Powder cup spray gun and spray-coating device comprising a powder cup spray gun

At the rear end, the powder cup spray gun has an injector, a powder cup and a receptacle for the powder cup. The powder inlet of the injector is connected to the receptacle. The powder cup and the receptacle are designed in such a way that the powder cup can be fitted into the receptacle. In addition, a grip with a connection for conveying air, a connection for atomising air, and a connection for metering air is provided. The connection for the conveying air and the connection for the metering air are connected to the injector via lines running in the grip.

TECHNICAL FIELD

The invention relates to a powder cup spray gun and to a spray-coating device comprising a powder cup spray gun, which are suitable for spraying coating powder.

For the powder coating of individual parts and very small volumes as well as for laboratory and development purposes, it is expedient to use a handy, flexible and yet powerful piece of equipment. The industry has developed powder cup guns for these applications. In contrast to the powder spray guns used for batch coating and job coating, with these powder cup spray guns the powder storage container is located directly on the spray gun. The powder storage container, which will also be referred to hereinafter as a powder cup or cup for short, has a relatively small capacity. When processing minimal and medium powder volumes, the user can save powder because the powder does not have to be transported to the spray gun via a powder tube from a remote, large powder storage container. The user also does not have to clean the powder tube in the event of a colour change. The small powder cup can also be cleaned much more easily than the large storage container.

BACKGROUND

A cup gun for the above-mentioned uses is known from the instruction manual “Tribo Becherpistole PEM-TG3” as of April 2006, no. 0351716, which is published on the Internet as prior art and is distributed by Wagner GmbH under product no. 0351036. FIG. 1 is taken from the instruction manual and shows a three-dimensional view of the cup gun D. The cup gun D is a manually actuatable powder spray gun with a powder storage container H, which is screwed from above onto the gun D in the rear region. The cup gun D has a screw thread J for this purpose.

A similar cup gun operating with triboelectric charging is known from the service manual “Hand- and Automatikpistolen” June 2006 edition, no. 0351883, page 121 et seq which is likewise published on the Internet as prior art.

Lastly, a powder cup gun operating with corona charging (high voltage) is known from the instruction manual “Pulver Becherpistole PEM-CG4-HiCoat”, February 2007 edition, no. 0390821.

These cup guns have the common feature that they have an electrical connection G and a supply connection F for compressed air at the lower end of the hand grip. The electrical connection G is connected to a control unit via an electrical cable, and the supply connection F is connected to a control unit via a compressed air tube. The compressed air supply to the cup gun can be adjusted with the aid of the control unit. These cup guns have the disadvantage however that a colour change cannot be implemented quickly enough. The user has to first carefully unscrew the storage cup from the gun. To this end, he holds the gun with one hand and takes hold of the cup with the other hand and starts to unscrew it. He will generally grasp the cup a number of times in order to be able to unscrew it completely. However, it is awkward to grasp around the cup, in particular if there is still powder in the storage cup, because there is then a risk that the powder will be spilled or will trickle out from the outlet opening of the powder cup.

With the above-described powder cup guns, the compressed air supplied to the gun via the supply connection is divided into a conveying air, a tribo air, (in the case of tribo guns) or an atomising air (in the case of corona guns), a metering air and an air for fluidising the powder. To this end, a manually adjustable valve for the conveying air, a manually adjustable valve for the metering air, a manually adjustable valve for the atomising air or tribo air, and a manually adjustable valve for the fluidising air are located to the rear on the powder cup gun. All valves are connected on the input side to the supply connection. If a valve is then adjusted, it is not possible to ensure that this has no effect on the other airflows. The actual magnitude of the four air pressures is unknown to the user. The four valve settings give only rather inaccurate information regarding said air pressures. This in turn means that it is not easily possible to make recommendations as to how the individual air pressures are to be set in other powder spray guns, in particular in powder spray guns used in batch production. The results achieved are thus only reproducible to a limited extent, and the compressed air settings are not easily transferrable to other spray guns. This is desirable however, inter alia with the development of coating powder.

DISCLOSURE OF THE INVENTION

An object of the invention is to specify a powder cup spray gun with which the colour change can be implemented quickly and smoothly.

The object is achieved by a powder cup spray gun having the features described herein.

The powder cup spray gun according to an embodiment of the invention has an injector with a powder inlet, a powder cup, and a receptacle for the powder cup. The powder inlet of the injector is connected to the receptacle. The powder cup and the receptacle are designed in such a way that the powder cup can be fitted into the receptacle. In addition, a grip having a connection for conveying air, a connection for atomising air, and a connection for metering air is provided. The connection for the conveying air and the connection for the metering air are connected to the injector via lines running in the grip.

Advantageous developments of the invention will emerge from the features described herein.

With the powder cup spray gun according to an embodiment of the invention, a gun housing can thus be provided, which is designed in such a way that the injector can be screwed on from the outside. The injector is thus quickly and easily accessible and can be unscrewed in a few simple steps. The user can then service and clean the injector.

In one embodiment of the powder cup spray gun according to the invention, a ring seal is provided in the receptacle for the powder cup. A secure and reliably sealing connection between the receptacle and the powder cup is thus achieved.

In a further embodiment of the powder cup spray gun according to the invention, a further ring seal is provided in the receptacle for the powder cup. The connection between the receptacle and the powder cup is thus sealed yet more securely and reliably.

In another embodiment of the powder cup spray gun according to the invention, a powder line and a metering air duct are provided, wherein the metering air duct discharges annularly into the powder line.

The injector of the powder cup spray gun according to the invention may have a driving nozzle and a collector nozzle, wherein the driving nozzle has a driving nozzle duct and the collector nozzle has a mixing tube portion. The ratio between the diameter of the driving nozzle duct and the inner diameter of the mixing tube portion is preferably in the range between 1.9 and 2.5.

The powder cup used for the above-described powder cup spray gun may have a side wall, which is funnel-shaped. In addition, a powder outlet, which is tubular, may be provided with the powder cup. The powder is thus drawn continuously into the injector without additional measures. Fluidisation with fluidising air is no longer necessary.

In another embodiment, the powder cup has a lid with a detachable cap. The cap is designed in such a way that it is suitable for closing the powder outlet.

In addition, a spray-coating device comprising the above-described powder cup spray gun and a control unit are proposed. The control unit is designed and operable in such a way that the conveying air, the atomising air and the metering air can be controlled thereby. In addition, compressed air tubes are provided, with which the control unit is connected to the connection for the conveying air, to the connection for the metering air, and to the connection for the atomising air of the powder cup spray gun. An extraordinarily high and permanently constant quality of the powder spray jet is advantageously achieved by the powder spray gun according to the invention in conjunction with the control apparatus.

EMBODIMENTS OF THE INVENTION

A three-dimensional view of a possible embodiment of the powder cup spray gun according to the invention is illustrated inFIG. 2. The powder cup spray gun will also be referred to hereinafter as a cup spray gun or as a spray gun for short. The cup spray gun has a housing1. A pneumatically operated powder injector2, which will also be referred to hereinafter as an injector for the sake of simplicity, is located at the rear end1.2of said housing. The cup spray gun additionally has a grip1.1, via which the operator can hold and operate the spray gun. In the embodiment shown here, the grip1.1is part of the housing1, although this does not necessarily have to be the case. The grip1.1can also be a separate component. The operator can control the powder flow and, as required, also the high voltage via a trigger10, which is incorporated into the grip1.1. If the trigger10is actuated, the high voltage is applied to a high-voltage electrode12.1(seeFIG. 4). The coating powder, or powder for short, flowing past the high-voltage electrode12.1is electrostatically charged and is sprayed through a powder jet nozzle9.

A plurality of connections5,6,7and11is located at the lower end of the grip10.FIG. 3shows a three-dimensional view of this part of the grip. The injector2is supplied with conveying air via a connection5for conveying air, which will also be referred to as a conveying air connection. The injector2is supplied with metering air via a connection6for metering air, also referred to as a metering air connection. In addition, a connection7for atomising air, which will also be referred to as an atomising air connection, is also located at the lower end of the grip10. The atomising air is guided in the spray gun as far as the discharge thereof. The operator can set the shape of the powder cloud with the aid of the atomising air. In addition, the atomising air can be used to cool the high-voltage cascade and to remove the ozone produced. The atomising air may also protect the electrode12.1against powder deposits. The atomising air additionally prevents powder from reaching the opening of the electrode holder12, from which the electrode12.1protrudes. If a round jet nozzle with a baffle plate arranged in front is used instead of the flat jet nozzle shown inFIG. 2, the atomising air can also protect the baffle plate against powder deposits. Lastly, an electrical connection11, via which a high-frequency low voltage is guided to the gun, is also located at the lower end of the grip10. A high-voltage generator, which comprises a transformer and a downstream high-voltage cascade, is located in the spray gun and transforms the high-frequency low voltage into a high voltage. Control signals and information signals can also be guided to the spray gun from a control unit30shown inFIG. 5via the electrical connection11. In addition, control signals and information signals can also be conveyed from the spray gun to the control unit30. As soon as the trigger10has been actuated, the coating powder is sprayed via the spray nozzle9.

A control panel27with buttons, via which for example a formulation can be selected from a list of a plurality of formulations stored in the control apparatus30, can be located to the rear on the spray gun. The control apparatus30then controls the individual parameters accordingly, such as metering air, conveying air, atomising air and voltage. The formulations or airs can however also be selected directly at the control apparatus30. A rinse formulation for thorough cleaning of the powder ducts within the gun can also be selected.

The powder to be sprayed is located in a powder cup3, which sits at the rear end of the spray gun in the embodiment shown inFIG. 2. The powder cup3has a removable lid4with a closable air inlet opening4.3(seeFIG. 7). During the coating operation, the air inlet opening4.3is generally open, such that no partial vacuum is produced in the powder cup3. If necessary, for example if the spray gun is not in operation or if the powder cup3is not fitted on the spray gun, the air inlet opening4.3can be closed by a closure4.2. To this end, the nipple of the closure4.2is pressed into the air inlet opening4.3. The lid4additionally carries a cap4.1, which can be removed and is used so as to close the powder outlet opening3.1(FIG. 6) of the powder cup3at the bottom. If it is desired to fill the powder cup3with coating powder, the cap4.1can be removed from the lid4and can be used to close the powder outlet opening3.1at the lower end of the powder cup3. The powder cup3can then be filled and, if desired, the powder cup can be closed at the top by the lid4. It is thus ensured that the powder located in the powder cup3cannot escape. If it is then desired to place the powder cup3on the spray gun, the powder cup3with the powder outlet opening3.1is turned upwardly and the cap4.1is removed. The powder outlet opening3.1is then fitted into the receptacle2.1provided therefor in the injector2. Due to the two O-rings16and17(seeFIG. 9), a secure and reliably sealing connection is achieved between the receptacle2.1and the powder outlet opening3.1of the powder cup3. The coating powder then passes through the powder outlet opening3.1into the directly adjoining inlet2.2of the injector2. The inlet2.2is also referred to as a suction duct. The coating powder thus reaches the injector2via the shortest path from the powder cup3and then passes to the powder spray nozzle9via the powder line15located in the interior of the spray gun.

The injector2operates by the Venturi principle. Here, a partial vacuum is produced in the injector with the aid of a continuous conveying air flow and causes powder to be drawn from the powder cup3and transported together with the conveying air flow in the direction of the powder spray nozzle9. Metering air is additionally fed to the injector2so as to assist the conveyance of the powder to the spray nozzle9. To this end, the injector2comprises a driving nozzle13(seeFIGS. 6 and 7), which can be supplied with conveying air via a compressed air line19(FIG. 8). The conveying air flowing from the driving nozzle13produces a partial vacuum in the suction duct2.2, such that the powder is drawn from the powder cup3. A collector nozzle14, which discharges into the powder line15, is located downstream after the driving nozzle13.

A compressed air duct, which discharges into the powder line15, is additionally located in the injector2. The metering air can be fed into the powder line15via the compressed air duct. The compressed air duct advantageously discharges annularly into the powder line. The volume of metering air to be fed depends on the desired total air volume. Here, the total air volume means the sum of metering air and conveying air.

FIG. 4shows a three-dimensional view of the powder cup spray gun according to the invention in a partly disassembled state. In order to clean and service the front part of the powder cup gun, that is to say the downstream part of the powder cup gun, a cap nut8unscrewable by hand is first removed. The spray nozzle9and the electrode holder2with the high-voltage electrode12.1can then be removed.

FIG. 5shows a possible embodiment of a control apparatus30for the powder cup spray gun according to the invention. In this embodiment the control apparatus30, which is also referred to as a control unit, has a first control knob31, via which the conveying air volume per unit of time can be set. In addition, a second control knob32is provided, via which the metering air volume per unit of time can be set. Lastly, a third control knob33is provided, via which the atomising air volume per unit of time can be set. The control unit30comprises corresponding control circuits, which ensure that the set target values of the conveying air, metering air and atomising air are also actually observed. The actual values of the conveying air, metering air and atomising air can be read on the respective displays34, and36.

FIG. 6shows a three-dimensional view of the powder cup spray gun according to the invention in a partly disassembled state. With the aid of the two screws28, the injector2can be quickly and easily released from the flange26in a few simple steps. The driving nozzle13and the collector nozzle14can then be removed and checked, cleaned or replaced where necessary. In addition, a short connecting tube37is provided, which connects the conveying air line arranged in the gun to the injector2and likewise can be removed. The O-rings38and39are used as seals.

FIG. 7shows a longitudinal sectional view of the powder cup spray gun according to the invention.

FIG. 8illustrates, inter alia, the compressed air lines and connections housed in the grip1.1of the spray gun.

The conveying air connection5is connected to one end of the compressed air line19via a connection nipple21. A further connection nipple23connects the other end of the compressed air line19to a conveying air duct in the flange26, which is in turn connected to the conveying air duct of the injector2.

The metering air connection6is connected to one end of the compressed air line18via a connection nipple22. A further connection nipple24connects the other end of the compressed air line18to a metering air duct in the flange26, which is in turn connected to the metering air duct in the injector2.

In addition, a cascade plug25, which is connected to cables coming from the electrical connection11, is located in the spray gun. The plug contacts of the high-voltage cascade are plugged into the cascade plug2. The cascade plug25is also used to hold the compressed air line20(=atomising air line) at the correct position. The downstream end of the atomising air line20fits on a connection nipple29. This is likewise fastened to the cascade plug25. From here, the atomising air flows past the high-voltage cascade. It is then conveyed through the electrode holder and is guided to the discharge of the spray gun.

FIG. 9shows an enlarged longitudinal sectional view of the rear part of the powder cup spray gun according to the invention. The collector nozzle14has a downstream portion located downstream, after the O-ring. This downstream portion and the duct surrounding it in the flange26as well as the powder line15surrounding it form a metering air duct40. Here, the metering air duct40is designed such that it discharges annularly into the powder line15. Incidentally, the powder line15is also referred to as a powder tube.

The following dimensions for the injector2have proven to be particularly advantageous with the powder spray gun.

Diameter of the driving nozzle duct d1=1.5 mm

Diameter of the inlet discharge of the collector nozzle d2=3.3 mm.

The diameter of the inlet discharge d2is identical to the inner diameter of the mixing tube.

Diameter of the outlet discharge of the collector nozzle d3=5.05 mm

Spacing between the driving nozzle and collector nozzle I1=2.5 mm

Spacing between the collector nozzle discharge and the start of the diffuser I2=6 mm. The spacing I2is identical to the length of the mixing tube.

Spacing between the start of the diffuser and the end of the collector nozzle I3=25 mm

Spacing between the driving nozzle and the start of the collector nozzle D=1.5 mm

Spacing between the start of the collector nozzle and the end of the collector nozzle E=32 mm

A ratio of the diameter d1to d2of

1.9≤d⁢⁢1d⁢⁢2≤2.5
has proven to be particularly advantageous with regard to the conveying capacity.

The above description of the exemplary embodiments according to the present invention is used merely for illustrative purposes and is not used for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and equivalents thereof. For example, not all components shown inFIGS. 2 to 9are therefore necessary in order to produce the powder cup spray gun.

In an alternative embodiment, the powder cup3has a radially protruding lug in the region of the tube portion3.1, and the receptacle2.1has one or more radial convexities. The convexities are used to receive the lug. The lug and convexities form a type of bayonet closure. Once the powder cup3has been fitted into the receptacle2.1, it is rotated through a specific angle. The powder cup3is thus fixed even more securely on the spray gun.

LIST OF REFERENCE SIGNS