EP0805718A2

EP0805718A2 - Atomiser head for liquids and a device for spraying workpieces with liquids using atomiser heads of said type

Info

Publication number: EP0805718A2
Application number: EP96941034A
Authority: EP
Inventors: Hans G. Platsch
Original assignee: Klaschka GmbH and Co
Current assignee: PLATSCH Hans G; Klaschka GmbH and Co
Priority date: 1995-11-27
Filing date: 1996-11-26
Publication date: 1997-11-12
Also published as: DE19544016A1; EP1153664A3; WO1997019757A3; US5989344A; EP1153664A2; WO1997019757A2

Abstract

In an atomiser head (28) which produces a conical droplet mist, two diametrically opposing shaping air ducts (156) are provided in the vicinity of the mist outlet aperture. The shaping air jets emerging from these ducts flatten the droplet mist which thus has a larger cone angle in one direction and a smaller cone angle in the other direction. A droplet mist thus flattened can be used to apply a layer of liquid to areas of a workpiece surface in a manner particularly true to the surface contours.

Description

Atomizing head for liquids and device for spraying workpieces with liquids with such atomizing heads

The invention relates to an atomizing head according to the preamble of claim 1 and a device for spraying workpieces with liquids using such atomizing heads according to the preamble of claim 11.

Atomizing heads of the type specified in the preamble of claim 1 are found in different ways as atomizing heads in spray guns on the market.

Such atomizing heads generally produce a rotationally symmetrical droplet cone with a predetermined one

Opening angle. If you want to spray workpieces with a liquid with such atomizing heads within a precisely specified edge contour, which is often rectangular or polygonal, you have to choose a small opening angle of the droplet cone and move it with a moving atomizing head over the surface to be sprayed, what is time-consuming and, in the case of automation, requires a lot of effort for a coordinate drive of the atomizing head and its control. If one works with a larger number of atomizing heads distributed according to the surface area to be covered, this in turn means considerable effort in view of the costs of an atomizing head and the installation associated with it. In addition, the change of a corresponding arrangement of fixed atomizing heads from one

ORIGINAL DOCUMENTS surface geometry to be sprayed onto another with many mechanical changes and a lot of time.

It has now been found that, in many cases, the spraying of partial areas of workpiece surfaces which have a rectangular or polygonal edge contour can be simplified by using nozzle heads which produce a droplet cone with a non-round cross section. Such cross sections are e.g. narrow rectangles. With such cross sections of the droplet cone, moving workpieces can be sprayed very precisely in front of an atomizing head or a row of atomizing heads.

In order to obtain this advantage, the invention proposes an atomizing head in which, in addition to the nozzle atomizing the liquid, a droplet cone-shaped nozzle device is provided which directs air jets against the initially rotationally symmetrical droplet cone and thus polygonal Cross-sectional shape there, in particular pushing it wide into a flat rectangular cone.

The features of such an atomizing head are specified in claim 1.

Advantageous developments of the invention are the subject of dependent claims.

An atomizing head, as specified in claim 2, produces a droplet cone whose transverse cross section corresponds to a narrow rectangle, the narrow sides of which are formed by small semicircles. In other words: the droplet cone is flattened by the control nozzle device specified in claim 2, whereby its dimension is shortened in one direction and enlarged in the other direction.

In the case of a spray head according to claim 6, the droplet cone generated by the spray nozzle device can also be asymmetrically flattened.

In the case of an atomizing head according to claim 7, together with the exposure to atomizing air, the liquid supply to the atomizing nozzle device is also switched on.

The development of the invention according to claim 8 allows the liquid throughput through the atomizing nozzle device to be specified precisely in a simple manner.

In the case of an atomizing head according to claim 9, the liquid throughput can be adjusted by an external control unit.

An atomizing head according to claim 10 is particularly well suited for atomizing highly viscous liquids.

In a device for spraying workpieces as specified in claim 11, the atomizing heads are switched on and off depending on the position of the workpiece with respect to the atomizing head arrangement.

In a device according to claim 12, a partial spraying of the workpiece surfaces in the desired manner is obtained in a simple manner.

With the development of the invention according to claim 13 it is ensured that the on the workpiece surface the amount of liquid applied per unit area is independent of the speed at which the workpiece is moved past the atomizing head arrangement.

It is automatically taken into account in a device according to claim 14 that the droplet cones emitted by the atomizing heads require a certain period of time to reach the workpiece surface.

The development of the invention according to claim 15 is particularly suitable for spraying workpiece surfaces with highly viscous liquids. This ensures that the viscosity of these liquids is not increased by cooling in the feed lines leading to the atomizing heads.

In a device according to claim 16, the width of the droplet cone emitted by the atomizing heads can also be controlled depending on the position of the workpiece relative to the atomizing head arrangement.

The further development of the invention according to claim 17 is also advantageous with regard to uniform spraying of a workpiece surface with a highly viscous liquid.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this show:

Figure 1: a schematic block diagram of a street for deep drawing of metal sheets, which are provided with a device for spraying selected surface sections of the metal sheets is;

FIG. 2 shows a schematic illustration of an atomizing head arrangement of the device shown in FIG. 1 for spraying partial areas of the sheet metal plates and an associated control and supply unit;

FIG. 3: an axial section through one of the atomizing heads, which are only shown schematically in FIG. 2;

FIG. 4: an axial section through the atomizing head shown in FIG. 3 in a section plane perpendicular to the plane of the drawing in FIG. 3;

Figure 5: an axial view of the free end of a

Shaped air nozzle body of the in Figures 3 and

4 atomizing head shown;

Figure 6: an axial section through the shaped air nozzle body shown in Figure 5 along the one there

Section line VI - VI;

FIG. 7: a side view of the molded air nozzle body in FIG. 6 seen from the left;

FIG. 8: a side view of an atomizing air nozzle body of the atomizing head shown in FIGS. 2 and 4;

FIG. 9: a schematic representation of a modified atomizing head; and

Figure 10: the circuit diagram of a control circuit for selective Activation of atomizing heads depending on the position of a workpiece.

In FIG. 1, 10 denotes a stack of individual sheet metal pockets 12. The metal sheets 12 are brought into a waiting position by a first transport system 14, which is only indicated schematically. The sheet metal sheet lying in the waiting position is placed on a lower mold 18 of a deep-drawing tool by a further transport system 16. An upper mold 20 of the deep-drawing tool is moved by a press drive 22, also indicated only schematically.

When the metal sheets 12 are deep drawn between the lower mold 18 and the upper mold 20, the different areas of the metal sheet 12 are subjected to different stresses. Most of the deformation work has to be performed on the side walls of the trough-shaped recess 24 of the lower mold 18 or of the complementary stamp section 26 of the upper mold. In these areas is supposed to

Lubrication with a high viscosity lubricating fluid reduces the friction between the sheet metal surfaces and the surfaces of lower mold 18 and upper mold 20. In order to coat these strongly deformed sheet areas with the lubricating liquid, atomizing heads 28 are arranged one behind the other perpendicular to the plane of the drawing above and below the path on which the sheet sheets 12 are moved by the second transport system 16. These each deliver a droplet cone 30, which consists of small droplets of the highly viscous lubricant. The latter is supplied via a common lubricant feed line 32. The latter comes from a total of 24 control / supply unit. The various atomizing heads 28 also have individual ones Activation lines 36, which are connected to assigned output terminals of the control / supply unit 34.

The atomizing heads 28 are also connected to a common atomizing compressed air line 38 and a common jet-shaped compressed air line 40. Furthermore, the various atomizing heads 28 are connected to a common heating current line 42.

A first displacement sensor 44, which is shown as a resolver, works together with the second transport system 16. From its output signal, the control / supply unit 34 can, on the one hand, recognize where a metal sheet 12 to be sprayed is currently located with respect to the atomizing head arrangement, and can also recognize the speed at which the metal sheet 12 is being actuated at the moment.

A second travel encoder works with the press drive 22

46 together, whose output signal is used by the control / supply unit 34 to recognize when the transport systems 14 and 16 must be started, which are also controlled by the control / supply unit 34.

In FIG. 2, parts of the device for spraying the sheet metal plates, which have already been explained above with reference to FIG. 1, are again provided with the same reference symbols.

Each of the activation lines 36 works on a solenoid valve 50 attached to the atomizing head 28 under consideration, via which the atomizing air reaches the interior of the atomizing head. The atomizing air Compressed air line 38 is connected via a pressure regulator 52 and a 2/2 solenoid valve 54 to the outlet of a cleaning unit 56, the input of which is connected to a compressed air supply line 60 via a further 2/2 solenoid valve 58 representing an air main valve.

The jet shape compressed air line 38 is connected to the outlet of the cleaning unit 56 via a second pressure regulator 62 and a further 2/2 solenoid valve 64. The output of the cleaning unit 56 is finally connected via a further pressure regulator 66 to a compressed air motor 68 which works on a diaphragm pump 70.

The outlet of the diaphragm pump 70 is connected to the lubricant feed line 32 via a pressure regulator 72. An electric heater 78 is inserted into a suction line 74 of the diaphragm pump 70, which leads to a reservoir 76 for the lubricant.

The lubricant in the reservoir 76 is a high-viscosity, milk-like emulsion. At room temperature it has an approximately gel-like consistency (0.85 Pa s). At the outlet of the heater 78, the lubricant is heated to approximately 50 ° C. and still has a viscosity of 0.4 Pa s).

The parts of the supply of the atomizing heads with atomizing air, jet air and lubricant described above together form the supply part of the control / supply unit 34 designated with 80. The control part of the control / supply unit 34 designated with 82 serves for supplying the heating elements assigned to the atomizing heads for selective Activation of the various atomizing heads 28 for actuation of the various solenoid valves of the supply part 80 and for coordinating the temporal working window of the dusting heads 28 and the liquid quantities dispensed by them depending on the current position of the respectively sprayed sheet metal plate 12 for the atomizing head arrangement and depending on the speed of the sheet metal plate 12, both of which can be derived from the output signal of the displacement sensor 44. The control part 82 can count the pressing cycles on the basis of the output signal of the displacement sensor 46. If desired, only every second, third, etc. sheet of metal can be sprayed with lubricant if the deformation of the sheet of metal is only slight, so that the lubricant left by a previous sheet of metal in the mold for one, two or more subsequent ones Sheet metal is sufficient.

Analogously, predetermined areas of a sheet metal sheet can always be sprayed with lubricant for each pressing cycle, while less strongly deformed surface sections of the sheet metal sheet are sprayed with lubricant only on every second, third, fourth, etc. sheet metal sheet.

3 and 4, a housing of an atomizing head 28 is designated 84 overall. It has a main housing part 86, which is closed at the top by a cover 88.

The housing main part 86 has an annular shoulder 90 at the upper end, on which a holding plate 92 is seated, via which the atomizing head 28 is fastened to a supporting structure (not shown). The holding plate 92 is sandwiched between the cover 88 and the main housing part 86 and sealed against the inside of the housing by an O-ring 94. A cylinder bore 96 is provided in the main housing part 86, in which a piston 98 runs. This is fixedly connected to a long metering needle 100, which has a pointed, conical control section 102.

The piston 98 is biased downwards by a spring 104 in FIG. 3, which is accommodated in a sleeve-shaped spring chamber 106 which is screw-supported by the cover 88. The lower end face of the sleeve-shaped spring chamber 106 at the same time forms a stop face which specifies the top dead center of the piston 98 in an adjustable manner. To fix the spring chamber 106 in the selected axial position, a threaded locking ring 108 is provided, which runs on the external thread of the spring chamber 106 and cooperates with the top of the cover 88. A damper plate 112 connected by screws 110 to the bottom of the cylinder bore 96 prevents the piston 98 from hitting hard against the bottom of the cylinder bore 96.

The working space 114 delimited between the piston 98 and the cylinder bore 96 is connected to an atomizing air connection channel 118 via an axial bore 116 of the main housing part 86. The bore 116 extends beyond the connection channel 118 and ends in a counter bore 120 which is machined into the underside of the main housing part 86. A threaded bore runs upward from the counterbore 120, which is coaxial with the cylinder bore 96 and into which a atomizing nozzle body 122 is screwed. The upper end of this threaded bore is connected to a lubricant connection channel 124.

The nozzle body 122 has a central bore 126 which surrounds the dispensing needle 100 at a distance. In the conical lower end section of the nozzle body 122, a conical metering opening 128 is provided, which has the same cone opening angle as the control section 102 of the metering needle 100. In the transition region between its shaft section and the control section 102, the metering needle 100 carries an O-ring 130 which also a reduced diameter end portion 131 of the bore 126 engages before the end portion 102 abuts the metering opening 128 in order to be able to completely close the metering opening 128 without a high surface pressure between the opposing surfaces of the control section 102 and the metering opening 128 would be necessary.

As can be seen from FIG. 8, two diametrically opposed nozzle grooves 132 are provided in the outer circumferential surface of the nozzle body 122, which have an incline of approximately 45 and connect the counterbore 120 with a space 134 which is located between the conical lower end face of the Nozzle body 122 and a cylindrical / tapered counterbore 136 is limited, which is provided in a jet-shaped nozzle body 138 coaxial to the atomizing nozzle body 122.

The space 134 communicates with the surroundings via a central opening 140 in the lower wall of the nozzle body 138. An end portion 142 of the nozzle body 122 extends through the opening 140 with radial play.

The nozzle body 138 is arranged in the interior of a mounting ring 144, which is screwed onto a lower, threaded end section 146 of the main housing part 86 and is sealed against this by an O-ring 148. The mounting ring 144, in turn, delimits a space 150 with the nozzle body 138, which is connected via an axial channel 152 (cf. FIG. 4) to a shaped air connection opening 154.

As can be seen from FIGS. 3-7, the nozzle body 138 has a conical lower end face, the opening angle of this conical area being approximately 120. Two diametrically opposed shaped air nozzle grooves 156 are pierced into the conical surface. Teeth 158 protruding from the end face of the nozzle body 138 serve to set a predetermined angular position of the nozzle grooves 156 with respect to the housing 84 which has a substantially square cross section.

The atomizing head described above works as follows:

The piston 98 normally assumes its lower end position under the force of the spring 104, in which the metering opening 128 is closed by the O-ring 130 carried by the metering needle 100.

When the connecting channel 118 is pressurized by actuating the associated solenoid valve 50, the piston 98 is moved upward against the force of the spring 104, so that the lubricant present in the connecting channel 124 reaches the metering opening 128. At the same time, compressed air is fed into the space 134 via the nozzle grooves 132 and passed through the opening 140 which surrounds the discharge end of the nozzle opening 128. A droplet cone thus emerges from the opening 140, which has an opening angle of approximately at the above-mentioned viscosity of the lubricant 28 °

At the same time, further compressed air reaches the end face of the nozzle body 138 via the connection opening 154 and the nozzle grooves 156. The two opposite compressed air jets emerging from the nozzle grooves 156 act on opposite lateral sections of the droplet cone emerging from the opening 140. As a result, the cone is flattened and instead of a circular cross section is given the cross section of a flat rectangle with rounded narrow sides. The opening angle of the flattened droplet cone, measured in the direction of the major axis of the cross section, is approximately 50, measured in the direction of the minor axis less, namely approximately 15, according to the cross-sectional rearrangement.

Due to the deformed droplet cone created by the atomizing head, an approximately bar-shaped pattern of lubricant is obtained on a stationary workpiece.

When the workpiece is moved, an approximately rectangular lubricant pattern is obtained on the workpiece surface.

As indicated by dashed lines in FIG. 4, one can also see 154 solenoid valves 160 for the shaped air connection openings 154, so that the various atomizing heads can be controlled differently with regard to the cross-sectional shape of the dispensed cone of droplets.

In order to keep the quantity of lubricant dispensed independently of the conveying speed of the sheet metal plates 12, the pressure regulator 72 can be set in accordance with a sheet plate speed signal by the control part 82 with respect to the control pressure, the sheet metal speed signal by differentiating the Output signals of the encoder 44 is obtained.

Alternatively, the amount of liquid dispensed by the atomizing heads 28 can also be kept constant and the conveying speed of the transport system 16 can be varied in order to vary the lubricant application on the workpiece surfaces.

In order to prevent the lubricant lines from becoming blocked by the lubricant becoming cold, a constant basic flow of heated lubricant can be maintained by, as shown in FIG. 9, the lubricant inlet of the atomizing heads in each case via a pressure relief valve 162 with a return line 164 connects.

Instead, a 3/2-way solenoid valve can also be provided at the lubricant inlet of the atomizing heads, which is reversed in opposition to the solenoid valve 50 of the atomizing head in order to supply 128 lubricant to the return line 164 when the metering opening is closed, but to the metering opening when the metering opening is open 128 feed.

FIG. 9 also shows a trace heating 166 and a heating element 168 assigned to the housing of the atomizing head.

FIG. 10 shows a control circuit for activating the atomizing heads 28 as a function of the position of the metal sheet to be sprayed relative to the atomizing heads.

The output of the displacement sensor 44 is connected to the input of an analog / digital converter 170. Its output signal is rounded by a digital rounding circuit 172. This receives a digital signal corresponding to the desired rounding via line 174, which is a measure of is the flattening of the droplet cone 30 and is derived, for example, from the output signal of a pressure sensor (not shown) to which the molding air pressure is applied.

In a summing circuit 176, a speed-dependent lead signal is added to the rounded path signal. The corrected path signal obtained in this way serves to address a memory 178, in the cells of which signal words are stored, the number of bits of which corresponds to (or is greater than) the number of atomizing heads to be controlled. On

Bit "1" stands for an atomizing head to be activated, a bit that is not set indicates that the associated atomizing head is currently not required for generating the lubricant pattern.

It can be seen that the bit pattern, entered as an example in the memory 178, corresponds to a coating of the edge of a metal sheet with emphasis on the corner areas and a weaker coating of the middle areas of the sheet.

To generate the lead signal, the output of the A / D converter 170 is additionally connected to a digital differentiating circuit 180. The table speed signal thus obtained is converted into the lead signal in a computing circuit 182, the computing circuit 182 receiving a further signal via a line 184 which corresponds to the velocity of the droplets in the droplet cone. This further signal can e.g. be derived from the output signal of a pressure sensor (not shown) which is pressurized with the pressure of the atomizing air.

The summing circuit 176 thus effectively forms a controllable phase shifter or a controllable timing element for synchronizing the working heads with the movement of the Metal sheets.

The word of the memory 178 selected by the output signal of the summing circuit is transferred to a register 186, the individual memory elements of which operate on the activation lines 36 via amplifiers 188.

In the atomizing heads described above, the shaped air nozzle grooves 156 were both connected to the annular space 150, so that the droplet cone is flattened symmetrically. Instead, the two air nozzle grooves can also be connected with separate housing connections and with separate molded air sources. An asymmetrical cone flattening is then obtained. For this purpose, too, the shaped air nozzle grooves can be distributed asymmetrically around the axis of the opening 140.

The droplet cone can be flattened several times by increasing the number of shaped air nozzle grooves, e.g. to a substantially square cross-sectional shape.

In the case of the atomizing heads described above, the atomizing rate was set manually by screwing the spring chamber 106 in place. Instead, the spring chamber can be screwed in by omitting the locking ring 108 by means of a self-locking gear servomotor, as indicated by dashed lines in FIG.

Claims

claims

1. Atomizing head for liquids with a housing

(80), with a atomizing nozzle body (122) which has a metering opening (128) and can be connected to a source (76) for liquid to be atomized, with a metering needle (100) which is coaxial with the metering opening (128) and with This together specifies a preferably adjustable passage area for the liquid to be atomized, with an atomizing air nozzle device (132) surrounding the metering opening (128), which can be connected to an atomizing air source (38) and provides a rotationally symmetrical, preferably swirling air flow, characterized thereby net, that around the atomizing nozzle device (132) around a shaped air nozzle device (156) is arranged, which can be connected to a shaped air source (40) and generates a shaped air flow which is directed so that it is directed through the nozzle body (122 ) and the atomizing nozzle device (132) produced a droplet having a conical outer contour fchenstrom (30) hits

2. Atomizing head according to claim 1, characterized gekenn¬ characterized in that the shaped air nozzle device (156) two

Has shaped air channels, which are opposite each other with respect to the axis of the metering opening (128).

3. Atomizing head according to claim 2, characterized gekenn¬ characterized in that the shaped air channels (156) lie in an axial plane of the metering opening (128).

4. atomizing head according to claim 3, characterized shows that the shaped air channels (156) run obliquely to the axis of the metering opening (128).

5. atomizing head according to claim 4, characterized in that between the shaped air channels

(156) included angle is about 120 °.

6. Atomizing head according to one of claims 1-5, characterized in that the shaped air nozzle device (156) has at least two sets of shaped air nozzles which can be connected independently of one another to the shaped air source (40) or to different shaped air sources .

7. Atomizing head according to one of claims 1-6, characterized in that a connection opening (118) of the housing (80) to be connected to the atomizing air source (38) with the working space (114) of a compressed air servomotor (96, 98) is connected, the driven part works on the metering needle (100).

8. atomizing head according to any one of claims 1-7, characterized by an adjustable stop

(106) for the open position of the metering needle (100).

9. atomizing head according to claim 8, characterized by a servomotor on the adjustable stop (106).

10. Atomizing head according to one of claims 1-9, characterized in that a heating element (168) is thermally coupled to the housing (80).

11. Device for spraying workpieces with a liquid, with a plurality of atomizing heads (28) according to one of claims 1-10, with a storage container (76) for the liquid to be atomized, with a pump (70) for conveying the liquid to be atomized from the storage container (76) to the atomizing heads (28) , with an atomizing air control valve arrangement (50), which is connected between an atomizing air source (38) and the atomizing air connections (118) of the atomizing heads (28), and with a shaped air source (40), which is connected to the shaped air Connections (152) of the atomizing heads (28) are connected, characterized in that the control valve arrangement (50) is activated by a control unit (82) in dependence on the output signal of a displacement sensor (44), which together with the workpiece (12) to be sprayed works, which is moved by a transport device (16) past the atomizing heads (28).

12. The device according to claim 11, characterized gekennzeich¬ net that the control unit (82) has a memory (178) which is addressed according to the output signal of the displacement sensor (44) and in its memory cells each at the found position of the workpiece (12th ) with respect to the atomizing heads (28) to be controlled, the atomizing heads (28) are stored.

13. Device according to claim 12, characterized in that the control unit (82) controls a pressure adjusting valve (72) as a function of the conveying speed of the workpiece (12) in order to keep the amount of liquid applied to the workpiece per unit area constant.

14. Device according to claim 12 or 13, characterized in that the control unit (82), the atomizing heads (28) via a controllable phase element (176) controls whose phase is set proportional to the speed of the workpiece (12).

15. Device according to one of claims 11-14, characterized by a heating device (78) acting on the supplied liquid and by 2/2 bypass valves or pressure relief valves (162), which are each assigned to the atomizing heads (28) and above which the non-atomized quantities of liquid are led into a return line (164).

16. Device according to one of claims 11-15, characterized in that the control unit (82) one

Form air pressure controller (62) is controlled depending on the output signal of the position sensor (44).

17. Device according to one of claims 11-16, gekenn¬ characterized by a line trace heating for the atomizing heads (28) leading liquid feed lines (32).