced.

According to one accompanying aspect, the disclosure thus also relates to a powder conveying injector for conveying coating powder which comprises a drive nozzle and a collecting nozzle, wherein the collecting nozzle comprises a stream collecting channel disposed axially opposite from the drive nozzle at a distance, and wherein the drive nozzle comprises a powder inlet disposed axially opposite from the stream collecting channel at a distance.

According to a further accompanying aspect, the disclosure lastly also relates to a Venturi nozzle assembly for powder conveying injectors, wherein the nozzle assembly has a first region serving as a drive nozzle and a second region serving as a collecting nozzle, wherein the second region comprises a channel having a longitudinal axis serving as a stream collecting channel, and wherein the first region comprises a nozzle opening axially opposite the stream collecting channel, wherein the first and the second region of the nozzle assembly are inseparably connected or connectable together as one consolidated component.

The various aspects of the disclosure are summarized below:

First Aspect of the Present Disclosure:

According to a first aspect, the present disclosure relates to a powder conveying injector for conveying coating powder, wherein the powder conveying injector comprises a drive nozzle and a collecting nozzle, and wherein the collecting nozzle comprises a stream collecting channel disposed axially opposite from the drive nozzle at a distance. It is thereby in particular provided in the present disclosure for the collecting nozzle and the drive nozzle to be inseparably connected together as one consolidated component. A further development provides for the drive nozzle to comprise a powder inlet disposed axially opposite the stream collecting channel at a distance. Particularly thereby provided is for the drive nozzle to comprise a powder inlet which is disposed axially opposite the stream collecting channel at a distance and aligned with respect to an axis coinciding with a longitudinal axis defined by the stream collecting channel or running parallel to a longitudinal axis defined by the stream collecting channel. Alternatively thereto, embodiments of the disclosure provide for the drive nozzle to comprise a powder inlet aligned with respect to an axis intersecting a longitudinal axis defined by the stream collecting channel, preferably at 90° or at an obtuse angle.

Second Aspect of the Present Disclosure:

According to a second aspect, the present disclosure relates to a powder conveying injector for conveying coating powder, wherein the powder conveying injector comprises a drive nozzle and a collecting nozzle, and wherein the collecting nozzle comprises a stream collecting channel disposed axially opposite from the drive nozzle at a distance. It is thereby in particular provided in the present disclosure for the drive nozzle to comprise a powder inlet disposed axially opposite the stream collecting channel at a distance. A further development provides for the collecting nozzle and the drive nozzle to be inseparably connected together as one consolidated component.

Fundamental Aspects of the Present Disclosure:

An injector housing can be provided in the powder conveying injector according to the disclosure in which at least the drive nozzle is at least partially accommodated in preferably removable or replaceable manner. The collecting and drive nozzle inseparably connected together as one consolidated component preferably comprises at least one seal for sealing the component relative to the injector housing.

The disclosed powder conveying injector can provide for an injector housing in which at least the drive nozzle is at least partially accommodated, whereby the injector housing has a powder inlet region connectable to a powder line in which a powder inlet channel is formed axially with respect to the longitudinal axis of the collecting nozzle and fluidly connected to the powder inlet of the drive nozzle. An axial seal can be provided in the powder inlet channel, in particular in an upstream end region of said powder inlet channel.

The disclosed powder conveying injector can provide for an injector housing in which at least part of the collecting and drive nozzle consolidated preferably as a single component can be accommodated, whereby a mount is formed in the injector housing in which at least an upstream region of the collecting and drive nozzle preferably consolidated as a single component is accommodated, wherein the mount is of circular cylindrical and axial configuration with respect to the longitudinal axis of the collecting nozzle. A conveying air connection can be provided in the injector housing which is fluidly connected to the conveying air channel by an annular space formed between the mount of the injector housing and the collecting and drive nozzle consolidated as one component. The drive nozzle can comprise a conveying air inlet fluidly connected to the conveying air channel which is non-axially arranged and aligned with respect to the longitudinal axis of the collecting nozzle.

The collecting and drive nozzle preferably consolidated as one component in the disclosed powder conveying injector can be rotationally symmetric with respect to the longitudinal axis of the collecting nozzle.

A powder line connection can be further provided in the disclosed powder conveying injector for connecting a powder line, in particular a powder hose, to a downstream end region of the collecting nozzle, wherein the powder line connection is in particular detachably connected to the downstream end region of the collecting nozzle.

An injector housing can be provided in the disclosed powder conveying injector in which at least part of the collecting and drive nozzle preferably consolidated as a single component can be accommodated, wherein an upstream end region of the powder line connection is at least partially accommodated in the injector housing and detachably connected to the injector housing by means of a locking mechanism.

The collecting nozzle in the disclosed powder conveying injector can be made of a first material and the drive nozzle made of a second material, whereby the first material is different from the second material or identical to the second material.

The stream collecting channel in the disclosed powder conveying injector can be configured rotationally symmetric with respect to the longitudinal axis of the collecting nozzle. The collecting nozzle can be configured rotationally symmetric relative to the longitudinal axis.

The drive nozzle in the disclosed powder conveying injector can comprise a drive nozzle housing having a conveying air channel and a nozzle tip fluidly connected to the conveying air channel which is disposed axially opposite from the stream collecting channel. The nozzle tip can be configured as an insert and inseparably connected to the drive nozzle housing.

Third Aspect of the Present Disclosure:

According to a third aspect, the present disclosure relates to a Venturi nozzle assembly for powder conveying injectors, wherein the nozzle assembly has a first region serving as a drive nozzle and a second region serving as a collecting nozzle, whereby the second region comprises a channel having a longitudinal axis serving as a stream collecting channel, and whereby the first region comprises a nozzle opening axially opposite the stream collecting channel, wherein the first and the second region of the nozzle assembly are inseparably connected together as one consolidated component.

The first region serving as the drive nozzle can comprise a powder inlet which is disposed axially opposite the channel of the second region serving as the stream collecting channel at a distance. The nozzle assembly can preferably be removably or replaceably accommodated in an injector housing in such a manner that at least the first region of the nozzle assembly is at least partially accommodated in the injector housing. The nozzle assembly can comprise at least one seal for sealing the nozzle assembly relative to the injector housing.

The first region serving as the drive nozzle can comprise a conveying air inlet which is non-axially arranged and aligned with respect to the longitudinal axis of the second region channel serving as the stream collecting channel. The nozzle assembly can be configured rotationally symmetric with respect to the longitudinal axis of the channel serving as the stream collecting channel.

DETAILED DESCRIPTION

To convey powder from a drum or a container to a spray gun or other spraying device, particularly for the electrostatic spray coating of objects, an injector pump is usually used with a powder conveying injector which works according to the injector principle or Venturi tube principle. In said powder conveying injector, a current of air in a negative pressure area formed by channel widening produces a negative pressure which is used to draw coating powder from the container or drum. The extracted coating powder is carried along by the current of air and conveyed to the spraying device. The negative pressure and thus the amount of powder conveyed can be adjusted by adjusting the flow rate of the airflow.

The present disclosure is based on the problem of the known types of powder conveying injectors having the disadvantage of the air flow and the powder particles wearing away the drive nozzle and the stream collecting channel. This has more than just the disadvantage of the volumetric powder flow (amount of powder conveyed per unit of time) also changing as a function of the degree of wear, resulting in unequal coating thicknesses and coating qualities on an article to be coated.

It has at present in particular been recognized that not only can the collecting nozzle or respectively the stream collecting channel of the collecting nozzle be subjected to increased wear but also the drive nozzle as used in powder conveying injectors, although not usually to the extent as experienced by the stream collecting channel of the collecting nozzle since the drive nozzle is not normally exposed to the powder particles. Nevertheless, it is unavoidable that the drive nozzle will also wear over time in the operation of the powder conveying injector.

An exemplary embodiment of the Venturi nozzle assembly according to the present disclosure will first be described in greater detail in the following with reference to the representations provided inFIGS. 1 and 2. The Venturi nozzle assembly100is particularly suitable for powder conveying injectors50for conveying coating powder from a reservoir using conveying air.

The exemplary embodiment of the Venturi nozzle assembly100comprises a first region which serves as a drive nozzle1and a second region which serves as a collecting nozzle11. The second region of the nozzle assembly100, which serves as the collecting nozzle11, comprises a channel with a longitudinal axis L in its interior which serves as a stream collecting channel12. A mixture of coating powder and conveying air flows through this channel when the Venturi nozzle assembly100is for example used in a powder conveying injector50for conveying powder.

The channel, which is also referred to as stream collecting channel12or powder flow channel in the following, exhibits a longitudinal axis L, whereby the direction of flow is indicated inFIG. 1by an arrow. The mixture of coating powder and conveying air to be conveyed enters into the second region serving as the collecting nozzle11at a funnel-shaped nozzle inlet13and exits the collecting nozzle11again at a nozzle outlet14.

At least in the area of the nozzle inlet13and the area of the nozzle outlet14, the second region, serving as collecting nozzle11, is externally of cylindrical con-figuration so that corresponding cylindrical guide surfaces15,15′ will be formed.

The first region of the nozzle assembly100arranged upstream of the second region (collecting nozzle11) assumes the function of a drive nozzle1. The second region (drive nozzle1) essentially consists of a drive nozzle housing2having a conveying air channel3and a nozzle4fluidly connected to the conveying air channel3, the nozzle opening of which is disposed axially opposite the stream collecting channel12.

Although not depicted inFIG. 1, it is conceivable for the nozzle4, or nozzle opening respectively, to be formed by a nozzle tip configured as a metal insert and in particular able to be inseparably connected to the drive nozzle housing2.

The Venturi nozzle assembly100shown in schematic sectional view inFIG. 1is in particular characterized by the first region serving as the drive nozzle1and the second region serving as the collecting nozzle11being consolidated as one single component and inseparably connected together. In principle conceivable in this context is for the first and second region1,11of the nozzle assembly100to be integrally formed from one and the same material, for example as an injection-molded component.

Alternatively thereto, and as schematically suggested inFIG. 1, the first and second region1,11of the nozzle assembly100can initially be formed separately, whereby these two regions1,11are then inseparably connected together, for example by bonding or grouting. This would have the advantage of the two regions1,11of the Venturi nozzle assembly100being able to be formed from different materials, in particular different plastic materials.

A further advantage of this embodiment is that the second region11of the nozzle assembly100, which is of rotationally symmetrical configuration relative to the longitudinal axis L of the stream collecting channel12, can be designed as a rotating part. This simplifies in particular the manufacture and assembly of the second region11of the nozzle assembly100.

The nozzle assembly100, as shown for example in schematic sectional view inFIG. 1, is moreover characterized by being a so-called “inline” nozzle assembly100, which means that the coating powder to be conveyed by the nozzle assembly100flows axially through the entire nozzle assembly100along the longitudinal axis L of the stream collecting channel12.

In particular provided with the exemplary embodiment of the nozzle assembly100is for the first region1of the nozzle assembly100to comprise a powder inlet5axially opposite from the nozzle outlet14(powder outlet) of the second region (collecting nozzle11).

What this axial arrangement of the powder inlet5and powder outlet14is able to achieve is no deflecting, or at least only slightly, of the coating powder to be conveyed within the nozzle assembly100, which significantly reduces the turbulence of the coating powder/air mixture in the nozzle assembly100. Moreover, the coating powder/air mixture in the nozzle assembly100only experiences minimum flow resistance, which overall increases the conveying capacity achievable with the nozzle assembly100at the same volume of conveying air.

Specifically, and as schematically suggested inFIG. 1, the first region of the nozzle assembly100, which serves as the drive nozzle1, is of essentially cylindrical configuration and exhibits a drive nozzle housing2having a substantially cylindrical outer surface. This drive nozzle housing2at least partly defines an interior conveying air channel3arranged axially or at least substantially axially with respect to the longitudinal axis L of the stream collecting channel1. A nozzle projection6in which the nozzle opening4of the drive nozzle1is formed extends into the conveying air channel3.

The nozzle opening4is fluidly connected to a conveying air inlet7which is non-axially arranged and aligned with respect to the longitudinal axis L of the channel of the second region11serving as the stream collecting channel12. Otherwise—as already stated above—the nozzle opening4of the drive nozzle1is axially arranged with respect to the longitudinal axis L of the stream collecting channel12.

During operation of the nozzle assembly100, conveying air is supplied via the conveying air inlet7of the drive nozzle1, same flowing from the nozzle opening4of the drive nozzle1toward the stream collecting channel12. Due to the nozzle-shaped assembly of at least the upstream region of the stream collecting channel12, the conveying air is forced into the collecting nozzle11and due to the relatively small diameter of the nozzle opening4of the drive nozzle1, a high velocity air flow forms, whereby negative pressure forms in the area of the powder inlet5of the nozzle assembly100. Due to the negative pressure developing in the powder inlet region during the operation of the nozzle assembly100, coating powder is drawn in when the powder inlet5of the first region1of the nozzle assembly100serving as the drive nozzle1is fluidly connected to a suitable powder container or the like via powder line, etc.

As schematically indicated inFIG. 1, the drive nozzle housing2exhibits a cylindrical inner contour at its downstream end region into which the upstream end region of the second region11of the nozzle assembly100; i.e. the upstream end region of the nozzle assembly100region serving as the collecting nozzle11can be inserted and accordingly inseparably connected to the drive nozzle housing2(for example by bonding or grouting).

In all, the first and second region1,11of the nozzle assembly100are thus inseparably connected together as one consolidated component. These two regions1,11inseparably connected together as one consolidated component exhibit an overall external contour which is preferably rotationally symmetric with respect to the longitudinal axis L of the stream collecting channel12. The nozzle assembly100can in this way be arbitrarily inserted into a mount21of a injector housing20without the user needing to pay attention to a specific alignment of the nozzle assembly100.

As can be further inferred from the schematic sectional view according toFIG. 1, the nozzle assembly100is provided with suitable seals8, via which the nozzle assembly100can be sealed with respect to an injector housing20when the nozzle assembly100is accommodated in the injector housing20.

It is thereby specifically preferential for at least two circumferential sealing areas8a,8bto be provided, wherein a groove or annular groove22is formed between the two circumferential sealing areas8a,8b. The conveying air inlet7of the drive nozzle1also empties into this region where the groove or annular groove22is formed between the two circumferential sealing areas8a,8b.

In schematic and sectional view,FIG. 2shows the exemplary embodiment of the nozzle assembly100according toFIG. 1in a state in which the nozzle assembly100is at least partly accommodated in a housing, in particular injector housing20.

As depicted, the housing/injector housing20comprises a mount21to that end, the size of which is adapted to the outer diameter and external configuration of at least the upstream end region of the first region (drive nozzle1) of the nozzle assembly100. At least the upstream end region of the nozzle assembly100is sealed with respect to the wall of the mount21provided in the injector housing20by the sealing rings8a,8bof the nozzle assembly100.

TheFIG. 2depiction further indicates that the groove or annular groove22formed between the two circumferential sealing areas8a,8bof the nozzle assembly100forms an annular space with the wall of the mount21of the injector housing20, wherein said annular space is fluidly connected via a conveying air connection23formed in the injector housing20.

Further able to be inferred from theFIG. 2schematic sectional view is that a powder line connection24is attached to the downstream end region of the second region of the nozzle assembly100(collecting nozzle11) and in particular detachably connected to the downstream end region.

The powder line connection24to that end comprises a receiving channel axially arranged with respect to the longitudinal axis L of the stream collecting channel12in which at least part of the downstream end region of the collecting nozzle can be accommodated. Furthermore, the powder line connection24can exhibit—asFIG. 2schematically indicates—a corresponding seal25so as to in particular seal the powder line connection24vis-à-vis the injector housing20.

The powder line connection24is attachable to the downstream end region of the collecting nozzle11such that an annular space26limited by the injector housing20, the powder line connection24as well as the nozzle assembly100is formed which is fluidly connected to a metering air channel27formed in the injector housing20. Metering air, which can be added to the coating powder/air mixture conveyed by the nozzle assembly100, can be fed to the annular space26via said metering air channel27.

An exemplary embodiment of the powder conveying injector50will be described in greater detail in the following with reference to the representations provided inFIGS. 3, 4 and 5a-e.

Briefly summarized, the exemplary embodiment of the powder conveying injector50comprises a nozzle assembly100as well as an injector housing20. The nozzle assembly100is in particular a nozzle assembly100as described above with reference to the representations inFIGS. 1 and 2.

The nozzle assembly100as used with the powder conveying injector50depicted schematically inFIGS. 3, 4 and 5a-eis thus a nozzle assembly100consisting of a drive nozzle1and a collecting nozzle11, wherein the collecting nozzle11com-prises a stream collecting channel12disposed axially opposite the drive nozzle1at a distance. The collecting nozzle11and the drive nozzle1are thereby in particular inseparably connected together as one consolidated component.

The nozzle assembly100employed in the exemplary embodiment of the powder conveying injector50is further characterized by the drive nozzle1of the nozzle assembly100comprising a powder inlet5disposed axially opposite the stream collecting channel12at a distance.

At least part of the nozzle assembly100and in particular the drive nozzle1of the nozzle assembly100is preferably removably or replaceably accommodated in the injector housing20of the powder conveying injector50.

The nozzle assembly100is preferably configured rotationally symmetrical with respect to the longitudinal axis L of the stream collecting channel12. Consequently, the nozzle assembly100can be at least partially accommodated in the injector housing20irrespective of its rotational orientation, which simplifies the replaceability of the nozzle assembly100.

Further to be learned from theFIG. 3representation is, for example, that the nozzle assembly100comprises two circumferential ring seals8a,8bat least in the region of the drive nozzle1, between which a groove or channel22respectively is formed. This groove/channel22defines an annular space in the inserted state of the nozzle assembly100which is fluidly connected to a conveying air channel3configured in the injector housing20and in particular non-axially aligned so that regardless of the rotational orientation of the nozzle assembly100, the conveying air channel3of the nozzle assembly100can always be supplied with conveying air. This is directly shown by the schematic sectional view according toFIG. 3.

The representation according toFIG. 3further shows that the exemplary embodiment of the powder conveying injector50further comprises a powder line connection24which serves to connect a powder line, in particular a powder hose, to the downstream end region of the collecting nozzle11of the nozzle assembly100. Hereby in particular provided is for the powder line connection24to be detachably connected to the downstream end region of the collecting nozzle11of the nozzle assembly100.

For example—as shown inFIG. 3—the powder line connection24can be configured as a hose connector able to be slipped over the downstream end region of the collecting nozzle11.

Conceivable in this context is for the powder line connection24configured for example as a hose connector to be secured to the injector housing20by means of a union nut when slipped over the downstream end region of the collecting nozzle11.

In accordance with the exemplary embodiment of the powder conveying injector50depicted in the drawings, however, a locking mechanism60with which the powder line connection24can be detachably connected to the injector housing20is used in place of such a union nut.

The powder line connection24realized in particular as a hose connector is detachably connected to the downstream end region of the collecting nozzle11such that an annular space26defined by the nozzle assembly100, the injector housing20and the powder line connection24is formed when the nozzle assembly100together with the powder line connection24is at least partly accommodated in the injector housing20(for this, see the schematic sectional view according toFIG. 3).

This annular space26is fluidly connected to a metering air channel27formed in the injector housing20, via which metering air can be supplied to the annular space26as needed.

The upstream end region of the powder line connection24realized in particular as a hose connector preferably exhibits helical ribs28which in a state in which the nozzle assembly100together with the powder line connection24is at least partly accommodated in the injector housing20, defines corresponding metering air channels which are fluidly connected to the annular space26, or the metering air channel27formed in the injector housing20respectively. The metering air fed into the metering air channel27of the injector housing20via these metering air channels then can be added to the mixture of conveying air and coating powder.

It is advantageous in this context for the ribs28provided in particular at the upstream end region of the powder line connection preferably realized as a hose connector24to be of helical configuration so as to give the metering air to be supplied to the conveying air/coating powder mixture a certain angular momentum. The ribs28also have the advantage of increasing the grip of the powder line connection24.

After the locking mechanism60has been unlocked, the nozzle assembly100together with the powder line connection24can be easily manually pulled out of the injector housing20, or the mount21provided in the injector housing20for the nozzle assembly100respectively.

The powder line connection24configured in particular as a hose connector can consist of an electrically non-conductive material and its exterior enclosed by a layer or a sleeve of electrically conductive material. The sleeve enclosing the powder line connection24in particular configured as a hose connector can be made for example of metal or an electrically conductive plastic. Using a hose connector as described in the DE 202 04 116 U1 printed publication as the powder line connection24would for example be conceivable.

The following will reference theFIG. 6depiction in describing a further exemplary embodiment of the powder conveying injector50.

Briefly summarized, the exemplary embodiment of the powder conveying injector50exhibits a structure which corresponds in principle to the structure of the powder conveying injector50previously described with reference to the depictions inFIGS. 3 to 5.

Accordingly, the powder conveying injector50comprises an injector housing20with a mount21in which a nozzle assembly100realized as a single component is replaceably accommodated. The nozzle assembly100used in the powder conveying injector50according to the embodiment depicted inFIG. 6preferably corresponds to the nozzle assembly100as previously described with reference to the depictions inFIGS. 1 and 2. To avoid repetition, reference is therefore made to the previous remarks.

The powder conveying injector50comprises a powder supply channel29which is fluidly connected to a powder container (or “hopper”), wherein the powder supply channel29preferably runs at least substantially axially to the conveying axis (seeFIG. 3). As indicated inFIGS. 6 and 7, it is however also conceivable for the powder supply channel29of powder conveying injector50to be slightly angled relative to the conveying axis.

The advantage obtained as a result is the achieving of improved coating powder conveying capacity at the same volume of conveying air and the same negative pressure generated by the conveying air flow in the powder supply channel29compared to conventional powder conveying injectors50, their powder supply channels extending at an angle of for instance 90° to the conveying axis.

The powder conveying injector50further comprises a conveying air connection24connectable to a conveying air hose or similar line by a suitable filter device30. A metering air connection27′ of the powder conveying injector50is also connectable to a conveying air hose or similar line by a suitable filter device30.

The further exemplary embodiment of the powder conveying injector50schematically depicted inFIG. 7essentially corresponds to the embodiment according toFIG. 6, whereby, however, no filter devices30are provided in the embodiment according toFIG. 7.

The coating powder conveyed by the powder conveying injector50according to the present disclosure can be routed by the powder conveying injector50to a further container or to a spraying device, for example a manual or automatic spray gun, by means of which the coating powder is sprayed onto articles to be coated.

The magnitude of the volumetric powder flow (volume of powder conveyed per unit of time) mainly depends on the magnitude of the negative pressure or vacuum in the negative pressure area at the upstream end of the drive nozzle1and thus primarily the magnitude of the conveying air flow.

With small volumes of powder per unit of time, the conveying air flow can be so weak that powder deposits develop in the powder line connecting the powder conveying injector50to where the powder is received. It is therefore customary to supply additional air in the form of metering air to the coating powder/conveying air flow downstream of the negative pressure area in order to regulate the total volume of air required for deposit-free powder conveyance in the powder line.

Accordingly, one or more metering air connections27′ can be provided for the metering air downstream of the collecting nozzle11or in said collecting nozzle11or upstream of said collecting nozzle11.

As it can be inferred from the representation provided inFIG. 6andFIG. 7, it is not absolutely imperative for the powder supply channel29to be axially configured with respect to the longitudinal axis L of the stream collecting channel12. Indeed, the powder supply channel29here extends at an obtuse angle of approximately 45°. This preferably does not apply, however, to the powder inlet5of the nozzle assembly100, which is preferably axially configured with respect to the longitudinal axis L of the stream collecting channel12.

The coating powder conveyed by the powder conveying injector50serves in particular for the electrostatic spray coating of objects and can consist for example of plastic, ceramic or another coating material. The invention is however not limited to systems for electrostatically spray coating objects with coating powder but can also be used to convey powder for other purposes.