EP0482569B1 - Pneumatically controlled spray gun - Google Patents

Abstract

The invention relates to a spray gun for the atomised spraying of fluid spraying medium. The spray gun is equipped with a pneumatically controlled spraying medium feed control. For this purpose, the internal pressure (P1) of the reservoir (71) which holds the spraying medium can be continuously adjusted, as an overpressure or underpressure, by closing or opening an outlet orifice (86) which is connected to an evacuation (83) and control air channel (84). The spray device can also be used as an airbrush for drawing or labelling. Using fine-grain sand as spraying medium, the spray gun can also be used as a sandblasting device. <IMAGE>

Description

The invention relates to a spray gun for the atomized spraying of a flowable spray according to the preamble of claim 1. In a known spray gun of this type (DE-C-97344) a compressed air nozzle channel and a spray medium channel, the other end of which dips into a paint container, coaxially in one Jet. The upper space of the container is connected to the atmosphere via a special ventilation channel, the atmosphere opening being adjustable. In addition, a control air duct leads from the nozzle duct into the ventilation duct. The pressure in the upper chamber is therefore between the atmospheric pressure and the nozzle channel, it being possible for the setting of the atmosphere opening to bring it closer and closer to one or the other limit value. When the atmosphere opening is closed, there is overpressure in the container, which sends the spray to the nozzle drives. If the atmosphere opening is completely opened, the upper pressure vessel space is so little above the atmospheric pressure that the pressure difference is not sufficient to lift the spray medium up to the nozzle. By adjusting the atmosphere opening, the liquid supply to the nozzle can thus be set between zero and a maximum. However, because of the inevitable drop in pressure in the atmosphere opening, the pressure in the container cannot quite reach atmospheric pressure or even drop below it. For this reason, the amount of spraying agent supplied to the nozzle can only be reduced to zero if the spraying agent container is arranged geodetically below the nozzle. This forces the user to hold the spray gun in a certain position, which is undesirable in some applications.

Such known devices (DE-A-3922561) do not have this disadvantage, in which the supply of the spraying agent to the nozzle is adjusted by means of a valve. These devices have an inaccurate spray when the valve needle is dirty. The adjustability of the spraying agent supply also proves to be insufficient, particularly in the case of fine spraying work. Finally, the valve control is also prone to failure.

The disadvantages of both systems are avoided by the features of claim 1, preferably also of the subclaims. Characterized in that the outlet opening of the control air duct opening into the ventilation duct points towards the outlet opening closing off the ventilation duct on the atmosphere side, the compressed air emerging from the control air duct forms a jet in the direction of the outlet opening of the ventilation duct, which leads to an injector effect and thus to a suction effect. If the outlet opening of the ventilation duct is open, this suction effect can develop fully and leads to a negative pressure in the ventilation duct. If the outlet opening is closed to a greater or lesser extent, the suction effect is suppressed, the venting channel comes under the excess pressure of the nozzle channel and thereby causes in the known from the prior art, the promotion of the spray to the nozzle. This has the advantage that the supply of the spray medium to the nozzle can be adjusted independently of the respective position of the spray gun. Even if the ink supply is at the same height as the nozzle or even above it, the negative pressure prevents the supply of the spray medium to the nozzle when the opening of the ventilation duct is open. This enables the production of particularly fine spraying devices, for example for the graphics industry, which on the one hand are particularly easy to control and can be handled without regard to their position and on the other hand are particularly small and precise because the control of the spraying agent does not depend on a needle valve. The mouth of the spray agent can be bought without risk of clogging Approx. 1/10 of the conventional opening diameter can be reduced so that even very small amounts of spray can be dosed and applied homogeneously. For the purpose of simple operation, the outlet opening is preferably designed as a storage gap, which can be covered, for example, by means of a fingertip resting on it. This enables one-handed operation and control of the color flow control. In a simple manner, the venting channel can be extended on the output side, for example, by a flexible, elastically deformable hose, with which in particular the color flow can be adjusted by mouth control.

According to the invention, a particularly simple, compact and therefore inexpensive construction of the spray gun results if the control air duct is directly connected to the compressed air duct carrying the atomizing pressure.

In order to be able to meter the spray medium flow very precisely, an adjustable valve is provided in the ventilation duct, with which an exact comparison between the internal pressure of the supply container and the suction pressure is possible. To limit the spray medium flow to a maximum value, an adjustable outlet valve is provided parallel to the outlet opening, by means of which the overpressure which forms in the ventilation duct is limited to a maximum pressure.

The spray gun according to the invention can also be used as an ink pen. For this purpose, the spray medium channel protrudes from the air nozzle in the manner of a paint tube, so that the paint liquid can be applied directly to a drawing pad by means of its tip and without atomizing pressure.

The spray gun according to the invention is also a sandblasting device device can be used. For this purpose, the sand used as a spray agent is swirled in a storage container with the control air supplied to form a sand-air mixture which is discharged via the nozzle channel projecting into the storage container.

In order to be able to set the atomizing air pressure according to the intended use, the spray gun has a continuously adjustable pressure reducing valve inserted between a conventional compressed air source and the compressed air inlet of the spray gun.

Figur 1 -

die bekannte, schematisch dargestellte pneumatische Anordnung bei einer erfindungsgemäßen Spritzpistole,

Figur 2 -

einen Axialschnitt mit teilweiser Seitenansicht einer erfindungsgemäßen Spritzpistole nach einem ersten Ausführungsbeispiel,

Figur 3 -

eine Schnittansicht entlang der Linie III-III in Figur 2,

Figur 4 -

das in Figur 2 dargestellte Ausführungsbeispiel in perspektivischer Ansicht,

Figur 5 -

in vergrößerter Schnittdarstellung den Steuerkopf des in Figur 2 dargestellten Ausführungsbeispiels,

Figur 6 -

einen teilweise im Schnitt dargestellten Schlauch für den Steuerkopf gemäß Figur 5,

Figur 7 -

in vergrößerter perspektivischer Darstellung den in Figur 5 dargestellten Spritzmittelkanal und die Zentrierhülse,

Figur 8 -

in perspektivischer vergrößerter Darstellung eine Detailansicht der in Figur 5 dargestellten Kanülenhalterung,

Figur 9 -

einen Axialschnitt eines zweiten Ausführungsbeispiels,

Figur 10 -

einen Schnitt entlang der in Figur 11 dargestellten Schnittlinie X-X,

Figur 11 -

eine Seitenansicht eines axial geschnittenen Druckreduzierventils,

Figur 12 -

einen Schnitt einer Variante der in Figur 9 dargestellten Absperrvorrichtung des Behälterteils,

Figur 13 -

einen Axialschnitt des in Figur 9 dargestellten Steuerkopfes nach einem weiteren Ausführungsbeispiel in vergrößerter Darstellung und

Figur 14 -

einen Axialschnitt eines Behälterteils in vergrößerter Darstellung nach einer zweiten Variante.

The invention is explained in more detail below with the aid of two preferred exemplary embodiments shown in the drawings. Show it

Figure 1 -

the known, schematically illustrated pneumatic arrangement in a spray gun according to the invention,

Figure 2 -

3 shows an axial section with a partial side view of a spray gun according to the invention according to a first exemplary embodiment,

Figure 3 -

3 shows a sectional view along the line III-III in FIG. 2,

Figure 4 -

the embodiment shown in Figure 2 in perspective view,

Figure 5 -

FIG. 2 shows an enlarged sectional view of the control head of the exemplary embodiment shown in FIG.

Figure 6 -

5 shows a hose, shown partly in section, for the control head according to FIG. 5,

Figure 7 -

5 shows an enlarged perspective view of the spray medium channel shown in FIG. 5 and the centering sleeve,

Figure 8 -

5 shows a detailed enlarged perspective view of the cannula holder shown in FIG. 5,

Figure 9 -

3 shows an axial section of a second exemplary embodiment,

Figure 10 -

11 shows a section along the section line XX shown in FIG. 11,

Figure 11 -

a side view of an axially sectioned pressure reducing valve,

Figure 12 -

9 shows a section of a variant of the shut-off device of the container part shown in FIG. 9,

Figure 13 -

an axial section of the control head shown in Figure 9 according to another embodiment in an enlarged view and

Figure 14 -

an axial section of a container part in an enlarged view according to a second variant.

The known basic structure of a pneumatically controlled spray gun is shown in FIG. 1. This comprises a nozzle channel 16, which tapers towards its mouth towards a mouthpiece 14. The spray medium channel 26 is arranged coaxially fixed in the nozzle channel 16, which ends at one end in a storage container 10 and ends at the other end in the mouthpiece 14. The compressed air supplied to the nozzle channel 16 via a compressed air channel 20 connected to it flows around the spray medium channel 26 in the axial direction and emerges from the mouthpiece 14 exerting a suction effect on the spray medium channel 26 from the nozzle channel 16. The emerging air stream entrains the emerging from the spray medium channel, whereby it is atomized and mixed with air, so that it e.g. can be applied to workpieces. In order to meter the amount of spray medium emerging from the container 10 into the spray medium channel 26, the internal pressure P1 of the container 10 can be adjusted by means of a ventilation channel 22 which connects the container 10 to the ambient atmosphere P2 near its outlet opening 28. Compressed air flows into the ventilation duct 22 via a control air duct 24 connected at one end to the ventilation duct 22 and at the other end to the compressed air duct 20, as symbolically indicated by vector arrows, the air flow being directed in the direction of the outlet opening 28. This creates an air flow directed to the outlet opening 28 in the ventilation duct 22. By changing the effective cross-sectional area of the outlet opening 28, the amount of air flow can be continuously adjusted between a maximum negative pressure when the outlet opening 28 is fully open and a maximum excess pressure when the outlet opening 28 is closed.

The spray gun according to the invention shown in Figure 4 consists of a Device shaft 30 with a control head 32, a container part 34 arranged at the rear end thereof and a stylus part 36 which can be locked with the container part 34 by means of a bayonet lock 37. A nozzle body 38 is screwed into its front end. The structure of the air duct distributor system formed in the nozzle body 38 and in the control head 32 is shown in FIGS. 2 and 5. This includes the coaxial in the control head 32 and axially continuing in the nozzle body 38 nozzle channel 42 or 42 '(Figure 5), the compressed air inlet pipe 41 inserted into the control head 32 and opening into the nozzle channel 42, one the control head 32 and the container part 34 in essentially coaxially penetrating and flush merging ventilation channels 44 and 44 ', and a control air channel 45 connecting the nozzle channel 42 with the ventilation channel 44. In order to effect a defined air flow in the ventilation channel 44, the control air channel 45 points with its inlet opening in the direction of the ventilation channel 44 on the atmosphere side final outlet opening 46. On the side facing away from the outlet opening 46, the ventilation channel 44 merges into an annular channel 25 which is arranged coaxially in the control head 32 in the rear end thereof. The inner circumferential surface of the ring channel 25 has an internal thread 23 into which the container part 34 with the filter receptacle 64 can be screwed. The external thread 21 of the filter receptacle 64 is pierced by an axially extending longitudinal groove 35 (FIG. 3), which continues in the reservoir 40 as a tubular ventilation channel 44 ′.

The outlet opening 46 is shaped as a storage gap 63 for manual control of the internal pressure P1 of the storage container 40. The internal pressure P1 is independent of the overlap by means of a valve rod 57, which can be screwed into the ventilation channel 44 by means of its knurled head 47 of the stowage gap 63 adjustable. The ring channel 25 and the container part 34 are sealed airtight to one another by means of an annular seal 62a arranged coaxially in the ring channel 25 and an annular seal 62b arranged coaxially in the control head 32.

The spray medium channel system has a spray medium channel 49 arranged coaxially in the control head 32 and passing through the nozzle channel 42, 42 '. The spray medium channel 49 is inserted within the control head 32 into a cannula holder 27 which is screwed into the nozzle channel 42. On the side of the nozzle head, the spray medium channel 49 is supported in a centering sleeve 60, which is pressed against the inner circumferential surface of the nozzle body 38 by means of a helical spring 59 supported on the cannula holder 27. At its front end, the centering sleeve 60 (see FIG. 7) has axially extending incision grooves 61a, 61b, through which a compressed air flow from the nozzle channel 42 to the nozzle channel 42 'is maintained.

The filter device 50 arranged coaxially on the container part 34 essentially consists of the filter receptacle 64 and a bore disk 19.

The venting channel 44 can be extended at its outlet opening 46 by means of the hose 68 shown in FIG. For this purpose, an adapter 17 is inserted at one end into the hose 68, which can be inserted or screwed into the outlet opening 46. The effective cross-sectional area of the outlet opening can be changed by pressure F1 applied radially to the hose jacket 67.

The spray gun shown in FIG. 9 consists of an essentially two-part device shaft 70, namely one Control head 72 and a container part 74. At its front end, the control head 72 has a receiving bore into which a nozzle body 76 with an insert part formed in one piece is inserted. At its rear end, the control head 72 is formed into an integrally molded coupling part 13, the outer surface of which has a circumferential ring extension 15. The coupling part 13 is inserted into a receiving part 11 formed at the front end of the container part 74 in order to establish a firm connection with the container part 74. The container part 74 is pressure-tightly closed at its rear end by an attached container cap 29a.

The air duct distributor system formed in the control head 72 and in the container part 74 consists of a compressed air duct 82, into which a nipple 80 is inserted on the input side for connecting a compressed air supply 9. At the other end, the compressed air channel 82 merges into the nozzle channel 81 which is formed and axially arranged in the nozzle body 76. In parallel to the nozzle channel 81, a ventilation channel 83 is formed in the upper part of the control head 72, which opens into an outlet opening 86 at the front end of the control head 72. At the other end, the ventilation channel 83 continues into the ventilation channel 83 ′, which projects into the container part 74. Furthermore, a control air duct 84 is provided in the control head 72, which opens at one end into the compressed air duct 82 and at the other end with a curved outlet opening 8 into the ventilation duct 83. Here, the outlet opening 8 is aligned in the direction of the outlet opening 86, as a result of which the air flow flowing through the ventilation duct is given a preferred direction.

The amount of air flowing through the ventilation duct 83, 83 'can be adjusted by means of a valve arranged on the top of the control head 72.

For this purpose, a valve rod 88, which is screwed into the control head 72 and is formed at one end into a pointed cone seal 89, projects into the ventilation duct 83 and has a knurled head 87 at the other end. By actuating the knurled head 87, the effective cross-sectional area of the ventilation duct 83 can be changed, as a result of which the air flow in the ventilation duct 83 and 83 'and thus the internal pressure P1 can be adjusted. In particular, the suction pressure P3 generated at the mouthpiece 93 can be completely compensated for by actuating the valve rod 88. The limitation of the internal pressure P1 to a maximum value is served by the exhaust valve 73, which is screwed into a ram air duct 85 branching off from the ventilation duct 83 in the control head 72. By actuating the knurled head 75 connected to the outlet valve 73, the maximum back pressure which can be achieved in the ventilation duct 83 is set.

To operate the spray gun, compressed air is fed from a conventional compressed air source via the compressed air supply line 9, the nipple 80, the compressed air duct 82 to the nozzle duct 81 and blown out of the mouthpiece 93 of the nozzle body 76. The suction effect of the compressed air jet creates a negative pressure in the spray medium channel 90c, 90b arranged coaxially in the nozzle channel 81, through which the spray medium 91 is sucked in from the reservoir 71 via the spray medium channel 90a and the filter device 91 arranged in the container part 74. The spray medium emerging from the spray medium channel 90c is atomized into fine droplets which are mixed with the compressed air and carried away. To control the atomization pressure, a pressure reducing valve 69 is provided between the compressed air source and the compressed air supply line. As shown in Figures 10 and 11, the pressure reducing valve 69 is essentially from a base body 6, in which a hose 66 made of elastic material is preferably inserted axially. A wedge pin 65, which is displaceable in this, is inserted perpendicular to the axial direction of the base body 6. The tube 66 rests on the inclined surface 5 of the wedge pin and its cross-sectional area is changed depending on the position of the wedge pin 65, as a result of which the quantity flow and the pressure in the compressed air line 9 can be adjusted.

In order to replace the container part 74 e.g. To enable cleaning of the reservoir 71, a shut-off valve is provided between the filter device 91 and the receiving part 11, which, as shown in Figure 9, consists of a manually operable flow channel 52. According to FIG. 12, the shut-off valve is designed as a ball seat valve 53 which has a sealing ball 54 and a helical spring 55. Here, the sealing ball 54 is pressed into its sealing position by the helical spring 55 when the control head 72 is removed from the container part 74, and is lifted off the sealing surface 4 again when these parts are engaged.

FIG. 13 shows a nozzle body 78 inserted into the control head 72, which is designed in such a way that the spray gun can be used like a tube drawing device. For this purpose, a spray medium channel 90c protruding from this is inserted into the nozzle body 78 and is designed as a color tube.

The spray gun can also be used as a sandblasting device if its container part 95 of the storage container 96 is designed in the manner shown in FIG. This storage container 96 can contain fine-grained solid substances, preferably sand particles. The control air is conducted into the reservoir 96 via the ventilation duct 97 'and the air-permeable spray filter 98 arranged between the ventilation duct 97' and the reservoir 96. The inflowing control air swirls the sand particles into a spray sand mixture, which flows as a flowable air-sand mixture into the nozzle channel 99 ', which extends almost over the entire axial length of the container part. To fill or refill the reservoir 96, the container cap 29b which closes the container part 95 can be removed.

Claims (19)

1. A spray gun for the atomised spraying of a flowable spraying medium, comprising a reservoir (40,71) for the spraying medium, a nozzle device (32,38;72,76,78) which has a nozzle duct (42,42';81,94) merging into an orifice, in which nozzle duct there is disposed an axially extending spraying-medium duct (49,90a,90b,90c) leading from the reservoir to the orifice, and a compressed-air duct (41,82) which, at one end, can be connected to a compressed-air supply and which, at the other end, discharges into the nozzle duct (42,42';81,94), further comprising a vent duct (44,44';83,83') connecting the reservoir (40,71) with the ambient atmosphere (P2) via an outlet opening (46,86), and a air control duct (45,84) which, at one end, is connected to a compressed-air supply and which, at the other end, discharges into the vent duct (44,44';83,83') in such a way that the compressed air leaving the air control duct (45,84) flows in a preferred direction towards the outlet opening (46,86) into the vent duct (44,83), wherein by opening and closing the outlet opening (46,86) the internal pressure (P1) of the reservoir (40,71) can be adjusted as a pressure above or below atomspheric pressure, whereby the flow rate of the spraying medium leaving the spraying-medium duct (49,90a,90b,90c) can be continuously controlled, characterised in that the outlet opening (8) of the air control duct (45,84) discharging into the vent duct (44,44';83,83') faces towards the outlet opening (46) closing off the vent duct (44) on the atmosphere side, so that the compressed air leaving the air control duct (45,84) flows towards the outlet opening (46,86) of the vent duct (44,44';83,83') into the vent duct (44,83).
2. A spray gun according to Claim 1, characterised in that means (47,57,87,88,89) for regulating the air flow are provided in the vent duct (44,83), by means of which the internal pressure (P1) can be adjusted in such a way that the suction pressure (P3) generated in the spraying-medium duct (49,90a,90b,90c) can be fully compensated by the air flow leaving the orifice (56,93).
3. A spray gun according to Claim 1 and/or 2, characterised in that the vent duct (83) is provided with means (73,75,85) which enable the internal pressure (P1) to be limited to a maximum pressure value.
4. A spray gun according to any one of Claims 1 to 3, characterised in that the air control duct (45,84) is connected at the inlet side with the compressed-air duct (84) or with the nozzle duct (42).
5. A spray gun according to any one of Claims 1 to 4, characterised by a filter device (50,91) disposed in the spraying-medium duct (49,90a), by means of which the spraying medium flowing from the reservoir (40,71) can be filtered.
6. A spray gun according to any one of Claims 1 to 5, characterised in that the outlet opening (46) is shaped to form a closure slot (63) which can preferably be covered by a finger dome in such a way that the cross-sectional area of the outlet opening (46) can be varied according to a logarithmic operating curve and the internal pressure (P1) can be adjusted.
7. A spray gun according to any one of Claims 1 to 5, characterised in that the vent duct (46) can be lengthened by means of a flexible tube (68) which preferably consists of elastically deformable material, wherein by a pressure (F1) applied radially to the tube outer surface (67) the cross-sectional area of the outlet opening (46) can varied and the internal pressure (P1) can be adjusted.
8. A spray gun according to any one of Claims 1 to 7, characterised by an appliance shaft (30,70) which comprises a control head (32,72) with a nozzle body (38,76) arranged axially in alignment with its front end and a container part (34,74), which is arranged axially in alignment with its rear end, with a reservoir (40,71).
9. A spray gun according to Claim 8, characterised in that in the nozzle body (38,76) and in the control head (32,72) the nozzle ducts (42,42';81) merge coaxially and in alignment into one another, and the vent duct (44,44'; 83,83') is provided substantially in alignment in the control head (32,72) and the container part (34,74).
10. A spray gun according to any one of Claims 1 to 9, characterised in that an adjustable valve stem (57,88) projects into the vent duct (44,87) between the air control duct (45,84) and the outlet opening (46,86).
11. A spray gun according to either Claim 8 or 9, characterised in that the spraying-medium duct (49,90a, 90b,90c) discharging into the nozzle body (38,76) is arranged coaxially in the nozzle duct (42,81).
12. A spray gun according to any one of Claims 5 to 11, characterised in that a shut-off valve is disposed between the spraying-medium duct (90a) and the filtering device (91), by means of which the reservoir (71) can be closed when the control head (72) is detached from the container part (74).
13. A spray gun according to Claim 12, characterised in that the shut-off valve essentially comprises a control tap (51) which is rotatably mounted in the container part (74) and which has a flow passage (52).
14. A spray gun according to Claim 12, characterised in that the shut-off valve is in the form of ball seat valve (53) which has a sealing ball (54) which, when the container part (74) is detached from the control head (72), can preferably be pressed into its sealing position by mean of a coil spring (55) and which can be urged from its sealing position against the spring force when the container part (74) is being fitted.
15. A spray gun according to at least one of the preceding Claims, characterised in that an air-permeable spraying-medium fine filter (98) is disposed between the vent duct (97') and the reservoir (96) which contains fine-grained solid substances, preferably sand particles, as the spraying medium, and in that the nozzle duct (99') projects into the reservoir (92) almost over its entire length.
16. A spray gun according to at least one of Claims 8 to 15, characterised in that a shank part (36) is locked to the container part (34), preferably by means of a bayonet fastening (37).
17. A spray gun according to at least one of the preceding Claims 8 to 16, characterised in that at its rear end the nozzle body (38,76) is shaped to form an insert part (39,77,79) which is fitted or screwed into a socket formed in the front end of the control head (32,72).
18. A spray gun according to any one of Claims 1 to 14 or 16 and 17, characterised in that the spraying-medium duct (90c) projects from the front end of the nozzle body (78) in the form of a paint tube with a drawing tip.
19. A spray gun according to at least one of the preceding Claims, characterised in that the nozzle duct (42,42',81) has a Teflon coating.

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