EP1201314B1 - High speed rotary atomizer for applying a powder coating - Google Patents

Description

The invention relates to a high-speed rotary atomizer for applying powder coating with a housing; With a rotatable one located at the front of the housing Bell cup; with one housed in the housing Motor that drives the bell cup; With at least one through the housing and Powder feed channel emerging at the front of the housing and with a coaxial to the bell plate Steering air device with which are under pressure Steering air in the direction of that generated by the bell cup Powder cloud is blowable.

The powder cloud generated by high-speed rotary atomizers needs to be shaped. EP 0 857 515 A2 describes this this purpose a steering air device in the form of several bores on the front of the housing. The pressurized hole passes through these holes Steering air against the powder cloud and exercises the desired shaping effect. A disadvantage of this known steering air device is that the steering air at Passing through the different holes forming vortices, which adversely affect the powder cloud. Also, the amount of steering air that way the powder cloud can be fed, limited.

The object of the present invention is a high-speed rotary atomizer of the type mentioned at the outset, that the steering air as evenly and flows vortex-free towards the powder cloud.

This object is achieved in that the steering air device comprises a rotationally symmetrical air guide which is attached to the front of the housing and has a lateral surface, which the steering air can be supplied such that it along the lateral surface in the direction of the bell plate as a substantially rotationally symmetrical Air curtain flows out
wherein the air guide body has an axial through hole which leads the paint powder in the direction of the bell cup.

According to the invention, the steering air is not small Drilled holes but along an outer surface of a more or less massive body without the Steering air radially outwards is a physical limitation experiences. The steering air curtain shows no interruptions is not divided into individual partial flows, that only reunite with vortex formation could. About the relatively large surface area the air baffle can also be proportionate move large amounts of steering air, so the effect the steering air on the powder cloud much larger than at known high-speed rotary atomizers.

That embodiment of the is particularly preferred Invention in which a rear radial surface of the Air guiding body and a part adjacent to it limit radial gap, radially after the steering air can flow outside, the outer surface of the air guide one in the front area, after front tapered conical surface and one the rear radial surface with the truncated cone surface connecting transition area. In this embodiment first finds the gap radially due to the flowing through, but then deflected forward Lead air instead of increasing the air flow, that ambient air from the steering air supplied from the inside gets carried away. The on the outer surface of the air baffle air flowing forward thus exposes itself the incoming steering air and the entrained ambient air together. This also increases the possibility of to influence the shape of the powder cloud.

It is preferred if the transition area is off several conical ring surfaces with different Cone angles is composed. With one Design remains the steering air when it is deflected from the radial to the essentially axial flow direction better on the outer surface of the air baffle "stick" as if it were continuously curved.

It is also advantageous if there is steering air in the housing leading annular space is provided, which with the Air guide communicating adjacent gap. Within this annulus can be pressure equalized, which further homogenizes the steering air flow.

A particularly cheap way of communication between the annular space and the gap is a thread-like one Groove, which in an axially extending surface area cut a part delimiting the annular space is.

When using the air guide body according to the invention the case may occur that the on the lateral surface of air flowing along the air guide body at its front end, where the through hole opens, one has higher pressure than the powder stream which the Flows through hole. This can be undesirable Lead whirl. To prevent this, after a a further embodiment of the present invention Support air device can be provided with which in the flowing through the through hole of the air guide Powder stream pressurized supporting air like this can be fed that at the mouth of the through hole prevailing pressure not among those there pressure on the lateral surface drops. Let it be vortices that interfere with the formation of the powder cloud could reliably avoid.

Figur 1

einen Axialschnitt durch einen Hochrotationszerstäuber;

Figur 2

eine Detailvergrößerung aus Figur 1.

An embodiment of the invention is explained below with reference to the drawing; show it

Figure 1

an axial section through a high-speed rotary atomizer;

Figure 2

an enlarged detail of Figure 1.

The high-speed rotary atomizer shown in Figure 1 has a housing 1, which is made in one piece a rear housing section 1a, a radially extending Ring shoulder 1b and a front housing section 1c composed. The rear housing section 1a expands with a small cone angle towards the back the high-speed atomizer; also the front housing section 1c is conical, but the cone angle larger than that of the rear housing section 1a. The housing 1 is made entirely of plastic.

From the radially outer edge of step 1b of housing 1 runs also a conical and also made of plastic manufactured ring part 2 to the front area the outer surface of the front housing section 1c. The ring part 2 is on the ring shoulder 1b sealed adjacent circular edge of the housing 1, while in the inner lateral surface of its front area, which bears against the front area of the housing section 1b, for reasons that will become clear later, a groove 60 in the form a trapezoidal thread is formed. This groove 60 provides a connection between the annular space 3, which between the Ring part 2 and the housing 1 is located, and the front End face of the ring part 2 ago.

An electrode insert is coaxial within the housing 1 4 arranged, the one in the axial direction relatively short, circular cylindrical rear area 4a and has a conical front region 4b. The front one Area 4b of the electrode insert 4 ends nearby the front end of the front housing portion 1c.

In the suitably graduated interior of the electrode insert 4 an air-driven motor 13 is used, whose shaft 14 coaxial with the housing 1 and the electrode insert 4 runs and a through hole 15 in Electrode insert 4 passes through. On the shaft 14 is the Hub of a bell plate 16 snapped in such a way that the bell plate 16 together with the shaft 14 twisted.

The motor 13 is by means of a larger radius region 13a on the electrode insert 4 established. This happens because the engine area 13a between the rear face of the electrode insert 4 and a cup-shaped holding insert 17 is clamped is. This is done with screws, not shown, what through holes in the motor section 13a and in threaded holes in the electrode insert 4 are screwed in.

The rear end of the housing 1 is through a connection plate 26 closed on the back of the holding insert 17 is present, various, partly in the drawing carries air connections, not shown, and also the attachment to the arm of a not shown Robot. The connection plate 26 is with the help a union nut 34 held on the housing 1, the a stop on a circumferential step of the housing 1 finds and on an external thread 35 of the connection plate 26 is turned up.

The connecting plate 26 is pierced by two sockets 27, 28, that protrude from the inside of the connecting plate 26 and protrude into a stepped bore of the holding insert 17. On the outside of the connection sockets 27, 28 a connection nipple 29 or 30 is attached, to which a compressed air supply hose is attached can.

A tube 31 extends from the connector socket 27 through the stepped bore of the holding insert 17 and through a hole in the ring shoulder 1b of the Housing 1 and opens into the annular space 3, which is between the ring part 2 and the front housing section 1c located. Another tube 32 leads from the connection socket 28 through the corresponding stepped bore of the holding insert 17 through a further hole in the annular shoulder 1b of the Housing 1 through. On this tube 32 is another angled tube 33 which passes through the annular space 3 passed and in a bore 36 of the front Housing section 1c is inserted. The bore 36 opens into a groove in the front annular end face of the front housing section 1c. In this Groove is a ring 70 made of soft plastic, e.g. PTFE, the one with a sealing edge radially on an outer surface of the housing section 1c.

The high-speed rotary atomizer also has two powder feed channels on that is not shown in the drawing and are arranged on the connection plate 26 Connection for the paint powder to an annular gap between the electrode insert 4 and the front housing section 1c lead. These two powder feed channels are through passed through the space lying radially outside of the motor 13.

On the front end of the front housing section 1c, an air guide 37 is placed. He has one Through hole 38 on which the hub of the bell cup 16 surrounds at a distance. Has on the front the air baffle 37 a tapered Truncated cone surface 39. The rear of the air baffle 37 comprises two connected to one another by a step radial annular surfaces 40, 41. Between the radial ring surface 40 and the end face lying further out the ring part 2 remains a narrow, radially directed Gap 42. On the radially inner ring surface 41 the air baffle 37 is the ring 70.

The radially outer, rear annular surface 40 of the air guide 37 is over with the conical surface 39 a transition region 43 connected from each other attached cone surfaces.

The high-speed rotary atomizer described works as follows:

That via the powder feed channels, not shown Paint powder applied brushes along metallic Surfaces of the electrode insert 4 and becomes direct ionized. It passes through in this ionized form between the front end of the housing 1 and the front end of the electrode insert 4 lying gap the powder feed channels, passes through the through hole 38 of the air guide 37 and is on it following from the rotating bell plate 16 swirled.

About the connection nipple 29 and the tube 31 is the Annulus 3 between the ring part 2 and the front housing section 1c compressed air supplied. This compressed air is distributed itself in the annular space 3. It passes over the trapezoidal thread 60 in the front end region of the ring part 2 in the gap 42 between the air guide 37 and the ring part 2, flows radially outward along this gap 42 and is then through the transition region 43 of the air guide 37 deflected. With the help of the conical ring surfaces, which is a detachment and swirling of this air flow prevent the air from settling on the conical surface 39 of the air guide 37 and flows onto the powder cloud to which is generated by the rotating bell plate 16. The type of flow along the air baffle 37 is so that ambient air is entrained at the same time, so that the total current running along the front area of the air guide body 37 flows, is significantly reinforced. This common flow from flowing across the gap 42 and air drawn in from the ambient air now forms the powder cloud coming from the rotating bell plate 16 is generated.

Via the connection nipple 30, the pipes 32, 33, the bore 36 in the front housing section 1c, this air flows in the annulus between the ring 70 and the front face of the front housing section 1c. With a certain Minimum pressure lifts the sealing edge of ring 70 from that Housing section 1c and lets the air pass. In this way it reaches the foremost area of the powder feed channels and increases the pressure of the through hole 38 of the air guide body 37 flowing flow. On this prevents the pressure in the through hole 38 of the air guide 37 among those of the Steering air on the conical surface 39 drops, causing turbulence when the paint powder flow emerges from the Air guide 37 could lead. For this reason the compressed air supplied via the connection nipple 30 here also called "support air".

By controlling the pressure that the steering air within of the annular space 3, and by the choice of geometry the groove 60 in the ring part 2, the gap 42 between Air guide 37 and ring part 2 and the choice of Geometry of the air guide 37 itself can be Shape of the powder cloud generated by the high-speed rotary atomizer influence largely as desired; in particular can be very slim, a small diameter exhibiting powder clouds as they do for many Applications are desired.

Claims (6)

1. High-speed rotary atomiser for applying powder coating with a housing (1); with a rotatable bell disc (16) arranged at the front of the housing (1); with a motor (13) driving the bell disc (16) accommodated in the housing (1); with at least one powder supply channel passing through the housing (1) and emerging at the front of the housing (1) and with a guidance air arrangement coaxial with the bell disc (16), by which pressurised guidance air is blowable in the direction of the powder cloud generated by the bell disc (16),
   characterised in that
   the guidance air arrangement comprises a rotationally symmetrical air guidance body (37) mounted at the front of housing (1) and having a jacket surface (39, 43) to which the guidance air can be so supplied that it flows along the jacket surface (39, 43) in the direction towards the bell disc (16) as a substantially rotationally symmetrical air curtain,
   the air guidance body (37) having an axial through-bore (38) through which the coating powder flows in the direction towards the bell disc (16).
2. High-speed rotary atomiser according to Claim 1, characterised in that a rear, radial face (40) of the air guidance body (37) and a part (2) adjacent to said face (40) delimit a radial gap (42) through which the guidance air can flow radially outwards, the jacket surface of the air guidance body (37) having in its front section a frusto conical jacket surface (39) tapering conically towards the front and a transitional section (43) connecting the rear radial face (40) to the frusto conical jacket surface (39).
3. High-speed rotary atomiser according to Claim 2, characterised in that transitional section (43) is composed of a plurality of conical annular faces with differing cone angles.
4. High-speed rotary atomiser according to Claim 2 or 3, characterised in that a guidance air conducting annular space (3) is provided in the housing (1), which space (3) communicates with the gap (42) bordering the air guidance body (37).
5. High-speed rotary atomiser according to Claim 4, characterised in that the communication between annular space (3) and gap (42) is formed by a screw thread-like groove (60) cut into an axially extending surface section of the part (2) bordering the annular space (3).
6. High-speed rotary atomiser according to one of the preceding claims, characterised in that a supporting air arrangement (28, 30, 32, 33, 36) is provided, with which pressurised supporting air can be fed into the powder stream flowing through the through-bore (38) of the air guidance body (37) such that the pressure prevailing at the point where the through-bore (38) emerges does not fall below the pressure prevailing on the jacket face (39) at that point.

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